cmimealgo.cpp

BASE64编码/解码 处理的VC源代码

#include "stdafx.h"
#include "CMimeAlgo.h"



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


CMimeAlgo::CMimeAlgo()
{

}

CMimeAlgo::~CMimeAlgo()
{

}



//-------------------------------------------------------------
//interface

void CMimeAlgo::Encode( unsigned char ** outBuf, int & outBufLen, unsigned char * inSrcBuf, int inSrcLen )
{

	//
	// xxxxxxyy xxxxxxzz xxxxxxpp
	// to 
	// 0xxxxxx1 0xxxxxx1 0xxxxxx1 0yyzzpp1
	//



	outBufLen = (inSrcLen / 3 * 4) + (inSrcLen % 3) + (inSrcLen % 3 ? 1 : 0);
	*outBuf = new unsigned char [outBufLen + 1];//another byte for '\0'
	(*outBuf)[outBufLen] = '\0';//only for easy to use, len not include this byte


	unsigned char * p = *outBuf;//use as cursor
	unsigned char c;//use as worker unit

	for(int i=0; i<inSrcLen; i++ )
	{
		c = inSrcBuf[i] & ~ MakeBitSectionByOrder07(6, 7);
		c = c >> 1;
		* ( p ++ ) = ClearHeadAndSetTail(c);

		if( i % 3 == 2 )
		{
			c = inSrcBuf[i-2] & MakeBitSectionByOrder07(6, 7);
			c = c << 2;
			c |= inSrcBuf[i-1] & MakeBitSectionByOrder07(6, 7);
			c = c << 2;
			c |= inSrcBuf[i] & MakeBitSectionByOrder07(6, 7);
			c = c << 1;
			* ( p ++ ) = ClearHeadAndSetTail(c);
		}
		else if( i == (inSrcLen -1) )
		{
			if( i % 3 == 0 )
			{
				c = inSrcBuf[i] & MakeBitSectionByOrder07(6, 7);
				c = c << 5;
				* ( p ++ ) = ClearHeadAndSetTail(c);
			}
			else if( i % 3 == 1 )
			{
				c = inSrcBuf[i-1] & MakeBitSectionByOrder07(6, 7);
				c = c << 2;
				c = inSrcBuf[i] & MakeBitSectionByOrder07(6, 7);
				c = c << 3;
				* ( p ++ ) = ClearHeadAndSetTail(c);
			}
			else if( i % 3 == 2 )
			{
				; // note here do nothing, the if( i % 3 == 2 ) had done it
			}
		}
	}//for

	ASSERT(outBufLen == (p - *outBuf));
}

void CMimeAlgo::Decode( unsigned char ** outBuf, int & outBufLen, unsigned char * inSrcBuf, int inSrcLen )
{
	//
	// 0xxxxxx1 0xxxxxx1 0xxxxxx1 0yyzzpp1
	// to 
	// xxxxxxyy xxxxxxzz xxxxxxpp
	//

	
	outBufLen = (inSrcLen / 4 * 3) + (inSrcLen % 4) - (inSrcLen % 4 ? 1 : 0);
	*outBuf = new unsigned char [outBufLen + 1];//another byte for '\0'
	(*outBuf)[outBufLen] = '\0';//only for easy to use, len not include this byte


	unsigned char * p = *outBuf;//use as cursor
	unsigned char c;

	for(int i=0; i<inSrcLen; i++ )
	{
		if( i % 4 == 3 )
		{
			c = inSrcBuf[i] & MakeBitSectionByOrder07(1, 2);
			c = c >> 5;
			* (p - 3) |= c;

			c |= inSrcBuf[i] & MakeBitSectionByOrder07(3, 4);
			c = c >> 3;
			* (p - 2) |= c;

			c |= inSrcBuf[i] & MakeBitSectionByOrder07(5, 6);
			c = c >> 1;
			* (p - 1) |= c;
		}
		else
		{
			if( i != (inSrcLen -1) )
			{
				c = inSrcBuf[i];
				c = c << 1;
				* ( p ++ ) = c;
			}
			else
			{
				if( i % 4 == 0 )
				{
					; // not imposible // because inBuf is encoded before by EncodeEvery3ByteTo4Byte()
				}
				else if( i % 4 == 1 )
				{
					c = inSrcBuf[i] & MakeBitSectionByOrder07(1, 2);
					c = c >> 5;
					* (p - 1) |= c;
				}
				else if( i % 4 == 2 )
				{
					c = inSrcBuf[i] & MakeBitSectionByOrder07(1, 2);
					c = c >> 5;
					* (p - 2) |= c;

					c |= inSrcBuf[i] & MakeBitSectionByOrder07(3, 4);
					c = c >> 3;
					* (p - 1) |= c;
				}
				else if( i % 4 == 3 )
				{
					; // note here do nothing, the if( i % 4 == 3 ) had done it
				}
			}

		}//if
	}//for

	ASSERT(outBufLen == (p - *outBuf));
}



//-------------------------------------------------------------
//basic helper

inline bool CMimeAlgo::TestBitByOrder07(unsigned char inChar, int inWhich)
{
	if( (inChar & MakeBitByOrder07(inWhich)) == 0 )
	{
		return false;
	}
	else
	{
		return true;
	}
}

inline unsigned char CMimeAlgo::MakeBitByOrder07(int inWhich)
{
	return 1U << (7-inWhich) ;
}

unsigned char CMimeAlgo::MakeBitSectionByOrder07(int inFrom, int inTo)
{
	unsigned char c = 0x00;
	for(int k = inFrom; k <= inTo; k++)
	{
		SetBitByOrder07(c, k);
	}
	return c;
}

inline unsigned char CMimeAlgo::SetBitByOrder07(unsigned char & inoutChar, int inWhich)
{
	inoutChar |= MakeBitByOrder07(inWhich);
	return inoutChar;
}

inline unsigned char CMimeAlgo::ClearBitByOrder07(unsigned char & inoutChar, int inWhich)
{
	inoutChar &= ~ MakeBitByOrder07(inWhich);
	return inoutChar;
}

inline unsigned char CMimeAlgo::ClearHeadAndSetTail( unsigned char & inoutChar )
{
	ClearBitByOrder07(inoutChar, 0);
	SetBitByOrder07(inoutChar, 7);
	//now inoutChar is like 0xxx xxx1
	return inoutChar;
}



//-------------------------------------------------------------