/*

 * Copyright (c) 2013 Nicira, Inc.

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at:

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <config.h>

#include "latch.h"

#include <errno.h>

#include <poll.h>

#include <unistd.h>

#include "openvswitch/poll-loop.h"

#include "socket-util.h"

/* Initializes 'latch' as initially unset. */

void

latch_init(struct latch *latch)

{

    xpipe_nonblocking(latch->fds);

}

/* Destroys 'latch'. */

void

latch_destroy(struct latch *latch)

{

    close(latch->fds[0]);

    close(latch->fds[1]);

}

/* Resets 'latch' to the unset state.  Returns true if 'latch' was previously

 * set, false otherwise. */

bool

latch_poll(struct latch *latch)

{

    char latch_buffer[16];

    bool result = false;

    int ret;

    do {

        ret = read(latch->fds[0], &latch_buffer, sizeof latch_buffer);

        result |= ret > 0;

    /* Repeat as long as read() reads a full buffer. */

    } while (ret == sizeof latch_buffer);

    return result;

}

/* Sets 'latch'.

 *

 * Calls are not additive: a single latch_poll() clears out any number of

 * latch_set(). */

void

latch_set(struct latch *latch)

{

    ignore(write(latch->fds[1], "", 1));

}

/* Returns true if 'latch' is set, false otherwise.  Does not reset 'latch'

 * to the unset state. */

bool

latch_is_set(const struct latch *latch)

{

    struct pollfd pfd;

    int retval;

    pfd.fd = latch->fds[0];

    pfd.events = POLLIN;

    do {

        retval = poll(&pfd, 1, 0);

    } while (retval < 0 && errno == EINTR);

    return pfd.revents & POLLIN;

}

/* Causes the next poll_block() to wake up when 'latch' is set.

 *

 * ('where' is used in debug logging.  Commonly one would use latch_wait() to

 * automatically provide the caller's source file and line number for

 * 'where'.) */

void

latch_wait_at(const struct latch *latch, const char *where)

{

    poll_fd_wait_at(latch->fds[0], POLLIN, where);

}