235 lines
7.9 KiB
C++
235 lines
7.9 KiB
C++
/*
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PIP - Platform Independent Primitives
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PIReadWriteLock, PIReadLocker, PIWriteLocker
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Ivan Pelipenko peri4ko@yandex.ru
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//! \addtogroup Thread
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//! \{
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//! \class PIReadWriteLock pireadwritelock.h
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//!
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//! \~\brief
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//! \~english Read/Write lock
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//! \~russian Блокировка чтения/записи
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//!
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//!
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//! \~\details
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//! \~english \section PIReadWriteLock_sec0 Synopsis
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//! \~russian \section PIReadWriteLock_sec0 Краткий обзор
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//!
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//! \~english
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//! %PIReadWriteLock provides more complex critical code section defence between several threads.
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//! %PIReadWriteLock permit only one thread to modify data, besides multiple thread can read data
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//! simultaneously. Conatains methods:
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//! \a lockWrite(), \a tryLockWrite(), \a unlockWrite(), \a lockRead(), \a tryLockRead() and \a unlockRead().
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//!
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//! For automatic read and write locks use \a PIReadLocker and \a PIWriteLocker.
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//!
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//! \~russian
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//! %PIReadWriteLock предоставляет более сложную межпотоковую защиту критических секций кода.
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//! %PIReadWriteLock разрешает только одному потоку изменять данные, в то время как читать данные
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//! могут одновременно несколько потоков.
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//! Содержит методы:
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//! \a lockWrite(), \a tryLockWrite(), \a unlockWrite(), \a lockRead(), \a tryLockRead() и \a unlockRead().
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//!
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//! Для автоматической блокировки на чтение и запись используйте \a PIReadLocker и \a PIWriteLocker.
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//!
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//! \~english \section PIReadWriteLock_sec1 Usage
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//! \~russian \section PIReadWriteLock_sec1 Использование
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//!
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//! \~english
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//! When one thread lock for write with \a lockWrite(), all other threads (read and write) can`t access data until this thread
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//! call \a unlockWrite(). In this way, write lock works similar to mutex.
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//!
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//! On the other hand, several threads can simultaneously read data. In other words, \a lockRead() increase read threads counter
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//! and \a unlockRead() decrease. But thread can`t read data while other thread locked for write.
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//!
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//! \~russian
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//! Когда один поток блокирует запись с помощью функции \a lockWrite(), все остальные потоки (чтение и запись) не смогут получить
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//! доступ к данным, пока этот поток не вызовет \a unlockWrite(). Таким образом, блокировка записи работает аналогично мьютексу.
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//!
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//! С другой стороны, несколько потоков могут одновременно считывать данные. Другими словами, функция \a lockRead() увеличивает счетчик
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//! потоков чтения, а функция \a unlockRead() уменьшает. Но поток не может считывать данные, пока другой поток заблокирован для записи.
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//!
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//! \~\code
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//! \endcode
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//! \}
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//! \addtogroup Thread
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//! \{
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//! \class PIReadLocker pireadwritelock.h
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//!
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//! \~\brief
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//! \~english %PIReadWriteLock read autolocker
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//! \~russian Автоблокировщик на чтение %PIReadWriteLock
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//!
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//!
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//! \~\details
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//!
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//! \~english
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//! When a %PIReadLocker object is created, it lock %PIReadWriteLock for read, if "condition" \c true.
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//! When control leaves the scope in which the %PIReadLocker object was created,
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//! the %PIReadLocker is destructed and unlock for read, if "condition" was \c true.
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//!
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//! If "condition" \c false this class do nothing.
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//!
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//! The %PIReadLocker class is non-copyable.
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//!
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//! \~russian
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//! При создании экземпляра %PIReadLocker он блокирует %PIReadWriteLock на чтение, если "condition" \c true.
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//! Когда выполнение покидает область жизни объекта, вызывается его деструктор и освобождается блокировка на чтение,
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//! если "condition" был \c true.
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//!
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//! Если "condition" \c false, то этот объект ничего не делает.
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//!
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//! Класс %PIReadLocker некопируемый.
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//!
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//! \~\code
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//! // critical section start
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//! {
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//! PIReadLocker locker(rw_lock);
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//! // ... your read code here
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//! }
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//! // critical section end
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//! \endcode
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//! \}
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//! \addtogroup Thread
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//! \{
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//! \class PIWriteLocker pireadwritelock.h
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//!
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//! \~\brief
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//! \~english %PIReadWriteLock write autolocker
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//! \~russian Автоблокировщик на запись %PIReadWriteLock
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//!
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//!
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//! \~\details
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//!
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//! \~english
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//! When a %PIWriteLocker object is created, it lock %PIReadWriteLock for write, if "condition" \c true.
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//! When control leaves the scope in which the %PIWriteLocker object was created,
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//! the %PIWriteLocker is destructed and unlock for write, if "condition" was \c true.
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//!
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//! If "condition" \c false this class do nothing.
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//!
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//! The %PIWriteLocker class is non-copyable.
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//!
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//! \~russian
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//! При создании экземпляра %PIWriteLocker он блокирует %PIReadWriteLock на запись, если "condition" \c true.
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//! Когда выполнение покидает область жизни объекта, вызывается его деструктор и освобождается блокировка на запись,
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//! если "condition" был \c true.
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//!
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//! Если "condition" \c false, то этот объект ничего не делает.
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//!
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//! Класс %PIWriteLocker некопируемый.
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//!
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//! \~\code
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//! // critical section start
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//! {
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//! PIWriteLocker locker(rw_lock);
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//! // ... your write code here
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//! }
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//! // critical section end
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//! \endcode
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//! \}
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#include "pireadwritelock.h"
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PIReadWriteLock::PIReadWriteLock() {}
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PIReadWriteLock::~PIReadWriteLock() {
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var.notifyAll();
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}
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void PIReadWriteLock::lockWrite() {
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PIMutexLocker _ml(mutex);
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while (reading > 0 || writing) {
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var.wait(mutex);
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}
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writing = true;
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}
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bool PIReadWriteLock::tryLockWrite() {
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PIMutexLocker _ml(mutex);
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if (reading > 0 || writing) return false;
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writing = true;
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return true;
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}
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bool PIReadWriteLock::tryLockWrite(PISystemTime timeout) {
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PITimeMeasurer tm;
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PIMutexLocker _ml(mutex);
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while (reading > 0 || writing) {
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PISystemTime remain = timeout - tm.elapsed();
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if (remain.isNegative()) return false;
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var.waitFor(mutex, remain);
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}
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writing = true;
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return true;
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}
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void PIReadWriteLock::unlockWrite() {
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PIMutexLocker _ml(mutex);
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writing = false;
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var.notifyAll();
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}
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void PIReadWriteLock::lockRead() {
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PIMutexLocker _ml(mutex);
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while (writing) {
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var.wait(mutex);
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}
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++reading;
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}
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bool PIReadWriteLock::tryLockRead() {
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PIMutexLocker _ml(mutex);
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if (writing) return false;
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++reading;
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return true;
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}
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bool PIReadWriteLock::tryLockRead(PISystemTime timeout) {
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PITimeMeasurer tm;
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PIMutexLocker _ml(mutex);
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while (writing) {
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PISystemTime remain = timeout - tm.elapsed();
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if (remain.isNegative()) return false;
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var.waitFor(mutex, remain);
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}
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++reading;
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return true;
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}
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void PIReadWriteLock::unlockRead() {
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PIMutexLocker _ml(mutex);
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--reading;
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var.notifyAll();
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}
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