llkeyusetracker.h
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- /**
- * @file llkeyusetracker.h
- * @brief Declaration of the LLKeyUseTracker class.
- *
- * $LicenseInfo:firstyear=2003&license=viewergpl$
- *
- * Copyright (c) 2003-2010, Linden Research, Inc.
- *
- * Second Life Viewer Source Code
- * The source code in this file ("Source Code") is provided by Linden Lab
- * to you under the terms of the GNU General Public License, version 2.0
- * ("GPL"), unless you have obtained a separate licensing agreement
- * ("Other License"), formally executed by you and Linden Lab. Terms of
- * the GPL can be found in doc/GPL-license.txt in this distribution, or
- * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
- *
- * There are special exceptions to the terms and conditions of the GPL as
- * it is applied to this Source Code. View the full text of the exception
- * in the file doc/FLOSS-exception.txt in this software distribution, or
- * online at
- * http://secondlifegrid.net/programs/open_source/licensing/flossexception
- *
- * By copying, modifying or distributing this software, you acknowledge
- * that you have read and understood your obligations described above,
- * and agree to abide by those obligations.
- *
- * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
- * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
- * COMPLETENESS OR PERFORMANCE.
- * $/LicenseInfo$
- */
- #ifndef LL_KEYUSETRACKER_H
- #define LL_KEYUSETRACKER_H
- // This is a generic cache for an arbitrary data type indexed against an
- // arbitrary key type. The cache length is determined by expiration time
- // tince against last use and set size. The age of elements and the size
- // of the cache are queryable.
- //
- // This is implemented as a list, which makes search O(n). If you reuse this
- // for something with a large dataset, consider reimplementing with a Boost
- // multimap based on both a map(key) and priority queue(last_use).
- template <class TKey, class TData>
- class KeyUseTrackerNodeImpl
- {
- public:
- U64 mLastUse;
- U32 mUseCount;
- TKey mKey;
- TData mData;
- KeyUseTrackerNodeImpl( TKey k, TData d ) :
- mLastUse(0),
- mUseCount(0),
- mKey( k ),
- mData( d )
- {
- }
- };
- template <class TKey, class TData>
- class LLKeyUseTracker
- {
- typedef KeyUseTrackerNodeImpl<TKey,TData> TKeyUseTrackerNode;
- typedef std::list<TKeyUseTrackerNode *> TKeyList;
- TKeyList mKeyList;
- U64 mMemUsecs;
- U64 mLastExpire;
- U32 mMaxCount;
- U32 mCount;
- static U64 getTime()
- {
- // This function operates on a frame basis, not instantaneous.
- // We can rely on its output for determining first use in a
- // frame.
- return LLFrameTimer::getTotalTime();
- }
- void ageKeys()
- {
- U64 now = getTime();
- if( now == mLastExpire )
- {
- return;
- }
- mLastExpire = now;
- while( !mKeyList.empty() && (now - mKeyList.front()->mLastUse > mMemUsecs ) )
- {
- delete mKeyList.front();
- mKeyList.pop_front();
- mCount--;
- }
- }
- TKeyUseTrackerNode *findNode( TKey key )
- {
- ageKeys();
- typename TKeyList::iterator i;
- for( i = mKeyList.begin(); i != mKeyList.end(); i++ )
- {
- if( (*i)->mKey == key )
- return *i;
- }
- return NULL;
- }
- TKeyUseTrackerNode *removeNode( TKey key )
- {
- TKeyUseTrackerNode *i;
- i = findNode( key );
- if( i )
- {
- mKeyList.remove( i );
- mCount--;
- return i;
- }
- return NULL;
- }
- public:
- LLKeyUseTracker( U32 memory_seconds, U32 max_count ) :
- mLastExpire(0),
- mMaxCount( max_count ),
- mCount(0)
- {
- mMemUsecs = ((U64)memory_seconds) * 1000000;
- }
- ~LLKeyUseTracker()
- {
- // Flush list
- while( !mKeyList.empty() )
- {
- delete mKeyList.front();
- mKeyList.pop_front();
- mCount--;
- }
- }
- void markUse( TKey key, TData data )
- {
- TKeyUseTrackerNode *node = removeNode( key );
- if( !node )
- {
- node = new TKeyUseTrackerNode(key, data);
- }
- else
- {
- // Update data
- node->mData = data;
- }
- node->mLastUse = getTime();
- node->mUseCount++;
- mKeyList.push_back( node );
- mCount++;
- // Too many items? Drop head
- if( mCount > mMaxCount )
- {
- delete mKeyList.front();
- mKeyList.pop_front();
- mCount--;
- }
- }
- void forgetKey( TKey key )
- {
- TKeyUseTrackerNode *node = removeNode( key );
- if( node )
- {
- delete node;
- }
- }
- U32 getUseCount( TKey key )
- {
- TKeyUseTrackerNode *node = findNode( key );
- if( node )
- {
- return node->mUseCount;
- }
- return 0;
- }
- U64 getTimeSinceUse( TKey key )
- {
- TKeyUseTrackerNode *node = findNode( key );
- if( node )
- {
- U64 now = getTime();
- U64 delta = now - node->mLastUse;
- return (U32)( delta / 1000000 );
- }
- return 0;
- }
- TData *getLastUseData( TKey key )
- {
- TKeyUseTrackerNode *node = findNode( key );
- if( node )
- {
- return &node->mData;
- }
- return NULL;
- }
- U32 getKeyCount()
- {
- return mCount;
- }
- };
- #endif