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Replace <sys/param.h> with <limits.h> and other less dirty headers where
possible.  Annotate <sys/param.h> lines with their current reasons.  Switch
to PATH_MAX, NGROUPS_MAX, HOST_NAME_MAX+1, LOGIN_NAME_MAX, etc.  Change
MIN() and MAX() to local definitions of MINIMUM() and MAXIMUM() where
sensible to avoid pulling in the pollution.  These are the files confirmed
through binary verification.
ok guenther, millert, doug (helped with the verification protocol)

/* $OpenBSD: atomicio.c,v 1.27 2015/01/16 06:40:12 deraadt 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/uio.h>

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

#include "atomicio.h"

/*
 * ensure all of data on socket comes through. f==read || f==vwrite
 */
size_t
atomicio6(ssize_t (*f) (int, void *, size_t), int fd, void *_s, size_t n,
    int (*cb)(void *, size_t), void *cb_arg)
{
	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) {
				(void)poll(&pfd, 1, -1);
				continue;
			}
			return 0;
		case 0:
			errno = EPIPE;
			return pos;
		default:
			pos += (size_t)res;
			if (cb != NULL && cb(cb_arg, (size_t)res) == -1) {
				errno = EINTR;
				return pos;
			}
		}
	}
	return pos;
}

size_t
atomicio(ssize_t (*f) (int, void *, size_t), int fd, void *_s, size_t n)
{
	return atomicio6(f, fd, _s, n, NULL, NULL);
}

/*
 * ensure all of data on socket comes through. f==readv || f==writev
 */
size_t
atomiciov6(ssize_t (*f) (int, const struct iovec *, int), int fd,
    const struct iovec *_iov, int iovcnt,
    int (*cb)(void *, size_t), void *cb_arg)
{
	size_t pos = 0, rem;
	ssize_t res;
	struct iovec iov_array[IOV_MAX], *iov = iov_array;
	struct pollfd pfd;

	if (iovcnt > IOV_MAX) {
		errno = EINVAL;
		return 0;
	}
	/* Make a copy of the iov array because we may modify it below */
	memcpy(iov, _iov, iovcnt * sizeof(*_iov));

	pfd.fd = fd;
	pfd.events = f == readv ? POLLIN : POLLOUT;
	for (; iovcnt > 0 && iov[0].iov_len > 0;) {
		res = (f) (fd, iov, iovcnt);
		switch (res) {
		case -1:
			if (errno == EINTR)
				continue;
			if (errno == EAGAIN) {
				(void)poll(&pfd, 1, -1);
				continue;
			}
			return 0;
		case 0:
			errno = EPIPE;
			return pos;
		default:
			rem = (size_t)res;
			pos += rem;
			/* skip completed iov entries */
			while (iovcnt > 0 && rem >= iov[0].iov_len) {
				rem -= iov[0].iov_len;
				iov++;
				iovcnt--;
			}
			/* This shouldn't happen... */
			if (rem > 0 && (iovcnt <= 0 || rem > iov[0].iov_len)) {
				errno = EFAULT;
				return 0;
			}
			if (iovcnt == 0)
				break;
			/* update pointer in partially complete iov */
			iov[0].iov_base = ((char *)iov[0].iov_base) + rem;
			iov[0].iov_len -= rem;
		}
		if (cb != NULL && cb(cb_arg, (size_t)res) == -1) {
			errno = EINTR;
			return pos;
		}
	}
	return pos;
}

size_t
atomiciov(ssize_t (*f) (int, const struct iovec *, int), int fd,
    const struct iovec *_iov, int iovcnt)
{
	return atomiciov6(f, fd, _iov, iovcnt, NULL, NULL);
}