base64.cpp

base64算法,前几天用来截获MSN协议时获取文件名时使用的。之前用的一个网上下下来的base64的源码

// base64.cpp : 定义 DLL 应用程序的入口点。
//

#include "stdafx.h"
#include "base64.h"


#ifdef _MANAGED
#pragma managed(push, off)
#endif

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
					 )
{
	switch (ul_reason_for_call)
	{
	case DLL_PROCESS_ATTACH:
	case DLL_THREAD_ATTACH:
	case DLL_THREAD_DETACH:
	case DLL_PROCESS_DETACH:
		break;
	}
    return TRUE;
}

#ifdef _MANAGED
#pragma managed(pop)
#endif


int Base64Index(BYTE base64Char)
{
	int index=0;
	for(;index<64;index++)
		if (base64Char==Base64Code[index])
			return index;
	return -1;
}

BASE64_API void Base64Encode(LPCBYTE source,ULONG sourceLength,LPBYTE destination,ULONG& destinationLength)
{
	int num = sourceLength/3;
	int rest = sourceLength%3;
	int destIndex = 0;
	int i=0;
	for (;i<num*3;i++)
	{
		BYTE curByte=source[i],prevByte=0;
		if(i>0)prevByte=source[i-1];
		if(i%3==0)
			destination[destIndex] = Base64Code[(curByte>>2)];
		if(i%3==1)
		{
			BYTE b = ((prevByte&0x3)<<4)+(curByte>>4);
			destination[destIndex] = Base64Code[b];
		}
		if(i%3==2)
		{
			BYTE b = ((prevByte&0xf)<<2)+(curByte>>6);
			destination[destIndex] = Base64Code[b];
			destIndex++;
			b = curByte&0x3f;
			destination[destIndex] = Base64Code[b];
		}

		destIndex++;
	}
	if(rest==1)
	{
		destination[destIndex] = Base64Code[source[i]>>2];
		destIndex++;
		destination[destIndex] = Base64Code[(source[i]&0x3)<<4];
		destIndex++;
		destination[destIndex] = '=';
		destIndex++;
		destination[destIndex] = '=';
		destIndex++;
	}
	if(rest==2)
	{
		destination[destIndex] = Base64Code[source[i]>>2];
		destIndex++;
		destination[destIndex] = Base64Code[((source[i]&0x3)<<4)+(source[i+1]>>4)];
		destIndex++;
		destination[destIndex] = Base64Code[(source[i+1]&0xf)<<2];
		destIndex++;
		destination[destIndex] = '=';
		destIndex++;
	}

	destinationLength = destIndex;
}

BASE64_API BOOL Base64Decode(LPCBYTE source,ULONG sourceLength,LPBYTE destination,ULONG& destinationLength)
{
	if(sourceLength<4||sourceLength%4)
		return FALSE;
	int eNum = 0;
	int num = 0;
	if(source[sourceLength-1] == '=')
		eNum++;
	if(source[sourceLength-2] == '=')
		eNum++;

	num = sourceLength/4;
	if(eNum!=0)
		num--;

	int i = 0, destIndex = 0;
	BYTE curByte = 0,nextByte = 0;
	for (;i<num*4;i++)
	{
		if(i%4==3)
			continue;

		curByte  = Base64Index(source[i]);
		nextByte = Base64Index(source[i+1]);

		if(i%4==0)
			destination[destIndex] = (curByte<<2)+(nextByte>>4);
		if(i%4==1)
			destination[destIndex] = ((curByte&0xf)<<4)+(nextByte>>2);
		if(i%4==2)
			destination[destIndex] = ((curByte&0x3)<<6)+nextByte;

		destIndex++;
	}
	if(eNum==1)
	{
		curByte  = Base64Index(source[i]);
		nextByte = Base64Index(source[i+1]);
		destination[destIndex] = (curByte<<2)+(nextByte>>4);
		curByte  = nextByte;
		nextByte = Base64Index(source[i+2]);
		destIndex++;
		destination[destIndex] = ((curByte&0xf)<<4)+(nextByte>>2);
		destIndex++;
		destination[destIndex] = 0;
	}
	if(eNum==2)
	{
		curByte  = Base64Index(source[i]);
		nextByte = Base64Index(source[i+1]);
		destination[destIndex] = (curByte<<2)+(nextByte>>4);
		destIndex++;
		destination[destIndex] = 0;
		destination[destIndex+1] = 0;
	}
	destinationLength = destIndex;

	return TRUE;
}