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      1 /* Create a pipe, with specific opening flags.
      2    Copyright (C) 2009-2012 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 #include "binary-io.h"
     26 #include "verify.h"
     27 
     28 #if GNULIB_defined_O_NONBLOCK
     29 # include "nonblocking.h"
     30 #endif
     31 
     32 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
     33 /* Native Windows API.  */
     34 
     35 # include <io.h>
     36 
     37 #endif
     38 
     39 int
     40 pipe2 (int fd[2], int flags)
     41 {
     42   /* Mingw _pipe() corrupts fd on failure; also, if we succeed at
     43      creating the pipe but later fail at changing fcntl, we want
     44      to leave fd unchanged: http://austingroupbugs.net/view.php?id=467  */
     45   int tmp[2];
     46   tmp[0] = fd[0];
     47   tmp[1] = fd[1];
     48 
     49 #if HAVE_PIPE2
     50 # undef pipe2
     51   /* Try the system call first, if it exists.  (We may be running with a glibc
     52      that has the function but with an older kernel that lacks it.)  */
     53   {
     54     /* Cache the information whether the system call really exists.  */
     55     static int have_pipe2_really; /* 0 = unknown, 1 = yes, -1 = no */
     56     if (have_pipe2_really >= 0)
     57       {
     58         int result = pipe2 (fd, flags);
     59         if (!(result < 0 && errno == ENOSYS))
     60           {
     61             have_pipe2_really = 1;
     62             return result;
     63           }
     64         have_pipe2_really = -1;
     65       }
     66   }
     67 #endif
     68 
     69   /* Check the supported flags.  */
     70   if ((flags & ~(O_CLOEXEC | O_NONBLOCK | O_BINARY | O_TEXT)) != 0)
     71     {
     72       errno = EINVAL;
     73       return -1;
     74     }
     75 
     76 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
     77 /* Native Windows API.  */
     78 
     79   if (_pipe (fd, 4096, flags & ~O_NONBLOCK) < 0)
     80     {
     81       fd[0] = tmp[0];
     82       fd[1] = tmp[1];
     83       return -1;
     84     }
     85 
     86   /* O_NONBLOCK handling.
     87      On native Windows platforms, O_NONBLOCK is defined by gnulib.  Use the
     88      functions defined by the gnulib module 'nonblocking'.  */
     89 # if GNULIB_defined_O_NONBLOCK
     90   if (flags & O_NONBLOCK)
     91     {
     92       if (set_nonblocking_flag (fd[0], true) != 0
     93           || set_nonblocking_flag (fd[1], true) != 0)
     94         goto fail;
     95     }
     96 # else
     97   {
     98     verify (O_NONBLOCK == 0);
     99   }
    100 # endif
    101 
    102   return 0;
    103 
    104 #else
    105 /* Unix API.  */
    106 
    107   if (pipe (fd) < 0)
    108     return -1;
    109 
    110   /* POSIX <http://www.opengroup.org/onlinepubs/9699919799/functions/pipe.html>
    111      says that initially, the O_NONBLOCK and FD_CLOEXEC flags are cleared on
    112      both fd[0] and fd[1].  */
    113 
    114   /* O_NONBLOCK handling.
    115      On Unix platforms, O_NONBLOCK is defined by the system.  Use fcntl().  */
    116   if (flags & O_NONBLOCK)
    117     {
    118       int fcntl_flags;
    119 
    120       if ((fcntl_flags = fcntl (fd[1], F_GETFL, 0)) < 0
    121           || fcntl (fd[1], F_SETFL, fcntl_flags | O_NONBLOCK) == -1
    122           || (fcntl_flags = fcntl (fd[0], F_GETFL, 0)) < 0
    123           || fcntl (fd[0], F_SETFL, fcntl_flags | O_NONBLOCK) == -1)
    124         goto fail;
    125     }
    126 
    127   if (flags & O_CLOEXEC)
    128     {
    129       int fcntl_flags;
    130 
    131       if ((fcntl_flags = fcntl (fd[1], F_GETFD, 0)) < 0
    132           || fcntl (fd[1], F_SETFD, fcntl_flags | FD_CLOEXEC) == -1
    133           || (fcntl_flags = fcntl (fd[0], F_GETFD, 0)) < 0
    134           || fcntl (fd[0], F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
    135         goto fail;
    136     }
    137 
    138 # if O_BINARY
    139   if (flags & O_BINARY)
    140     {
    141       setmode (fd[1], O_BINARY);
    142       setmode (fd[0], O_BINARY);
    143     }
    144   else if (flags & O_TEXT)
    145     {
    146       setmode (fd[1], O_TEXT);
    147       setmode (fd[0], O_TEXT);
    148     }
    149 # endif
    150 
    151   return 0;
    152 
    153 #endif
    154 
    155 #if GNULIB_defined_O_NONBLOCK || \
    156   !((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__)
    157  fail:
    158   {
    159     int saved_errno = errno;
    160     close (fd[0]);
    161     close (fd[1]);
    162     fd[0] = tmp[0];
    163     fd[1] = tmp[1];
    164     errno = saved_errno;
    165     return -1;
    166   }
    167 #endif
    168 }
    169