cache.h

用CJ60Lib界面库制作的SQL数据库客户与服务器程序。

// cache.h
//

#ifndef _CACHE_H_
#define _CACHE_H_

#include "Error.h"
#include <afxtempl.h>

//////////////////////////////////////////////////////////////////////////////////
// constantS definition

const UINT FIELD_NAME_LEN =	32;
const UINT FIELD_NUM	  =	32;
const UINT FILE_NAME_LEN  =	20;
const UINT MAIN_NAME_LEN  =	16;
const UINT TEMP_SIZE	  =	80;					//temp arrays size
const UINT INDEX_NUM	  =	12;

const UINT BLOCK_OFFSET	  = 12;					//offset of one block
const UINT BLOCK_SIZE     = 1 << BLOCK_OFFSET;	//block size. In this situation, the size is 4K.
const UINT CACHE_SIZE     = 16;					//number of blocks

//////////////////////////////////////////////////////////////////////////////////
// status of a block

typedef struct{
	bool	dirty;							//if be modified
	bool	lock;							//if be locked
	UINT	level;							//LRU level
	long	pos;							//position in File
	CFile*	pFile;							//pointer to current file
}Status;

//////////////////////////////////////////////////////////////////////////////////
// CLASS CBLOCK

class CBlock
{
private:
	char Block[ BLOCK_SIZE ];

public:
	Status status;

public:
	//ImplementS
	CBlock();
	~CBlock();

	void Clear();
	Status* GetStatus();
	char* GetBlock();

	bool& dirty()
	{
		return status.dirty;
	}
	bool& lock()
	{
		return status.lock;
	}

	UINT Read( CFile* pFile, long pos );
	bool Write();
};

//////////////////////////////////////////////////////////////////////////////////
// CLASS CCACHE

class CCache
{
private:
	CBlock Cache[ CACHE_SIZE ];
	int last;								//the last used block
	CList<CFile*, CFile*> FileList;

private:
	//attributes
	int Next();
	int Find( POSITION fPos, long pos );
	POSITION Find( CFile* pFile );

public:
	CCache() : last( -1 ) {}
	~CCache()
	{
		Clear();
	}

	//implements
	POSITION Open( const char* fname, const char* fsuf = ".msl" );
	void Close( POSITION fPos, bool reserve = true );

	void Clear();
	CBlock* FetchBlock( POSITION fPos, long pos );

	void Read( POSITION fPos, long address, void* des, UINT sz );
	void Write( POSITION fPos, long address, const void* src, UINT sz );
};

extern CCache cache;

//////////////////////////////////////////////////////////////////////////////////
// CLASS CFILEAPI

class CFileAPI
{
//variables
private:
	long		AllocList;			//rec list head which has been deleted
	long		RecLen;				//the length of a single record
	long		RecCount;			//the count of records
	long		AttrBlocks;			//blocks taken by file directory
	bool		DelSign;			//is it signed when record is removed
	POSITION	fPos;				//file position in the list

//attributes
private:
	void LoadHead();
	void SaveHead();

//attributes
public:
	CFileAPI( const char* fname, const char* fsuf );
	CFileAPI( const char* fname, const char* fsuf, long rec_len, long attr_len, bool del_sign);
	~CFileAPI();

//implementations
public:
	long ntop( long n );

	void ReadAttr( void* des, UINT len );
	void WriteAttr( const void* src, UINT len );
	void ReadRec( long n, void* des );
	void WriteRec( long n, const void* src );

	CBlock* FetchBlock( long bpos );

	long AllocRec();
	void RemoveRec( long n );
	long NextRec( long n );
	long FirstRec();
	
	void Close();
	void Drop();
};

#endif