PCRE2API(3) Library Functions Manual PCRE2API(3) NNAAMMEE PCRE2 - Perl-compatible regular expressions (revised API) ##iinncclluuddee <> PCRE2 is a new API for PCRE, starting at release 10.0. This document contains a description of all its native functions. See the ppccrree22 docu- ment for an overview of all the PCRE2 documentation. PPCCRREE22 NNAATTIIVVEE AAPPII BBAASSIICC FFUUNNCCTTIIOONNSS ppccrree22__ccooddee **ppccrree22__ccoommppiillee((PPCCRREE22__SSPPTTRR _p_a_t_t_e_r_n,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, uuiinntt3322__tt _o_p_t_i_o_n_s,, iinntt **_e_r_r_o_r_c_o_d_e,, PPCCRREE22__SSIIZZEE **_e_r_r_o_r_o_f_f_s_e_t_, ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ccooddee__ffrreeee((ppccrree22__ccooddee **_c_o_d_e));; ppccrree22__mmaattcchh__ddaattaa **ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee((uuiinntt3322__tt _o_v_e_c_s_i_z_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__mmaattcchh__ddaattaa **ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee__ffrroomm__ppaatttteerrnn(( ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; iinntt ppccrree22__mmaattcchh((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; iinntt ppccrree22__ddffaa__mmaattcchh((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, iinntt **_w_o_r_k_s_p_a_c_e,, PPCCRREE22__SSIIZZEE _w_s_c_o_u_n_t));; vvooiidd ppccrree22__mmaattcchh__ddaattaa__ffrreeee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; PPCCRREE22 NNAATTIIVVEE AAPPII AAUUXXIILLIIAARRYY MMAATTCCHH FFUUNNCCTTIIOONNSS PPCCRREE22__SSPPTTRR ppccrree22__ggeett__mmaarrkk((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; uuiinntt3322__tt ppccrree22__ggeett__oovveeccttoorr__ccoouunntt((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; PPCCRREE22__SSIIZZEE **ppccrree22__ggeett__oovveeccttoorr__ppooiinntteerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; PPCCRREE22__SSIIZZEE ppccrree22__ggeett__ssttaarrttcchhaarr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; PPCCRREE22 NNAATTIIVVEE AAPPII GGEENNEERRAALL CCOONNTTEEXXTT FFUUNNCCTTIIOONNSS ppccrree22__ggeenneerraall__ccoonntteexxtt **ppccrree22__ggeenneerraall__ccoonntteexxtt__ccrreeaattee(( vvooiidd **((**_p_r_i_v_a_t_e___m_a_l_l_o_c))((PPCCRREE22__SSIIZZEE,, vvooiidd **)),, vvooiidd ((**_p_r_i_v_a_t_e___f_r_e_e))((vvooiidd **,, vvooiidd **)),, vvooiidd **_m_e_m_o_r_y___d_a_t_a));; ppccrree22__ggeenneerraall__ccoonntteexxtt **ppccrree22__ggeenneerraall__ccoonntteexxtt__ccooppyy(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ggeenneerraall__ccoonntteexxtt__ffrreeee((ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; PPCCRREE22 NNAATTIIVVEE AAPPII CCOOMMPPIILLEE CCOONNTTEEXXTT FFUUNNCCTTIIOONNSS ppccrree22__ccoommppiillee__ccoonntteexxtt **ppccrree22__ccoommppiillee__ccoonntteexxtt__ccrreeaattee(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__ccoommppiillee__ccoonntteexxtt **ppccrree22__ccoommppiillee__ccoonntteexxtt__ccooppyy(( ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ccoommppiillee__ccoonntteexxtt__ffrreeee((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t));; iinntt ppccrree22__sseett__bbssrr((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; iinntt ppccrree22__sseett__cchhaarraacctteerr__ttaabblleess((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, ccoonnsstt uunnssiiggnneedd cchhaarr **_t_a_b_l_e_s));; iinntt ppccrree22__sseett__ccoommppiillee__eexxttrraa__ooppttiioonnss((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _e_x_t_r_a___o_p_t_i_o_n_s));; iinntt ppccrree22__sseett__mmaaxx__ppaatttteerrnn__lleennggtthh((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, PPCCRREE22__SSIIZZEE _v_a_l_u_e));; iinntt ppccrree22__sseett__nneewwlliinnee((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; iinntt ppccrree22__sseett__ppaarreennss__nneesstt__lliimmiitt((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; iinntt ppccrree22__sseett__ccoommppiillee__rreeccuurrssiioonn__gguuaarrdd((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, iinntt ((**_g_u_a_r_d___f_u_n_c_t_i_o_n))((uuiinntt3322__tt,, vvooiidd **)),, vvooiidd **_u_s_e_r___d_a_t_a));; PPCCRREE22 NNAATTIIVVEE AAPPII MMAATTCCHH CCOONNTTEEXXTT FFUUNNCCTTIIOONNSS ppccrree22__mmaattcchh__ccoonntteexxtt **ppccrree22__mmaattcchh__ccoonntteexxtt__ccrreeaattee(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__mmaattcchh__ccoonntteexxtt **ppccrree22__mmaattcchh__ccoonntteexxtt__ccooppyy(( ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; vvooiidd ppccrree22__mmaattcchh__ccoonntteexxtt__ffrreeee((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; iinntt ppccrree22__sseett__ccaalllloouutt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, iinntt ((**_c_a_l_l_o_u_t___f_u_n_c_t_i_o_n))((ppccrree22__ccaalllloouutt__bblloocckk **,, vvooiidd **)),, vvooiidd **_c_a_l_l_o_u_t___d_a_t_a));; iinntt ppccrree22__sseett__ooffffsseett__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, PPCCRREE22__SSIIZZEE _v_a_l_u_e));; iinntt ppccrree22__sseett__hheeaapp__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; iinntt ppccrree22__sseett__mmaattcchh__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; iinntt ppccrree22__sseett__ddeepptthh__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; PPCCRREE22 NNAATTIIVVEE AAPPII SSTTRRIINNGG EEXXTTRRAACCTTIIOONN FFUUNNCCTTIIOONNSS iinntt ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnaammee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; iinntt ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnuummbbeerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, uuiinntt3322__tt _n_u_m_b_e_r,, PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; vvooiidd ppccrree22__ssuubbssttrriinngg__ffrreeee((PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r));; iinntt ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnaammee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__UUCCHHAARR ****_b_u_f_f_e_r_p_t_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; iinntt ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnuummbbeerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, uuiinntt3322__tt _n_u_m_b_e_r,, PPCCRREE22__UUCCHHAARR ****_b_u_f_f_e_r_p_t_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; iinntt ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnaammee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__SSIIZZEE **_l_e_n_g_t_h));; iinntt ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnuummbbeerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, uuiinntt3322__tt _n_u_m_b_e_r,, PPCCRREE22__SSIIZZEE **_l_e_n_g_t_h));; iinntt ppccrree22__ssuubbssttrriinngg__nnaammeettaabbllee__ssccaann((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__SSPPTTRR **_f_i_r_s_t,, PPCCRREE22__SSPPTTRR **_l_a_s_t));; iinntt ppccrree22__ssuubbssttrriinngg__nnuummbbeerr__ffrroomm__nnaammee((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _n_a_m_e));; vvooiidd ppccrree22__ssuubbssttrriinngg__lliisstt__ffrreeee((PPCCRREE22__SSPPTTRR **_l_i_s_t));; iinntt ppccrree22__ssuubbssttrriinngg__lliisstt__ggeett((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__UUCCHHAARR ******_l_i_s_t_p_t_r,, PPCCRREE22__SSIIZZEE ****_l_e_n_g_t_h_s_p_t_r));; PPCCRREE22 NNAATTIIVVEE AAPPII SSTTRRIINNGG SSUUBBSSTTIITTUUTTIIOONN FFUUNNCCTTIIOONN iinntt ppccrree22__ssuubbssttiittuuttee((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, PPCCRREE22__SSPPTTRR _r_e_p_l_a_c_e_m_e_n_t_z_f_P_, PPCCRREE22__SSIIZZEE _r_l_e_n_g_t_h,, PPCCRREE22__UUCCHHAARR **_o_u_t_p_u_t_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE **_o_u_t_l_e_n_g_t_h_p_t_r));; PPCCRREE22 NNAATTIIVVEE AAPPII JJIITT FFUUNNCCTTIIOONNSS iinntt ppccrree22__jjiitt__ccoommppiillee((ppccrree22__ccooddee **_c_o_d_e,, uuiinntt3322__tt _o_p_t_i_o_n_s));; iinntt ppccrree22__jjiitt__mmaattcchh((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; vvooiidd ppccrree22__jjiitt__ffrreeee__uunnuusseedd__mmeemmoorryy((ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__jjiitt__ssttaacckk **ppccrree22__jjiitt__ssttaacckk__ccrreeaattee((PPCCRREE22__SSIIZZEE _s_t_a_r_t_s_i_z_e,, PPCCRREE22__SSIIZZEE _m_a_x_s_i_z_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; vvooiidd ppccrree22__jjiitt__ssttaacckk__aassssiiggnn((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, ppccrree22__jjiitt__ccaallllbbaacckk _c_a_l_l_b_a_c_k___f_u_n_c_t_i_o_n,, vvooiidd **_c_a_l_l_b_a_c_k___d_a_t_a));; vvooiidd ppccrree22__jjiitt__ssttaacckk__ffrreeee((ppccrree22__jjiitt__ssttaacckk **_j_i_t___s_t_a_c_k));; PPCCRREE22 NNAATTIIVVEE AAPPII SSEERRIIAALLIIZZAATTIIOONN FFUUNNCCTTIIOONNSS iinntt3322__tt ppccrree22__sseerriiaalliizzee__ddeeccooddee((ppccrree22__ccooddee ****_c_o_d_e_s,, iinntt3322__tt _n_u_m_b_e_r___o_f___c_o_d_e_s,, ccoonnsstt uuiinntt88__tt **_b_y_t_e_s,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; iinntt3322__tt ppccrree22__sseerriiaalliizzee__eennccooddee((ccoonnsstt ppccrree22__ccooddee ****_c_o_d_e_s,, iinntt3322__tt _n_u_m_b_e_r___o_f___c_o_d_e_s,, uuiinntt88__tt ****_s_e_r_i_a_l_i_z_e_d___b_y_t_e_s,, PPCCRREE22__SSIIZZEE **_s_e_r_i_a_l_i_z_e_d___s_i_z_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; vvooiidd ppccrree22__sseerriiaalliizzee__ffrreeee((uuiinntt88__tt **_b_y_t_e_s));; iinntt3322__tt ppccrree22__sseerriiaalliizzee__ggeett__nnuummbbeerr__ooff__ccooddeess((ccoonnsstt uuiinntt88__tt **_b_y_t_e_s));; PPCCRREE22 NNAATTIIVVEE AAPPII AAUUXXIILLIIAARRYY FFUUNNCCTTIIOONNSS ppccrree22__ccooddee **ppccrree22__ccooddee__ccooppyy((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e));; ppccrree22__ccooddee **ppccrree22__ccooddee__ccooppyy__wwiitthh__ttaabblleess((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e));; iinntt ppccrree22__ggeett__eerrrroorr__mmeessssaaggee((iinntt _e_r_r_o_r_c_o_d_e,, PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE _b_u_f_f_l_e_n));; ccoonnsstt uunnssiiggnneedd cchhaarr **ppccrree22__mmaakkeettaabblleess((ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; iinntt ppccrree22__ppaatttteerrnn__iinnffoo((ccoonnsstt ppccrree22 **_c_o_d_e,, uuiinntt3322__tt _w_h_a_t,, vvooiidd **_w_h_e_r_e));; iinntt ppccrree22__ccaalllloouutt__eennuummeerraattee((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, iinntt ((**_c_a_l_l_b_a_c_k))((ppccrree22__ccaalllloouutt__eennuummeerraattee__bblloocckk **,, vvooiidd **)),, vvooiidd **_u_s_e_r___d_a_t_a));; iinntt ppccrree22__ccoonnffiigg((uuiinntt3322__tt _w_h_a_t,, vvooiidd **_w_h_e_r_e));; PPCCRREE22 NNAATTIIVVEE AAPPII OOBBSSOOLLEETTEE FFUUNNCCTTIIOONNSS iinntt ppccrree22__sseett__rreeccuurrssiioonn__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; iinntt ppccrree22__sseett__rreeccuurrssiioonn__mmeemmoorryy__mmaannaaggeemmeenntt(( ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, vvooiidd **((**_p_r_i_v_a_t_e___m_a_l_l_o_c))((PPCCRREE22__SSIIZZEE,, vvooiidd **)),, vvooiidd ((**_p_r_i_v_a_t_e___f_r_e_e))((vvooiidd **,, vvooiidd **)),, vvooiidd **_m_e_m_o_r_y___d_a_t_a));; These functions became obsolete at release 10.30 and are retained only for backward compatibility. They should not be used in new code. The first is replaced by ppccrree22__sseett__ddeepptthh__lliimmiitt(()); the second is no longer needed and has no effect (it always returns zero). PPCCRREE22 EEXXPPEERRIIMMEENNTTAALL PPAATTTTEERRNN CCOONNVVEERRSSIIOONN FFUUNNCCTTIIOONNSS ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **ppccrree22__ccoonnvveerrtt__ccoonntteexxtt__ccrreeaattee(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **ppccrree22__ccoonnvveerrtt__ccoonntteexxtt__ccooppyy(( ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **_c_v_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ccoonnvveerrtt__ccoonntteexxtt__ffrreeee((ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **_c_v_c_o_n_t_e_x_t));; iinntt ppccrree22__sseett__gglloobb__eessccaappee((ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **_c_v_c_o_n_t_e_x_t,, uuiinntt3322__tt _e_s_c_a_p_e___c_h_a_r));; iinntt ppccrree22__sseett__gglloobb__sseeppaarraattoorr((ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **_c_v_c_o_n_t_e_x_t,, uuiinntt3322__tt _s_e_p_a_r_a_t_o_r___c_h_a_r));; iinntt ppccrree22__ppaatttteerrnn__ccoonnvveerrtt((PPCCRREE22__SSPPTTRR _p_a_t_t_e_r_n,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, uuiinntt3322__tt _o_p_t_i_o_n_s,, PPCCRREE22__UUCCHHAARR ****_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE **_b_l_e_n_g_t_h,, ppccrree22__ccoonnvveerrtt__ccoonntteexxtt **_c_v_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ccoonnvveerrtteedd__ppaatttteerrnn__ffrreeee((PPCCRREE22__UUCCHHAARR **_c_o_n_v_e_r_t_e_d___p_a_t_t_e_r_n));; These functions provide a way of converting non-PCRE2 patterns into patterns that can be processed by ppccrree22__ccoommppiillee(()). This facility is experimental and may be changed in future releases. At present, "globs" and POSIX basic and extended patterns can be converted. Details are given in the ppccrree22ccoonnvveerrtt documentation. PPCCRREE22 88--BBIITT,, 1166--BBIITT,, AANNDD 3322--BBIITT LLIIBBRRAARRIIEESS There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code units, respectively. However, there is just one header file, ppccrree22..hh. This contains the function prototypes and other definitions for all three libraries. One, two, or all three can be installed simul- taneously. On Unix-like systems the libraries are called lliibbppccrree22--88, lliibbppccrree22--1166, and lliibbppccrree22--3322, and they can also co-exist with the orig- inal PCRE libraries. Character strings are passed to and from a PCRE2 library as a sequence of unsigned integers in code units of the appropriate width. Every PCRE2 function comes in three different forms, one for each library, for example: ppccrree22__ccoommppiillee__88(()) ppccrree22__ccoommppiillee__1166(()) ppccrree22__ccoommppiillee__3322(()) There are also three different sets of data types: PPCCRREE22__UUCCHHAARR88,, PPCCRREE22__UUCCHHAARR1166,, PPCCRREE22__UUCCHHAARR3322 PPCCRREE22__SSPPTTRR88,, PPCCRREE22__SSPPTTRR1166,, PPCCRREE22__SSPPTTRR3322 The UCHAR types define unsigned code units of the appropriate widths. For example, PCRE2_UCHAR16 is usually defined as `uint16_t'. The SPTR types are constant pointers to the equivalent UCHAR types, that is, they are pointers to vectors of unsigned code units. Many applications use only one code unit width. For their convenience, macros are defined whose names are the generic forms such as ppccrree22__ccoomm-- ppiillee(()) and PCRE2_SPTR. These macros use the value of the macro PCRE2_CODE_UNIT_WIDTH to generate the appropriate width-specific func- tion and macro names. PCRE2_CODE_UNIT_WIDTH is not defined by default. An application must define it to be 8, 16, or 32 before including ppccrree22..hh in order to make use of the generic names. Applications that use more than one code unit width can be linked with more than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to be 0 before including ppccrree22..hh, and then use the real function names. Any code that is to be included in an environment where the value of PCRE2_CODE_UNIT_WIDTH is unknown should also use the real function names. (Unfortunately, it is not possible in C code to save and restore the value of a macro.) If PCRE2_CODE_UNIT_WIDTH is not defined before including ppccrree22..hh, a compiler error occurs. When using multiple libraries in an application, you must take care when processing any particular pattern to use only functions from a single library. For example, if you want to run a match using a pat- tern that was compiled with ppccrree22__ccoommppiillee__1166(()), you must do so with ppccrree22__mmaattcchh__1166(()), not ppccrree22__mmaattcchh__88(()) or ppccrree22__mmaattcchh__3322(()). In the function summaries above, and in the rest of this document and other PCRE2 documents, functions and data types are described using their generic names, without the _8, _16, or _32 suffix. PPCCRREE22 AAPPII OOVVEERRVVIIEEWW PCRE2 has its own native API, which is described in this document. There are also some wrapper functions for the 8-bit library that corre- spond to the POSIX regular expression API, but they do not give access to all the functionality of PCRE2. They are described in the ppccrree22ppoossiixx documentation. Both these APIs define a set of C function calls. The native API C data types, function prototypes, option values, and error codes are defined in the header file ppccrree22..hh, which also contains definitions of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release numbers for the library. Applications can use these to include support for different releases of PCRE2. In a Windows environment, if you want to statically link an application program against a non-dll PCRE2 library, you must define PCRE2_STATIC before including ppccrree22..hh. The functions ppccrree22__ccoommppiillee(()) and ppccrree22__mmaattcchh(()) are used for compiling and matching regular expressions in a Perl-compatible manner. A sample program that demonstrates the simplest way of using them is provided in the file called _p_c_r_e_2_d_e_m_o_._c in the PCRE2 source distribution. A listing of this program is given in the ppccrree22ddeemmoo documentation, and the ppccrree22ssaammppllee documentation describes how to compile and run it. The compiling and matching functions recognize various options that are passed as bits in an options argument. There are also some more compli- cated parameters such as custom memory management functions and resource limits that are passed in "contexts" (which are just memory blocks, described below). Simple applications do not need to make use of contexts. Just-in-time (JIT) compiler support is an optional feature of PCRE2 that can be built in appropriate hardware environments. It greatly speeds up the matching performance of many patterns. Programs can request that it be used if available by calling ppccrree22__jjiitt__ccoommppiillee(()) after a pattern has been successfully compiled by ppccrree22__ccoommppiillee(()). This does nothing if JIT support is not available. More complicated programs might need to make use of the specialist functions ppccrree22__jjiitt__ssttaacckk__ccrreeaattee(()), ppccrree22__jjiitt__ssttaacckk__ffrreeee(()), and ppccrree22__jjiitt__ssttaacckk__aassssiiggnn(()) in order to control the JIT code's memory usage. JIT matching is automatically used by ppccrree22__mmaattcchh(()) if it is available, unless the PCRE2_NO_JIT option is set. There is also a direct interface for JIT matching, which gives improved performance at the expense of less sanity checking. The JIT-specific functions are discussed in the ppccrree22jjiitt documentation. A second matching function, ppccrree22__ddffaa__mmaattcchh(()), which is not Perl-com- patible, is also provided. This uses a different algorithm for the matching. The alternative algorithm finds all possible matches (at a given point in the subject), and scans the subject just once (unless there are lookaround assertions). However, this algorithm does not return captured substrings. A description of the two matching algo- rithms and their advantages and disadvantages is given in the ppccrree22mmaattcchhiinngg documentation. There is no JIT support for ppccrree22__ddffaa__mmaattcchh(()). In addition to the main compiling and matching functions, there are convenience functions for extracting captured substrings from a subject string that has been matched by ppccrree22__mmaattcchh(()). They are: ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnaammee(()) ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnuummbbeerr(()) ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnaammee(()) ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnuummbbeerr(()) ppccrree22__ssuubbssttrriinngg__lliisstt__ggeett(()) ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnaammee(()) ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnuummbbeerr(()) ppccrree22__ssuubbssttrriinngg__nnaammeettaabbllee__ssccaann(()) ppccrree22__ssuubbssttrriinngg__nnuummbbeerr__ffrroomm__nnaammee(()) ppccrree22__ssuubbssttrriinngg__ffrreeee(()) and ppccrree22__ssuubbssttrriinngg__lliisstt__ffrreeee(()) are also pro- vided, to free memory used for extracted strings. The function ppccrree22__ssuubbssttiittuuttee(()) can be called to match a pattern and return a copy of the subject string with substitutions for parts that were matched. Functions whose names begin with ppccrree22__sseerriiaalliizzee__ are used for saving compiled patterns on disc or elsewhere, and reloading them later. Finally, there are functions for finding out information about a com- piled pattern (ppccrree22__ppaatttteerrnn__iinnffoo(())) and about the configuration with which PCRE2 was built (ppccrree22__ccoonnffiigg(())). Functions with names ending with __ffrreeee(()) are used for freeing memory blocks of various sorts. In all cases, if one of these functions is called with a NULL argument, it does nothing. SSTTRRIINNGG LLEENNGGTTHHSS AANNDD OOFFFFSSEETTSS The PCRE2 API uses string lengths and offsets into strings of code units in several places. These values are always of type PCRE2_SIZE, which is an unsigned integer type, currently always defined as _s_i_z_e___t. The largest value that can be stored in such a type (that is ~(PCRE2_SIZE)0) is reserved as a special indicator for zero-terminated strings and unset offsets. Therefore, the longest string that can be handled is one less than this maximum. NNEEWWLLIINNEESS PCRE2 supports five different conventions for indicating line breaks in strings: a single CR (carriage return) character, a single LF (line- feed) character, the two-character sequence CRLF, any of the three pre- ceding, or any Unicode newline sequence. The Unicode newline sequences are the three just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029). Each of the first three conventions is used by at least one operating system as its standard newline sequence. When PCRE2 is built, a default can be specified. The default default is LF, which is the Unix stan- dard. However, the newline convention can be changed by an application when calling ppccrree22__ccoommppiillee(()), or it can be specified by special text at the start of the pattern itself; this overrides any other settings. See the ppccrree22ppaatttteerrnn page for details of the special character sequences. In the PCRE2 documentation the word "newline" is used to mean "the character or pair of characters that indicate a line break". The choice of newline convention affects the handling of the dot, circumflex, and dollar metacharacters, the handling of #-comments in /x mode, and, when CRLF is a recognized line ending sequence, the match position advance- ment for a non-anchored pattern. There is more detail about this in the section on ppccrree22__mmaattcchh(()) options below. The choice of newline convention does not affect the interpretation of the \n or \r escape sequences, nor does it affect what \R matches; this has its own separate convention. MMUULLTTIITTHHRREEAADDIINNGG In a multithreaded application it is important to keep thread-specific data separate from data that can be shared between threads. The PCRE2 library code itself is thread-safe: it contains no static or global variables. The API is designed to be fairly simple for non-threaded applications while at the same time ensuring that multithreaded appli- cations can use it. There are several different blocks of data that are used to pass infor- mation between the application and the PCRE2 libraries. TThhee ccoommppiilleedd ppaatttteerrnn A pointer to the compiled form of a pattern is returned to the user when ppccrree22__ccoommppiillee(()) is successful. The data in the compiled pattern is fixed, and does not change when the pattern is matched. Therefore, it is thread-safe, that is, the same compiled pattern can be used by more than one thread simultaneously. For example, an application can compile all its patterns at the start, before forking off multiple threads that use them. However, if the just-in-time (JIT) optimization feature is being used, it needs separate memory stack areas for each thread. See the ppccrree22jjiitt documentation for more details. In a more complicated situation, where patterns are compiled only when they are first needed, but are still shared between threads, pointers to compiled patterns must be protected from simultaneous writing by multiple threads, at least until a pattern has been compiled. The logic can be something like this: Get a read-only (shared) lock (mutex) for pointer if (pointer == NULL) { Get a write (unique) lock for pointer pointer = pcre2_compile(... } Release the lock Use pointer in pcre2_match() Of course, testing for compilation errors should also be included in the code. If JIT is being used, but the JIT compilation is not being done immedi- ately, (perhaps waiting to see if the pattern is used often enough) similar logic is required. JIT compilation updates a pointer within the compiled code block, so a thread must gain unique write access to the pointer before calling ppccrree22__jjiitt__ccoommppiillee(()). Alternatively, ppccrree22__ccooddee__ccooppyy(()) or ppccrree22__ccooddee__ccooppyy__wwiitthh__ttaabblleess(()) can be used to obtain a private copy of the compiled code before calling the JIT com- piler. CCoonntteexxtt bblloocckkss The next main section below introduces the idea of "contexts" in which PCRE2 functions are called. A context is nothing more than a collection of parameters that control the way PCRE2 operates. Grouping a number of parameters together in a context is a convenient way of passing them to a PCRE2 function without using lots of arguments. The parameters that are stored in contexts are in some sense "advanced features" of the API. Many straightforward applications will not need to use contexts. In a multithreaded application, if the parameters in a context are val- ues that are never changed, the same context can be used by all the threads. However, if any thread needs to change any value in a context, it must make its own thread-specific copy. MMaattcchh bblloocckkss The matching functions need a block of memory for storing the results of a match. This includes details of what was matched, as well as addi- tional information such as the name of a (*MARK) setting. Each thread must provide its own copy of this memory. PPCCRREE22 CCOONNTTEEXXTTSS Some PCRE2 functions have a lot of parameters, many of which are used only by specialist applications, for example, those that use custom memory management or non-standard character tables. To keep function argument lists at a reasonable size, and at the same time to keep the API extensible, "uncommon" parameters are passed to certain functions in a ccoonntteexxtt instead of directly. A context is just a block of memory that holds the parameter values. Applications that do not need to adjust any of the context parameters can pass NULL when a context pointer is required. There are three different types of context: a general context that is relevant for several PCRE2 operations, a compile-time context, and a match-time context. TThhee ggeenneerraall ccoonntteexxtt At present, this context just contains pointers to (and data for) external memory management functions that are called from several places in the PCRE2 library. The context is named `general' rather than specifically `memory' because in future other fields may be added. If you do not want to supply your own custom memory management functions, you do not need to bother with a general context. A general context is created by: ppccrree22__ggeenneerraall__ccoonntteexxtt **ppccrree22__ggeenneerraall__ccoonntteexxtt__ccrreeaattee(( vvooiidd **((**_p_r_i_v_a_t_e___m_a_l_l_o_c))((PPCCRREE22__SSIIZZEE,, vvooiidd **)),, vvooiidd ((**_p_r_i_v_a_t_e___f_r_e_e))((vvooiidd **,, vvooiidd **)),, vvooiidd **_m_e_m_o_r_y___d_a_t_a));; The two function pointers specify custom memory management functions, whose prototypes are: vvooiidd **pprriivvaattee__mmaalllloocc((PPCCRREE22__SSIIZZEE,, vvooiidd **));; vvooiidd pprriivvaattee__ffrreeee((vvooiidd **,, vvooiidd **));; Whenever code in PCRE2 calls these functions, the final argument is the value of _m_e_m_o_r_y___d_a_t_a. Either of the first two arguments of the creation function may be NULL, in which case the system memory management func- tions _m_a_l_l_o_c_(_) and _f_r_e_e_(_) are used. (This is not currently useful, as there are no other fields in a general context, but in future there might be.) The _p_r_i_v_a_t_e___m_a_l_l_o_c_(_) function is used (if supplied) to obtain memory for storing the context, and all three values are saved as part of the context. Whenever PCRE2 creates a data block of any kind, the block contains a pointer to the _f_r_e_e_(_) function that matches the _m_a_l_l_o_c_(_) function that was used. When the time comes to free the block, this function is called. A general context can be copied by calling: ppccrree22__ggeenneerraall__ccoonntteexxtt **ppccrree22__ggeenneerraall__ccoonntteexxtt__ccooppyy(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; The memory used for a general context should be freed by calling: vvooiidd ppccrree22__ggeenneerraall__ccoonntteexxtt__ffrreeee((ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; TThhee ccoommppiillee ccoonntteexxtt A compile context is required if you want to provide an external func- tion for stack checking during compilation or to change the default values of any of the following compile-time parameters: What \R matches (Unicode newlines or CR, LF, CRLF only) PCRE2's character tables The newline character sequence The compile time nested parentheses limit The maximum length of the pattern string The extra options bits (none set by default) A compile context is also required if you are using custom memory man- agement. If none of these apply, just pass NULL as the context argu- ment of _p_c_r_e_2___c_o_m_p_i_l_e_(_). A compile context is created, copied, and freed by the following func- tions: ppccrree22__ccoommppiillee__ccoonntteexxtt **ppccrree22__ccoommppiillee__ccoonntteexxtt__ccrreeaattee(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__ccoommppiillee__ccoonntteexxtt **ppccrree22__ccoommppiillee__ccoonntteexxtt__ccooppyy(( ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ccoommppiillee__ccoonntteexxtt__ffrreeee((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t));; A compile context is created with default values for its parameters. These can be changed by calling the following functions, which return 0 on success, or PCRE2_ERROR_BADDATA if invalid data is detected. iinntt ppccrree22__sseett__bbssrr((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only CR, LF, or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any Unicode line ending sequence. The value is used by the JIT compiler and by the two interpreted matching functions, _p_c_r_e_2___m_a_t_c_h_(_) and _p_c_r_e_2___d_f_a___m_a_t_c_h_(_). iinntt ppccrree22__sseett__cchhaarraacctteerr__ttaabblleess((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, ccoonnsstt uunnssiiggnneedd cchhaarr **_t_a_b_l_e_s));; The value must be the result of a call to _p_c_r_e_2___m_a_k_e_t_a_b_l_e_s_(_), whose only argument is a general context. This function builds a set of char- acter tables in the current locale. iinntt ppccrree22__sseett__ccoommppiillee__eexxttrraa__ooppttiioonnss((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _e_x_t_r_a___o_p_t_i_o_n_s));; As PCRE2 has developed, almost all the 32 option bits that are avail- able in the _o_p_t_i_o_n_s argument of ppccrree22__ccoommppiillee(()) have been used up. To avoid running out, the compile context contains a set of extra option bits which are used for some newer, assumed rarer, options. This func- tion sets those bits. It always sets all the bits (either on or off). It does not modify any existing setting. The available options are defined in the section entitled "Extra compile options" below. iinntt ppccrree22__sseett__mmaaxx__ppaatttteerrnn__lleennggtthh((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, PPCCRREE22__SSIIZZEE _v_a_l_u_e));; This sets a maximum length, in code units, for any pattern string that is compiled with this context. If the pattern is longer, an error is generated. This facility is provided so that applications that accept patterns from external sources can limit their size. The default is the largest number that a PCRE2_SIZE variable can hold, which is effec- tively unlimited. iinntt ppccrree22__sseett__nneewwlliinnee((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; This specifies which characters or character sequences are to be recog- nized as newlines. The value must be one of PCRE2_NEWLINE_CR (carriage return only), PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the two-character sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any of the above), PCRE2_NEWLINE_ANY (any Unicode newline sequence), or PCRE2_NEWLINE_NUL (the NUL character, that is a binary zero). A pattern can override the value set in the compile context by starting with a sequence such as (*CRLF). See the ppccrree22ppaatttteerrnn page for details. When a pattern is compiled with the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option, the newline convention affects the recogni- tion of white space and the end of internal comments starting with #. The value is saved with the compiled pattern for subsequent use by the JIT compiler and by the two interpreted matching functions, _p_c_r_e_2___m_a_t_c_h_(_) and _p_c_r_e_2___d_f_a___m_a_t_c_h_(_). iinntt ppccrree22__sseett__ppaarreennss__nneesstt__lliimmiitt((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; This parameter ajusts the limit, set when PCRE2 is built (default 250), on the depth of parenthesis nesting in a pattern. This limit stops rogue patterns using up too much system stack when being compiled. The limit applies to parentheses of all kinds, not just capturing parenthe- ses. iinntt ppccrree22__sseett__ccoommppiillee__rreeccuurrssiioonn__gguuaarrdd((ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t,, iinntt ((**_g_u_a_r_d___f_u_n_c_t_i_o_n))((uuiinntt3322__tt,, vvooiidd **)),, vvooiidd **_u_s_e_r___d_a_t_a));; There is at least one application that runs PCRE2 in threads with very limited system stack, where running out of stack is to be avoided at all costs. The parenthesis limit above cannot take account of how much stack is actually available during compilation. For a finer control, you can supply a function that is called whenever ppccrree22__ccoommppiillee(()) starts to compile a parenthesized part of a pattern. This function can check the actual stack size (or anything else that it wants to, of course). The first argument to the callout function gives the current depth of nesting, and the second is user data that is set up by the last argu- ment of ppccrree22__sseett__ccoommppiillee__rreeccuurrssiioonn__gguuaarrdd(()). The callout function should return zero if all is well, or non-zero to force an error. TThhee mmaattcchh ccoonntteexxtt A match context is required if you want to: Set up a callout function Set an offset limit for matching an unanchored pattern Change the limit on the amount of heap used when matching Change the backtracking match limit Change the backtracking depth limit Set custom memory management specifically for the match If none of these apply, just pass NULL as the context argument of ppccrree22__mmaattcchh(()), ppccrree22__ddffaa__mmaattcchh(()), or ppccrree22__jjiitt__mmaattcchh(()). A match context is created, copied, and freed by the following func- tions: ppccrree22__mmaattcchh__ccoonntteexxtt **ppccrree22__mmaattcchh__ccoonntteexxtt__ccrreeaattee(( ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__mmaattcchh__ccoonntteexxtt **ppccrree22__mmaattcchh__ccoonntteexxtt__ccooppyy(( ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; vvooiidd ppccrree22__mmaattcchh__ccoonntteexxtt__ffrreeee((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; A match context is created with default values for its parameters. These can be changed by calling the following functions, which return 0 on success, or PCRE2_ERROR_BADDATA if invalid data is detected. iinntt ppccrree22__sseett__ccaalllloouutt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, iinntt ((**_c_a_l_l_o_u_t___f_u_n_c_t_i_o_n))((ppccrree22__ccaalllloouutt__bblloocckk **,, vvooiidd **)),, vvooiidd **_c_a_l_l_o_u_t___d_a_t_a));; This sets up a "callout" function for PCRE2 to call at specified points during a matching operation. Details are given in the ppccrree22ccaalllloouutt doc- umentation. iinntt ppccrree22__sseett__ooffffsseett__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, PPCCRREE22__SSIIZZEE _v_a_l_u_e));; The _o_f_f_s_e_t___l_i_m_i_t parameter limits how far an unanchored search can advance in the subject string. The default value is PCRE2_UNSET. The ppccrree22__mmaattcchh(()) and ppccrree22__ddffaa__mmaattcchh(()) functions return PCRE2_ERROR_NOMATCH if a match with a starting point before or at the given offset is not found. The ppccrree22__ssuubbssttiittuuttee(()) function makes no more substitutions. For example, if the pattern /abc/ is matched against "123abc" with an offset limit less than 3, the result is PCRE2_ERROR_NO_MATCH. A match can never be found if the _s_t_a_r_t_o_f_f_s_e_t argument of ppccrree22__mmaattcchh(()), ppccrree22__ddffaa__mmaattcchh(()), or ppccrree22__ssuubbssttiittuuttee(()) is greater than the offset limit set in the match context. When using this facility, you must set the PCRE2_USE_OFFSET_LIMIT option when calling ppccrree22__ccoommppiillee(()) so that when JIT is in use, differ- ent code can be compiled. If a match is started with a non-default match limit when PCRE2_USE_OFFSET_LIMIT is not set, an error is gener- ated. The offset limit facility can be used to track progress when searching large subject strings or to limit the extent of global substitutions. See also the PCRE2_FIRSTLINE option, which requires a match to start before or at the first newline that follows the start of matching in the subject. If this is set with an offset limit, a match must occur in the first line and also within the offset limit. In other words, which- ever limit comes first is used. iinntt ppccrree22__sseett__hheeaapp__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; The _h_e_a_p___l_i_m_i_t parameter specifies, in units of kilobytes, the maximum amount of heap memory that ppccrree22__mmaattcchh(()) may use to hold backtracking information when running an interpretive match. This limit does not apply to matching with the JIT optimization, which has its own memory control arrangements (see the ppccrree22jjiitt documentation for more details), nor does it apply to ppccrree22__ddffaa__mmaattcchh(()). If the limit is reached, the negative error code PCRE2_ERROR_HEAPLIMIT is returned. The default limit is set when PCRE2 is built; the default default is very large and is essentially "unlimited". A value for the heap limit may also be supplied by an item at the start of a pattern of the form (*LIMIT_HEAP=ddd) where ddd is a decimal number. However, such a setting is ignored unless ddd is less than the limit set by the caller of ppccrree22__mmaattcchh(()) or, if no such limit is set, less than the default. The ppccrree22__mmaattcchh(()) function starts out using a 20K vector on the system stack for recording backtracking points. The more nested backtracking points there are (that is, the deeper the search tree), the more memory is needed. Heap memory is used only if the initial vector is too small. If the heap limit is set to a value less than 21 (in particular, zero) no heap memory