pagemgr.cc

为数据库创建索引的B+树的算法实现。功能包括创建删除节点、条目等。最终将树递归打印于屏幕。（包含内存资源管理）

#include "pagemgr.h"

//------------------
// Page Pool Manager
//------------------

int blocklength;		// size of a page block
int cachesize;	 		// max. number of page blocks
char **cache;			// cache cont
vector<bool> isUsed;	// bitmap for used pages
int AvailBlockNum;		// # of avail blocks

int getNumBlockAvail() {
	return AvailBlockNum;
}

void InitPagePool(int csize,int blksize) {
	//assert(csize>0);	assert(blksize>0);
	cachesize=csize;	blocklength=blksize;	AvailBlockNum=csize;
	cache = new char*[cachesize];
	for (int i=0;i<cachesize;i++) cache[i] = new char[blocklength];
	isUsed.assign(cachesize,false);
}

void DestroyPagePool() {
	for (int i=0;i<cachesize;i++) delete[] cache[i];
	delete[] cache;
}

char* GetNewBlock(int& BlockId) {
	BlockId=-1;	
	for (int i=0;i<cachesize;i++)
		if (!isUsed[i]) {
			BlockId=i;
			isUsed[BlockId]=true;	AvailBlockNum--;
			return cache[BlockId];
		}
	return NULL;
}

void FreeBlock(int BlockId) {
	if  (isUsed[BlockId]) { isUsed[BlockId]=false;	AvailBlockNum++; }		
}