base64.cpp

MiniCA V2.0版本源码。《小型CA系统V2.1含源码》发表以来

/*
Module : Base64.cpp
Purpose: Implementation for a simple base64 decoding class
Created: PJN / 22-04-1999
History: None                    

Copyright (c) 1999 - 2004 by PJ Naughter.  

All rights reserved.

Copyright / Usage Details:

You are allowed to include the source code in any product (commercial, shareware, freeware or otherwise) 
when your product is released in binary form. You are allowed to modify the source code in any way you want 
except you cannot modify the copyright details at the top of each module. If you want to distribute source 
code with your application, then you are only allowed to distribute versions released by the author. This is 
to maintain a single distribution point for the source code. 

*/



//////////////// Includes ////////////////////////////////////////////

#include "stdafx.h"
#include "Base64.h"



//////////////// Statics / Macros ////////////////////////////////////

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



//////////////// Implementation //////////////////////////////////////

int CBase64::DecodeGetRequiredLength(int nSrcLen)
{
	return nSrcLen;
}

int CBase64::EncodeGetRequiredLength(int nSrcLen, DWORD dwFlags)
{
	int nRet = nSrcLen*4/3;

	if ((dwFlags & BASE64_FLAG_NOPAD) == 0)
		nRet += nSrcLen % 3;

	int nCRLFs = nRet / 76 + 1;
	int nOnLastLine = nRet % 76;

	if (nOnLastLine)
	{
		if (nOnLastLine % 4)
			nRet += 4-(nOnLastLine % 4);
	}

	nCRLFs *= 2;

	if ((dwFlags & BASE64_FLAG_NOCRLF) == 0)
		nRet += nCRLFs;

	return nRet;
}

BOOL CBase64::Encode(const BYTE* pbSrcData, int nSrcLen,	LPSTR szDest,	int* pnDestLen,	DWORD dwFlags)
{
	static const char s_chBase64EncodingTable[64] = 
  {
		'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',
		'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g',	'h',
		'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y',
		'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

  //Validate our parameters
	if (!pbSrcData || !szDest || !pnDestLen)
		return FALSE;

	ASSERT(*pnDestLen >= EncodeGetRequiredLength(nSrcLen, dwFlags));

	int nWritten( 0 );
	int nLen1( (nSrcLen/3)*4 );
	int nLen2( nLen1/76 );
	int nLen3( 19 );

	for (int i=0; i<=nLen2; i++)
	{
		if (i==nLen2)
			nLen3 = (nLen1%76)/4;

		for (int j=0; j<nLen3; j++)
		{
			DWORD dwCurr(0);
			for (int n=0; n<3; n++)
			{
				dwCurr |= *pbSrcData++;
				dwCurr <<= 8;
			}
			for (int k=0; k<4; k++)
			{
				BYTE b = (BYTE)(dwCurr>>26);
				*szDest++ = s_chBase64EncodingTable[b];
				dwCurr <<= 6;
			}
		}
		nWritten+= nLen3*4;

		if ((dwFlags & BASE64_FLAG_NOCRLF)==0)
		{
			*szDest++ = '\r';
			*szDest++ = '\n';
			nWritten+= 2;
		}
	}

	if (nWritten && (dwFlags & BASE64_FLAG_NOCRLF)==0)
	{
		szDest-= 2;
		nWritten -= 2;
	}

	nLen2 = nSrcLen%3 ? nSrcLen%3 + 1 : 0;
	if (nLen2)
	{
		DWORD dwCurr(0);
		for (int n=0; n<3; n++)
		{
			if (n<(nSrcLen%3))
				dwCurr |= *pbSrcData++;
			dwCurr <<= 8;
		}
		for (int k=0; k<nLen2; k++)
		{
			BYTE b = (BYTE)(dwCurr>>26);
			*szDest++ = s_chBase64EncodingTable[b];
			dwCurr <<= 6;
		}
		nWritten+= nLen2;
		if ((dwFlags & BASE64_FLAG_NOPAD)==0)
		{
			nLen3 = nLen2 ? 4-nLen2 : 0;
			for (int j=0; j<nLen3; j++)
			{
				*szDest++ = '=';
			}
			nWritten+= nLen3;
		}
	}

	*pnDestLen = nWritten;
	return TRUE;
}

int CBase64::DecodeChar(unsigned int ch)
{
	// returns -1 if the character is invalid
	// or should be skipped
	// otherwise, returns the 6-bit code for the character
	// from the encoding table
	if (ch >= 'A' && ch <= 'Z')
		return ch - 'A' + 0;	// 0 range starts at 'A'
	if (ch >= 'a' && ch <= 'z')
		return ch - 'a' + 26;	// 26 range starts at 'a'
	if (ch >= '0' && ch <= '9')
		return ch - '0' + 52;	// 52 range starts at '0'
	if (ch == '+')
		return 62;
	if (ch == '/')
		return 63;
	return -1;
}

BOOL CBase64::Decode(LPCSTR szSrc, int nSrcLen, BYTE *pbDest, int *pnDestLen)
{
	// walk the source buffer
	// each four character sequence is converted to 3 bytes
	// CRLFs and =, and any characters not in the encoding table
	// are skiped

  //Validate our parameters
	if (!szSrc || !pbDest || !pnDestLen)
		return FALSE;

	LPCSTR szSrcEnd = szSrc + nSrcLen;
	int nWritten = 0;
	while (szSrc < szSrcEnd)
	{
		DWORD dwCurr = 0;
		int i;
		int nBits = 0;
		for (i=0; i<4; i++)
		{
			if (szSrc >= szSrcEnd)
				break;
			int nCh = DecodeChar(*szSrc);
			szSrc++;
			if (nCh == -1)
			{
				// skip this char
				i--;
				continue;
			}
			dwCurr <<= 6;
			dwCurr |= nCh;
			nBits += 6;
		}
		// dwCurr has the 3 bytes to write to the output buffer
		// left to right
		dwCurr <<= 24-nBits;
		for (i=0; i<nBits/8; i++)
		{
			*pbDest = (BYTE) ((dwCurr & 0x00ff0000) >> 16);
			dwCurr <<= 8;
			pbDest++;
			nWritten++;
		}
	}

	*pnDestLen = nWritten;
	return TRUE;
}