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/* An interface to read and write that retries after interrupts.
Copyright (C) 1993-1994, 1998, 2002-2006, 2009-2017 Free Software
Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#ifdef SAFE_WRITE
# include "safe-write.h"
#else
# include "safe-read.h"
#endif
/* Get ssize_t. */
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#ifdef EINTR
# define IS_EINTR(x) ((x) == EINTR)
#else
# define IS_EINTR(x) 0
#endif
#include <limits.h>
#ifdef SAFE_WRITE
# define safe_rw safe_write
# define rw write
#else
# define safe_rw safe_read
# define rw read
# undef const
# define const /* empty */
#endif
/* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if
interrupted. Return the actual number of bytes read(written), zero for EOF,
or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error. */
size_t
safe_rw (int fd, void const *buf, size_t count)
{
/* Work around a bug in Tru64 5.1. Attempting to read more than
INT_MAX bytes fails with errno == EINVAL. See
<http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>.
When decreasing COUNT, keep it block-aligned. */
enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 };
for (;;)
{
ssize_t result = rw (fd, buf, count);
if (0 <= result)
return result;
else if (IS_EINTR (errno))
continue;
else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count)
count = BUGGY_READ_MAXIMUM;
else
return result;
}
}
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