68 lines
2.1 KiB
C
68 lines
2.1 KiB
C
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/*
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* LRUCache.h
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*
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* Created on: 2014-6-30
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* Author: hanshuo
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*/
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#ifndef LRUCACHE_H_
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#define LRUCACHE_H_
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#include<map>
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#include<string>
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class VNode;
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// before using the cache, you must loadCache or createCache.
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class LRUCache
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{
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public:
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static int DEFAULT_CAPACITY;
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LRUCache(int _capacity=-1);
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~LRUCache();
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/* load cache's elements from an exist data file. */
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bool loadCache(std::string _filePath="./tree_file");
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/* create a new empty data file, the original one will be overwrite. */
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bool createCache(std::string _filePath="./tree_file");
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/* get the value(node's pointer) by key(node's file line). */
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VNode* get(int _key);
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/* set the key(node's file line) and value(node's pointer). if the key exists now, the value of this key will be overwritten. */
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bool set(int _key, VNode * _value);
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/* update the _key's mapping _value. if the key do not exist, this operation will fail and return false. */
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bool update(int _key, VNode* _value);
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/* write out all the elements to hard disk. */
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bool flush();
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int getCapacity();
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int getRestAmount();
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void showAmount();
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bool isFull();
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private:
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int capacity;
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int size;
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int* next;
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int* prev;
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int* keys;
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VNode** values;
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std::map<int,int> key2pos; // mapping from key to pos.
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std::string dataFilePath;
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static const int DEFAULT_NUM = 2;
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static const int START_INDEX = 0;
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static const int END_INDEX = 1;
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static const int NULL_INDEX = -1;
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static const int EOF_FLAG = -1;
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/* put the new visited one to the tail */
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void refresh(int _pos);
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/* free the memory of the _pos element in cache. */
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void freeElem(int _pos);
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/* set the memory of the _pos element in cache */
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void setElem(int _pos, int _key, VNode* _value);
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/* just write the values[_pos] to the hard disk, the VNode in memory will not be free. */
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bool writeOut(int _pos, int _fileLine=-1);
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/* read the value from hard disk, and put it to the values[_pos].
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* before use it, you must make sure that the _pos element in cache is free(unoccupied).*/
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bool readIn(int _pos, int _fileLine);
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};
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#endif /* LRUCACHE_H_ */
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