src/common/Mutex.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck   *
 *   Copyright (C) 2005 - 2014 Christian Schoenebeck                       *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 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 General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the Free Software           *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#ifndef __MUTEX_H__
#define __MUTEX_H__

#if defined(WIN32)
#include <windows.h>
#else
#include <pthread.h>
#endif

namespace LinuxSampler {

/** @brief Mutual exclusive objects
 *
 * This class provides the classical thread / process synchronisation
 * technique called Mutex. It is used to protect critical sections, that is
 * resources (typically data structures) from being used at the same time by
 * different threads or processes which otherwise might turn into undefined
 * and of course undesired behavior.
 *
 * Note: as this technique might block the calling thread and also implies
 * a system call, this should not be used directly in realtime sensitive
 * threads!
 */
class Mutex {
    public:
        /**
         * Constructor
         */    
        Mutex();

        /**
         * Destructor
         */
        virtual ~Mutex();

        /** @brief Lock this Mutex.
         *
         * If this Mutex object is currently be locked by another thread,
         * then the calling thread will be blocked until the other thread
         * unlocks this Mutex object. The calling thread though can safely
         * call this method several times without danger to be blocked
         * himself.
         *
         * The calling thread should call Unlock() as soon as the critical
         * section was left.
         */      
        void Lock();

        /** @brief Try to lock this Mutex.
         *
         * Same as Lock() except that this method won't block the calling
         * thread in case this Mutex object is currently locked by another
         * thread. So this call will always immediately return and the
         * return value has to be checked if the locking request was
         * successful or not.
         *
         * @returns  true if the Mutex object could be locked, false if the
         *           Mutex is currently locked by another thread
         */
        bool Trylock();

        /** @brief Unlock this Mutex.
         *
         * If other threads are currently blocked and waiting due to a
         * Lock() call, one of them will be awaken.
         */
        void Unlock();

    protected:
    #if defined(WIN32)
        HANDLE hMutex;
    #else
        pthread_mutex_t     __posix_mutex;
        pthread_mutexattr_t __posix_mutexattr;
    #endif
};

// Lock guard for exception safe locking
class LockGuard {
public:
    LockGuard(Mutex& m) : pm(&m) {
        m.Lock();
    }

    /**
     * Empty LockGuard. This constructor can be used to implement conditional
     * mutex protection like:
     * @code
     * Mutex m;
     * LockGuard g;
     * if (requiresMutexProtection()) g = LockGuard(m);
     * @endcode
     */
    LockGuard() : pm(NULL) {
    }

    LockGuard(const LockGuard& g) : pm(g.pm) {
        if (pm) pm->Lock();
    }

    ~LockGuard() {
        if (pm) pm->Unlock();
    }
private:
    Mutex* pm;
};

} // namespace LinuxSampler

#endif // __MUTEX_H__
1	/***************************************************************************
2	* *
3	* LinuxSampler - modular, streaming capable sampler *
4	* *
5	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	* Copyright (C) 2005 - 2014 Christian Schoenebeck *
7	* *
8	* This program is free software; you can redistribute it and/or modify *
9	* it under the terms of the GNU General Public License as published by *
10	* the Free Software Foundation; either version 2 of the License, or *
11	* (at your option) any later version. *
12	* *
13	* This program is distributed in the hope that it will be useful, *
14	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
16	* GNU General Public License for more details. *
17	* *
18	* You should have received a copy of the GNU General Public License *
19	* along with this program; if not, write to the Free Software *
20	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
21	* MA 02111-1307 USA *
22	***************************************************************************/
23
24	#ifndef __MUTEX_H__
25	#define __MUTEX_H__
26
27	#if defined(WIN32)
28	#include <windows.h>
29	#else
30	#include <pthread.h>
31	#endif
32
33	namespace LinuxSampler {
34
35	/** @brief Mutual exclusive objects
36	*
37	* This class provides the classical thread / process synchronisation
38	* technique called Mutex. It is used to protect critical sections, that is
39	* resources (typically data structures) from being used at the same time by
40	* different threads or processes which otherwise might turn into undefined
41	* and of course undesired behavior.
42	*
43	* Note: as this technique might block the calling thread and also implies
44	* a system call, this should not be used directly in realtime sensitive
45	* threads!
46	*/
47	class Mutex {
48	public:
49	/**
50	* Constructor
51	*/
52	Mutex();
53
54	/**
55	* Destructor
56	*/
57	virtual ~Mutex();
58
59	/** @brief Lock this Mutex.
60	*
61	* If this Mutex object is currently be locked by another thread,
62	* then the calling thread will be blocked until the other thread
63	* unlocks this Mutex object. The calling thread though can safely
64	* call this method several times without danger to be blocked
65	* himself.
66	*
67	* The calling thread should call Unlock() as soon as the critical
68	* section was left.
69	*/
70	void Lock();
71
72	/** @brief Try to lock this Mutex.
73	*
74	* Same as Lock() except that this method won't block the calling
75	* thread in case this Mutex object is currently locked by another
76	* thread. So this call will always immediately return and the
77	* return value has to be checked if the locking request was
78	* successful or not.
79	*
80	* @returns true if the Mutex object could be locked, false if the
81	* Mutex is currently locked by another thread
82	*/
83	bool Trylock();
84
85	/** @brief Unlock this Mutex.
86	*
87	* If other threads are currently blocked and waiting due to a
88	* Lock() call, one of them will be awaken.
89	*/
90	void Unlock();
91
92	protected:
93	#if defined(WIN32)
94	HANDLE hMutex;
95	#else
96	pthread_mutex_t __posix_mutex;
97	pthread_mutexattr_t __posix_mutexattr;
98	#endif
99	};
100
101	// Lock guard for exception safe locking
102	class LockGuard {
103	public:
104	LockGuard(Mutex& m) : pm(&m) {
105	m.Lock();
106	}
107
108	/**
109	* Empty LockGuard. This constructor can be used to implement conditional
110	* mutex protection like:
111	* @code
112	* Mutex m;
113	* LockGuard g;
114	* if (requiresMutexProtection()) g = LockGuard(m);
115	* @endcode
116	*/
117	LockGuard() : pm(NULL) {
118	}
119
120	LockGuard(const LockGuard& g) : pm(g.pm) {
121	if (pm) pm->Lock();
122	}
123
124	~LockGuard() {
125	if (pm) pm->Unlock();
126	}
127	private:
128	Mutex* pm;
129	};
130
131	} // namespace LinuxSampler
132
133	#endif // __MUTEX_H__