56 lines
1.4 KiB
C++
56 lines
1.4 KiB
C++
#pragma once
|
|
#include "../object/queue.h"
|
|
#include "../types.h"
|
|
|
|
/*! \file
|
|
* \brief \ref Semaphore for synchronization of threads.
|
|
*/
|
|
|
|
/*!
|
|
* \defgroup ipc Inter-Process Communication
|
|
* \brief Communication between threads
|
|
*/
|
|
|
|
// Forward declarations to break cyclic includes
|
|
struct Vault;
|
|
class Thread;
|
|
|
|
/*! \brief Semaphore used for synchronization of threads.
|
|
* \ingroup ipc
|
|
*
|
|
* The class Semaphore implements the concept of counting semaphores.
|
|
* Waiting threads are parked inside a \ref Queue.
|
|
*/
|
|
class Semaphore {
|
|
// Prevent copies and assignments
|
|
Semaphore(const Semaphore&) = delete;
|
|
Semaphore(Semaphore&&) = delete;
|
|
Semaphore& operator=(const Semaphore&) = delete;
|
|
Semaphore& operator=(Semaphore&&) = delete;
|
|
unsigned counter;
|
|
Queue<Thread> waiting;
|
|
|
|
public:
|
|
/*! \param init Initial counter value
|
|
*/
|
|
explicit Semaphore(unsigned init = 0) : counter(init) {}
|
|
~Semaphore() = default;
|
|
|
|
/*! \brief Wait for access to the critical area.
|
|
*
|
|
* Enter/decrement/wait operation: If the counter is greater than 0, then
|
|
* it is decremented by one. Otherwise the calling thread will be enqueued
|
|
* to wait until it can do that.
|
|
*
|
|
*/
|
|
void p(Vault& vault);
|
|
|
|
/*! \brief Leave the critical area.
|
|
*
|
|
* Leave/increment operation: If there are threads waiting, wake the
|
|
* first one; otherwise increment the counter by one.
|
|
*
|
|
*/
|
|
void v(Vault& vault);
|
|
};
|