pipeutils.c

/* pipeutils.c -- Utilities for using pipes as signals
   This file is part of Redshift.

   Redshift is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Redshift is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Redshift.  If not, see <http://www.gnu.org/licenses/>.

   Copyright (c) 2017  Jon Lund Steffensen <jonlst@gmail.com>
*/

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>


#ifndef _WIN32

/* Create non-blocking set of pipe fds. */
int
pipeutils_create_nonblocking(int pipefds[2])
{
	int r = pipe(pipefds);
	if (r == -1) {
		perror("pipe");
		return -1;
	}

	int flags = fcntl(pipefds[0], F_GETFL);
	if (flags == -1) {
		perror("fcntl");
		close(pipefds[0]);
		close(pipefds[1]);
		return -1;
	}

	r = fcntl(pipefds[0], F_SETFL, flags | O_NONBLOCK);
	if (r == -1) {
		perror("fcntl");
		close(pipefds[0]);
		close(pipefds[1]);
		return -1;
	}

	flags = fcntl(pipefds[1], F_GETFL);
	if (flags == -1) {
		perror("fcntl");
		close(pipefds[0]);
		close(pipefds[1]);
		return -1;
	}

	r = fcntl(pipefds[1], F_SETFL, flags | O_NONBLOCK);
	if (r == -1) {
		perror("fcntl");
		close(pipefds[0]);
		close(pipefds[1]);
		return -1;
	}

	return 0;
}

#else /* _WIN32 */

/* Create non-blocking set of pipe fds.

   Not supported on Windows! Always fails. */
int
pipeutils_create_nonblocking(int pipefds[2])
{
	return -1;
}

#endif

/* Signal on write-end of pipe. */
void
pipeutils_signal(int write_fd)
{
	write(write_fd, "", 1);
}

/* Mark signal as handled on read-end of pipe. */
void
pipeutils_handle_signal(int read_fd)
{
	char data;
	read(read_fd, &data, 1);
}