lib/safe-read.h

   1 /* An interface to read() that retries after interrupts.
   2    Copyright (C) 2002, 2006, 2009-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Some system calls may be interrupted and fail with errno = EINTR in the
  18    following situations:
  19      - The process is stopped and restarted (signal SIGSTOP and SIGCONT, user
  20        types Ctrl-Z) on some platforms: Mac OS X.
  21      - The process receives a signal for which a signal handler was installed
  22        with sigaction() with an sa_flags field that does not contain
  23        SA_RESTART.
  24      - The process receives a signal for which a signal handler was installed
  25        with signal() and for which no call to siginterrupt(sig,0) was done,
  26        on some platforms: AIX, HP-UX, IRIX, OSF/1, Solaris.
  27
  28    This module provides a wrapper around read() that handles EINTR.  */
  29
  30 #include <stddef.h>
  31
  32 #include "idx.h"
  33
  34 #ifdef __cplusplus
  35 extern "C" {
  36 #endif
  37
  38
  39 /* This is present for backward compatibility with older versions of this code
  40    where safe_read returned size_t, so SAFE_READ_ERROR was SIZE_MAX.  */
  41 #define SAFE_READ_ERROR ((ptrdiff_t) -1)
  42
  43 /* Read up to COUNT bytes at BUF from descriptor FD, retrying if interrupted.
  44    Return the number of bytes read, zero for EOF, or -1 upon error.  */
  45 extern ptrdiff_t safe_read (int fd, void *buf, idx_t count);
  46
  47
  48 #ifdef __cplusplus
  49 }
  50 #endif