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//
// Mutex.h
//
// Library: Foundation
// Package: Threading
// Module: Mutex
//
// Definition of the Mutex and FastMutex classes.
//
// Copyright (c) 2004-2008, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_Mutex_INCLUDED
#define Foundation_Mutex_INCLUDED
#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include "Poco/ScopedLock.h"
#if defined(POCO_OS_FAMILY_WINDOWS)
#if defined(_WIN32_WCE)
#include "Poco/Mutex_WINCE.h"
#else
#include "Poco/Mutex_WIN32.h"
#endif
#elif defined(POCO_VXWORKS)
#include "Poco/Mutex_VX.h"
#else
#include "Poco/Mutex_POSIX.h"
#endif
namespace Poco {
class Foundation_API Mutex: private MutexImpl
/// A Mutex (mutual exclusion) is a synchronization
/// mechanism used to control access to a shared resource
/// in a concurrent (multithreaded) scenario.
/// Mutexes are recursive, that is, the same mutex can be
/// locked multiple times by the same thread (but, of course,
/// not by other threads).
/// Using the ScopedLock class is the preferred way to automatically
/// lock and unlock a mutex.
{
public:
typedef Poco::ScopedLock<Mutex> ScopedLock;
Mutex();
/// creates the Mutex.
~Mutex();
/// destroys the Mutex.
void lock();
/// Locks the mutex. Blocks if the mutex
/// is held by another thread.
void lock(long milliseconds);
/// Locks the mutex. Blocks up to the given number of milliseconds
/// if the mutex is held by another thread. Throws a TimeoutException
/// if the mutex can not be locked within the given timeout.
///
/// Performance Note: On most platforms (including Windows), this member function is
/// implemented using a loop calling (the equivalent of) tryLock() and Thread::sleep().
/// On POSIX platforms that support pthread_mutex_timedlock(), this is used.
bool tryLock();
/// Tries to lock the mutex. Returns false immediately
/// if the mutex is already held by another thread.
/// Returns true if the mutex was successfully locked.
bool tryLock(long milliseconds);
/// Locks the mutex. Blocks up to the given number of milliseconds
/// if the mutex is held by another thread.
/// Returns true if the mutex was successfully locked.
///
/// Performance Note: On most platforms (including Windows), this member function is
/// implemented using a loop calling (the equivalent of) tryLock() and Thread::sleep().
/// On POSIX platforms that support pthread_mutex_timedlock(), this is used.
void unlock();
/// Unlocks the mutex so that it can be acquired by
/// other threads.
private:
Mutex(const Mutex&);
Mutex& operator = (const Mutex&);
};
class Foundation_API FastMutex: private FastMutexImpl
/// A FastMutex (mutual exclusion) is similar to a Mutex.
/// Unlike a Mutex, however, a FastMutex is not recursive,
/// which means that a deadlock will occur if the same
/// thread tries to lock a mutex it has already locked again.
/// Locking a FastMutex is faster than locking a recursive Mutex.
/// Using the ScopedLock class is the preferred way to automatically
/// lock and unlock a mutex.
{
public:
typedef Poco::ScopedLock<FastMutex> ScopedLock;
FastMutex();
/// creates the Mutex.
~FastMutex();
/// destroys the Mutex.
void lock();
/// Locks the mutex. Blocks if the mutex
/// is held by another thread.
void lock(long milliseconds);
/// Locks the mutex. Blocks up to the given number of milliseconds
/// if the mutex is held by another thread. Throws a TimeoutException
/// if the mutex can not be locked within the given timeout.
///
/// Performance Note: On most platforms (including Windows), this member function is
/// implemented using a loop calling (the equivalent of) tryLock() and Thread::sleep().
/// On POSIX platforms that support pthread_mutex_timedlock(), this is used.
bool tryLock();
/// Tries to lock the mutex. Returns false immediately
/// if the mutex is already held by another thread.
/// Returns true if the mutex was successfully locked.
bool tryLock(long milliseconds);
/// Locks the mutex. Blocks up to the given number of milliseconds
/// if the mutex is held by another thread.
/// Returns true if the mutex was successfully locked.
///
/// Performance Note: On most platforms (including Windows), this member function is
/// implemented using a loop calling (the equivalent of) tryLock() and Thread::sleep().
/// On POSIX platforms that support pthread_mutex_timedlock(), this is used.
void unlock();
/// Unlocks the mutex so that it can be acquired by
/// other threads.
private:
FastMutex(const FastMutex&);
FastMutex& operator = (const FastMutex&);
};
class Foundation_API NullMutex
/// A NullMutex is an empty mutex implementation
/// which performs no locking at all. Useful in policy driven design
/// where the type of mutex used can be now a template parameter allowing the user to switch
/// between thread-safe and not thread-safe depending on his need
/// Works with the ScopedLock class
{
public:
typedef Poco::ScopedLock<NullMutex> ScopedLock;
NullMutex()
/// Creates the NullMutex.
{
}
~NullMutex()
/// Destroys the NullMutex.
{
}
void lock()
/// Does nothing.
{
}
void lock(long)
/// Does nothing.
{
}
bool tryLock()
/// Does nothing and always returns true.
{
return true;
}
bool tryLock(long)
/// Does nothing and always returns true.
{
return true;
}
void unlock()
/// Does nothing.
{
}
};
//
// inlines
//
inline void Mutex::lock()
{
lockImpl();
}
inline void Mutex::lock(long milliseconds)
{
if (!tryLockImpl(milliseconds))
throw TimeoutException();
}
inline bool Mutex::tryLock()
{
return tryLockImpl();
}
inline bool Mutex::tryLock(long milliseconds)
{
return tryLockImpl(milliseconds);
}
inline void Mutex::unlock()
{
unlockImpl();
}
inline void FastMutex::lock()
{
lockImpl();
}
inline void FastMutex::lock(long milliseconds)
{
if (!tryLockImpl(milliseconds))
throw TimeoutException();
}
inline bool FastMutex::tryLock()
{
return tryLockImpl();
}
inline bool FastMutex::tryLock(long milliseconds)
{
return tryLockImpl(milliseconds);
}
inline void FastMutex::unlock()
{
unlockImpl();
}
} // namespace Poco
#endif // Foundation_Mutex_INCLUDED
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