base64.cpp

完整的Base64加密和解密函数

#include <afx.h>

void* Base64Encode(const void *lpSoure, int cbSource, void *lpDest, int cbDest)
{
	int i, j;
	const unsigned char *lpSourceByte = (const unsigned char *)lpSoure;
	unsigned char *lpDestByte = (unsigned char *)lpDest;
	unsigned char byte[3];
    static const char key[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	
	if (cbDest < (cbSource + 2)/3 * 4){
		// No enough room to fill the encoded data
		return NULL;
	}
	
	memset(lpDest, 0, cbDest);
	
	for (i = 0, j = 0; i < cbSource; i += 3, j += 4){
		byte[0] = lpSourceByte[i + 0];
		lpDestByte[j + 0] = key[(byte[0] & 0xfc) >> 2];
		if (i + 1 < cbSource) {
			byte[1] = lpSourceByte[i + 1];
			lpDestByte[j + 1] = key[((byte[0] & 0x03) << 4) | ((byte[1] & 0xf0) >> 4)];
		} else {
			byte[1] = 0;
			lpDestByte[j + 1] = key[((byte[0] & 0x03) << 4) | ((byte[1] & 0xf0) >> 4)];
			lpDestByte[j + 2] = '=';
			lpDestByte[j + 3] = '=';
			break;
		}
		
		if (i + 2 < cbSource) {
			byte[2] = lpSourceByte[i + 2];
			lpDestByte[j + 2] = key[((byte[1] & 0x0f) << 2) | ((byte[2] & 0xc0) >> 6)];
			lpDestByte[j + 3] = key[(byte[2] & 0x3f)];
		} else {
			byte[2] = 0;
			lpDestByte[j + 2] = key[((byte[1] & 0x0f) << 2) | ((byte[2] & 0xc0) >> 6)];
			lpDestByte[j + 3] = '=';
		}
	}
	return lpDestByte;
}

void* Base64Encode(const void *lpSoure, int cbSource, CString &csDest)
{
	int cbDest = (cbSource + 2)/3 * 4 + 1;
	char *lpDest = new char[cbDest];
	void *lpResult = Base64Encode(lpSoure, cbSource, lpDest, cbDest);
	csDest = lpDest;
	delete lpDest;
	return lpResult;
}

void* Base64Encode(LPCSTR csSource, CString &csDest)
{
	return Base64Encode(csSource, strlen(csSource), csDest);
}

unsigned char DecodeByte(char ch)
{
    static const char key[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	for (unsigned i = 0; i < strlen(key); i ++){
		if (key[i] == ch) return i;
		if (ch == '=') return '\x80';
	}
	_ASSERT(FALSE);
	return '\x40';
}

int Base64Decode(const void *lpSoure, int cbSource, void *lpDest, int cbDest)
{
	int i, j;
	const unsigned char *lpSourceByte = (const unsigned char *)lpSoure;
	unsigned char *lpDestByte = (unsigned char *)lpDest;
	unsigned char byte[4];

	if (cbDest < cbSource * 3 / 4){
		// No enough room to fill the encoded data
		return -1;
	}

	memset(lpDest, 0, cbDest);

	for (i = 0, j = 0; i < cbSource; ){
		// 现在这4个字节都是 00ABCDEF 00GHIJKL 00MNOPQR 00STUVWX
		if (lpSourceByte[i + 0] <= ' '){
			i ++;
			continue;
		}
		byte[0] = DecodeByte(lpSourceByte[i + 0]);
		if (byte[0] & 0xC0) break;
		byte[1] = DecodeByte(lpSourceByte[i + 1]);
		if (byte[1] & 0xC0) break;
		lpDestByte[j++] = (unsigned char)(byte[0] << 2) | (unsigned char)((byte[1] & 0x30) >> 4); // ABCDEF-GH

		byte[2] = DecodeByte(lpSourceByte[i + 2]);
		if (byte[2] & 0xC0) break;
		lpDestByte[j++] = (unsigned char)(byte[1] << 4) | (unsigned char)((byte[2] & 0x3C) >> 2); // IJKL-MNOP

		byte[3] = DecodeByte(lpSourceByte[i + 3]);
		if (byte[3] & 0xC0) break;
		lpDestByte[j++] = (unsigned char)(byte[2] << 6) | (unsigned char)byte[3]; // QRSTUVWX
		i += 4;
	}

	return j;
}

int QuotedPrintableDecode(char * lpSource)
{
	char * p = lpSource;
	char * q = lpSource;

	while (*p){
		char ch = *p;
		if (ch == '='){
			int nValue = 0;
			sscanf(p, "=%02X", &nValue);
			*q = (char)nValue;
			p += 3;
		} else {
			*q = ch;
			p ++;
		}
		q ++;
	}
	*q = '\0';
	return q - lpSource;
}