will be used. In this case, only patterns that do not have a lot of nested backtracking can be successfully processed. iinntt ppccrree22__sseett__mmaattcchh__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; The _m_a_t_c_h___l_i_m_i_t parameter provides a means of preventing PCRE2 from using up too many computing resources when processing patterns that are not going to match, but which have a very large number of possibilities in their search trees. The classic example is a pattern that uses nested unlimited repeats. There is an internal counter in ppccrree22__mmaattcchh(()) that is incremented each time round its main matching loop. If this value reaches the match limit, ppccrree22__mmaattcchh(()) returns the negative value PCRE2_ERROR_MATCHLIMIT. This has the effect of limiting the amount of backtracking that can take place. For patterns that are not anchored, the count restarts from zero for each position in the subject string. This limit also applies to ppccrree22__ddffaa__mmaattcchh(()), though the counting is done in a different way. When ppccrree22__mmaattcchh(()) is called with a pattern that was successfully pro- cessed by ppccrree22__jjiitt__ccoommppiillee(()), the way in which matching is executed is entirely different. However, there is still the possibility of runaway matching that goes on for a very long time, and so the _m_a_t_c_h___l_i_m_i_t value is also used in this case (but in a different way) to limit how long the matching can continue. The default value for the limit can be set when PCRE2 is built; the default default is 10 million, which handles all but the most extreme cases. A value for the match limit may also be supplied by an item at the start of a pattern of the form (*LIMIT_MATCH=ddd) where ddd is a decimal number. However, such a setting is ignored unless ddd is less than the limit set by the caller of ppccrree22__mmaattcchh(()) or ppccrree22__ddffaa__mmaattcchh(()) or, if no such limit is set, less than the default. iinntt ppccrree22__sseett__ddeepptthh__lliimmiitt((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, uuiinntt3322__tt _v_a_l_u_e));; This parameter limits the depth of nested backtracking in ppccrree22__mmaattcchh(()). Each time a nested backtracking point is passed, a new memory "frame" is used to remember the state of matching at that point. Thus, this parameter indirectly limits the amount of memory that is used in a match. However, because the size of each memory "frame" depends on the number of capturing parentheses, the actual memory limit varies from pattern to pattern. This limit was more useful in versions before 10.30, where function recursion was used for backtracking. The depth limit is not relevant, and is ignored, when matching is done using JIT compiled code. However, it is supported by ppccrree22__ddffaa__mmaattcchh(()), which uses it to limit the depth of internal recursive function calls that implement atomic groups, lookaround assertions, and pattern recur- sions. This is, therefore, an indirect limit on the amount of system stack that is used. A recursive pattern such as /(.)(?1)/, when matched to a very long string using ppccrree22__ddffaa__mmaattcchh(()), can use a great deal of stack. The default value for the depth limit can be set when PCRE2 is built; the default default is the same value as the default for the match limit. If the limit is exceeded, ppccrree22__mmaattcchh(()) or ppccrree22__ddffaa__mmaattcchh(()) returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth limit may also be supplied by an item at the start of a pattern of the form (*LIMIT_DEPTH=ddd) where ddd is a decimal number. However, such a setting is ignored unless ddd is less than the limit set by the caller of ppccrree22__mmaattcchh(()) or ppccrree22__ddffaa__mmaattcchh(()) or, if no such limit is set, less than the default. CCHHEECCKKIINNGG BBUUIILLDD--TTIIMMEE OOPPTTIIOONNSS iinntt ppccrree22__ccoonnffiigg((uuiinntt3322__tt _w_h_a_t,, vvooiidd **_w_h_e_r_e));; The function ppccrree22__ccoonnffiigg(()) makes it possible for a PCRE2 client to discover which optional features have been compiled into the PCRE2 library. The ppccrree22bbuuiilldd documentation has more details about these optional features. The first argument for ppccrree22__ccoonnffiigg(()) specifies which information is required. The second argument is a pointer to memory into which the information is placed. If NULL is passed, the function returns the amount of memory that is needed for the requested information. For calls that return numerical values, the value is in bytes; when requesting these values, _w_h_e_r_e should point to appropriately aligned memory. For calls that return strings, the required length is given in code units, not counting the terminating zero. When requesting information, the returned value from ppccrree22__ccoonnffiigg(()) is non-negative on success, or the negative error code PCRE2_ERROR_BADOP- TION if the value in the first argument is not recognized. The follow- ing information is available: PCRE2_CONFIG_BSR The output is a uint32_t integer whose value indicates what character sequences the \R escape sequence matches by default. A value of PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The default can be overridden when a pattern is compiled. PCRE2_CONFIG_COMPILED_WIDTHS The output is a uint32_t integer whose lower bits indicate which code unit widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support, and the 2-bit and 4-bit indicate 16-bit and 32-bit sup- port, respectively. PCRE2_CONFIG_DEPTHLIMIT The output is a uint32_t integer that gives the default limit for the depth of nested backtracking in ppccrree22__mmaattcchh(()) or the depth of nested recursions and lookarounds in ppccrree22__ddffaa__mmaattcchh(()). Further details are given with ppccrree22__sseett__ddeepptthh__lliimmiitt(()) above. PCRE2_CONFIG_HEAPLIMIT The output is a uint32_t integer that gives, in kilobytes, the default limit for the amount of heap memory used by ppccrree22__mmaattcchh(()). Further details are given with ppccrree22__sseett__hheeaapp__lliimmiitt(()) above. PCRE2_CONFIG_JIT The output is a uint32_t integer that is set to one if support for just-in-time compiling is available; otherwise it is set to zero. PCRE2_CONFIG_JITTARGET The _w_h_e_r_e argument should point to a buffer that is at least 48 code units long. (The exact length required can be found by calling ppccrree22__ccoonnffiigg(()) with wwhheerree set to NULL.) The buffer is filled with a string that contains the name of the architecture for which the JIT compiler is configured, for example "x86 32bit (little endian + unaligned)". If JIT support is not available, PCRE2_ERROR_BADOPTION is returned, otherwise the number of code units used is returned. This is the length of the string, plus one unit for the terminating zero. PCRE2_CONFIG_LINKSIZE The output is a uint32_t integer that contains the number of bytes used for internal linkage in compiled regular expressions. When PCRE2 is configured, the value can be set to 2, 3, or 4, with the default being 2. This is the value that is returned by ppccrree22__ccoonnffiigg(()). However, when the 16-bit library is compiled, a value of 3 is rounded up to 4, and when the 32-bit library is compiled, internal linkages always use 4 bytes, so the configured value is not relevant. The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all but the most massive patterns, since it allows the size of the compiled pattern to be up to 64K code units. Larger values allow larger regular expressions to be compiled by those two libraries, but at the expense of slower matching. PCRE2_CONFIG_MATCHLIMIT The output is a uint32_t integer that gives the default match limit for ppccrree22__mmaattcchh(()). Further details are given with ppccrree22__sseett__mmaattcchh__lliimmiitt(()) above. PCRE2_CONFIG_NEWLINE The output is a uint32_t integer whose value specifies the default character sequence that is recognized as meaning "newline". The values are: PCRE2_NEWLINE_CR Carriage return (CR) PCRE2_NEWLINE_LF Linefeed (LF) PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) PCRE2_NEWLINE_ANY Any Unicode line ending PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF PCRE2_NEWLINE_NUL The NUL character (binary zero) The default should normally correspond to the standard sequence for your operating system. PCRE2_CONFIG_NEVER_BACKSLASH_C The output is a uint32_t integer that is set to one if the use of \C was permanently disabled when PCRE2 was built; otherwise it is set to zero. PCRE2_CONFIG_PARENSLIMIT The output is a uint32_t integer that gives the maximum depth of nest- ing of parentheses (of any kind) in a pattern. This limit is imposed to cap the amount of system stack used when a pattern is compiled. It is specified when PCRE2 is built; the default is 250. This limit does not take into account the stack that may already be used by the calling application. For finer control over compilation stack usage, see ppccrree22__sseett__ccoommppiillee__rreeccuurrssiioonn__gguuaarrdd(()). PCRE2_CONFIG_STACKRECURSE This parameter is obsolete and should not be used in new code. The out- put is a uint32_t integer that is always set to zero. PCRE2_CONFIG_UNICODE_VERSION The _w_h_e_r_e argument should point to a buffer that is at least 24 code units long. (The exact length required can be found by calling ppccrree22__ccoonnffiigg(()) with wwhheerree set to NULL.) If PCRE2 has been compiled without Unicode support, the buffer is filled with the text "Unicode not supported". Otherwise, the Unicode version string (for example, "8.0.0") is inserted. The number of code units used is returned. This is the length of the string plus one unit for the terminating zero. PCRE2_CONFIG_UNICODE The output is a uint32_t integer that is set to one if Unicode support is available; otherwise it is set to zero. Unicode support implies UTF support. PCRE2_CONFIG_VERSION The _w_h_e_r_e argument should point to a buffer that is at least 24 code units long. (The exact length required can be found by calling ppccrree22__ccoonnffiigg(()) with wwhheerree set to NULL.) The buffer is filled with the PCRE2 version string, zero-terminated. The number of code units used is returned. This is the length of the string plus one unit for the termi- nating zero. CCOOMMPPIILLIINNGG AA PPAATTTTEERRNN ppccrree22__ccooddee **ppccrree22__ccoommppiillee((PPCCRREE22__SSPPTTRR _p_a_t_t_e_r_n,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, uuiinntt3322__tt _o_p_t_i_o_n_s,, iinntt **_e_r_r_o_r_c_o_d_e,, PPCCRREE22__SSIIZZEE **_e_r_r_o_r_o_f_f_s_e_t_, ppccrree22__ccoommppiillee__ccoonntteexxtt **_c_c_o_n_t_e_x_t));; vvooiidd ppccrree22__ccooddee__ffrreeee((ppccrree22__ccooddee **_c_o_d_e));; ppccrree22__ccooddee **ppccrree22__ccooddee__ccooppyy((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e));; ppccrree22__ccooddee **ppccrree22__ccooddee__ccooppyy__wwiitthh__ttaabblleess((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e));; The ppccrree22__ccoommppiillee(()) function compiles a pattern into an internal form. The pattern is defined by a pointer to a string of code units and a length (in code units). If the pattern is zero-terminated, the length can be specified as PCRE2_ZERO_TERMINATED. The function returns a pointer to a block of memory that contains the compiled pattern and related data, or NULL if an error occurred. If the compile context argument _c_c_o_n_t_e_x_t is NULL, memory for the com- piled pattern is obtained by calling mmaalllloocc(()). Otherwise, it is obtained from the same memory function that was used for the compile context. The caller must free the memory by calling ppccrree22__ccooddee__ffrreeee(()) when it is no longer needed. The function ppccrree22__ccooddee__ccooppyy(()) makes a copy of the compiled code in new memory, using the same memory allocator as was used for the original. However, if the code has been processed by the JIT compiler (see below), the JIT information cannot be copied (because it is position- dependent). The new copy can initially be used only for non-JIT match- ing, though it can be passed to ppccrree22__jjiitt__ccoommppiillee(()) if required. The ppccrree22__ccooddee__ccooppyy(()) function provides a way for individual threads in a multithreaded application to acquire a private copy of shared com- piled code. However, it does not make a copy of the character tables used by the compiled pattern; the new pattern code points to the same tables as the original code. (See "Locale Support" below for details of these character tables.) In many applications the same tables are used throughout, so this behaviour is appropriate. Nevertheless, there are occasions when a copy of a compiled pattern and the relevant tables are needed. The ppccrree22__ccooddee__ccooppyy__wwiitthh__ttaabblleess(()) provides this facility. Copies of both the code and the tables are made, with the new code pointing to the new tables. The memory for the new tables is automati- cally freed when ppccrree22__ccooddee__ffrreeee(()) is called for the new copy of the compiled code. NOTE: When one of the matching functions is called, pointers to the compiled pattern and the subject string are set in the match data block so that they can be referenced by the substring extraction functions. After running a match, you must not free a compiled pattern (or a sub- ject string) until after all operations on the match data block have taken place. The _o_p_t_i_o_n_s argument for ppccrree22__ccoommppiillee(()) contains various bit settings that affect the compilation. It should be zero if no options are required. The available options are described below. Some of them (in particular, those that are compatible with Perl, but some others as well) can also be set and unset from within the pattern (see the detailed description in the ppccrree22ppaatttteerrnn documentation). For those options that can be different in different parts of the pat- tern, the contents of the _o_p_t_i_o_n_s argument specifies their settings at the start of compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and PCRE2_NO_UTF_CHECK options can be set at the time of matching as well as at compile time. Other, less frequently required compile-time parameters (for example, the newline setting) can be provided in a compile context (as described above). If _e_r_r_o_r_c_o_d_e or _e_r_r_o_r_o_f_f_s_e_t is NULL, ppccrree22__ccoommppiillee(()) returns NULL imme- diately. Otherwise, the variables to which these point are set to an error code and an offset (number of code units) within the pattern, respectively, when ppccrree22__ccoommppiillee(()) returns NULL because a compilation error has occurred. The values are not defined when compilation is suc- cessful and ppccrree22__ccoommppiillee(()) returns a non-NULL value. There are nearly 100 positive error codes that ppccrree22__ccoommppiillee(()) may return if it finds an error in the pattern. There are also some nega- tive error codes that are used for invalid UTF strings. These are the same as given by ppccrree22__mmaattcchh(()) and ppccrree22__ddffaa__mmaattcchh(()), and are described in the ppccrree22uunniiccooddee page. There is no separate documentation for the positive error codes, because the textual error messages that are obtained by calling the ppccrree22__ggeett__eerrrroorr__mmeessssaaggee(()) function (see "Obtaining a textual error message" below) should be self-explanatory. Macro names starting with PCRE2_ERROR_ are defined for both positive and negative error codes in ppccrree22..hh. The value returned in _e_r_r_o_r_o_f_f_s_e_t is an indication of where in the pat- tern the error occurred. It is not necessarily the furthest point in the pattern that was read. For example, after the error "lookbehind assertion is not fixed length", the error offset points to the start of the failing assertion. For an invalid UTF-8 or UTF-16 string, the off- set is that of the first code unit of the failing character. Some errors are not detected until the whole pattern has been scanned; in these cases, the offset passed back is the length of the pattern. Note that the offset is in code units, not characters, even in a UTF mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char- acter. This code fragment shows a typical straightforward call to ppccrree22__ccoomm-- ppiillee(()): pcre2_code *re; PCRE2_SIZE erroffset; int errorcode; re = pcre2_compile( "^A.*Z", /* the pattern */ PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */ 0, /* default options */ &errorcode, /* for error code */ &erroffset, /* for error offset */ NULL); /* no compile context */ The following names for option bits are defined in the ppccrree22..hh header file: PCRE2_ANCHORED If this bit is set, the pattern is forced to be "anchored", that is, it is constrained to match only at the first matching point in the string that is being searched (the "subject string"). This effect can also be achieved by appropriate constructs in the pattern itself, which is the only way to do it in Perl. PCRE2_ALLOW_EMPTY_CLASS By default, for compatibility with Perl, a closing square bracket that immediately follows an opening one is treated as a data character for the class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which therefore contains no characters and so can never match. PCRE2_ALT_BSUX This option request alternative handling of three escape sequences, which makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set: (1) \U matches an upper case "U" character; by default \U causes a com- pile time error (Perl uses \U to upper case subsequent characters). (2) \u matches a lower case "u" character unless it is followed by four hexadecimal digits, in which case the hexadecimal number defines the code point to match. By default, \u causes a compile time error (Perl uses it to upper case the following character). (3) \x matches a lower case "x" character unless it is followed by two hexadecimal digits, in which case the hexadecimal number defines the code point to match. By default, as in Perl, a hexadecimal number is always expected after \x, but it may have zero, one, or two digits (so, for example, \xz matches a binary zero character followed by z). PCRE2_ALT_CIRCUMFLEX In multiline mode (when PCRE2_MULTILINE is set), the circumflex metacharacter matches at the start of the subject (unless PCRE2_NOTBOL is set), and also after any internal newline. However, it does not match after a newline at the end of the subject, for compatibility with Perl. If you want a multiline circumflex also to match after a termi- nating newline, you must set PCRE2_ALT_CIRCUMFLEX. PCRE2_ALT_VERBNAMES By default, for compatibility with Perl, the name in any verb sequence such as (*MARK:NAME) is any sequence of characters that does not include a closing parenthesis. The name is not processed in any way, and it is not possible to include a closing parenthesis in the name. However, if the PCRE2_ALT_VERBNAMES option is set, normal backslash processing is applied to verb names and only an unescaped closing parenthesis terminates the name. A closing parenthesis can be included in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, unescaped whitespace in verb names is skipped and #-comments are recognized in this mode, exactly as in the rest of the pattern. PCRE2_AUTO_CALLOUT If this bit is set, ppccrree22__ccoommppiillee(()) automatically inserts callout items, all with number 255, before each pattern item, except immedi- ately before or after an explicit callout in the pattern. For discus- sion of the callout facility, see the ppccrree22ccaalllloouutt documentation. PCRE2_CASELESS If this bit is set, letters in the pattern match both upper and lower case letters in the subject. It is equivalent to Perl's /i option, and it can be changed within a pattern by a (?i) option setting. If PCRE2_UTF is set, Unicode properties are used for all characters with more than one other case, and for all characters whose code points are greater than U+007f. For lower valued characters with only one other case, a lookup table is used for speed. When PCRE2_UTF is not set, a lookup table is used for all code points less than 256, and higher code points (available only in 16-bit or 32-bit mode) are treated as not having another case. PCRE2_DOLLAR_ENDONLY If this bit is set, a dollar metacharacter in the pattern matches only at the end of the subject string. Without this option, a dollar also matches immediately before a newline at the end of the string (but not before any other newlines). The PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is set. There is no equivalent to this option in Perl, and no way to set it within a pattern. PCRE2_DOTALL If this bit is set, a dot metacharacter in the pattern matches any character, including one that indicates a newline. However, it only ever matches one character, even if newlines are coded as CRLF. Without this option, a dot does not match when the current position in the sub- ject is at a newline. This option is equivalent to Perl's /s option, and it can be changed within a pattern by a (?s) option setting. A neg- ative class such as [^a] always matches newline characters, independent of the setting of this option. PCRE2_DUPNAMES If this bit is set, names used to identify capturing subpatterns need not be unique. This can be helpful for certain types of pattern when it is known that only one instance of the named subpattern can ever be matched. There are more details of named subpatterns below; see also the ppccrree22ppaatttteerrnn documentation. PCRE2_ENDANCHORED If this bit is set, the end of any pattern match must be right at the end of the string being searched (the "subject string"). If the pattern match succeeds by reaching (*ACCEPT), but does not reach the end of the subject, the match fails at the current starting point. For unanchored patterns, a new match is then tried at the next starting point. How- ever, if the match succeeds by reaching the end of the pattern, but not the end of the subject, backtracking occurs and an alternative match may be found. Consider these two patterns: .