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/* safe-read.c -- an interface to read that retries after interrupts
Copyright (C) 1993, 1994, 1998, 2002 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, write to the Free Software Foundation,
Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
# include <config.h>
#endif
#include <sys/types.h>
#include <stdlib.h>
#if HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <errno.h>
#ifndef errno
extern int errno;
#endif
#include "safe-read.h"
/* Read LEN bytes at PTR from descriptor DESC, retrying if interrupted.
Return the actual number of bytes read, zero upon EOF,
or SAFE_READ_ERROR upon error.
Abort if LEN is SAFE_READ_ERROR (aka `(size_t) -1').
WARNING: although both LEN and the return value are of type size_t,
the range of the return value is restricted -- by virtue of being
returned from read(2) -- and will never be larger than SSIZE_MAX,
with the exception of SAFE_READ_ERROR, of course.
So don't test `safe_read (..., N) == N' unless you're sure that
N <= SSIZE_MAX. */
size_t
safe_read (int desc, void *ptr, size_t len)
{
ssize_t n_chars;
if (len == SAFE_READ_ERROR)
abort ();
if (len == 0)
return len;
#ifdef EINTR
do
{
n_chars = read (desc, ptr, len);
}
while (n_chars < 0 && errno == EINTR);
#else
n_chars = read (desc, ptr, len);
#endif
return n_chars;
}
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