lib/pipe-filter-aux.h

   1 /* Auxiliary code for filtering of data through a subprocess.
   2    Copyright (C) 2001-2003, 2008-2024 Free Software Foundation, Inc.
   3    Written by Bruno Haible <haible@clisp.cons.org>, 2009.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU 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 General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE.  */
  19 #if !_GL_CONFIG_H_INCLUDED
  20  #error "Please include config.h first."
  21 #endif
  22
  23 _GL_INLINE_HEADER_BEGIN
  24 #ifndef PIPE_FILTER_AUX_INLINE
  25 # define PIPE_FILTER_AUX_INLINE _GL_INLINE
  26 #endif
  27
  28 #if defined _WIN32 && ! defined __CYGWIN__
  29 /* In the pipe-filter-* modules we want to use the write() function that is
  30    not overridden to emulate SIGPIPE behaviour, because we don't want force
  31    the caller to do
  32      signal (SIGPIPE, SIG_DFL);
  33    To reproduce the problem, use a gnulib testdir for the modules
  34    'pipe-filter-gi', 'write', 'sigpipe'.  */
  35 # undef write
  36 # define write _write
  37 #endif
  38
  39 #ifndef SSIZE_MAX
  40 # define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
  41 #endif
  42 #ifdef _AIX
  43 /* On AIX, despite having select() and despite having put the file descriptor
  44    in non-blocking mode, it can happen that select() reports that fd[1] is
  45    writable but writing a large amount of data to fd[1] then fails with errno
  46    EAGAIN.  Seen with test-pipe-filter-gi1 on AIX 7.2, with data sizes of
  47    29 KB.  So, limit the size of data passed to the write() call to 4 KB.  */
  48 # undef SSIZE_MAX
  49 # define SSIZE_MAX 4096
  50 #endif
  51
  52 /* We use a child process, and communicate through a bidirectional pipe.
  53    To avoid deadlocks, let the child process decide when it wants to read
  54    or to write, and let the parent behave accordingly.  The parent uses
  55    select() to know whether it must write or read.  On platforms without
  56    select(), we use non-blocking I/O.  (This means the parent is busy
  57    looping while waiting for the child.  Not good.  But hardly any platform
  58    lacks select() nowadays.)  */
  59
  60 /* On BeOS and OS/2 kLIBC select() works only on sockets, not on normal file
  61    descriptors.  */
  62 #if defined __BEOS__ || defined __KLIBC__
  63 # undef HAVE_SELECT
  64 #endif
  65
  66 #ifdef EINTR
  67
  68 /* EINTR handling for close(), read(), write(), select().
  69    These functions can return -1/EINTR even though we don't have any
  70    signal handlers set up, namely when we get interrupted via SIGSTOP.  */
  71
  72 PIPE_FILTER_AUX_INLINE int
  73 nonintr_close (int fd)
  74 {
  75   int retval;
  76
  77   do
  78     retval = close (fd);
  79   while (retval < 0 && errno == EINTR);
  80
  81   return retval;
  82 }
  83 #undef close /* avoid warning related to gnulib module unistd */
  84 #define close nonintr_close
  85
  86 PIPE_FILTER_AUX_INLINE ssize_t
  87 nonintr_read (int fd, void *buf, size_t count)
  88 {
  89   ssize_t retval;
  90
  91   do
  92     retval = read (fd, buf, count);
  93   while (retval < 0 && errno == EINTR);
  94
  95   return retval;
  96 }
  97 #undef read /* avoid warning related to gnulib module unistd */
  98 #define read nonintr_read
  99
 100 PIPE_FILTER_AUX_INLINE ssize_t
 101 nonintr_write (int fd, const void *buf, size_t count)
 102 {
 103   ssize_t retval;
 104
 105   do
 106     retval = write (fd, buf, count);
 107   while (retval < 0 && errno == EINTR);
 108
 109   return retval;
 110 }
 111 #undef write /* avoid warning on VMS */
 112 #define write nonintr_write
 113
 114 #endif
 115
 116 /* Non-blocking I/O.  */
 117 #if HAVE_SELECT
 118 # define IS_EAGAIN(errcode) 0
 119 #else
 120 # ifdef EWOULDBLOCK
 121 #  define IS_EAGAIN(errcode) ((errcode) == EAGAIN || (errcode) == EWOULDBLOCK)
 122 # else
 123 #  define IS_EAGAIN(errcode) ((errcode) == EAGAIN)
 124 # endif
 125 #endif
 126
 127 _GL_INLINE_HEADER_END