view lib/sys-limits.h @ 39326:c82e97c04ab4

sys-limits.h: new file for crypto and safe I/O * lib/af_alg.c: Include sys-limits.h. (MAX_RW_COUNT): Remove. Use replaced by SYS_BUFSIZE_MAX. (afalg_stream): Also reject negative sizes for sendfile; they should not happen and the code is a bit cleaner and faster this way. * lib/safe-read.c: Include sys-limits.h. (BUGGY_READ_MAXIMUM): Remove. All uses replaced by SYS_BUFSIZE_MAX. * lib/sys-limits.h: New file, with values and commentary derived from the old safe-read.c and from GNU Emacs sysdep.c. * modules/crypto/md5, modules/crypto/sha1, modules/crypto/sha256: * modules/crypto/sha512, modules/safe-read, modules/safe-write: Add lib/sys-limits.h to Files section.
author Paul Eggert <eggert@cs.ucla.edu>
date Sat, 05 May 2018 10:27:38 -0700
parents
children b06060465f09
line wrap: on
line source

/* System call limits

   Copyright 2018 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

#ifndef _SYS_LIMITS_H
#define _SYS_LIMITS_H

#include <limits.h>

/* Maximum number of bytes to read or write in a single system call.
   This can be useful for system calls like sendfile on GNU/Linux,
   which do not handle more than MAX_RW_COUNT bytes correctly.
   The Linux kernel MAX_RW_COUNT is at least INT_MAX >> 20 << 20,
   where the 20 comes from the Hexagon port with 1 MiB pages; use that
   as an approximation, as the exact value may not be available to us.

   Using this also works around a serious Linux bug before 2.6.16; see
   <https://bugzilla.redhat.com/show_bug.cgi?id=612839>.

   Using this also works around a Tru64 5.1 bug, where attempting
   to read INT_MAX bytes fails with errno == EINVAL.  See
   <https://lists.gnu.org/r/bug-gnu-utils/2002-04/msg00010.html>.

   Using this is likely to work around similar bugs in other operating
   systems.  */

enum { SYS_BUFSIZE_MAX = INT_MAX >> 20 << 20 };

#endif