lib/pipe-filter-aux.h

   1 /* Auxiliary code for filtering of data through a subprocess.
   2    Copyright (C) 2001-2003, 2008-2021 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 #ifndef _GL_INLINE_HEADER_BEGIN
  19  #error "Please include config.h first."
  20 #endif
  21 _GL_INLINE_HEADER_BEGIN
  22 #ifndef PIPE_FILTER_AUX_INLINE
  23 # define PIPE_FILTER_AUX_INLINE _GL_INLINE
  24 #endif
  25
  26 #ifndef SSIZE_MAX
  27 # define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
  28 #endif
  29 #ifdef _AIX
  30 /* On AIX, despite having select() and despite having put the file descriptor
  31    in non-blocking mode, it can happen that select() reports that fd[1] is
  32    writable but writing a large amount of data to fd[1] then fails with errno
  33    EAGAIN.  Seen with test-pipe-filter-gi1 on AIX 7.2, with data sizes of
  34    29 KB.  So, limit the size of data passed to the write() call to 4 KB.  */
  35 # undef SSIZE_MAX
  36 # define SSIZE_MAX 4096
  37 #endif
  38
  39 /* We use a child process, and communicate through a bidirectional pipe.
  40    To avoid deadlocks, let the child process decide when it wants to read
  41    or to write, and let the parent behave accordingly.  The parent uses
  42    select() to know whether it must write or read.  On platforms without
  43    select(), we use non-blocking I/O.  (This means the parent is busy
  44    looping while waiting for the child.  Not good.  But hardly any platform
  45    lacks select() nowadays.)  */
  46
  47 /* On BeOS and OS/2 kLIBC select() works only on sockets, not on normal file
  48    descriptors.  */
  49 #if defined __BEOS__ || defined __KLIBC__
  50 # undef HAVE_SELECT
  51 #endif
  52
  53 #ifdef EINTR
  54
  55 /* EINTR handling for close(), read(), write(), select().
  56    These functions can return -1/EINTR even though we don't have any
  57    signal handlers set up, namely when we get interrupted via SIGSTOP.  */
  58
  59 PIPE_FILTER_AUX_INLINE int
  60 nonintr_close (int fd)
  61 {
  62   int retval;
  63
  64   do
  65     retval = close (fd);
  66   while (retval < 0 && errno == EINTR);
  67
  68   return retval;
  69 }
  70 #undef close /* avoid warning related to gnulib module unistd */
  71 #define close nonintr_close
  72
  73 PIPE_FILTER_AUX_INLINE ssize_t
  74 nonintr_read (int fd, void *buf, size_t count)
  75 {
  76   ssize_t retval;
  77
  78   do
  79     retval = read (fd, buf, count);
  80   while (retval < 0 && errno == EINTR);
  81
  82   return retval;
  83 }
  84 #undef read /* avoid warning related to gnulib module unistd */
  85 #define read nonintr_read
  86
  87 PIPE_FILTER_AUX_INLINE ssize_t
  88 nonintr_write (int fd, const void *buf, size_t count)
  89 {
  90   ssize_t retval;
  91
  92   do
  93     retval = write (fd, buf, count);
  94   while (retval < 0 && errno == EINTR);
  95
  96   return retval;
  97 }
  98 #undef write /* avoid warning on VMS */
  99 #define write nonintr_write
 100
 101 #endif
 102
 103 /* Non-blocking I/O.  */
 104 #if HAVE_SELECT
 105 # define IS_EAGAIN(errcode) 0
 106 #else
 107 # ifdef EWOULDBLOCK
 108 #  define IS_EAGAIN(errcode) ((errcode) == EAGAIN || (errcode) == EWOULDBLOCK)
 109 # else
 110 #  define IS_EAGAIN(errcode) ((errcode) == EAGAIN)
 111 # endif
 112 #endif
 113
 114 _GL_INLINE_HEADER_END