(*ACCEPT)|.. .|.. If matched against "abc" with PCRE2_ENDANCHORED set, the first matches "c" whereas the second matches "bc". The effect of PCRE2_ENDANCHORED can also be achieved by appropriate constructs in the pattern itself, which is the only way to do it in Perl. For DFA matching with ppccrree22__ddffaa__mmaattcchh(()), PCRE2_ENDANCHORED applies only to the first (that is, the longest) matched string. Other parallel matches, which are necessarily substrings of the first one, must obvi- ously end before the end of the subject. PCRE2_EXTENDED If this bit is set, most white space characters in the pattern are totally ignored except when escaped or inside a character class. How- ever, white space is not allowed within sequences such as (?> that introduce various parenthesized subpatterns, nor within numerical quan- tifiers such as {1,3}. Ignorable white space is permitted between an item and a following quantifier and between a quantifier and a follow- ing + that indicates possessiveness. PCRE2_EXTENDED also causes characters between an unescaped # outside a character class and the next newline, inclusive, to be ignored, which makes it possible to include comments inside complicated patterns. Note that the end of this type of comment is a literal newline sequence in the pattern; escape sequences that happen to represent a newline do not count. PCRE2_EXTENDED is equivalent to Perl's /x option, and it can be changed within a pattern by a (?x) option setting. Which characters are interpreted as newlines can be specified by a set- ting in the compile context that is passed to ppccrree22__ccoommppiillee(()) or by a special sequence at the start of the pattern, as described in the sec- tion entitled "Newline conventions" in the ppccrree22ppaatttteerrnn documentation. A default is defined when PCRE2 is built. PCRE2_EXTENDED_MORE This option has the effect of PCRE2_EXTENDED, but, in addition, unescaped space and horizontal tab characters are ignored inside a character class. PCRE2_EXTENDED_MORE is equivalent to Perl's 5.26 /xx option, and it can be changed within a pattern by a (?xx) option set- ting. PCRE2_FIRSTLINE If this option is set, the start of an unanchored pattern match must be before or at the first newline in the subject string following the start of matching, though the matched text may continue over the new- line. If _s_t_a_r_t_o_f_f_s_e_t is non-zero, the limiting newline is not necessar- ily the first newline in the subject. For example, if the subject string is "abc\nxyz" (where \n represents a single-character newline) a pattern match for "yz" succeeds with PCRE2_FIRSTLINE if _s_t_a_r_t_o_f_f_s_e_t is greater than 3. See also PCRE2_USE_OFFSET_LIMIT, which provides a more general limiting facility. If PCRE2_FIRSTLINE is set with an offset limit, a match must occur in the first line and also within the offset limit. In other words, whichever limit comes first is used. PCRE2_LITERAL If this option is set, all meta-characters in the pattern are disabled, and it is treated as a literal string. Matching literal strings with a regular expression engine is not the most efficient way of doing it. If you are doing a lot of literal matching and are worried about effi- ciency, you should consider using other approaches. The only other main options that are allowed with PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE and PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an error. PCRE2_MATCH_UNSET_BACKREF If this option is set, a back reference to an unset subpattern group matches an empty string (by default this causes the current matching alternative to fail). A pattern such as (\1)(a) succeeds when this option is set (assuming it can find an "a" in the subject), whereas it fails by default, for Perl compatibility. Setting this option makes PCRE2 behave more like ECMAscript (aka JavaScript). PCRE2_MULTILINE By default, for the purposes of matching "start of line" and "end of line", PCRE2 treats the subject string as consisting of a single line of characters, even if it actually contains newlines. The "start of line" metacharacter (^) matches only at the start of the string, and the "end of line" metacharacter ($) matches only at the end of the string, or before a terminating newline (except when PCRE2_DOL- LAR_ENDONLY is set). Note, however, that unless PCRE2_DOTALL is set, the "any character" metacharacter (.) does not match at a newline. This behaviour (for ^, $, and dot) is the same as Perl. When PCRE2_MULTILINE it is set, the "start of line" and "end of line" constructs match immediately following or immediately before internal newlines in the subject string, respectively, as well as at the very start and end. This is equivalent to Perl's /m option, and it can be changed within a pattern by a (?m) option setting. Note that the "start of line" metacharacter does not match after a newline at the end of the subject, for compatibility with Perl. However, you can change this by setting the PCRE2_ALT_CIRCUMFLEX option. If there are no newlines in a subject string, or no occurrences of ^ or $ in a pattern, setting PCRE2_MULTILINE has no effect. PCRE2_NEVER_BACKSLASH_C This option locks out the use of \C in the pattern that is being com- piled. This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because it may leave the current matching point in the middle of a multi-code-unit character. This option may be useful in applications that process patterns from external sources. Note that there is also a build-time option that permanently locks out the use of \C. PCRE2_NEVER_UCP This option locks out the use of Unicode properties for handling \B, \b, \D, \d, \S, \s, \W, \w, and some of the POSIX character classes, as described for the PCRE2_UCP option below. In particular, it prevents the creator of the pattern from enabling this facility by starting the pattern with (*UCP). This option may be useful in applications that process patterns from external sources. The option combination PCRE_UCP and PCRE_NEVER_UCP causes an error. PCRE2_NEVER_UTF This option locks out interpretation of the pattern as UTF-8, UTF-16, or UTF-32, depending on which library is in use. In particular, it pre- vents the creator of the pattern from switching to UTF interpretation by starting the pattern with (*UTF). This option may be useful in applications that process patterns from external sources. The combina- tion of PCRE2_UTF and PCRE2_NEVER_UTF causes an error. PCRE2_NO_AUTO_CAPTURE If this option is set, it disables the use of numbered capturing paren- theses in the pattern. Any opening parenthesis that is not followed by ? behaves as if it were followed by ?: but named parentheses can still be used for capturing (and they acquire numbers in the usual way). This is the same as Perl's /n option. Note that, when this option is set, references to capturing groups (back references or recursion/subroutine calls) may only refer to named groups, though the reference can be by name or by number. PCRE2_NO_AUTO_POSSESS If this option is set, it disables "auto-possessification", which is an optimization that, for example, turns a+b into a++b in order to avoid backtracks into a+ that can never be successful. However, if callouts are in use, auto-possessification means that some callouts are never taken. You can set this option if you want the matching functions to do a full unoptimized search and run all the callouts, but it is mainly provided for testing purposes. PCRE2_NO_DOTSTAR_ANCHOR If this option is set, it disables an optimization that is applied when .* is the first significant item in a top-level branch of a pattern, and all the other branches also start with .* or with \A or \G or ^. The optimization is automatically disabled for .* if it is inside an atomic group or a capturing group that is the subject of a back refer- ence, or if the pattern contains (*PRUNE) or (*SKIP). When the opti- mization is not disabled, such a pattern is automatically anchored if PCRE2_DOTALL is set for all the .* items and PCRE2_MULTILINE is not set for any ^ items. Otherwise, the fact that any match must start either at the start of the subject or following a newline is remembered. Like other optimizations, this can cause callouts to be skipped. PCRE2_NO_START_OPTIMIZE This is an option whose main effect is at matching time. It does not change what ppccrree22__ccoommppiillee(()) generates, but it does affect the output of the JIT compiler. There are a number of optimizations that may occur at the start of a match, in order to speed up the process. For example, if it is known that an unanchored match must start with a specific code unit value, the matching code searches the subject for that value, and fails imme- diately if it cannot find it, without actually running the main match- ing function. This means that a special item such as (*COMMIT) at the start of a pattern is not considered until after a suitable starting point for the match has been found. Also, when callouts or (*MARK) items are in use, these "start-up" optimizations can cause them to be skipped if the pattern is never actually used. The start-up optimiza- tions are in effect a pre-scan of the subject that takes place before the pattern is run. The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations, possibly causing performance to suffer, but ensuring that in cases where the result is "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK) are considered at every possible starting position in the subject string. Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching operation. Consider the pattern (*COMMIT)ABC When this is compiled, PCRE2 records the fact that a match must start with the character "A". Suppose the subject string is "DEFABC". The start-up optimization scans along the subject, finds "A" and runs the first match attempt from there. The (*COMMIT) item means that the pat- tern must match the current starting position, which in this case, it does. However, if the same match is run with PCRE2_NO_START_OPTIMIZE set, the initial scan along the subject string does not happen. The first match attempt is run starting from "D" and when this fails, (*COMMIT) prevents any further matches being tried, so the overall result is "no match". There are also other start-up optimizations. For example, a minimum length for the subject may be recorded. Consider the pattern (*MARK:A)(X|Y) The minimum length for a match is one character. If the subject is "ABC", there will be attempts to match "ABC", "BC", and "C". An attempt to match an empty string at the end of the subject does not take place, because PCRE2 knows that the subject is now too short, and so the (*MARK) is never encountered. In this case, the optimization does not affect the overall match result, which is still "no match", but it does affect the auxiliary information that is returned. PCRE2_NO_UTF_CHECK When PCRE2_UTF is set, the validity of the pattern as a UTF string is automatically checked. There are discussions about the validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the ppccrree22uunniiccooddee document. If an invalid UTF sequence is found, ppccrree22__ccoommppiillee(()) returns a negative error code. If you know that your pattern is a valid UTF string, and you want to skip this check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option. When it is set, the effect of passing an invalid UTF string as a pattern is undefined. It may cause your program to crash or loop. Note that this option can also be passed to ppccrree22__mmaattcchh(()) and ppccrree__ddffaa__mmaattcchh(()), to suppress UTF validity checking of the subject string. Note also that setting PCRE2_NO_UTF_CHECK at compile time does not dis- able the error that is given if an escape sequence for an invalid Uni- code code point is encountered in the pattern. In particular, the so- called "surrogate" code points (0xd800 to 0xdfff) are invalid. If you want to allow escape sequences such as \x{d800} you can set the PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra option, as described in the section entitled "Extra compile options" below. However, this is pos- sible only in UTF-8 and UTF-32 modes, because these values are not rep- resentable in UTF-16. PCRE2_UCP This option changes the way PCRE2 processes \B, \b, \D, \d, \S, \s, \W, \w, and some of the POSIX character classes. By default, only ASCII characters are recognized, but if PCRE2_UCP is set, Unicode properties are used instead to classify characters. More details are given in the section on generic character types in the ppccrree22ppaatttteerrnn page. If you set PCRE2_UCP, matching one of the items it affects takes much longer. The option is available only if PCRE2 has been compiled with Unicode sup- port (which is the default). PCRE2_UNGREEDY This option inverts the "greediness" of the quantifiers so that they are not greedy by default, but become greedy if followed by "?". It is not compatible with Perl. It can also be set by a (?U) option setting within the pattern. PCRE2_USE_OFFSET_LIMIT This option must be set for ppccrree22__ccoommppiillee(()) if ppccrree22__sseett__ooffffsseett__lliimmiitt(()) is going to be used to set a non-default offset limit in a match con- text for matches that use this pattern. An error is generated if an offset limit is set without this option. For more details, see the description of ppccrree22__sseett__ooffffsseett__lliimmiitt(()) in the section that describes match contexts. See also the PCRE2_FIRSTLINE option above. PCRE2_UTF This option causes PCRE2 to regard both the pattern and the subject strings that are subsequently processed as strings of UTF characters instead of single-code-unit strings. It is available when PCRE2 is built to include Unicode support (which is the default). If Unicode support is not available, the use of this option provokes an error. Details of how PCRE2_UTF changes the behaviour of PCRE2 are given in the ppccrree22uunniiccooddee page. EExxttrraa ccoommppiillee ooppttiioonnss Unlike the main compile-time options, the extra options are not saved with the compiled pattern. The option bits that can be set in a compile context by calling the ppccrree22__sseett__ccoommppiillee__eexxttrraa__ooppttiioonnss(()) function are as follows: PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES This option applies when compiling a pattern in UTF-8 or UTF-32 mode. It is forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode "surrogate" code points in the range 0xd800 to 0xdfff are used in pairs in UTF-16 to encode code points with values in the range 0x10000 to 0x10ffff. The surrogates cannot therefore be represented in UTF-16. They can be represented in UTF-8 and UTF-32, but are defined as invalid code points, and cause errors if encountered in a UTF-8 or UTF-32 string that is being checked for validity by PCRE2. These values also cause errors if encountered in escape sequences such as \x{d912} within a pattern. However, it seems that some applications, when using PCRE2 to check for unwanted characters in UTF-8 strings, explicitly test for the surrogates using escape sequences. The PCRE2_NO_UTF_CHECK option does not disable the error that occurs, because it applies only to the testing of input strings for UTF valid- ity. If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surro- gate code point values in UTF-8 and UTF-32 patterns no longer provoke errors and are incorporated in the compiled pattern. However, they can only match subject characters if the matching function is called with PCRE2_NO_UTF_CHECK set. PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL This is a dangerous option. Use with care. By default, an unrecognized escape such as \j or a malformed one such as \x{2z} causes a compile- time error when detected by ppccrree22__ccoommppiillee(()). Perl is somewhat inconsis- tent in handling such items: for example, \j is treated as a literal "j", and non-hexadecimal digits in \x{} are just ignored, though warn- ings are given in both cases if Perl's warning switch is enabled. How- ever, a malformed octal number after \o{ always causes an error in Perl. If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to ppccrree22__ccoommppiillee(()), all unrecognized or erroneous escape sequences are treated as single-character escapes. For example, \j is a literal "j" and \x{2z} is treated as the literal string "x{2z}". Setting this option means that typos in patterns may go undetected and have unex- pected results. This is a dangerous option. Use with care. PCRE2_EXTRA_MATCH_LINE This option is provided for use by the --xx option of ppccrree22ggrreepp. It causes the pattern only to match complete lines. This is achieved by automatically inserting the code for "^(?:" at the start of the com- piled pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set, the matched line may be in the middle of the subject string. This option can be used with PCRE2_LITERAL. PCRE2_EXTRA_MATCH_WORD This option is provided for use by the --ww option of ppccrree22ggrreepp. It causes the pattern only to match strings that have a word boundary at the start and the end. This is achieved by automatically inserting the code for "\b(?:" at the start of the compiled pattern and ")\b" at the end. The option may be used with PCRE2_LITERAL. However, it is ignored if PCRE2_EXTRA_MATCH_LINE is also set. JJUUSSTT--IINN--TTIIMMEE ((JJIITT)) CCOOMMPPIILLAATTIIOONN iinntt ppccrree22__jjiitt__ccoommppiillee((ppccrree22__ccooddee **_c_o_d_e,, uuiinntt3322__tt _o_p_t_i_o_n_s));; iinntt