alertpipe.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2017, Sean Bright
 *
 * Sean Bright <[email protected]>
 *
 * 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;
}