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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* 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 .
*/
#pragma once
#include <sal/config.h>
#include <cassert>
#include <cstddef>
#include <map>
#include <list>
#include <sal/types.h>
namespace binaryurp {
namespace cache {
enum { size = 256, ignore = 0xFFFF };
}
template< typename T > class Cache {
public:
typedef sal_uInt16 IdxType;
explicit Cache(std::size_t size):
size_(size)
{
assert(size < cache::ignore);
}
IdxType add( const T& rContent, bool* pbFound) {
assert( pbFound != nullptr);
if( !size_) {
*pbFound = false;
return cache::ignore;
}
// try to insert into the map
list_.push_front( rContent); // create a temp entry
auto const [it, inserted] = map_.emplace( list_.begin(), 0 );
*pbFound = !inserted;
if( !inserted) { // insertion not needed => found the entry
list_.pop_front(); // remove the temp entry
list_.splice( list_.begin(), list_, it->first); // the found entry is moved to front
return it->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 lru = map_.find( --list_.end());
n = lru->second;
map_.erase( lru); // remove it from the map
list_.pop_back(); // remove from the list
}
it->second = n;
return n;
}
private:
Cache(const Cache&) = delete;
Cache& operator=(const Cache&) = delete;
typedef std::list<T> LruList; // last recently used list
typedef typename LruList::iterator LruListIt;
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
std::size_t size_;
LruItMap map_;
LruList list_;
};
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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