97 lines
3.5 KiB
C++
97 lines
3.5 KiB
C++
/*=============================================================================
|
|
# Filename: LRUCache.h
|
|
# Author: Bookug Lobert
|
|
# Mail: zengli-bookug@pku.edu.cn
|
|
# Last Modified: 2016-04-11 14:05
|
|
# Description: written by hanshuo
|
|
=============================================================================*/
|
|
|
|
#ifndef _VSTREE_LRUCACHE_H
|
|
#define _VSTREE_LRUCACHE_H
|
|
|
|
#include "../Util/Util.h"
|
|
|
|
class VNode;
|
|
|
|
//NOTICE: we should implement the LRU, not simply FIFO
|
|
//not only consider updates, but also visits
|
|
//TODO:this may cause the cost of mutiple-thread-sync very high
|
|
|
|
// before using the cache, you must loadCache or createCache.
|
|
class LRUCache
|
|
{
|
|
public:
|
|
|
|
static int DEFAULT_CAPACITY;
|
|
|
|
LRUCache(int _capacity=-1);
|
|
~LRUCache();
|
|
//load cache's elements from an exist data file.
|
|
bool loadCache(std::string _filePath="./tree_file");
|
|
//create a new empty data file, the original one will be overwrite.
|
|
bool createCache(std::string _filePath="./tree_file");
|
|
//get the value(node's pointer) by key(node's file line).
|
|
VNode* get(int _key);
|
|
//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.
|
|
bool set(int _key, VNode * _value);
|
|
//delete a node from LRUcache and file
|
|
bool del(int _key);
|
|
//update the _key's mapping _value. if the key do not exist, this operation will fail and return false.
|
|
bool update(int _key, VNode* _value);
|
|
//write out all the elements to hard disk.
|
|
bool flush();
|
|
int getCapacity();
|
|
int getRestAmount();
|
|
void showAmount();
|
|
bool isFull();
|
|
|
|
private:
|
|
int capacity;
|
|
int size;
|
|
int* next;
|
|
int* prev;
|
|
//NOTICE:pos is the index of keys and values, while file_line(key) is the ID of VNode,
|
|
//as well as the file part number
|
|
//(pos is needed due to swap-in-out and insert/delete)
|
|
int* keys;
|
|
VNode** values;
|
|
//NOTICE: the key is node file line, i.e. vstree node ID
|
|
std::map<int,int> key2pos; // mapping from key to pos.
|
|
std::string dataFilePath;
|
|
static const int DEFAULT_NUM = 2;
|
|
static const int START_INDEX = 0;
|
|
static const int END_INDEX = 1;
|
|
static const int NULL_INDEX = -1;
|
|
static const int EOF_FLAG = -1;
|
|
//put the new visited one to the tail
|
|
void refresh(int _pos);
|
|
//free the memory of the _pos element in cache.
|
|
void freeElem(int _pos);
|
|
//set the memory of the _pos element in cache
|
|
void setElem(int _pos, int _key, VNode* _value);
|
|
//move pos2 ele to pos1, and pos1 ele should be freed
|
|
void fillElem(int _pos1, int _pos2);
|
|
bool freeDisk(int _pos);
|
|
//just write the values[_pos] to the hard disk, the VNode in memory will not be free.
|
|
bool writeOut(int _pos, int _fileLine=-1);
|
|
//read the value from hard disk, and put it to the values[_pos].
|
|
//before use it, you must make sure that the _pos element in cache is free(unoccupied).
|
|
bool readIn(int _pos, int _fileLine);
|
|
|
|
//NOTICE: cost of rw lock is higher than mutex
|
|
//By default, read lock is recursive, write lock not, we can set mutex as recursive
|
|
//You can acquire read lock first and then upgrade to write lock, finally unlock twice
|
|
//R/W lock only fits for many-read and rare-write cases
|
|
//
|
|
//lock the whole buffer if get/set/swap element
|
|
#ifdef THREAD_ON
|
|
pthread_rwlock_t cache_lock;
|
|
//TODO:if find no unlocked one to swap out, then need to wait by cond
|
|
//pthread_cond_t cache_cond;
|
|
#endif
|
|
|
|
};
|
|
|
|
#endif //_VSTREE_LRUCACHE_H
|
|
|