File: readn.c

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/* Copyright (C) 2005 Mads Martin Joergensen <mmj at mmj.dk>
 *
 * $Id: readn.c,v 1.1 2005/05/02 18:20:15 mmj Exp $
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <unistd.h>
#include <errno.h>

#include "wrappers.h"

/* classic read wrapper from Stevens */
ssize_t readn(int fd, void *vptr, size_t n)
{
	size_t  nleft;
	ssize_t nread;
	char    *ptr;

	ptr = vptr;
	nleft = n;
	while(nleft > 0) {
		if((nread = read(fd, ptr, nleft)) < 0) {
			if(errno == EINTR)
				nread = 0;      /* and call read() again */
			else
				return -1; /* Caller can check errno */
		} else if (nread == 0)
			break;              /* EOF */

		nleft -= nread;
		ptr += nread;
	}
	return n - nleft;         /* return >= 0 */
}