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/**************************************************************
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*************************************************************/
#ifndef INCLUDED_BINARYURP_SOURCE_CACHE_HXX
#define INCLUDED_BINARYURP_SOURCE_CACHE_HXX
#include "sal/config.h"
#include <cstddef>
#include <list>
#ifdef USE_UNORDERED_MAP
#include <unordered_map>
#else
#include <map>
#endif
#include "boost/noncopyable.hpp"
#include "osl/diagnose.h"
#include "sal/types.h"
namespace binaryurp {
namespace cache {
enum { size = 256, ignore = 0xFFFF };
}
template< typename T > class Cache : private boost::noncopyable {
public:
typedef sal_uInt16 IdxType;
explicit Cache(std::size_t size):
size_(size)
{
OSL_ASSERT(size < cache::ignore);
}
IdxType add( const T& rContent, bool* pbFound) {
OSL_ASSERT( pbFound != NULL);
if( !size_) {
*pbFound = false;
return cache::ignore;
}
// try to insert into the map
list_.push_front( rContent); // create a temp entry
typedef std::pair<typename LruList::iterator, IdxType> MappedType;
typedef std::pair<typename LruItMap::iterator,bool> MapPair;
MapPair aMP = map_.insert( MappedType( list_.begin(), 0));
*pbFound = !aMP.second;
if( !aMP.second) { // insertion not needed => found the entry
list_.pop_front(); // remove the temp entry
list_.splice( list_.begin(), list_, aMP.first->first); // the found entry is moved to front
return aMP.first->second;
}
// test insertion successful => it was new so we keep it
IdxType n = static_cast<IdxType>( map_.size() - 1);
if( n >= size_) { // cache full => replace the LRU entry
// find the least recently used element in the map
typename LruItMap::iterator it = map_.find( --list_.end());
n = it->second;
map_.erase( it); // remove it from the map
list_.pop_back(); // remove from the list
}
aMP.first->second = n;
return n;
}
private:
typedef std::list<T> LruList; // last recently used list
typedef typename LruList::iterator LruListIt;
#ifdef URPCACHE_USES_UNORDERED_MAP
struct HashT{ size_t operator()( const LruListIt& rA) const { return hash(*rA;);};
struct EqualT{ bool operator()( const LruListIt& rA, const LruListIt& rB) const { return *rA==*rB;}};
typedef ::std::unordered_map< LruListIt, IdxType, HashT, EqualT > LruItMap; // a map into a LruList
#else
struct CmpT{ bool operator()( const LruListIt& rA, const LruListIt& rB) const { return (*rA<*rB);}};
typedef ::std::map< LruListIt, IdxType, CmpT > LruItMap; // a map into a LruList
#endif
std::size_t size_;
LruItMap map_;
LruList list_;
};
}
#endif
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