ppccrree22__jjiitt__mmaattcchh((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; vvooiidd ppccrree22__jjiitt__ffrreeee__uunnuusseedd__mmeemmoorryy((ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__jjiitt__ssttaacckk **ppccrree22__jjiitt__ssttaacckk__ccrreeaattee((PPCCRREE22__SSIIZZEE _s_t_a_r_t_s_i_z_e,, PPCCRREE22__SSIIZZEE _m_a_x_s_i_z_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; vvooiidd ppccrree22__jjiitt__ssttaacckk__aassssiiggnn((ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, ppccrree22__jjiitt__ccaallllbbaacckk _c_a_l_l_b_a_c_k___f_u_n_c_t_i_o_n,, vvooiidd **_c_a_l_l_b_a_c_k___d_a_t_a));; vvooiidd ppccrree22__jjiitt__ssttaacckk__ffrreeee((ppccrree22__jjiitt__ssttaacckk **_j_i_t___s_t_a_c_k));; These functions provide support for JIT compilation, which, if the just-in-time compiler is available, further processes a compiled pat- tern into machine code that executes much faster than the ppccrree22__mmaattcchh(()) interpretive matching function. Full details are given in the ppccrree22jjiitt documentation. JIT compilation is a heavyweight optimization. It can take some time for patterns to be analyzed, and for one-off matches and simple pat- terns the benefit of faster execution might be offset by a much slower compilation time. Most (but not all) patterns can be optimized by the JIT compiler. LLOOCCAALLEE SSUUPPPPOORRTT PCRE2 handles caseless matching, and determines whether characters are letters, digits, or whatever, by reference to a set of tables, indexed by character code point. This applies only to characters whose code points are less than 256. By default, higher-valued code points never match escapes such as \w or \d. However, if PCRE2 is built with Uni- code support, all characters can be tested with \p and \P, or, alterna- tively, the PCRE2_UCP option can be set when a pattern is compiled; this causes \w and friends to use Unicode property support instead of the built-in tables. The use of locales with Unicode is discouraged. If you are handling characters with code points greater than 128, you should either use Unicode support, or use locales, but not try to mix the two. PCRE2 contains an internal set of character tables that are used by default. These are sufficient for many applications. Normally, the internal tables recognize only ASCII characters. However, when PCRE2 is built, it is possible to cause the internal tables to be rebuilt in the default "C" locale of the local system, which may cause them to be dif- ferent. The internal tables can be overridden by tables supplied by the appli- cation that calls PCRE2. These may be created in a different locale from the default. As more and more applications change to using Uni- code, the need for this locale support is expected to die away. External tables are built by calling the ppccrree22__mmaakkeettaabblleess(()) function, in the relevant locale. The result can be passed to ppccrree22__ccoommppiillee(()) as often as necessary, by creating a compile context and calling ppccrree22__sseett__cchhaarraacctteerr__ttaabblleess(()) to set the tables pointer therein. For example, to build and use tables that are appropriate for the French locale (where accented characters with values greater than 128 are treated as letters), the following code could be used: setlocale(LC_CTYPE, "fr_FR"); tables = pcre2_maketables(NULL); ccontext = pcre2_compile_context_create(NULL); pcre2_set_character_tables(ccontext, tables); re = pcre2_compile(..., ccontext); The locale name "fr_FR" is used on Linux and other Unix-like systems; if you are using Windows, the name for the French locale is "french". It is the caller's responsibility to ensure that the memory containing the tables remains available for as long as it is needed. The pointer that is passed (via the compile context) to ppccrree22__ccoommppiillee(()) is saved with the compiled pattern, and the same tables are used by ppccrree22__mmaattcchh(()) and ppccrree__ddffaa__mmaattcchh(()). Thus, for any single pattern, com- pilation and matching both happen in the same locale, but different patterns can be processed in different locales. IINNFFOORRMMAATTIIOONN AABBOOUUTT AA CCOOMMPPIILLEEDD PPAATTTTEERRNN iinntt ppccrree22__ppaatttteerrnn__iinnffoo((ccoonnsstt ppccrree22 **_c_o_d_e,, uuiinntt3322__tt _w_h_a_t,, vvooiidd **_w_h_e_r_e));; The ppccrree22__ppaatttteerrnn__iinnffoo(()) function returns general information about a compiled pattern. For information about callouts, see the next section. The first argument for ppccrree22__ppaatttteerrnn__iinnffoo(()) is a pointer to the com- piled pattern. The second argument specifies which piece of information is required, and the third argument is a pointer to a variable to receive the data. If the third argument is NULL, the first argument is ignored, and the function returns the size in bytes of the variable that is required for the information requested. Otherwise, the yield of the function is zero for success, or one of the following negative num- bers: PCRE2_ERROR_NULL the argument _c_o_d_e was NULL PCRE2_ERROR_BADMAGIC the "magic number" was not found PCRE2_ERROR_BADOPTION the value of _w_h_a_t was invalid PCRE2_ERROR_UNSET the requested field is not set The "magic number" is placed at the start of each compiled pattern as an simple check against passing an arbitrary memory pointer. Here is a typical call of ppccrree22__ppaatttteerrnn__iinnffoo(()), to obtain the length of the com- piled pattern: int rc; size_t length; rc = pcre2_pattern_info( re, /* result of pcre2_compile() */ PCRE2_INFO_SIZE, /* what is required */ &length); /* where to put the data */ The possible values for the second argument are defined in ppccrree22..hh, and are as follows: PCRE2_INFO_ALLOPTIONS PCRE2_INFO_ARGOPTIONS PCRE2_INFO_EXTRAOPTIONS Return copies of the pattern's options. The third argument should point to a uuiinntt3322__tt variable. PCRE2_INFO_ARGOPTIONS returns exactly the options that were passed to ppccrree22__ccoommppiillee(()), whereas PCRE2_INFO_ALLOP- TIONS returns the compile options as modified by any top-level (*XXX) option settings such as (*UTF) at the start of the pattern itself. PCRE2_INFO_EXTRAOPTIONS returns the extra options that were set in the compile context by calling the pcre2_set_compile_extra_options() func- tion. For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EXTENDED option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED and PCRE2_UTF. Option settings such as (?i) that can change within a pattern do not affect the result of PCRE2_INFO_ALLOP- TIONS, even if they appear right at the start of the pattern. (This was different in some earlier releases.) A pattern compiled without PCRE2_ANCHORED is automatically anchored by PCRE2 if the first significant item in every top-level branch is one of the following: ^ unless PCRE2_MULTILINE is set \A always \G always .* sometimes - see below When .* is the first significant item, anchoring is possible only when all the following are true: .* is not in an atomic group .* is not in a capturing group that is the subject of a back reference PCRE2_DOTALL is in force for .* Neither (*PRUNE) nor (*SKIP) appears in the pattern PCRE2_NO_DOTSTAR_ANCHOR is not set For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in the options returned for PCRE2_INFO_ALLOPTIONS. PCRE2_INFO_BACKREFMAX Return the number of the highest back reference in the pattern. The third argument should point to an uuiinntt3322__tt variable. Named subpatterns acquire numbers as well as names, and these count towards the highest back reference. Back references such as \4 or \g{12} match the cap- tured characters of the given group, but in addition, the check that a capturing group is set in a conditional subpattern such as (?(3)a|b) is also a back reference. Zero is returned if there are no back refer- ences. PCRE2_INFO_BSR The output is a uint32_t whose value indicates what character sequences the \R escape sequence matches. A value of PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a value of PCRE2_BSR_ANY- CRLF means that \R matches only CR, LF, or CRLF. PCRE2_INFO_CAPTURECOUNT Return the highest capturing subpattern number in the pattern. In pat- terns where (?| is not used, this is also the total number of capturing subpatterns. The third argument should point to an uuiinntt3322__tt variable. PCRE2_INFO_DEPTHLIMIT If the pattern set a backtracking depth limit by including an item of the form (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The third argument should point to an unsigned 32-bit integer. If no such value has been set, the call to ppccrree22__ppaatttteerrnn__iinnffoo(()) returns the error PCRE2_ERROR_UNSET. Note that this limit will only be used during match- ing if it is less than the limit set or defaulted by the caller of the match function. PCRE2_INFO_FIRSTBITMAP In the absence of a single first code unit for a non-anchored pattern, ppccrree22__ccoommppiillee(()) may construct a 256-bit table that defines a fixed set of values for the first code unit in any match. For example, a pattern that starts with [abc] results in a table with three bits set. When code unit values greater than 255 are supported, the flag bit for 255 means "any code unit of value 255 or above". If such a table was con- structed, a pointer to it is returned. Otherwise NULL is returned. The third argument should point to an ccoonnsstt uuiinntt88__tt ** variable. PCRE2_INFO_FIRSTCODETYPE Return information about the first code unit of any matched string, for a non-anchored pattern. The third argument should point to an uuiinntt3322__tt variable. If there is a fixed first value, for example, the letter "c" from a pattern such as (cat|cow|coyote), 1 is returned, and the value can be retrieved using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but it is known that a match can occur only at the start of the subject or following a newline in the subject, 2 is returned. Otherwise, and for anchored patterns, 0 is returned. PCRE2_INFO_FIRSTCODEUNIT Return the value of the first code unit of any matched string for a pattern where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third argument should point to an uuiinntt3322__tt variable. In the 8-bit library, the value is always less than 256. In the 16-bit library the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode. PCRE2_INFO_FRAMESIZE Return the size (in bytes) of the data frames that are used to remember backtracking positions when the pattern is processed by ppccrree22__mmaattcchh(()) without the use of JIT. The third argument should point to an ssiizzee__tt variable. The frame size depends on the number of capturing parentheses in the pattern. Each additional capturing group adds two PCRE2_SIZE variables. PCRE2_INFO_HASBACKSLASHC Return 1 if the pattern contains any instances of \C, otherwise 0. The third argument should point to an uuiinntt3322__tt variable. PCRE2_INFO_HASCRORLF Return 1 if the pattern contains any explicit matches for CR or LF characters, otherwise 0. The third argument should point to an uuiinntt3322__tt variable. An explicit match is either a literal CR or LF character, or \r or \n or one of the equivalent hexadecimal or octal escape sequences. PCRE2_INFO_HEAPLIMIT If the pattern set a heap memory limit by including an item of the form (*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argu- ment should point to an unsigned 32-bit integer. If no such value has been set, the call to ppccrree22__ppaatttteerrnn__iinnffoo(()) returns the error PCRE2_ERROR_UNSET. Note that this limit will only be used during match- ing if it is less than the limit set or defaulted by the caller of the match function. PCRE2_INFO_JCHANGED Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise 0. The third argument should point to an uuiinntt3322__tt variable. (?J) and (?-J) set and unset the local PCRE2_DUPNAMES option, respec- tively. PCRE2_INFO_JITSIZE If the compiled pattern was successfully processed by ppccrree22__jjiitt__ccoomm-- ppiillee(()), return the size of the JIT compiled code, otherwise return zero. The third argument should point to a ssiizzee__tt variable. PCRE2_INFO_LASTCODETYPE Returns 1 if there is a rightmost literal code unit that must exist in any matched string, other than at its start. The third argument should point to an uuiinntt3322__tt variable. If there is no such value, 0 is returned. When 1 is returned, the code unit value itself can be retrieved using PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is recorded only if it follows something of variable length. For example, for the pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned from PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0. PCRE2_INFO_LASTCODEUNIT Return the value of the rightmost literal code unit that must exist in any matched string, other than at its start, for a pattern where PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argu- ment should point to an uuiinntt3322__tt variable. PCRE2_INFO_MATCHEMPTY Return 1 if the pattern might match an empty string, otherwise 0. The third argument should point to an uuiinntt3322__tt variable. When a pattern contains recursive subroutine calls it is not always possible to deter- mine whether or not it can match an empty string. PCRE2 takes a cau- tious approach and returns 1 in such cases. PCRE2_INFO_MATCHLIMIT If the pattern set a match limit by including an item of the form (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third argument should point to an unsigned 32-bit integer. If no such value has been set, the call to ppccrree22__ppaatttteerrnn__iinnffoo(()) returns the error PCRE2_ERROR_UNSET. Note that this limit will only be used during match- ing if it is less than the limit set or defaulted by the caller of the match function. PCRE2_INFO_MAXLOOKBEHIND Return the number of characters (not code units) in the longest lookbe- hind assertion in the pattern. The third argument should point to an unsigned 32-bit integer. This information is useful when doing multi- segment matching using the partial matching facilities. Note that the simple assertions \b and \B require a one-character lookbehind. \A also registers a one-character lookbehind, though it does not actually inspect the previous character. This is to ensure that at least one character from the old segment is retained when a new segment is pro- cessed. Otherwise, if there are no lookbehinds in the pattern, \A might match incorrectly at the start of a second or subsequent segment. PCRE2_INFO_MINLENGTH If a minimum length for matching subject strings was computed, its value is returned. Otherwise the returned value is 0. The value is a number of characters, which in UTF mode may be different from the num- ber of code units. The third argument should point to an uuiinntt3322__tt variable. The value is a lower bound to the length of any matching string. There may not be any strings of that length that do actually match, but every string that does match is at least that long. PCRE2_INFO_NAMECOUNT PCRE2_INFO_NAMEENTRYSIZE PCRE2_INFO_NAMETABLE PCRE2 supports the use of named as well as numbered capturing parenthe- ses. The names are just an additional way of identifying the parenthe- ses, which still acquire numbers. Several convenience functions such as ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnaammee(()) are provided for extracting captured sub- strings by name. It is also possible to extract the data directly, by first converting the name to a number in order to access the correct pointers in the output vector (described with ppccrree22__mmaattcchh(()) below). To do the conversion, you need to use the name-to-number map, which is described by these three values. The map consists of a number of fixed-size entries. PCRE2_INFO_NAME- COUNT gives the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives the size of each entry in code units; both of these return a uuiinntt3322__tt value. The entry size depends on the length of the longest name. PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table. This is a PCRE2_SPTR pointer to a block of code units. In the 8-bit library, the first two bytes of each entry are the number of the cap- turing parenthesis, most significant byte first. In the 16-bit library, the pointer points to 16-bit code units, the first of which contains the parenthesis number. In the 32-bit library, the pointer points to 32-bit code units, the first of which contains the parenthesis number. The rest of the entry is the corresponding name, zero terminated. The names are in alphabetical order. If (?| is used to create multiple groups with the same number, as described in the section on duplicate subpattern numbers in the ppccrree22ppaatttteerrnn page, the groups may be given the same name, but there is only one entry in the table. Different names for groups of the same number are not permitted. Duplicate names for subpatterns with different numbers are permitted, but only if PCRE2_DUPNAMES is set. They appear in the table in the order in which they were found in the pattern. In the absence of (?| this is the order of increasing number; when (?| is used this is not necessarily the case because later subpatterns may have lower numbers. As a simple example of the name/number table, consider the following pattern after compilation by the 8-bit library (assume PCRE2_EXTENDED is set, so white space - including newlines - is ignored): (? (?(\d\d)?\d\d) - (?\d\d) - (?\d\d) ) There are four named subpatterns, so the table has four entries, and each entry in the table is eight bytes long. The table is as follows, with non-printing bytes shows in hexadecimal, and undefined bytes shown as ??: 00 01 d a t e 00 ?? 00 05 d a y 00 ?? ?? 