Mail Archives: djgpp/1997/03/20/23:41:52
Regis BOSSUT wrote:
>
> Hi all!
>
> I wrote a small program to find out my LAN card MAC address, based on
> the example provided by Microsoft, using Netbios, adapted with help of
> intwin.hlp (interrupt 0x5c).
>
> It works fine when run as is, but gives incorrect results when run
> under GDB. Seems that memory is used differently, but I don't see why.
>
>
> _____ Start of adapt.c _____
> #include <stdio.h>
> #include <stdlib.h>
> #include <dpmi.h>
> #include <go32.h>
>
> #define BYTE unsigned char
> #define WORD unsigned short
> #define DWORD unsigned int
>
> typedef struct {
> BYTE ncb_command;
> #define NCBASTAT 0x33
> BYTE ncb_retcode, ncb_lsn, ncb_num;
> char *ncb_buffer; WORD ncb_length;
> BYTE ncb_callname[16], ncb_name[16];
> BYTE ncb_rto, ncb_sto;
> int (*ncb_post)();
> BYTE ncb_lana_num, ncb_cmd_cplt;
> char *ncb_vname;
> BYTE ncb_vnamelen;
> BYTE ncb_reserve[9];
> } NCB;
>
i don't know what you mean "memory is used differently". however, when
you are dealing with 16-bit interfaces that expect certain data at
certain offsets (into the struct), you need to pack your structs to
override the default 32 bit alignment of struct members.
here is how i did it:
/* Network Control Block (NCB) */
typedef struct {
BYTE cmd;
BYTE ret_code;
BYTE lsn;
BYTE ncb_num;
WORD io_off;
WORD io_seg;
WORD len;
BYTE rmt_name[NBNAMELENGTH];
BYTE lcl_name[NBNAMELENGTH];
BYTE rec_to;
BYTE snd_to;
WORD post_off;
WORD post_seg;
BYTE lana;
BYTE cmp_code;
BYTE rsrv[14];
}__attribute__((packed)) NCB;
basically, the sizeof your ncb struct has to be 64. check yours. BTW, why
is there a #define in the midle of the struct?
further, you cannot pass djgpp pointers (32-bit protected mode) to 16 bit
interfaces, you need to allocate dos memory (or use the transfer buffer;
see the FAQ) and communicate with netbios via that memory block.
if you promise not to advertise to the world how crappy a page it is, you
can take a look at:
http://www.people.cornell.edu/pages/asu1/netbios.htm
-- sinan.
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