lib/write.c

   1 /* POSIX compatible write() function.
   2    Copyright (C) 2008-2024 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2008.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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 <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include <unistd.h>
  22
  23 /* On native Windows platforms, SIGPIPE does not exist.  When write() is
  24    called on a pipe with no readers, WriteFile() fails with error
  25    GetLastError() = ERROR_NO_DATA, and write() in consequence fails with
  26    error EINVAL.  */
  27
  28 #if defined _WIN32 && ! defined __CYGWIN__
  29
  30 # include <errno.h>
  31 # include <signal.h>
  32 # include <io.h>
  33
  34 # define WIN32_LEAN_AND_MEAN  /* avoid including junk */
  35 # include <windows.h>
  36
  37 # if HAVE_MSVC_INVALID_PARAMETER_HANDLER
  38 #  include "msvc-inval.h"
  39 # endif
  40 # if GNULIB_MSVC_NOTHROW
  41 #  include "msvc-nothrow.h"
  42 # else
  43 #  include <io.h>
  44 # endif
  45
  46 /* Don't assume that UNICODE is not defined.  */
  47 # undef GetNamedPipeHandleState
  48 # define GetNamedPipeHandleState GetNamedPipeHandleStateA
  49
  50 # undef write
  51
  52 # if HAVE_MSVC_INVALID_PARAMETER_HANDLER
  53 static ssize_t
  54 write_nothrow (int fd, const void *buf, size_t count)
  55 {
  56   ssize_t result;
  57
  58   TRY_MSVC_INVAL
  59     {
  60       result = _write (fd, buf, count);
  61     }
  62   CATCH_MSVC_INVAL
  63     {
  64       result = -1;
  65       errno = EBADF;
  66     }
  67   DONE_MSVC_INVAL;
  68
  69   return result;
  70 }
  71 # else
  72 #  define write_nothrow _write
  73 # endif
  74
  75 ssize_t
  76 rpl_write (int fd, const void *buf, size_t count)
  77 {
  78   for (;;)
  79     {
  80       ssize_t ret = write_nothrow (fd, buf, count);
  81
  82       if (ret < 0)
  83         {
  84 # if GNULIB_NONBLOCKING
  85           if (errno == ENOSPC)
  86             {
  87               HANDLE h = (HANDLE) _get_osfhandle (fd);
  88               if (GetFileType (h) == FILE_TYPE_PIPE)
  89                 {
  90                   /* h is a pipe or socket.  */
  91                   DWORD state;
  92                   if (GetNamedPipeHandleState (h, &state, NULL, NULL, NULL,
  93                                                NULL, 0)
  94                       && (state & PIPE_NOWAIT) != 0)
  95                     {
  96                       /* h is a pipe in non-blocking mode.
  97                          We can get here in four situations:
  98                            1. When the pipe buffer is full.
  99                            2. When count <= pipe_buf_size and the number of
 100                               free bytes in the pipe buffer is < count.
 101                            3. When count > pipe_buf_size and the number of free
 102                               bytes in the pipe buffer is > 0, < pipe_buf_size.
 103                            4. When count > pipe_buf_size and the pipe buffer is
 104                               entirely empty.
 105                          The cases 1 and 2 are POSIX compliant.  In cases 3 and
 106                          4 POSIX specifies that write() must split the request
 107                          and succeed with a partial write.  We fix case 4.
 108                          We don't fix case 3 because it is not essential for
 109                          programs.  */
 110                       DWORD out_size; /* size of the buffer for outgoing data */
 111                       DWORD in_size;  /* size of the buffer for incoming data */
 112                       if (GetNamedPipeInfo (h, NULL, &out_size, &in_size, NULL))
 113                         {
 114                           size_t reduced_count = count;
 115                           /* In theory we need only one of out_size, in_size.
 116                              But I don't know which of the two.  The description
 117                              is ambiguous.  */
 118                           if (out_size != 0 && out_size < reduced_count)
 119                             reduced_count = out_size;
 120                           if (in_size != 0 && in_size < reduced_count)
 121                             reduced_count = in_size;
 122                           if (reduced_count < count)
 123                             {
 124                               /* Attempt to write only the first part.  */
 125                               count = reduced_count;
 126                               continue;
 127                             }
 128                         }
 129                       /* Change errno from ENOSPC to EAGAIN.  */
 130                       errno = EAGAIN;
 131                     }
 132                 }
 133             }
 134           else
 135 # endif
 136             {
 137 # if GNULIB_SIGPIPE
 138               if (GetLastError () == ERROR_NO_DATA
 139                   && GetFileType ((HANDLE) _get_osfhandle (fd))
 140                      == FILE_TYPE_PIPE)
 141                 {
 142                   /* Try to raise signal SIGPIPE.  */
 143                   raise (SIGPIPE);
 144                   /* If it is currently blocked or ignored, change errno from
 145                      EINVAL to EPIPE.  */
 146                   errno = EPIPE;
 147                 }
 148 # endif
 149             }
 150         }
 151       return ret;
 152     }
 153 }
 154
 155 #endif