00 04 m o n t h 00 00 02 y e a r 00 ?? When writing code to extract data from named subpatterns using the name-to-number map, remember that the length of the entries is likely to be different for each compiled pattern. PCRE2_INFO_NEWLINE The output is one of the following uuiinntt3322__tt values: PCRE2_NEWLINE_CR Carriage return (CR) PCRE2_NEWLINE_LF Linefeed (LF) PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) PCRE2_NEWLINE_ANY Any Unicode line ending PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF PCRE2_NEWLINE_NUL The NUL character (binary zero) This identifies the character sequence that will be recognized as mean- ing "newline" while matching. PCRE2_INFO_SIZE Return the size of the compiled pattern in bytes (for all three libraries). The third argument should point to a ssiizzee__tt variable. This value includes the size of the general data block that precedes the code units of the compiled pattern itself. The value that is used when ppccrree22__ccoommppiillee(()) is getting memory in which to place the compiled pat- tern may be slightly larger than the value returned by this option, because there are cases where the code that calculates the size has to over-estimate. Processing a pattern with the JIT compiler does not alter the value returned by this option. IINNFFOORRMMAATTIIOONN AABBOOUUTT AA PPAATTTTEERRNN''SS CCAALLLLOOUUTTSS iinntt ppccrree22__ccaalllloouutt__eennuummeerraattee((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, iinntt ((**_c_a_l_l_b_a_c_k))((ppccrree22__ccaalllloouutt__eennuummeerraattee__bblloocckk **,, vvooiidd **)),, vvooiidd **_u_s_e_r___d_a_t_a));; A script language that supports the use of string arguments in callouts might like to scan all the callouts in a pattern before running the match. This can be done by calling ppccrree22__ccaalllloouutt__eennuummeerraattee(()). The first argument is a pointer to a compiled pattern, the second points to a callback function, and the third is arbitrary user data. The callback function is called for every callout in the pattern in the order in which they appear. Its first argument is a pointer to a callout enumer- ation block, and its second argument is the _u_s_e_r___d_a_t_a value that was passed to ppccrree22__ccaalllloouutt__eennuummeerraattee(()). The contents of the callout enu- meration block are described in the ppccrree22ccaalllloouutt documentation, which also gives further details about callouts. SSEERRIIAALLIIZZAATTIIOONN AANNDD PPRREECCOOMMPPIILLIINNGG It is possible to save compiled patterns on disc or elsewhere, and reload them later, subject to a number of restrictions. The functions whose names begin with ppccrree22__sseerriiaalliizzee__ are used for this purpose. They are described in the ppccrree22sseerriiaalliizzee documentation. TTHHEE MMAATTCCHH DDAATTAA BBLLOOCCKK ppccrree22__mmaattcchh__ddaattaa **ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee((uuiinntt3322__tt _o_v_e_c_s_i_z_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; ppccrree22__mmaattcchh__ddaattaa **ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee__ffrroomm__ppaatttteerrnn(( ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, ppccrree22__ggeenneerraall__ccoonntteexxtt **_g_c_o_n_t_e_x_t));; vvooiidd ppccrree22__mmaattcchh__ddaattaa__ffrreeee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; Information about a successful or unsuccessful match is placed in a match data block, which is an opaque structure that is accessed by function calls. In particular, the match data block contains a vector of offsets into the subject string that define the matched part of the subject and any substrings that were captured. This is known as the _o_v_e_c_t_o_r. Before calling ppccrree22__mmaattcchh(()), ppccrree22__ddffaa__mmaattcchh(()), or ppccrree22__jjiitt__mmaattcchh(()) you must create a match data block by calling one of the creation func- tions above. For ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee(()), the first argument is the number of pairs of offsets in the _o_v_e_c_t_o_r. One pair of offsets is required to identify the string that matched the whole pattern, with an additional pair for each captured substring. For example, a value of 4 creates enough space to record the matched portion of the subject plus three captured substrings. A minimum of at least 1 pair is imposed by ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee(()), so it is always possible to return the over- all matched string. The second argument of ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee(()) is a pointer to a gen- eral context, which can specify custom memory management for obtaining the memory for the match data block. If you are not using custom memory management, pass NULL, which causes mmaalllloocc(()) to be used. For ppccrree22__mmaattcchh__ddaattaa__ccrreeaattee__ffrroomm__ppaatttteerrnn(()), the first argument is a pointer to a compiled pattern. The ovector is created to be exactly the right size to hold all the substrings a pattern might capture. The sec- ond argument is again a pointer to a general context, but in this case if NULL is passed, the memory is obtained using the same allocator that was used for the compiled pattern (custom or default). A match data block can be used many times, with the same or different compiled patterns. You can extract information from a match data block after a match operation has finished, using functions that are described in the sections on matched strings and other match data below. When a call of ppccrree22__mmaattcchh(()) fails, valid data is available in the match block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one of the error codes for an invalid UTF string. Exactly what is available depends on the error, and is detailed below. When one of the matching functions is called, pointers to the compiled pattern and the subject string are set in the match data block so that they can be referenced by the extraction functions. After running a match, you must not free a compiled pattern or a subject string until after all operations on the match data block (for that match) have taken place. When a match data block itself is no longer needed, it should be freed by calling ppccrree22__mmaattcchh__ddaattaa__ffrreeee(()). MMAATTCCHHIINNGG AA PPAATTTTEERRNN:: TTHHEE TTRRAADDIITTIIOONNAALL FFUUNNCCTTIIOONN iinntt ppccrree22__mmaattcchh((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t));; The function ppccrree22__mmaattcchh(()) is called to match a subject string against a compiled pattern, which is passed in the _c_o_d_e argument. You can call ppccrree22__mmaattcchh(()) with the same _c_o_d_e argument as many times as you like, in order to find multiple matches in the subject string or to match dif- ferent subject strings with the same pattern. This function is the main matching facility of the library, and it operates in a Perl-like manner. For specialist use there is also an alternative matching function, which is described below in the section about the ppccrree22__ddffaa__mmaattcchh(()) function. Here is an example of a simple call to ppccrree22__mmaattcchh(()): pcre2_match_data *md = pcre2_match_data_create(4, NULL); int rc = pcre2_match( re, /* result of pcre2_compile() */ "some string", /* the subject string */ 11, /* the length of the subject string */ 0, /* start at offset 0 in the subject */ 0, /* default options */ md, /* the match data block */ NULL); /* a match context; NULL means use defaults */ If the subject string is zero-terminated, the length can be given as PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common matching parameters are to be changed. For details, see the sec- tion on the match context above. TThhee ssttrriinngg ttoo bbee mmaattcchheedd bbyy ppccrree22__mmaattcchh(()) The subject string is passed to ppccrree22__mmaattcchh(()) as a pointer in _s_u_b_j_e_c_t, a length in _l_e_n_g_t_h, and a starting offset in _s_t_a_r_t_o_f_f_s_e_t. The length and offset are in code units, not characters. That is, they are in bytes for the 8-bit library, 16-bit code units for the 16-bit library, and 32-bit code units for the 32-bit library, whether or not UTF pro- cessing is enabled. If _s_t_a_r_t_o_f_f_s_e_t is greater than the length of the subject, ppccrree22__mmaattcchh(()) returns PCRE2_ERROR_BADOFFSET. When the starting offset is zero, the search for a match starts at the beginning of the subject, and this is by far the most common case. In UTF-8 or UTF-16 mode, the starting off- set must point to the start of a character, or to the end of the sub- ject (in UTF-32 mode, one code unit equals one character, so all off- sets are valid). Like the pattern string, the subject may contain binary zeroes. A non-zero starting offset is useful when searching for another match in the same subject by calling ppccrree22__mmaattcchh(()) again after a previous success. Setting _s_t_a_r_t_o_f_f_s_e_t differs from passing over a shortened string and setting PCRE2_NOTBOL in the case of a pattern that begins with any kind of lookbehind. For example, consider the pattern \Biss\B which finds occurrences of "iss" in the middle of words. (\B matches only if the current position in the subject is not a word boundary.) When applied to the string "Mississipi" the first call to ppccrree22__mmaattcchh(()) finds the first occurrence. If ppccrree22__mmaattcchh(()) is called again with just the remainder of the subject, namely "issipi", it does not match, because \B is always false at the start of the subject, which is deemed to be a word boundary. However, if ppccrree22__mmaattcchh(()) is passed the entire string again, but with _s_t_a_r_t_o_f_f_s_e_t set to 4, it finds the second occur- rence of "iss" because it is able to look behind the starting point to discover that it is preceded by a letter. Finding all the matches in a subject is tricky when the pattern can match an empty string. It is possible to emulate Perl's /g behaviour by first trying the match again at the same offset, with the PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED options, and then if that fails, advancing the starting offset and trying an ordinary match again. There is some code that demonstrates how to do this in the ppccrree22ddeemmoo sample program. In the most general case, you have to check to see if the newline convention recognizes CRLF as a newline, and if so, and the current character is CR followed by LF, advance the start- ing offset by two characters instead of one. If a non-zero starting offset is passed when the pattern is anchored, a single attempt to match at the given offset is made. This can only suc- ceed if the pattern does not require the match to be at the start of the subject. In other words, the anchoring must be the result of set- ting the PCRE2_ANCHORED option or the use of .* with PCRE2_DOTALL, not by starting the pattern with ^ or \A. OOppttiioonn bbiittss ffoorr ppccrree22__mmaattcchh(()) The unused bits of the _o_p_t_i_o_n_s argument for ppccrree22__mmaattcchh(()) must be zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PAR- TIAL_SOFT. Their action is described below. Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not sup- ported by the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the interpretive code in ppccrree22__mmaattcchh(()) is run. Apart from PCRE2_NO_JIT (obviously), the remaining options are supported for JIT matching. PCRE2_ANCHORED The PCRE2_ANCHORED option limits ppccrree22__mmaattcchh(()) to matching at the first matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out to be anchored by virtue of its contents, it cannot be made unachored at matching time. Note that setting the option at match time disables JIT matching. PCRE2_ENDANCHORED If the PCRE2_ENDANCHORED option is set, any string that ppccrree22__mmaattcchh(()) matches must be right at the end of the subject string. Note that set- ting the option at match time disables JIT matching. PCRE2_NOTBOL This option specifies that first character of the subject string is not the beginning of a line, so the circumflex metacharacter should not match before it. Setting this without having set PCRE2_MULTILINE at compile time causes circumflex never to match. This option affects only the behaviour of the circumflex metacharacter. It does not affect \A. PCRE2_NOTEOL This option specifies that the end of the subject string is not the end of a line, so the dollar metacharacter should not match it nor (except in multiline mode) a newline immediately before it. Setting this with- out having set PCRE2_MULTILINE at compile time causes dollar never to match. This option affects only the behaviour of the dollar metacharac- ter. It does not affect \Z or \z. PCRE2_NOTEMPTY An empty string is not considered to be a valid match if this option is set. If there are alternatives in the pattern, they are tried. If all the alternatives match the empty string, the entire match fails. For example, if the pattern a?b? is applied to a string not beginning with "a" or "b", it matches an empty string at the start of the subject. With PCRE2_NOTEMPTY set, this match is not valid, so ppccrree22__mmaattcchh(()) searches further into the string for occurrences of "a" or "b". PCRE2_NOTEMPTY_ATSTART This is like PCRE2_NOTEMPTY, except that it locks out an empty string match only at the first matching position, that is, at the start of the subject plus the starting offset. An empty string match later in the subject is permitted. If the pattern is anchored, such a match can occur only if the pattern contains \K. PCRE2_NO_JIT By default, if a pattern has been successfully processed by ppccrree22__jjiitt__ccoommppiillee(()), JIT is automatically used when ppccrree22__mmaattcchh(()) is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use of JIT; it forces matching to be done by the interpreter. PCRE2_NO_UTF_CHECK When PCRE2_UTF is set at compile time, the validity of the subject as a UTF string is checked by default when ppccrree22__mmaattcchh(()) is subsequently called. If a non-zero starting offset is given, the check is applied only to that part of the subject that could be inspected during match- ing, and there is a check that the starting offset points to the first code unit of a character or to the end of the subject. If there are no lookbehind assertions in the pattern, the check starts at the starting offset. Otherwise, it starts at the length of the longest lookbehind before the starting offset, or at the start of the subject if there are not that many characters before the starting offset. Note that the sequences \b and \B are one-character lookbehinds. The check is carried out before any other processing takes place, and a negative error code is returned if the check fails. There are several UTF error codes for each code unit width, corresponding to different problems with the code unit sequence. There are discussions about the validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the ppccrree22uunniiccooddee page. If you know that your subject is valid, and you want to skip these checks for performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling ppccrree22__mmaattcchh(()). You might want to do this for the second and subsequent calls to ppccrree22__mmaattcchh(()) if you are making repeated calls to find other matches in the same subject string. WARNING: When PCRE2_NO_UTF_CHECK is set, the effect of passing an invalid string as a subject, or an invalid value of _s_t_a_r_t_o_f_f_s_e_t, is undefined. Your program may crash or loop indefinitely. PCRE2_PARTIAL_HARD PCRE2_PARTIAL_SOFT These options turn on the partial matching feature. A partial match occurs if the end of the subject string is reached successfully, but there are not enough subject characters to complete the match. If this happens when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) is set, matching continues by testing any remaining alternatives. Only if no complete match can be found is PCRE2_ERROR_PARTIAL returned instead of PCRE2_ERROR_NOMATCH. In other words, PCRE2_PARTIAL_SOFT specifies that the caller is prepared to handle a partial match, but only if no com- plete match can be found. If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if a partial match is found, ppccrree22__mmaattcchh(()) immediately returns PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other words, when PCRE2_PARTIAL_HARD is set, a partial match is consid- ered to be more important that an alternative complete match. There is a more detailed discussion of partial and multi-segment match- ing, with examples, in the ppccrree22ppaarrttiiaall documentation. NNEEWWLLIINNEE HHAANNDDLLIINNGG WWHHEENN MMAATTCCHHIINNGG When PCRE2 is built, a default newline convention is set; this is usu- ally the standard convention for the operating system. The default can be overridden in a compile context by calling ppccrree22__sseett__nneewwlliinnee(()). It can also be overridden by starting a pattern string with, for example, (*CRLF), as described in the section on newline conventions in the ppccrree22ppaatttteerrnn page. During matching, the newline choice affects the be- haviour of the dot, circumflex, and dollar metacharacters. It may also alter the way the match starting position is advanced after a match failure for an unanchored pattern. When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as the newline convention, and a match attempt for an unanchored pattern fails when the current starting position is at a CRLF sequence, and the pattern contains no explicit matches for CR or LF characters, the match position is advanced by two characters instead of one, in other words, to after the CRLF. The above rule is a compromise that makes the most common cases work as expected. For example, if the pattern is .+A (and the PCRE2_DOTALL option is not set), it does not match the string "\r\nA" because, after failing at the start, it skips both the CR and the LF before retrying. However, the pattern [\r\n]A does match that string, because it con- tains an explicit CR or LF reference, and so advances only by one char- acter after the first failure. An explicit match for CR of LF is either a literal appearance of one of those characters in the pattern, or one of the \r or \n or equivalent octal or hexadecimal escape sequences. Implicit matches such as [^X] do not count, nor does \s, even though it includes CR and LF in the char- acters that it matches. Notwithstanding the above, anomalous effects may still occur when CRLF is a valid newline sequence and explicit \r or \n escapes appear in the pattern. HHOOWW PPCCRREE22__MMAATTCCHH(()) RREETTUURRNNSS AA SSTTRRIINNGG AANNDD CCAAPPTTUURREEDD SSUUBBSSTTRRIINNGGSS uuiinntt3322__tt ppccrree22__ggeett__oovveeccttoorr__ccoouunntt((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; PPCCRREE22__SSIIZZEE **ppccrree22__ggeett__oovveeccttoorr__ppooiinntteerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; In general, a pattern matches a certain portion of the subject, and in addition, further substrings from the subject may be picked out by parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's book, this is called "capturing" in what follows, and the phrase "capturing subpattern" or "capturing group" is used for a frag- ment of a pattern that picks out a substring. PCRE2 supports several other kinds of parenthesized subpattern that do not cause substrings to be captured. The ppccrree22__ppaatttteerrnn__iinnffoo(()) function can be used to find out how many capturing subpatterns there are in a compiled pattern. You can use auxiliary functions for accessing captured substrings by number or by name, as described in sections below. Alternatively, you can make direct use of the vector of PCRE2_SIZE val- ues, called the oovveeccttoorr, which contains the offsets of captured strings. It is part of the match data block. The function ppccrree22__ggeett__oovveeccttoorr__ppooiinntteerr(()) returns the address of the ovector, and ppccrree22__ggeett__oovveeccttoorr__ccoouunntt(()) returns the number of pairs of values it con- tains. Within the ovector, the first in each pair of values is set to the off- set of the first code unit of a substring, and the second is set to the offset of the first code unit after the end of a substring. These val- ues are always code unit offsets, not character offsets. That is, they are byte offsets in the 8-bit library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit library. After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair of offsets (that is, _o_v_e_c_t_o_r_[_0_] and _o_v_e_c_t_o_r_[_1_]) are set. They identify the part of the subject that was partially matched. See the ppccrree22ppaarrttiiaall documentation for details of partial matching. After a fully successful match, the first pair of offsets identifies the portion of the subject string that was matched by the entire pat- tern. The next pair is used for the first captured substring, and so on. The value returned by ppccrree22__mmaattcchh(()) is one more than the highest numbered pair that has been set. For example, if two substrings have been captured, the returned value is 3. If there are no captured sub- strings, the return value from a successful match is 1, indicating that just the first pair of offsets has been set. If a pattern uses the \K escape sequence within a positive assertion, the reported start of a successful match can be greater than the end of the match. For example, if the pattern (?