crc.cpp

SQLBig5BugTool 宽字符操作问题

// CRC.cpp: implementation of the CCRC class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "CRC.h"

#define CRC_TABLE_SIZE 256

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

CCRC::CCRC()
{

}

CCRC::~CCRC()
{

}

// Reflection is a requirement for the official CRC-32 standard.
// You can create CRCs without it, but they won't conform to the standard.
ULONG CCRC::Reflect(ULONG ref, char ch)
{// Used only by Init_CRC32_Table()
	
	ULONG value(0);
	
	// Swap bit 0 for bit 7 , bit 1 for bit 6, etc.
	for(int i = 1; i < (ch + 1); i++)
	{
		if(ref & 1)
			value |= 1 << (ch - i);
		ref >>= 1;
	}
	return value;
}

void CCRC::Init_CRC32_Table(ULONG *crc32_table)
{
	// This is the official polynomial used by CRC-32 in PKZip, WinZip and Ethernet. 
	ULONG ulPolynomial = 0x04c11db7;
	
	// 256 values representing ASCII character codes.
	for(int i = 0; i <= 0xFF; i++)
	{
		crc32_table[i]=Reflect(i, 8) << 24;
		for (int j = 0; j < 8; j++)
			crc32_table[i] = (crc32_table[i] << 1) ^ (crc32_table[i] & (1 << 31) ? ulPolynomial : 0);
		crc32_table[i] = Reflect(crc32_table[i], 32);
	}
	
}


// This function uses the crc32_table lookup table to generate a CRC for csData
int CCRC::Get_CRC(PBYTE pbBuf, DWORD dwSize)
{
	static BOOL bInitiated=FALSE;

	static ULONG crc32_table[256]={0,}; // Lookup table arrays
	
	if(!bInitiated)
	{
		Init_CRC32_Table(crc32_table);
		bInitiated=TRUE;
	}
	// Be sure to use unsigned variables,
	// because negative values introduce high bits
	// where zero bits are required.
	ULONG  crc(0xffffffff);
	int len;
	unsigned char* buffer=pbBuf;
	
	len = dwSize;
	
	// Perform the algorithm on each character
	// in the string, using the lookup table values.
	while(len--)
		crc = (crc >> 8) ^ crc32_table[(crc & 0xFF) ^ *buffer++];
	// Exclusive OR the result with the beginning value.
	return crc^0xffffffff;
}

BOOL CCRC::GetFileCRC32(const char * pszFilePath,ULONG& ulCRC)
{
	ulCRC=0;
	
	HANDLE hFile=CreateFile(pszFilePath, GENERIC_READ , FILE_SHARE_READ, NULL,OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);  
	if(!hFile)
	{
		return FALSE;
	}
	DWORD dwSize=GetFileSize(hFile,0);
	if(dwSize==0)
	{
		return TRUE;
	}
  
	HANDLE  hFileMap = CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, dwSize,NULL);  
	if(!hFileMap)
	{
		CloseHandle(hFile);
		return FALSE;	
	}
	PBYTE pbBuf=(PBYTE)MapViewOfFile(hFileMap,FILE_MAP_READ, 0, 0,dwSize); 
	if(!pbBuf)
	{
		CloseHandle(hFileMap);
		CloseHandle(hFile);
		return FALSE;	
	}
	
	ulCRC = Get_CRC(pbBuf,dwSize);

	UnmapViewOfFile(pbBuf);
	CloseHandle(hFileMap);
	CloseHandle(hFile);

	return TRUE;
}