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deps/g3dlite/include/G3D/GMutex.h

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+/** 
+  \file G3D/GMutex.h
+   
+  \created 2005-09-22
+  \edited  2013-04-03
+ */
+
+#ifndef G3D_GMutex_h
+#define G3D_GMutex_h
+
+#include "G3D/platform.h"
+#include "G3D/AtomicInt32.h"
+#include "G3D/debugAssert.h"
+#include <string>
+
+#ifndef G3D_WINDOWS
+#   include <pthread.h>
+#   include <signal.h>
+#endif
+
+#if defined(G3D_LINUX) || defined(G3D_OSX)
+#   include <unistd.h> // For usleep
+#endif
+
+
+namespace G3D {
+
+/**
+   \brief A mutual exclusion lock that busy-waits when locking.
+
+   On a machine with one (significant) thread per processor core,
+   a Spinlock may be substantially faster than a mutex.
+
+   \sa G3D::GThread, G3D::GMutex, G3D::AtomicInt32
+ */
+class Spinlock {
+private:
+
+    AtomicInt32   x;
+
+public:
+
+    inline Spinlock() : x(0) {}
+
+    /** Busy waits until the lock is unlocked, then locks it
+        exclusively.  Returns true if the lock succeeded on the first
+        try (indicating no contention). 
+        
+        Unlike a G3D::GMutex, a single thread cannot re-enter
+        Spinlock::lock() that it already locked.
+     */
+    inline bool lock() {
+        bool first = true;
+        while (x.compareAndSet(0, 1) == 1) {
+            first = false;
+#           ifdef G3D_WINDOWS
+                Sleep(0);
+#           else
+                usleep(0);
+#           endif
+        }
+        return first;
+    }
+
+    inline void unlock() {
+        x.compareAndSet(1, 0);
+    }
+
+};
+
+/**
+ \brief Mutual exclusion lock used for synchronization.
+
+ @sa G3D::GThread, G3D::AtomicInt32, G3D::Spinlock
+*/
+class GMutex {
+private:
+#   ifdef G3D_WINDOWS
+    CRITICAL_SECTION                    m_handle;
+#   else
+    pthread_mutex_t                     m_handle;
+    pthread_mutexattr_t                 m_attr;
+#   endif
+
+    // Not implemented on purpose, don't use
+    GMutex(const GMutex &mlock);
+    GMutex &operator=(const GMutex &);
+    bool operator==(const GMutex&);
+
+public:
+    GMutex();
+    ~GMutex();
+
+    /** Locks the mutex or blocks until available. */
+    void lock();
+
+    /** Locks the mutex if it not already locked.
+        Returns true if lock successful, false otherwise. */
+    bool tryLock();
+
+    /** Unlocks the mutex. */
+    void unlock();
+};
+
+
+/**
+    Automatically locks while in scope.
+*/
+class GMutexLock {
+private:
+    GMutex* m;
+
+    // Not implemented on purpose, don't use
+    GMutexLock(const GMutexLock &mlock);
+    GMutexLock &operator=(const GMutexLock &);
+    bool operator==(const GMutexLock&);
+
+public:
+    GMutexLock(GMutex* mutex) {
+        m = mutex;
+        m->lock();
+    }
+
+    ~GMutexLock() {
+        m->unlock();
+    }
+};
+
+} // G3D
+
+#endif