=ab\K) is matched against "ab", the start and end offset values for the match are 2 and 0. If a capturing subpattern group is matched repeatedly within a single match operation, it is the last portion of the subject that it matched that is returned. If the ovector is too small to hold all the captured substring offsets, as much as possible is filled in, and the function returns a value of zero. If captured substrings are not of interest, ppccrree22__mmaattcchh(()) may be called with a match data block whose ovector is of minimum length (that is, one pair). It is possible for capturing subpattern number _n_+_1 to match some part of the subject when subpattern _n has not been used at all. For example, if the string "abc" is matched against the pattern (a|(z))(bc) the return from the function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this happens, both values in the offset pairs corre- sponding to unused subpatterns are set to PCRE2_UNSET. Offset values that correspond to unused subpatterns at the end of the expression are also set to PCRE2_UNSET. For example, if the string "abc" is matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The return from the function is 2, because the high- est used capturing subpattern number is 1. The offsets for for the sec- ond and third capturing subpatterns (assuming the vector is large enough, of course) are set to PCRE2_UNSET. Elements in the ovector that do not correspond to capturing parentheses in the pattern are never changed. That is, if a pattern contains _n cap- turing parentheses, no more than _o_v_e_c_t_o_r_[_0_] to _o_v_e_c_t_o_r_[_2_n_+_1_] are set by ppccrree22__mmaattcchh(()). The other elements retain whatever values they previ- ously had. OOTTHHEERR IINNFFOORRMMAATTIIOONN AABBOOUUTT AA MMAATTCCHH PPCCRREE22__SSPPTTRR ppccrree22__ggeett__mmaarrkk((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; PPCCRREE22__SSIIZZEE ppccrree22__ggeett__ssttaarrttcchhaarr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a));; As well as the offsets in the ovector, other information about a match is retained in the match data block and can be retrieved by the above functions in appropriate circumstances. If they are called at other times, the result is undefined. After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure to match (PCRE2_ERROR_NOMATCH), a (*MARK), (*PRUNE), or (*THEN) name may be available. The function ppccrree22__ggeett__mmaarrkk(()) can be called to access this name. The same function applies to all three verbs. It returns a pointer to the zero-terminated name, which is within the com- piled pattern. If no name is available, NULL is returned. The length of the name (excluding the terminating zero) is stored in the code unit that precedes the name. You should use this length instead of relying on the terminating zero if the name might contain a binary zero. After a successful match, the name that is returned is the last (*MARK), (*PRUNE), or (*THEN) name encountered on the matching path through the pattern. Instances of (*PRUNE) and (*THEN) without names are ignored. Thus, for example, if the matching path contains (*MARK:A)(*PRUNE), the name "A" is returned. After a "no match" or a partial match, the last encountered name is returned. For example, consider this pattern: ^(*MARK:A)((*MARK:B)a|b)c When it matches "bc", the returned name is A. The B mark is "seen" in the first branch of the group, but it is not on the matching path. On the other hand, when this pattern fails to match "bx", the returned name is B. After a successful match, a partial match, or one of the invalid UTF errors (for example, PCRE2_ERROR_UTF8_ERR5), ppccrree22__ggeett__ssttaarrttcchhaarr(()) can be called. After a successful or partial match it returns the code unit offset of the character at which the match started. For a non-partial match, this can be different to the value of _o_v_e_c_t_o_r_[_0_] if the pattern contains the \K escape sequence. After a partial match, however, this value is always the same as _o_v_e_c_t_o_r_[_0_] because \K does not affect the result of a partial match. After a UTF check failure, ppccrree22__ggeett__ssttaarrttcchhaarr(()) can be used to obtain the code unit offset of the invalid UTF character. Details are given in the ppccrree22uunniiccooddee page. EERRRROORR RREETTUURRNNSS FFRROOMM ppccrree22__mmaattcchh(()) If ppccrree22__mmaattcchh(()) fails, it returns a negative number. This can be con- verted to a text string by calling the ppccrree22__ggeett__eerrrroorr__mmeessssaaggee(()) func- tion (see "Obtaining a textual error message" below). Negative error codes are also returned by other functions, and are documented with them. The codes are given names in the header file. If UTF checking is in force and an invalid UTF subject string is detected, one of a number of UTF-specific negative error codes is returned. Details are given in the ppccrree22uunniiccooddee page. The following are the other errors that may be returned by ppccrree22__mmaattcchh(()): PCRE2_ERROR_NOMATCH The subject string did not match the pattern. PCRE2_ERROR_PARTIAL The subject string did not match, but it did match partially. See the ppccrree22ppaarrttiiaall documentation for details of partial matching. PCRE2_ERROR_BADMAGIC PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to catch the case when it is passed a junk pointer. This is the error that is returned when the magic number is not present. PCRE2_ERROR_BADMODE This error is given when a compiled pattern is passed to a function in a library of a different code unit width, for example, a pattern com- piled by the 8-bit library is passed to a 16-bit or 32-bit library function. PCRE2_ERROR_BADOFFSET The value of _s_t_a_r_t_o_f_f_s_e_t was greater than the length of the subject. PCRE2_ERROR_BADOPTION An unrecognized bit was set in the _o_p_t_i_o_n_s argument. PCRE2_ERROR_BADUTFOFFSET The UTF code unit sequence that was passed as a subject was checked and found to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of _s_t_a_r_t_o_f_f_s_e_t did not point to the beginning of a UTF character or the end of the subject. PCRE2_ERROR_CALLOUT This error is never generated by ppccrree22__mmaattcchh(()) itself. It is provided for use by callout functions that want to cause ppccrree22__mmaattcchh(()) or ppccrree22__ccaalllloouutt__eennuummeerraattee(()) to return a distinctive error code. See the ppccrree22ccaalllloouutt documentation for details. PCRE2_ERROR_DEPTHLIMIT The nested backtracking depth limit was reached. PCRE2_ERROR_HEAPLIMIT The heap limit was reached. PCRE2_ERROR_INTERNAL An unexpected internal error has occurred. This error could be caused by a bug in PCRE2 or by overwriting of the compiled pattern. PCRE2_ERROR_JIT_STACKLIMIT This error is returned when a pattern that was successfully studied using JIT is being matched, but the memory available for the just-in- time processing stack is not large enough. See the ppccrree22jjiitt documenta- tion for more details. PCRE2_ERROR_MATCHLIMIT The backtracking match limit was reached. PCRE2_ERROR_NOMEMORY If a pattern contains many nested backtracking points, heap memory is used to remember them. This error is given when the memory allocation function (default or custom) fails. Note that a different error, PCRE2_ERROR_HEAPLIMIT, is given if the amount of memory needed exceeds the heap limit. PCRE2_ERROR_NULL Either the _c_o_d_e, _s_u_b_j_e_c_t, or _m_a_t_c_h___d_a_t_a argument was passed as NULL. PCRE2_ERROR_RECURSELOOP This error is returned when ppccrree22__mmaattcchh(()) detects a recursion loop within the pattern. Specifically, it means that either the whole pat- tern or a subpattern has been called recursively for the second time at the same position in the subject string. Some simple patterns that might do this are detected and faulted at compile time, but more com- plicated cases, in particular mutual recursions between two different subpatterns, cannot be detected until matching is attempted. OOBBTTAAIINNIINNGG AA TTEEXXTTUUAALL EERRRROORR MMEESSSSAAGGEE iinntt ppccrree22__ggeett__eerrrroorr__mmeessssaaggee((iinntt _e_r_r_o_r_c_o_d_e,, PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE _b_u_f_f_l_e_n));; A text message for an error code from any PCRE2 function (compile, match, or auxiliary) can be obtained by calling ppccrree22__ggeett__eerrrroorr__mmeess-- ssaaggee(()). The code is passed as the first argument, with the remaining two arguments specifying a code unit buffer and its length in code units, into which the text message is placed. The message is returned in code units of the appropriate width for the library that is being used. The returned message is terminated with a trailing zero, and the func- tion returns the number of code units used, excluding the trailing zero. If the error number is unknown, the negative error code PCRE2_ERROR_BADDATA is returned. If the buffer is too small, the mes- sage is truncated (but still with a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned. None of the messages are very long; a buffer size of 120 code units is ample. EEXXTTRRAACCTTIINNGG CCAAPPTTUURREEDD SSUUBBSSTTRRIINNGGSS BBYY NNUUMMBBEERR iinntt ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnuummbbeerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, uuiinntt3322__tt _n_u_m_b_e_r,, PPCCRREE22__SSIIZZEE **_l_e_n_g_t_h));; iinntt ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnuummbbeerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, uuiinntt3322__tt _n_u_m_b_e_r,, PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; iinntt ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnuummbbeerr((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, uuiinntt3322__tt _n_u_m_b_e_r,, PPCCRREE22__UUCCHHAARR ****_b_u_f_f_e_r_p_t_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; vvooiidd ppccrree22__ssuubbssttrriinngg__ffrreeee((PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r));; Captured substrings can be accessed directly by using the ovector as described above. For convenience, auxiliary functions are provided for extracting captured substrings as new, separate, zero-terminated strings. A substring that contains a binary zero is correctly extracted and has a further zero added on the end, but the result is not, of course, a C string. The functions in this section identify substrings by number. The number zero refers to the entire matched substring, with higher numbers refer- ring to substrings captured by parenthesized groups. After a partial match, only substring zero is available. An attempt to extract any other substring gives the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for extracting captured substrings by name. If a pattern uses the \K escape sequence within a positive assertion, the reported start of a successful match can be greater than the end of the match. For example, if the pattern (?=ab\K) is matched against "ab", the start and end offset values for the match are 2 and 0. In this situation, calling these functions with a zero substring number extracts a zero-length empty string. You can find the length in code units of a captured substring without extracting it by calling ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnuummbbeerr(()). The first argument is a pointer to the match data block, the second is the group number, and the third is a pointer to a variable into which the length is placed. If you just want to know whether or not the substring has been captured, you can pass the third argument as NULL. The ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnuummbbeerr(()) function copies a captured sub- string into a supplied buffer, whereas ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnuummbbeerr(()) copies it into new memory, obtained using the same memory allocation function that was used for the match data block. The first two argu- ments of these functions are a pointer to the match data block and a capturing group number. The final arguments of ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnuummbbeerr(()) are a pointer to the buffer and a pointer to a variable that contains its length in code units. This is updated to contain the actual number of code units used for the extracted substring, excluding the terminating zero. For ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnuummbbeerr(()) the third and fourth arguments point to variables that are updated with a pointer to the new memory and the number of code units that comprise the substring, again excluding the terminating zero. When the substring is no longer needed, the memory should be freed by calling ppccrree22__ssuubbssttrriinngg__ffrreeee(()). The return value from all these functions is zero for success, or a negative error code. If the pattern match failed, the match failure code is returned. If a substring number greater than zero is used after a partial match, PCRE2_ERROR_PARTIAL is returned. Other possible error codes are: PCRE2_ERROR_NOMEMORY The buffer was too small for ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnuummbbeerr(()), or the attempt to get memory failed for ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnuummbbeerr(()). PCRE2_ERROR_NOSUBSTRING There is no substring with that number in the pattern, that is, the number is greater than the number of capturing parentheses. PCRE2_ERROR_UNAVAILABLE The substring number, though not greater than the number of captures in the pattern, is greater than the number of slots in the ovector, so the substring could not be captured. PCRE2_ERROR_UNSET The substring did not participate in the match. For example, if the pattern is (abc)|(def) and the subject is "def", and the ovector con- tains at least two capturing slots, substring number 1 is unset. EEXXTTRRAACCTTIINNGG AA LLIISSTT OOFF AALLLL CCAAPPTTUURREEDD SSUUBBSSTTRRIINNGGSS iinntt ppccrree22__ssuubbssttrriinngg__lliisstt__ggeett((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__UUCCHHAARR ******_l_i_s_t_p_t_r,, PPCCRREE22__SSIIZZEE ****_l_e_n_g_t_h_s_p_t_r));; vvooiidd ppccrree22__ssuubbssttrriinngg__lliisstt__ffrreeee((PPCCRREE22__SSPPTTRR **_l_i_s_t));; The ppccrree22__ssuubbssttrriinngg__lliisstt__ggeett(()) function extracts all available sub- strings and builds a list of pointers to them. It also (optionally) builds a second list that contains their lengths (in code units), excluding a terminating zero that is added to each of them. All this is done in a single block of memory that is obtained using the same memory allocation function that was used to get the match data block. This function must be called only after a successful match. If called after a partial match, the error code PCRE2_ERROR_PARTIAL is returned. The address of the memory block is returned via _l_i_s_t_p_t_r, which is also the start of the list of string pointers. The end of the list is marked by a NULL pointer. The address of the list of lengths is returned via _l_e_n_g_t_h_s_p_t_r. If your strings do not contain binary zeros and you do not therefore need the lengths, you may supply NULL as the lleennggtthhssppttrr argu- ment to disable the creation of a list of lengths. The yield of the function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the mem- ory block could not be obtained. When the list is no longer needed, it should be freed by calling ppccrree22__ssuubbssttrriinngg__lliisstt__ffrreeee(()). If this function encounters a substring that is unset, which can happen when capturing subpattern number _n_+_1 matches some part of the subject, but subpattern _n has not been used at all, it returns an empty string. This can be distinguished from a genuine zero-length substring by inspecting the appropriate offset in the ovector, which contain PCRE2_UNSET for unset substrings, or by calling ppccrree22__ssuubb-- ssttrriinngg__lleennggtthh__bbyynnuummbbeerr(()). EEXXTTRRAACCTTIINNGG CCAAPPTTUURREEDD SSUUBBSSTTRRIINNGGSS BBYY NNAAMMEE iinntt ppccrree22__ssuubbssttrriinngg__nnuummbbeerr__ffrroomm__nnaammee((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _n_a_m_e));; iinntt ppccrree22__ssuubbssttrriinngg__lleennggtthh__bbyynnaammee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__SSIIZZEE **_l_e_n_g_t_h));; iinntt ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnaammee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; iinntt ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnaammee((ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__UUCCHHAARR ****_b_u_f_f_e_r_p_t_r,, PPCCRREE22__SSIIZZEE **_b_u_f_f_l_e_n));; vvooiidd ppccrree22__ssuubbssttrriinngg__ffrreeee((PPCCRREE22__UUCCHHAARR **_b_u_f_f_e_r));; To extract a substring by name, you first have to find associated num- ber. For example, for this pattern: (a+)b(?\d+)... the number of the subpattern called "xxx" is 2. If the name is known to be unique (PCRE2_DUPNAMES was not set), you can find the number from the name by calling ppccrree22__ssuubbssttrriinngg__nnuummbbeerr__ffrroomm__nnaammee(()). The first argu- ment is the compiled pattern, and the second is the name. The yield of the function is the subpattern number, PCRE2_ERROR_NOSUBSTRING if there is no subpattern of that name, or PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one subpattern of that name. Given the number, you can extract the substring directly from the ovector, or use one of the "bynumber" functions described above. For convenience, there are also "byname" functions that correspond to the "bynumber" functions, the only difference being that the second argument is a name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate names, these functions scan all the groups with the given name, and return the first named string that is set. If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is returned. If all groups with the name have numbers that are greater than the number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there is at least one group with a slot in the ovector, but no group is found to be set, PCRE2_ERROR_UNSET is returned. WWaarrnniinngg:: If the pattern uses the (?