PosixCond.hxx

/*
 * Copyright (C) 2009-2015 Max Kellermann <max.kellermann@gmail.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef THREAD_POSIX_COND_HXX
#define THREAD_POSIX_COND_HXX

#include "PosixMutex.hxx"

#include <chrono>

#include <sys/time.h>

/**
 * Low-level wrapper for a pthread_cond_t.
 */
class PosixCond {
	pthread_cond_t cond;

public:
#if defined(__GLIBC__) && !defined(__gnu_hurd__)
	/* optimized constexpr constructor for pthread implementations
	   that support it */
	constexpr PosixCond() noexcept:cond(PTHREAD_COND_INITIALIZER) {}
#else
	/* slow fallback for pthread implementations that are not
	   compatible with "constexpr" */
	PosixCond() noexcept {
		pthread_cond_init(&cond, nullptr);
	}

	~PosixCond() noexcept {
		pthread_cond_destroy(&cond);
	}
#endif

	PosixCond(const PosixCond &other) = delete;
	PosixCond &operator=(const PosixCond &other) = delete;

	void signal() noexcept {
		pthread_cond_signal(&cond);
	}

	void broadcast() noexcept {
		pthread_cond_broadcast(&cond);
	}

	void wait(PosixMutex &mutex) noexcept {
		pthread_cond_wait(&cond, &mutex.mutex);
	}

private:
	bool timed_wait(PosixMutex &mutex, uint_least32_t timeout_us) noexcept {
		struct timeval now;
		gettimeofday(&now, nullptr);

		struct timespec ts;
		ts.tv_sec = now.tv_sec + timeout_us / 1000000;
		ts.tv_nsec = (now.tv_usec + (timeout_us % 1000000)) * 1000;
		// Keep tv_nsec < 1E9 to prevent return of EINVAL
		if (ts.tv_nsec >= 1000000000) {
			ts.tv_nsec -= 1000000000;
			ts.tv_sec++;
		}

		return pthread_cond_timedwait(&cond, &mutex.mutex, &ts) == 0;
	}

public:
	bool timed_wait(PosixMutex &mutex,
			std::chrono::steady_clock::duration timeout) noexcept {
		auto timeout_us = std::chrono::duration_cast<std::chrono::microseconds>(timeout).count();
		if (timeout_us < 0)
			timeout_us = 0;
		else if (timeout_us > std::numeric_limits<uint_least32_t>::max())
			timeout_us = std::numeric_limits<uint_least32_t>::max();

		return timed_wait(mutex, timeout_us);
	}
};

#endif