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/* $OpenBSD: atomicio.c,v 1.10 2011/01/08 00:47:19 jeremy Exp $ */
/*
 * Copyright (c) 2006 Damien Miller. All rights reserved.
 * Copyright (c) 2005 Anil Madhavapeddy. All rights reserved.
 * Copyright (c) 1995,1999 Theo de Raadt.  All rights reserved.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/param.h>

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

#include "atomicio.h"

/*
 * ensure all of data on socket comes through. f==read || f==vwrite
 */
size_t
atomicio(ssize_t (*f) (int, void *, size_t), int fd, void *_s, size_t n)
{
        char *s = _s;
        size_t pos = 0;
        ssize_t res;
        struct pollfd pfd;

        pfd.fd = fd;
        pfd.events = f == read ? POLLIN : POLLOUT;
        while (n > pos) {
                res = (f) (fd, s + pos, n - pos);
                switch (res) {
                case -1:
                        if (errno == EINTR)
                                continue;
                        if ((errno == EAGAIN) || (errno == ENOBUFS)) {
                                (void)poll(&pfd, 1, -1);
                                continue;
                        }
                        return 0;
                case 0:
                        errno = EPIPE;
                        return pos;
                default:
                        pos += (size_t)res;
                }
        }
        return (pos);
}