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+/** 
+ * @file llmutex.h
+ * @brief Base classes for mutex and condition handling.
+ *
+ * $LicenseInfo:firstyear=2004&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2012, Linden Research, Inc.
+ * 
+ * This library 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;
+ * version 2.1 of the License only.
+ * 
+ * This library 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 library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+
+#ifndef LL_LLMUTEX_H
+#define LL_LLMUTEX_H
+
+#include "stdtypes.h"
+
+//============================================================================
+
+#define MUTEX_DEBUG (LL_DEBUG || LL_RELEASE_WITH_DEBUG_INFO)
+
+struct apr_thread_mutex_t;
+struct apr_pool_t;
+struct apr_thread_cond_t;
+
+class LL_COMMON_API LLMutex
+{
+public:
+	typedef enum
+	{
+		NO_THREAD = 0xFFFFFFFF
+	} e_locking_thread;
+
+	LLMutex(apr_pool_t *apr_poolp = NULL); // NULL pool constructs a new pool for the mutex
+	virtual ~LLMutex();
+	
+	void lock();		// blocks
+	bool trylock();		// non-blocking, returns true if lock held.
+	void unlock();		// undefined behavior when called on mutex not being held
+	bool isLocked(); 	// non-blocking, but does do a lock/unlock so not free
+	bool isSelfLocked(); //return true if locked in a same thread
+	U32 lockingThread() const; //get ID of locking thread
+	
+protected:
+	apr_thread_mutex_t *mAPRMutexp;
+	mutable U32			mCount;
+	mutable U32			mLockingThread;
+	
+	apr_pool_t			*mAPRPoolp;
+	BOOL				mIsLocalPool;
+	
+#if MUTEX_DEBUG
+	std::map<U32, BOOL> mIsLocked;
+#endif
+};
+
+// Actually a condition/mutex pair (since each condition needs to be associated with a mutex).
+class LL_COMMON_API LLCondition : public LLMutex
+{
+public:
+	LLCondition(apr_pool_t* apr_poolp); // Defaults to global pool, could use the thread pool as well.
+	~LLCondition();
+	
+	void wait();		// blocks
+	void signal();
+	void broadcast();
+	
+protected:
+	apr_thread_cond_t* mAPRCondp;
+};
+
+class LLMutexLock
+{
+public:
+	LLMutexLock(LLMutex* mutex)
+	{
+		mMutex = mutex;
+		
+		if(mMutex)
+			mMutex->lock();
+	}
+	~LLMutexLock()
+	{
+		if(mMutex)
+			mMutex->unlock();
+	}
+private:
+	LLMutex* mMutex;
+};
+
+//============================================================================
+
+// Scoped locking class similar in function to LLMutexLock but uses
+// the trylock() method to conditionally acquire lock without
+// blocking.  Caller resolves the resulting condition by calling
+// the isLocked() method and either punts or continues as indicated.
+//
+// Mostly of interest to callers needing to avoid stalls who can
+// guarantee another attempt at a later time.
+
+class LLMutexTrylock
+{
+public:
+	LLMutexTrylock(LLMutex* mutex)
+		: mMutex(mutex),
+		  mLocked(false)
+	{
+		if (mMutex)
+			mLocked = mMutex->trylock();
+	}
+
+	~LLMutexTrylock()
+	{
+		if (mMutex && mLocked)
+			mMutex->unlock();
+	}
+
+	bool isLocked() const
+	{
+		return mLocked;
+	}
+	
+private:
+	LLMutex*	mMutex;
+	bool		mLocked;
+};
+#endif // LL_LLTHREAD_H