From:	"Mark E." <snowball3 AT bigfoot DOT com>
To:	djgpp-workers AT delorie DOT com
Date:	Thu, 22 Mar 2001 00:07:55 -0500
MIME-Version:	1.0
Subject:	pipe() emulation
Message-ID:	<3AB9425B.11812.36ACFC@localhost>
X-mailer:	Pegasus Mail for Win32 (v3.12c)
Reply-To:	djgpp-workers AT delorie DOT com

Hi all,

This patch implements pipe() using a temporary file. It's based on the pipe.c 
replacement in bash 2.04 and is updated to use O_TEMPORARY. Comments and 
objections?

Index: pipe.c
===================================================================
RCS file: /cvs/djgpp/djgpp/src/libc/posix/unistd/pipe.c,v
retrieving revision 1.1
diff -c -p -r1.1 pipe.c
*** pipe.c	1995/04/01 23:49:02	1.1
--- pipe.c	2001/03/22 05:01:59
***************
*** 1,10 ****
  /* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
  #include <unistd.h>
! #include <errno.h>
  
  int
  pipe(int _fildes[2])
  {
!   errno = EACCES;
!   return -1;
  }
--- 1,53 ----
+ /* Copyright (C) 2001 DJ Delorie, see COPYING.DJ for details */
  /* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
  #include <unistd.h>
! #include <stdlib.h>
! #include <fcntl.h>
! #include <stdio.h>
! #include <sys/stat.h>
  
+ /* Emulate a pipe using a temporary file.  */
  int
  pipe(int _fildes[2])
  {
!   int ifd, ofd;
!   char temp_name[FILENAME_MAX + 1];
!   char *tname;
! 
!   tname = tmpnam(temp_name);
!   if (tname == NULL)
!     return -1;
!     
!   ofd = open(tname, O_WRONLY | O_CREAT | O_TRUNC | O_TEMPORARY, S_IWUSR);
!   if (ofd < 0)
!     return -1;
!     
!   /* Move the handle up so it doesn't count against the 20 handle
!      inherit limit.  */
!   if (ofd < 20)
!   {
!     int high_fd;
! 
!     high_fd = fcntl(ofd, F_DUPFD, 20);
!     close(ofd);
!     ofd = high_fd;
!   }
! 
!   ifd = open(tname, O_RDONLY | O_TEMPORARY, S_IWUSR);
!   if (ifd < 0)
!     return -1;
! 
!   /* Move this handle up too.  */
!   if (ifd < 20)
!   {
!     int high_fd;
!     high_fd = fcntl (ifd, F_DUPFD, 20);
!     close(ifd);
!     ifd = high_fd;
!   }
! 
!   _fildes[0] = ifd;
!   _fildes[1] = ofd;
!     
!   return 0;
  }

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