lib/write.c

   1 /* POSIX compatible write() function.
   2    Copyright (C) 2008-2011 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2008.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include <unistd.h>
  22
  23 /* Replace this function only if module 'nonblocking' or module 'sigpipe' is
  24    requested.  */
  25 #if GNULIB_NONBLOCKING || GNULIB_SIGPIPE
  26
  27 /* On native Windows platforms, SIGPIPE does not exist.  When write() is
  28    called on a pipe with no readers, WriteFile() fails with error
  29    GetLastError() = ERROR_NO_DATA, and write() in consequence fails with
  30    error EINVAL.  */
  31
  32 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  33
  34 #  include <errno.h>
  35 #  include <signal.h>
  36 #  include <io.h>
  37
  38 #  define WIN32_LEAN_AND_MEAN  /* avoid including junk */
  39 #  include <windows.h>
  40
  41 ssize_t
  42 rpl_write (int fd, const void *buf, size_t count)
  43 #undef write
  44 {
  45   for (;;)
  46     {
  47       ssize_t ret = write (fd, buf, count);
  48
  49       if (ret < 0)
  50         {
  51 #  if GNULIB_NONBLOCKING
  52           if (errno == ENOSPC)
  53             {
  54               HANDLE h = (HANDLE) _get_osfhandle (fd);
  55               if (GetFileType (h) == FILE_TYPE_PIPE)
  56                 {
  57                   /* h is a pipe or socket.  */
  58                   DWORD state;
  59                   if (GetNamedPipeHandleState (h, &state, NULL, NULL, NULL,
  60                                                NULL, 0)
  61                       && (state & PIPE_NOWAIT) != 0)
  62                     {
  63                       /* h is a pipe in non-blocking mode.
  64                          We can get here in four situations:
  65                            1. When the pipe buffer is full.
  66                            2. When count <= pipe_buf_size and the number of
  67                               free bytes in the pipe buffer is < count.
  68                            3. When count > pipe_buf_size and the number of free
  69                               bytes in the pipe buffer is > 0, < pipe_buf_size.
  70                            4. When count > pipe_buf_size and the pipe buffer is
  71                               entirely empty.
  72                          The cases 1 and 2 are POSIX compliant.  In cases 3 and
  73                          4 POSIX specifies that write() must split the request
  74                          and succeed with a partial write.  We fix case 4.
  75                          We don't fix case 3 because it is not essential for
  76                          programs.  */
  77                       DWORD out_size; /* size of the buffer for outgoing data */
  78                       DWORD in_size;  /* size of the buffer for incoming data */
  79                       if (GetNamedPipeInfo (h, NULL, &out_size, &in_size, NULL))
  80                         {
  81                           size_t reduced_count = count;
  82                           /* In theory we need only one of out_size, in_size.
  83                              But I don't know which of the two.  The description
  84                              is ambiguous.  */
  85                           if (out_size != 0 && out_size < reduced_count)
  86                             reduced_count = out_size;
  87                           if (in_size != 0 && in_size < reduced_count)
  88                             reduced_count = in_size;
  89                           if (reduced_count < count)
  90                             {
  91                               /* Attempt to write only the first part.  */
  92                               count = reduced_count;
  93                               continue;
  94                             }
  95                         }
  96                       /* Change errno from ENOSPC to EAGAIN.  */
  97                       errno = EAGAIN;
  98                     }
  99                 }
 100             }
 101           else
 102 #  endif
 103             {
 104 #  if GNULIB_SIGPIPE
 105               if (GetLastError () == ERROR_NO_DATA
 106                   && GetFileType ((HANDLE) _get_osfhandle (fd))
 107                      == FILE_TYPE_PIPE)
 108                 {
 109                   /* Try to raise signal SIGPIPE.  */
 110                   raise (SIGPIPE);
 111                   /* If it is currently blocked or ignored, change errno from
 112                      EINVAL to EPIPE.  */
 113                   errno = EPIPE;
 114                 }
 115 #  endif
 116             }
 117         }
 118       return ret;
 119     }
 120 }
 121
 122 # endif
 123 #endif