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C++

/**
* Copyright 2013-2021 Software Radio Systems Limited
*
* This file is part of srsRAN.
*
* srsRAN is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version.
*
* srsRAN 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 Affero General Public License for more details.
*
* A copy of the GNU Affero General Public License can be found in
* the LICENSE file in the top-level directory of this distribution
* and at http://www.gnu.org/licenses/.
*
*/
#include <assert.h>
#include <condition_variable>
#include <deque>
#include <inttypes.h>
#include <mutex>
#ifndef SRSRAN_TTI_SEMPAHORE_H_
#define SRSRAN_TTI_SEMPAHORE_H_
namespace srsran {
/**
* Implements priority semaphore based on a FIFO queue wait . This class enqueues T type element identifiers (method
* push) and waits until the enqueued object is the first (method wait). The first element is released by method
* release. The method release_all waits for all the elements to be released.
*
* @tparam T Object identifier type
*/
template <class T>
class tti_semaphore
{
private:
std::mutex mutex; ///< Used for scope mutexes
std::condition_variable cvar; ///< Used for notifying element identifier releases
std::deque<T> fifo; ///< Queue to keep order
public:
/**
* Waits for the first element of the queue match the element identifier provided.
*
* @param id the element identifier
*/
void wait(T id)
{
std::unique_lock<std::mutex> lock(mutex);
// While the FIFO is not empty and the front ID does not match the provided element identifier, keep waiting
while (not fifo.empty() and fifo.front() != id) {
// Wait for a release
cvar.wait(lock);
}
}
/**
* Enqueue (push) an element identifier to the queue
*
* @param id the element identifier
*/
void push(T id)
{
std::unique_lock<std::mutex> lock(mutex);
// Append the element identifier
fifo.push_back(id);
}
/**
* Releases (pops) the first element
*/
void release()
{
std::unique_lock<std::mutex> lock(mutex);
// Pop first element
fifo.pop_front();
// Notify release
cvar.notify_all();
}
/**
* Waits for all the elements to be released
*/
void wait_all()
{
std::unique_lock<std::mutex> lock(mutex);
// Wait until the FIFO is empty
while (not fifo.empty()) {
cvar.wait(lock);
}
}
};
} // namespace srsran
#endif // SRSRAN_TTI_SEMPAHORE_H_