alertpipe.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2017, Sean Bright
 *
 * Sean Bright <sean.bright@gmail.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
 
/*! \file
 *
 * \brief Alert Pipe API
 *
 * \author Sean Bright
 */
 
#include "asterisk.h"
 
#include <unistd.h>
#include <fcntl.h>
 
#ifdef HAVE_EVENTFD
# include <sys/eventfd.h>
#endif
 
#include "asterisk/alertpipe.h"
#include "asterisk/logger.h"
 
int ast_alertpipe_init(int alert_pipe[2])
{
#ifdef HAVE_EVENTFD
 
    int fd = eventfd(0, EFD_NONBLOCK | EFD_SEMAPHORE);
    if (fd > -1) {
        alert_pipe[0] = alert_pipe[1] = fd;
        return 0;
    }
 
    ast_log(LOG_WARNING, "Failed to create alert pipe with eventfd(), falling back to pipe(): %s\n",
        strerror(errno));
    ast_alertpipe_clear(alert_pipe);
 
#endif
 
#ifdef HAVE_PIPE2
 
    if (pipe2(alert_pipe, O_NONBLOCK)) {
        ast_log(LOG_WARNING, "Failed to create alert pipe: %s\n", strerror(errno));
        return -1;
    }
 
#else
 
    if (pipe(alert_pipe)) {
        ast_log(LOG_WARNING, "Failed to create alert pipe: %s\n", strerror(errno));
        return -1;
    } else {
        if (ast_fd_set_flags(alert_pipe[0], O_NONBLOCK)
           || ast_fd_set_flags(alert_pipe[1], O_NONBLOCK)) {
            ast_alertpipe_close(alert_pipe);
            return -1;
        }
    }
 
#endif
 
    return 0;
}
 
void ast_alertpipe_close(int alert_pipe[2])
{
#ifdef HAVE_EVENTFD
 
    if (alert_pipe[0] == alert_pipe[1]) {
        if (alert_pipe[0] > -1) {
            close(alert_pipe[0]);
            ast_alertpipe_clear(alert_pipe);
        }
        return;
    }
 
#endif
 
    if (alert_pipe[0] > -1) {
        close(alert_pipe[0]);
    }
    if (alert_pipe[1] > -1) {
        close(alert_pipe[1]);
    }
    ast_alertpipe_clear(alert_pipe);
}
 
ast_alert_status_t ast_alertpipe_read(int alert_pipe[2])
{
    uint64_t tmp;
 
    if (!ast_alertpipe_readable(alert_pipe)) {
        return AST_ALERT_NOT_READABLE;
    }
 
    if (read(alert_pipe[0], &tmp, sizeof(tmp)) < 0) {
        if (errno != EINTR && errno != EAGAIN) {
            ast_log(LOG_WARNING, "read() failed: %s\n", strerror(errno));
            return AST_ALERT_READ_FAIL;
        }
    }
 
    return AST_ALERT_READ_SUCCESS;
}
 
ssize_t ast_alertpipe_write(int alert_pipe[2])
{
    uint64_t tmp = 1;
 
    if (!ast_alertpipe_writable(alert_pipe)) {
        errno = EBADF;
        return 0;
    }
 
    /* preset errno in case returned size does not match */
    errno = EPIPE;
    return write(alert_pipe[1], &tmp, sizeof(tmp)) != sizeof(tmp);
}
 
ast_alert_status_t ast_alertpipe_flush(int alert_pipe[2])
{
    int bytes_read;
    uint64_t tmp[16];
 
    if (!ast_alertpipe_readable(alert_pipe)) {
        return AST_ALERT_NOT_READABLE;
    }
 
    /* Read the alertpipe until it is exhausted. */
    for (;;) {
        bytes_read = read(alert_pipe[0], tmp, sizeof(tmp));
        if (bytes_read < 0) {
            if (errno == EINTR) {
                continue;
            }
            if (errno == EAGAIN || errno == EWOULDBLOCK) {
                /*
                 * Would block so nothing left to read.
                 * This is the normal loop exit.
                 */
                break;
            }
            ast_log(LOG_WARNING, "read() failed flushing alertpipe: %s\n",
                strerror(errno));
            return AST_ALERT_READ_FAIL;
        }
        if (!bytes_read) {
            /* Read nothing so we are done */
            break;
        }
    }
 
    return AST_ALERT_READ_SUCCESS;
}