gnu/dist/gettext/gettext-tools/lib/safe-read.c

   1 /* An interface to read and write that retries after interrupts.
   2
   3    Copyright (C) 1993, 1994, 1998, 2002, 2003, 2004 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 /* Specification.  */
  25 #ifdef SAFE_WRITE
  26 # include "safe-write.h"
  27 #else
  28 # include "safe-read.h"
  29 #endif
  30
  31 /* Get ssize_t.  */
  32 #include <sys/types.h>
  33 #if HAVE_UNISTD_H
  34 # include <unistd.h>
  35 #endif
  36
  37 #include <errno.h>
  38
  39 #ifdef EINTR
  40 # define IS_EINTR(x) ((x) == EINTR)
  41 #else
  42 # define IS_EINTR(x) 0
  43 #endif
  44
  45 #include <limits.h>
  46
  47 #ifdef SAFE_WRITE
  48 # define safe_rw safe_write
  49 # define rw write
  50 #else
  51 # define safe_rw safe_read
  52 # define rw read
  53 # undef const
  54 # define const /* empty */
  55 #endif
  56
  57 /* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if
  58    interrupted.  Return the actual number of bytes read(written), zero for EOF,
  59    or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error.  */
  60 size_t
  61 safe_rw (int fd, void const *buf, size_t count)
  62 {
  63   /* Work around a bug in Tru64 5.1.  Attempting to read more than
  64      INT_MAX bytes fails with errno == EINVAL.  See
  65      <http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>.
  66      When decreasing COUNT, keep it block-aligned.  */
  67   enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 };
  68
  69   for (;;)
  70     {
  71       ssize_t result = rw (fd, buf, count);
  72
  73       if (0 <= result)
  74         return result;
  75       else if (IS_EINTR (errno))
  76         continue;
  77       else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count)
  78         count = BUGGY_READ_MAXIMUM;
  79       else
  80         return result;
  81     }
  82 }