| feature to set up multiple subpat- terns with the same number, as described in the section on duplicate subpattern numbers in the ppccrree22ppaatttteerrnn page, you cannot use names to distinguish the different subpatterns, because names are not included in the compiled code. The matching process uses only numbers. For this reason, the use of different names for subpatterns of the same number causes an error at compile time. CCRREEAATTIINNGG AA NNEEWW SSTTRRIINNGG WWIITTHH SSUUBBSSTTIITTUUTTIIOONNSS iinntt ppccrree22__ssuubbssttiittuuttee((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, PPCCRREE22__SSPPTTRR _r_e_p_l_a_c_e_m_e_n_t,, PPCCRREE22__SSIIZZEE _r_l_e_n_g_t_h,, PPCCRREE22__UUCCHHAARR **_o_u_t_p_u_t_b_u_f_f_e_r_f_P_, PPCCRREE22__SSIIZZEE **_o_u_t_l_e_n_g_t_h_p_t_r));; This function calls ppccrree22__mmaattcchh(()) and then makes a copy of the subject string in _o_u_t_p_u_t_b_u_f_f_e_r, replacing the part that was matched with the _r_e_p_l_a_c_e_m_e_n_t string, whose length is supplied in rrlleennggtthh. This can be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. Matches in which a \K item in a lookahead in the pattern causes the match to end before it starts are not supported, and give rise to an error return. The first seven arguments of ppccrree22__ssuubbssttiittuuttee(()) are the same as for ppccrree22__mmaattcchh(()), except that the partial matching options are not permit- ted, and _m_a_t_c_h___d_a_t_a may be passed as NULL, in which case a match data block is obtained and freed within this function, using memory manage- ment functions from the match context, if provided, or else those that were used to allocate memory for the compiled code. The _o_u_t_l_e_n_g_t_h_p_t_r argument must point to a variable that contains the length, in code units, of the output buffer. If the function is suc- cessful, the value is updated to contain the length of the new string, excluding the trailing zero that is automatically added. If the function is not successful, the value set via _o_u_t_l_e_n_g_t_h_p_t_r depends on the type of error. For syntax errors in the replacement string, the value is the offset in the replacement string where the error was detected. For other errors, the value is PCRE2_UNSET by default. This includes the case of the output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set (see below), in which case the value is the minimum length needed, including space for the trailing zero. Note that in order to compute the required length, ppccrree22__ssuubbssttiittuuttee(()) has to simulate all the matching and copying, instead of giving an error return as soon as the buffer overflows. Note also that the length is in code units, not bytes. In the replacement string, which is interpreted as a UTF string in UTF mode, and is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option is set, a dollar character is an escape character that can spec- ify the insertion of characters from capturing groups or (*MARK), (*PRUNE), or (*THEN) items in the pattern. The following forms are always recognized: $$ insert a dollar character $ or ${} insert the contents of group $*MARK or ${*MARK} insert a (*MARK), (*PRUNE), or (*THEN) name Either a group number or a group name can be given for . Curly brackets are required only if the following character would be inter- preted as part of the number or name. The number may be zero to include the entire matched string. For example, if the pattern a(b)c is matched with "=abc=" and the replacement string "+$1$0$1+", the result is "=+babcb+=". $*MARK inserts the name from the last encountered (*MARK), (*PRUNE), or (*THEN) on the matching path that has a name. (*MARK) must always include a name, but (*PRUNE) and (*THEN) need not. For example, in the case of (*MARK:A)(*PRUNE) the name inserted is "A", but for (*MARK:A)(*PRUNE:B) the relevant name is "B". This facility can be used to perform simple simultaneous substitutions, as this ppccrree22tteesstt example shows: /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK} apple lemon 2: pear orange As well as the usual options for ppccrree22__mmaattcchh(()), a number of additional options can be set in the _o_p_t_i_o_n_s argument of ppccrree22__ssuubbssttiittuuttee(()). PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string, replacing every matching substring. If this option is not set, only the first matching substring is replaced. The search for matches takes place in the original subject string (that is, previous replace- ments do not affect it). Iteration is implemented by advancing the _s_t_a_r_t_o_f_f_s_e_t value for each search, which is always passed the entire subject string. If an offset limit is set in the match context, search- ing stops when that limit is reached. You can restrict the effect of a global substitution to a portion of the subject string by setting either or both of _s_t_a_r_t_o_f_f_s_e_t and an off- set limit. Here is a _p_c_r_e_2_t_e_s_t example: /B/g,replace=!,use_offset_limit ABC ABC ABC ABC\=offset=3,offset_limit=12 2: ABC A!C A!C ABC When continuing with global substitutions after matching a substring with zero length, an attempt to find a non-empty match at the same off- set is performed. If this is not successful, the offset is advanced by one character except when CRLF is a valid newline sequence and the next two characters are CR, LF. In this case, the offset is advanced by two characters. PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is too small. The default action is to return PCRE2_ERROR_NOMEM- ORY immediately. If this option is set, however, ppccrree22__ssuubbssttiittuuttee(()) continues to go through the motions of matching and substituting (with- out, of course, writing anything) in order to compute the size of buf- fer that is needed. This value is passed back via the _o_u_t_l_e_n_g_t_h_p_t_r variable, with the result of the function still being PCRE2_ERROR_NOMEMORY. Passing a buffer size of zero is a permitted way of finding out how much memory is needed for given substitution. However, this does mean that the entire operation is carried out twice. Depending on the appli- cation, it may be more efficient to allocate a large buffer and free the excess afterwards, instead of using PCRE2_SUBSTITUTE_OVER- FLOW_LENGTH. PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capturing groups that do not appear in the pattern to be treated as unset groups. This option should be used with care, because it means that a typo in a group name or number no longer causes the PCRE2_ERROR_NOSUBSTRING error. PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capturing groups (including unknown groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty strings when inserted as described above. If this option is not set, an attempt to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does not influence the extended substitution syntax described below. PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the replacement string. Without this option, only the dollar character is special, and only the group insertion forms listed above are valid. When PCRE2_SUBSTITUTE_EXTENDED is set, two things change: Firstly, backslash in a replacement string is interpreted as an escape character. The usual forms such as \n or \x{ddd} can be used to specify particular character codes, and backslash followed by any non-alphanu- meric character quotes that character. Extended quoting can be coded using \Q...\E, exactly as in pattern strings. There are also four escape sequences for forcing the case of inserted letters. The insertion mechanism has three states: no case forcing, force upper case, and force lower case. The escape sequences change the current state: \U and \L change to upper or lower case forcing, respec- tively, and \E (when not terminating a \Q quoted sequence) reverts to no case forcing. The sequences \u and \l force the next character (if it is a letter) to upper or lower case, respectively, and then the state automatically reverts to no case forcing. Case forcing applies to all inserted characters, including those from captured groups and let- ters within \Q...\E quoted sequences. Note that case forcing sequences such as \U...\E do not nest. For exam- ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no effect. The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more flexibility to group substitution. The syntax is similar to that used by Bash: ${:-} ${:+:} As before, may be a group number or a name. The first form speci- fies a default value. If group is set, its value is inserted; if not, is expanded and the result inserted. The second form specifies strings that are expanded and inserted when group is set or unset, respectively. The first form is just a convenient shorthand for ${:+${}:} Backslash can be used to escape colons and closing curly brackets in the replacement strings. A change of the case forcing state within a replacement string remains in force afterwards, as shown in this ppccrree22tteesstt example: /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo body 1: hello somebody 1: HELLO The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown groups in the extended syntax forms to be treated as unset. If successful, ppccrree22__ssuubbssttiittuuttee(()) returns the number of replacements that were made. This may be zero if no matches were found, and is never greater than 1 unless PCRE2_SUBSTITUTE_GLOBAL is set. In the event of an error, a negative error code is returned. Except for PCRE2_ERROR_NOMATCH (which is never returned), errors from ppccrree22__mmaattcchh(()) are passed straight back. PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring inser- tion, unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set. PCRE2_ERROR_UNSET is returned for an unset substring insertion (includ- ing an unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple (non-extended) syntax is used and PCRE2_SUBSTI- TUTE_UNSET_EMPTY is not set. PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is needed is returned via _o_u_t_l_e_n_g_t_h_p_t_r. Note that this does not happen by default. PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REP- MISSINGBRACE (closing curly bracket not found), PCRE2_ERROR_BADSUBSTI- TUTION (syntax error in extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before it started, which can happen if \K is used in an assertion). As for all PCRE2 errors, a text message that describes the error can be obtained by calling the ppccrree22__ggeett__eerrrroorr__mmeessssaaggee(()) function (see "Obtaining a textual error message" above). DDUUPPLLIICCAATTEE SSUUBBPPAATTTTEERRNN NNAAMMEESS iinntt ppccrree22__ssuubbssttrriinngg__nnaammeettaabbllee__ssccaann((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _n_a_m_e,, PPCCRREE22__SSPPTTRR **_f_i_r_s_t,, PPCCRREE22__SSPPTTRR **_l_a_s_t));; When a pattern is compiled with the PCRE2_DUPNAMES option, names for subpatterns are not required to be unique. Duplicate names are always allowed for subpatterns with the same number, created by using the (?| feature. Indeed, if such subpatterns are named, they are required to use the same names. Normally, patterns with duplicate names are such that in any one match, only one of the named subpatterns participates. An example is shown in the ppccrree22ppaatttteerrnn documentation. When duplicates are present, ppccrree22__ssuubbssttrriinngg__ccooppyy__bbyynnaammee(()) and ppccrree22__ssuubbssttrriinngg__ggeett__bbyynnaammee(()) return the first substring corresponding to the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is returned. The ppccrree22__ssuubbssttrriinngg__nnuummbbeerr__ffrroomm__nnaammee(()) function returns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names. If you want to get full details of all captured substrings for a given name, you must use the ppccrree22__ssuubbssttrriinngg__nnaammeettaabbllee__ssccaann(()) function. The first argument is the compiled pattern, and the second is the name. If the third and fourth arguments are NULL, the function returns a group number for a unique name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise. When the third and fourth arguments are not NULL, they must be pointers to variables that are updated by the function. After it has run, they point to the first and last entries in the name-to-number table for the given name, and the function returns the length of each entry in code units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name. The format of the name table is described above in the section entitled _I_n_f_o_r_m_a_t_i_o_n _a_b_o_u_t _a _p_a_t_t_e_r_n. Given all the relevant entries for the name, you can extract each of their numbers, and hence the captured data. FFIINNDDIINNGG AALLLL PPOOSSSSIIBBLLEE MMAATTCCHHEESS AATT OONNEE PPOOSSIITTIIOONN The traditional matching function uses a similar algorithm to Perl, which stops when it finds the first match at a given point in the sub- ject. If you want to find all possible matches, or the longest possible match at a given position, consider using the alternative matching function (see below) instead. If you cannot use the alternative func- tion, you can kludge it up by making use of the callout facility, which is described in the ppccrree22ccaalllloouutt documentation. What you have to do is to insert a callout right at the end of the pat- tern. When your callout function is called, extract and save the cur- rent matched substring. Then return 1, which forces ppccrree22__mmaattcchh(()) to backtrack and try other alternatives. Ultimately, when it runs out of matches, ppccrree22__mmaattcchh(()) will yield PCRE2_ERROR_NOMATCH. MMAATTCCHHIINNGG AA PPAATTTTEERRNN:: TTHHEE AALLTTEERRNNAATTIIVVEE FFUUNNCCTTIIOONN iinntt ppccrree22__ddffaa__mmaattcchh((ccoonnsstt ppccrree22__ccooddee **_c_o_d_e,, PPCCRREE22__SSPPTTRR _s_u_b_j_e_c_t,, PPCCRREE22__SSIIZZEE _l_e_n_g_t_h,, PPCCRREE22__SSIIZZEE _s_t_a_r_t_o_f_f_s_e_t,, uuiinntt3322__tt _o_p_t_i_o_n_s,, ppccrree22__mmaattcchh__ddaattaa **_m_a_t_c_h___d_a_t_a,, ppccrree22__mmaattcchh__ccoonntteexxtt **_m_c_o_n_t_e_x_t,, iinntt **_w_o_r_k_s_p_a_c_e,, PPCCRREE22__SSIIZZEE _w_s_c_o_u_n_t));; The function ppccrree22__ddffaa__mmaattcchh(()) is called to match a subject string against a compiled pattern, using a matching algorithm that scans the subject string just once (not counting lookaround assertions), and does not backtrack. This has different characteristics to the normal algo- rithm, and is not compatible with Perl. Some of the features of PCRE2 patterns are not supported. Nevertheless, there are times when this kind of matching can be useful. For a discussion of the two matching algorithms, and a list of features that ppccrree22__ddffaa__mmaattcchh(()) does not sup- port, see the ppccrree22mmaattcchhiinngg documentation. The arguments for the ppccrree22__ddffaa__mmaattcchh(()) function are the same as for ppccrree22__mmaattcchh(()), plus two extras. The ovector within the match data block is used in a different way, and this is described below. The other com- mon arguments are used in the same way as for ppccrree22__mmaattcchh(()), so their description is not repeated here. The two additional arguments provide workspace for the function. The workspace vector should contain at least 20 elements. It is used for keeping track of multiple paths through the pattern tree. More workspace is needed for patterns and subjects where there are a lot of potential matches. Here is an example of a simple call to ppccrree22__ddffaa__mmaattcchh(()): int wspace[20]; pcre2_match_data *md = pcre2_match_data_create(4, NULL); int rc = pcre2_dfa_match( re, /* result of pcre2_compile() */ "some string", /* the subject string */ 11, /* the length of the subject string */ 0, /* start at offset 0 in the subject */ 0, /* default options */ md, /* the match data block */ NULL, /* a match context; NULL means use defaults */ wspace, /* working space vector */ 20); /* number of elements (NOT size in bytes) */ OOppttiioonn bbiittss ffoorr ppccrree__ddffaa__mmaattcchh(()) The unused bits of the _o_p_t_i_o_n_s argument for ppccrree22__ddffaa__mmaattcchh(()) must be zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDAN- CHORED, PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, and PCRE2_DFA_RESTART. All but the last four of these are exactly the same as for ppccrree22__mmaattcchh(()), so their description is not repeated here. PCRE2_PARTIAL_HARD PCRE2_PARTIAL_SOFT These have the same general effect as they do for ppccrree22__mmaattcchh(()), but the details are slightly different. When PCRE2_PARTIAL_HARD is set for ppccrree22__ddffaa__mmaattcchh(()), it returns PCRE2_ERROR_PARTIAL if the end of the subject is reached and there is still at least one matching possibility that requires additional characters. This happens even if some complete matches have already been found. When PCRE2_PARTIAL_SOFT is set, the return code PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL if the end of the subject is reached, there have been no complete matches, but there is still at least one matching possibility. The por- tion of the string that was inspected when the longest partial match was found is set as the first matching string in both cases. There is a more detailed discussion of partial and multi-segment matching, with examples, in the ppccrree22ppaarrttiiaall documentation. PCRE2_DFA_SHORTEST Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to stop as soon as it has found one match. Because of the way the alterna- tive algorithm works, this is necessarily the shortest possible match at the first possible matching point in the subject string. PCRE2_DFA_RESTART When ppccrree22__ddffaa__mmaattcchh(()) returns a partial match, it is possible to call it again, with additional subject characters, and have it continue with the same match. The PCRE2_DFA_RESTART option requests this action; when it is set, the _w_o_r_k_s_p_a_c_e and _w_s_c_o_u_n_t options must reference the same vector as before because data about the match so far is left in them after a partial match. There is more discussion of this facility in the ppccrree22ppaarrttiiaall documentation. SSuucccceessssffuull rreettuurrnnss ffrroomm ppccrree22__ddffaa__mmaattcchh(()) When ppccrree22__ddffaa__mmaattcchh(()) succeeds, it may have matched more than one sub- string in the subject. Note, however, that all the matches from one run of the function start at the same point in the subject. The shorter matches are all initial substrings of the longer matches. For example, if the pattern <.*> is matched against the string This is no more the three matched strings are On success, the yield of the function is a number greater than zero, which is the number of matched substrings. The offsets of the sub- strings are returned in the ovector, and can be extracted by number in the same way as for ppccrree22__mmaattcchh(()), but the numbers bear no relation to any capturing groups that may exist in the pattern, because DFA match- ing does not support group capture. Calls to the convenience functions that extract substrings by name return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a DFA match. The convenience functions that extract substrings by number never return PCRE2_ERROR_NOSUBSTRING, and the meanings of some other errors are slightly different: PCRE2_ERROR_UNAVAILABLE The ovector is not big enough to include a slot for the given substring number. PCRE2_ERROR_UNSET There is a slot in the ovector for this substring, but there were insufficient matches to fill it. The matched strings are stored in the ovector in reverse order of length; that is, the longest matching string is first. If there were too many matches to fit into the ovector, the yield of the function is zero, and the vector is filled with the longest matches. NOTE: PCRE2's "auto-possessification" optimization usually applies to character repeats at the end of a pattern (as well as internally). For example, the pattern "a\d+" is compiled as if it were "a\d++". For DFA matching, this means that only one possible match is found. If you really do want multiple matches in such cases, either use an ungreedy repeat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when compiling. EErrrroorr rreettuurrnnss ffrroomm ppccrree22__ddffaa__mmaattcchh(()) The ppccrree22__ddffaa__mmaattcchh(()) function returns a negative number when it fails. Many of the errors are the same as for ppccrree22__mmaattcchh(()), as described above. There are in addition the following errors that are specific to ppccrree22__ddffaa__mmaattcchh(()): PCRE2_ERROR_DFA_UITEM This return is given if ppccrree22__ddffaa__mmaattcchh(()) encounters an item in the pattern that it does not support, for instance, the use of \C in a UTF mode or a back reference. PCRE2_ERROR_DFA_UCOND This return is given if ppccrree22__ddffaa__mmaattcchh(()) encounters a condition item that uses a back reference for the condition, or a test for recursion in a specific group. These are not supported. PCRE2_ERROR_DFA_WSSIZE This return is given if ppccrree22__ddffaa__mmaattcchh(()) runs out of space in the _w_o_r_k_s_p_a_c_e vector. PCRE2_ERROR_DFA_RECURSE When a recursive subpattern is processed, the matching function calls itself recursively, using private memory for the ovector and _w_o_r_k_s_p_a_c_e. This error is given if the internal ovector is not large enough. This should be extremely rare, as a vector of size 1000 is used. PCRE2_ERROR_DFA_BADRESTART When ppccrree22__ddffaa__mmaattcchh(()) is called with the PPCCRREE22__DDFFAA__RREESSTTAARRTT option, some plausibility checks are made on the contents of the workspace, which should contain data about the previous partial match. If any of these checks fail, this error is given. SSEEEE AALLSSOO ppccrree22bbuuiilldd(3), ppccrree22ccaalllloouutt(3), ppccrree22ddeemmoo((33)), ppccrree22mmaattcchhiinngg(3), ppccrree22ppaarrttiiaall(3), ppccrree22ppoossiixx(3), ppccrree22ssaammppllee(3), ppccrree22uunniiccooddee(3). AAUUTTHHOORR Philip Hazel University Computing Service Cambridge, England. RREEVVIISSIIOONN Last updated: 31 December 2017 Copyright (c) 1997-2017 University of Cambridge. PCRE2 10.31 31 December 2017 PCRE2API(3)