glibc/sysdeps/posix/pread.c
Ulrich Drepper 778c59c850 Update.
1999-12-18  Ulrich Drepper  <drepper@cygnus.com>

	* include/unistd.h: Declare __libc_open64, __libc_lseek64,
	__libc_pread, __libc_pread64, __libc_pwrite, and __libc_pwrite64.
	* io/Versions: Export __libc_open64 and __libc_lseek64.
	* posix/Versions: Export __libc_pread, __libc_pread64, __libc_pwrite,
	and __libc_pwrite64.
	* sysdeps/generic/open64.c: Define __libc_* variant for cancelation
	wrapper.
	* sysdeps/generic/pread.c: Likewise.
	* sysdeps/generic/pread64.c: Likewise.
	* sysdeps/generic/pwrite.c: Likewise.
	* sysdeps/generic/pwrite64.c: Likewise.
	* sysdeps/posix/open64.c: Likewise.
	* sysdeps/posix/pread.c: Likewise.
	* sysdeps/posix/pread64.c: Likewise.
	* sysdeps/posix/pwrite.c: Likewise.
	* sysdeps/posix/pwrite64.c: Likewise.
	* sysdeps/unix/sysv/linux/llseek.c: Likewise.
	* sysdeps/unix/sysv/linux/pread.c: Likewise.
	* sysdeps/unix/sysv/linux/pread64.c: Likewise.
	* sysdeps/unix/sysv/linux/pwrite.c: Likewise.
	* sysdeps/unix/sysv/linux/pwrite64.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/pread.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/pread64.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/pwrite.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/pwrite64.c: Likewise.

	* sysdeps/posix/open64.c: Help gcc generating better code.

	* sysdeps/generic/libc-start.c (check_one_fd): Use __libc_open
	instead of __open.
1999-12-19 05:29:07 +00:00

62 lines
2.0 KiB
C

/* Read block from given position in file without changing file pointer.
POSIX version.
Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <unistd.h>
ssize_t
__libc_pread (int fd, void *buf, size_t nbyte, off_t offset)
{
/* Since we must not change the file pointer preserve the value so that
we can restore it later. */
int save_errno;
ssize_t result;
off_t old_offset = __libc_lseek (fd, 0, SEEK_CUR);
if (old_offset == (off_t) -1)
return -1;
/* Set to wanted position. */
if (__libc_lseek (fd, offset, SEEK_SET) == (off_t) -1)
return -1;
/* Write out the data. */
result = __libc_read (fd, buf, nbyte);
/* Now we have to restore the position. If this fails we have to
return this as an error. But if the writing also failed we
return this error. */
save_errno = errno;
if (__libc_lseek (fd, old_offset, SEEK_SET) == (off_t) -1)
{
if (result == -1)
__set_errno (save_errno);
return -1;
}
__set_errno (save_errno);
return result;
}
#ifndef __libc_pread
strong_alias (__libc_pread, __pread)
weak_alias (__libc_pread, pread)
#endif