lib/pipe2.c

   1 /* Create a pipe, with specific opening flags.
   2    Copyright (C) 2009-2013 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, see <http://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <unistd.h>
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24
  25 #if GNULIB_BINARY_IO
  26 # include "binary-io.h"
  27 #endif
  28
  29 #include "verify.h"
  30
  31 #if GNULIB_defined_O_NONBLOCK
  32 # include "nonblocking.h"
  33 #endif
  34
  35 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  36 /* Native Windows API.  */
  37
  38 # include <io.h>
  39
  40 #endif
  41
  42 int
  43 pipe2 (int fd[2], int flags)
  44 {
  45   /* Mingw _pipe() corrupts fd on failure; also, if we succeed at
  46      creating the pipe but later fail at changing fcntl, we want
  47      to leave fd unchanged: http://austingroupbugs.net/view.php?id=467  */
  48   int tmp[2];
  49   tmp[0] = fd[0];
  50   tmp[1] = fd[1];
  51
  52 #if HAVE_PIPE2
  53 # undef pipe2
  54   /* Try the system call first, if it exists.  (We may be running with a glibc
  55      that has the function but with an older kernel that lacks it.)  */
  56   {
  57     /* Cache the information whether the system call really exists.  */
  58     static int have_pipe2_really; /* 0 = unknown, 1 = yes, -1 = no */
  59     if (have_pipe2_really >= 0)
  60       {
  61         int result = pipe2 (fd, flags);
  62         if (!(result < 0 && errno == ENOSYS))
  63           {
  64             have_pipe2_really = 1;
  65             return result;
  66           }
  67         have_pipe2_really = -1;
  68       }
  69   }
  70 #endif
  71
  72   /* Check the supported flags.  */
  73   if ((flags & ~(O_CLOEXEC | O_NONBLOCK | O_BINARY | O_TEXT)) != 0)
  74     {
  75       errno = EINVAL;
  76       return -1;
  77     }
  78
  79 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  80 /* Native Windows API.  */
  81
  82   if (_pipe (fd, 4096, flags & ~O_NONBLOCK) < 0)
  83     {
  84       fd[0] = tmp[0];
  85       fd[1] = tmp[1];
  86       return -1;
  87     }
  88
  89   /* O_NONBLOCK handling.
  90      On native Windows platforms, O_NONBLOCK is defined by gnulib.  Use the
  91      functions defined by the gnulib module 'nonblocking'.  */
  92 # if GNULIB_defined_O_NONBLOCK
  93   if (flags & O_NONBLOCK)
  94     {
  95       if (set_nonblocking_flag (fd[0], true) != 0
  96           || set_nonblocking_flag (fd[1], true) != 0)
  97         goto fail;
  98     }
  99 # else
 100   {
 101     verify (O_NONBLOCK == 0);
 102   }
 103 # endif
 104
 105   return 0;
 106
 107 #else
 108 /* Unix API.  */
 109
 110   if (pipe (fd) < 0)
 111     return -1;
 112
 113   /* POSIX <http://www.opengroup.org/onlinepubs/9699919799/functions/pipe.html>
 114      says that initially, the O_NONBLOCK and FD_CLOEXEC flags are cleared on
 115      both fd[0] and fd[1].  */
 116
 117   /* O_NONBLOCK handling.
 118      On Unix platforms, O_NONBLOCK is defined by the system.  Use fcntl().  */
 119   if (flags & O_NONBLOCK)
 120     {
 121       int fcntl_flags;
 122
 123       if ((fcntl_flags = fcntl (fd[1], F_GETFL, 0)) < 0
 124           || fcntl (fd[1], F_SETFL, fcntl_flags | O_NONBLOCK) == -1
 125           || (fcntl_flags = fcntl (fd[0], F_GETFL, 0)) < 0
 126           || fcntl (fd[0], F_SETFL, fcntl_flags | O_NONBLOCK) == -1)
 127         goto fail;
 128     }
 129
 130   if (flags & O_CLOEXEC)
 131     {
 132       int fcntl_flags;
 133
 134       if ((fcntl_flags = fcntl (fd[1], F_GETFD, 0)) < 0
 135           || fcntl (fd[1], F_SETFD, fcntl_flags | FD_CLOEXEC) == -1
 136           || (fcntl_flags = fcntl (fd[0], F_GETFD, 0)) < 0
 137           || fcntl (fd[0], F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
 138         goto fail;
 139     }
 140
 141 # if O_BINARY
 142   if (flags & O_BINARY)
 143     {
 144       setmode (fd[1], O_BINARY);
 145       setmode (fd[0], O_BINARY);
 146     }
 147   else if (flags & O_TEXT)
 148     {
 149       setmode (fd[1], O_TEXT);
 150       setmode (fd[0], O_TEXT);
 151     }
 152 # endif
 153
 154   return 0;
 155
 156 #endif
 157
 158 #if GNULIB_defined_O_NONBLOCK || \
 159   !((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__)
 160  fail:
 161   {
 162     int saved_errno = errno;
 163     close (fd[0]);
 164     close (fd[1]);
 165     fd[0] = tmp[0];
 166     fd[1] = tmp[1];
 167     errno = saved_errno;
 168     return -1;
 169   }
 170 #endif
 171 }