hashtable.cpp

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// HashTable.cpp: implementation of the CHashTable class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "Database.h"
#include "HashTable.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CHashTable::CHashTable()
{
    end=MAIN_BLOCK;
	ID=0;
    RcdLength=0;
	::memset(pHashBlock,0,HASH*sizeof(CHashBlock *));
}
CHashTable::CHashTable(UINT RcdLen,UINT id)
{
	CString s;
	s.Format("D:\\DB\\%d.hash",id);
	CFile file(LPCTSTR(s),CFile::modeCreate|CFile::modeReadWrite);
	UINT filelength=file.GetLength();
	if(filelength==0)//是新文件
	{
		const char *magic="Has";
		file.SetLength(MAIN_BLOCK);//初始4096字节
		ID=id;
		end=MAIN_BLOCK;//2048*4096
		RcdLength=RcdLen;
		::memset(pHashBlock,0,HASH*sizeof(CHashBlock *));

        file.SeekToBegin();
		file.Write(magic,MAGIC);
		file.Write(&ID,sizeof(UINT));
		file.Write(&end,sizeof(UINT));
		file.Write(&RcdLength,sizeof(UINT));
	}
	else
	{
		char *magic[4];
		file.SeekToBegin();
		file.Read(magic,MAGIC);
		//if(strcmp(magic,"Has"))
			//::AfxThrowFileException(
		file.Read(&ID,sizeof(UINT));
		file.Read(&end,sizeof(UINT));
		file.Read(&RcdLength,sizeof(UINT));
		::memset(pHashBlock,0,HASH*sizeof(CHashBlock *));
	}
}
CHashTable::~CHashTable()
{
	if(RcdLength!=0)
	{
		UINT i;
		for(i=0;i<HASH;i++)
			delete pHashBlock[i];
	}
}

BOOL CHashTable::InsertRecord(Record *rcd,bool Dup)
{
	ASSERT(rcd->m_length==this->RcdLength);
    WORD HashCode=rcd->Hash();
	ASSERT(HashCode>=0 && HashCode<=2046);
	
	if(!pHashBlock[HashCode])
	{
		BYTE *buf=new BYTE[MAIN_BLOCK];
		pHashBlock[HashCode]=new CHashBlock(buf,MAIN_BLOCK,DB_NULL,RcdLength,FALSE);//dirty
	}
	if(pHashBlock[HashCode]->MemCompare(rcd,Dup)==TRUE && !Dup)
	{
		return FALSE;
	}
	BOOL finish=FALSE;

	CString s;
	s.Format("D:\\DB\\%d.hash",ID);
	CFile f(LPCTSTR(s),CFile::modeReadWrite);
	UINT FileLength=f.GetLength();
	PDB newblock=0;

    CHashBlock *phblk=pHashBlock[HashCode];
	do
	{
		do
		{
		    finish=phblk->AppendRecord(rcd);
			if(!finish)
			{
				phblk=CMemory::ReadHashBlock(phblk->NextBlock,RcdLength,TRUE);//clean
			}
		}
		while(!finish && pHashBlock);
		if(!finish)
		{
            f.SetLength(FileLength+MAIN_BLOCK);
			newblock=(PDB(ID)<<32)+PDB(end);
			phblk->NextBlock=newblock;
			end+=MAIN_BLOCK;
			phblk=CMemory::ReadHashBlock(newblock,RcdLength,FALSE);//dirty
		}
	}
	while(!finish);
	f.Close();

	return TRUE;
}