/*

 *  sync abstraction

 *  Copyright 2015-2016 Collabora Ltd.

 *

 *  Based on the implementation from the Android Open Source Project,

 *

 *  Copyright 2012 Google, Inc

 *

 *  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.

 */

#ifndef _LIBSYNC_H

#define _LIBSYNC_H

#include <assert.h>

#include <errno.h>

#include <stdint.h>

#include <string.h>

#include <sys/ioctl.h>

#include <sys/poll.h>

#include <unistd.h>

#if defined(__cplusplus)

extern "C" {

#endif

#ifndef SYNC_IOC_MERGE

/* duplicated from linux/sync_file.h to avoid build-time dependency

 * on new (v4.7) kernel headers.  Once distro's are mostly using

 * something newer than v4.7 drop this and #include <linux/sync_file.h>

 * instead.

 */

struct sync_merge_data {

	char	name[32];

	int32_t	fd2;

	int32_t	fence;

	uint32_t	flags;

	uint32_t	pad;

};

#define SYNC_IOC_MAGIC		'>'

#define SYNC_IOC_MERGE		_IOWR(SYNC_IOC_MAGIC, 3, struct sync_merge_data)

#endif

static inline int sync_wait(int fd, int timeout)

{

	struct pollfd fds = {0};

	int ret;

	fds.fd = fd;

	fds.events = POLLIN;

	do {

		ret = poll(&fds, 1, timeout);

		if (ret > 0) {

			if (fds.revents & (POLLERR | POLLNVAL)) {

				errno = EINVAL;

				return -1;

			}

			return 0;

		} else if (ret == 0) {

			errno = ETIME;

			return -1;

		}

	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));

	return ret;

}

static inline int sync_merge(const char *name, int fd1, int fd2)

{

	struct sync_merge_data data = {0};

	int ret;

	data.fd2 = fd2;

	strncpy(data.name, name, sizeof(data.name));

	do {

		ret = ioctl(fd1, SYNC_IOC_MERGE, &data);

	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));

	if (ret < 0)

		return ret;

	return data.fence;

}

/* accumulate fd2 into fd1.  If *fd1 is not a valid fd then dup fd2,

 * otherwise sync_merge() and close the old *fd1.  This can be used

 * to implement the pattern:

 *

 *    init()

 *    {

 *       batch.fence_fd = -1;

 *    }

 *

 *    // does *NOT* take ownership of fd

 *    server_sync(int fd)

 *    {

 *       if (sync_accumulate("foo", &batch.fence_fd, fd)) {

 *          ... error ...

 *       }

 *    }

 */

static inline int sync_accumulate(const char *name, int *fd1, int fd2)

{

	int ret;

	assert(fd2 >= 0);

	if (*fd1 < 0) {

		*fd1 = dup(fd2);

		return 0;

	}

	ret = sync_merge(name, *fd1, fd2);

	if (ret < 0) {

		/* leave *fd1 as it is */

		return ret;

	}

	close(*fd1);

	*fd1 = ret;

	return 0;

}

#if defined(__cplusplus)

}

#endif

#endif