new class PISemaphore

doc for PIProtectedVariable

libs/main/thread/pisemaphore.cpp

@@ -0,0 +1,152 @@
+/*
+    PIP - Platform Independent Primitives
+	PISemaphore, PISemaphoreLocker
+	Ivan Pelipenko peri4ko@yandex.ru
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program 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 Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+//! \addtogroup Thread
+//! \{
+//! \class PISemaphore pisemaphore.h
+//!
+//! \~\brief
+//! \~english Basic semaphore
+//! \~russian Простой семафор
+//!
+//!
+//! \~\details
+//! \~english \section PISemaphore_sec0 Synopsis
+//! \~russian \section PISemaphore_sec0 Краткий обзор
+//!
+//! \~english
+//! %PISemaphore provides critical code section defence between several threads with resource counting.
+//! Semaphore contains logic counter and functions to change it:
+//! \a release(), \a acquire() and \a tryAcquire().
+//!
+//! For automatic acquire-release use \a PISemaphoreLocker.
+//!
+//! \~russian
+//! %PISemaphore предоставляет межпотоковую защиту критических секций кода с подсчетом ресурсов.
+//! Семафор состоит из логического счетчика и методов для его изменения:
+//! \a release(), \a acquire() and \a tryAcquire().
+//!
+//! Для автоматического захвата-освобождения используйте \a PISemaphoreLocker.
+//!
+//! \~english \section PISemaphore_sec1 Usage
+//! \~russian \section PISemaphore_sec1 Использование
+//!
+//! \~english
+//!
+//! \~russian
+//!
+//! \~\code
+//! \endcode
+//! \}
+
+
+//! \addtogroup Thread
+//! \{
+//! \class PISemaphoreLocker pisemaphore.h
+//!
+//! \~\brief
+//! \~english %PISemaphore autolocker
+//! \~russian Автоблокировщик %PISemaphore
+//!
+//!
+//! \~\details
+//!
+//! \~english
+//! When a %PISemaphoreLocker object is created, it attempts to acquire the semaphore resources, if "condition" \c true.
+//! When control leaves the scope in which the %PISemaphoreLocker object was created,
+//! the %PISemaphoreLocker is destructed and the resources are released, if "condition" was \c true.
+//!
+//! If "condition" \c false this class do nothing.
+//!
+//! The %PISemaphoreLocker class is non-copyable.
+//!
+//! \~russian
+//! При создании экземпляра %PISemaphoreLocker захватываются ресурсы семафора, если "condition" \c true.
+//! Когда выполнение покидает область жизни объекта, вызывается его деструктор и ресурсы
+//! освобождаются, если "condition" был \c true.
+//!
+//! Если "condition" \c false, то этот объект ничего не делает.
+//!
+//! Класс %PISemaphoreLocker некопируемый.
+//!
+//! \~\code
+//! // critical section start
+//! {
+//! PISemaphoreLocker locker(mutex, 5);
+//! // ... your code here
+//! }
+//! // critical section end
+//! \endcode
+//! \}
+
+
+#include "pisemaphore.h"
+
+
+PISemaphore::PISemaphore(int initial) {
+	count = initial;
+}
+
+
+PISemaphore::~PISemaphore() {
+	var.notifyAll();
+}
+
+
+void PISemaphore::acquire(int cnt) {
+	PIMutexLocker _ml(mutex);
+	while (count < cnt) {
+		var.wait(mutex);
+	}
+	count -= cnt;
+}
+
+
+bool PISemaphore::tryAcquire(int cnt) {
+	PIMutexLocker _ml(mutex);
+	if (count < cnt) return false;
+	count -= cnt;
+	return true;
+}
+
+
+bool PISemaphore::tryAcquire(int cnt, PISystemTime timeout) {
+	PITimeMeasurer tm;
+	PIMutexLocker _ml(mutex);
+	while (count < cnt) {
+		PISystemTime remain = timeout - tm.elapsed();
+		if (remain.isNegative()) return false;
+		var.waitFor(mutex, remain);
+	}
+	count -= cnt;
+	return true;
+}
+
+
+void PISemaphore::release(int cnt) {
+	PIMutexLocker _ml(mutex);
+	count += cnt;
+	var.notifyAll();
+}
+
+
+int PISemaphore::available() const {
+	PIMutexLocker _ml(mutex);
+	return count;
+}