/************************ Copyright (c) 2006 ************************

程序作者:

    張魯奪(zhangluduo) : 為所有愛我的人和我愛的人努力!

聯系方式:

    zhangluduo@msn.com
	[oopfans]群:34064264

修改時間:

    2007-03-04

功能描述:

    Base64編碼和解碼

版權聲明:

    許可任何單位,個人隨意使用,拷貝,修改,散布及出售這份代碼,但是必須保
    留此版權信息,以慰藉作者辛勤的勞動,及表明此代碼的來源,如若此份代碼
    有任何BUG,請通知作者,以便彌補作者由于水平所限而導致的一些錯誤和不
    足,謝謝!

	注:
	先前寫的代碼有Bug,不能對文件進行base64計算,后根據網上例子修改而來!

************************ Copyright (c) 2006 ************************/

#include "stdAfx.h"
#include "ZBase64.h"

string ZBase64::Encode(const unsigned char* Data,int DataByte)
{
	//編碼表
	const char EncodeTable[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

	//返回值
	string strEncode;

	unsigned char Tmp[3]={0};
	int LineLength=0;

	for(int i=0;i<(int)(DataByte / 3);i++)
	{
        Tmp[1] = *Data++;
        Tmp[2] = *Data++;
        Tmp[3] = *Data++;

        strEncode+= EncodeTable[Tmp[1] >> 2];
        strEncode+= EncodeTable[((Tmp[1] << 4) | (Tmp[2] >> 4)) & 0x3F];
        strEncode+= EncodeTable[((Tmp[2] << 2) | (Tmp[3] >> 6)) & 0x3F];
        strEncode+= EncodeTable[Tmp[3] & 0x3F];
		if(LineLength+=4,LineLength==76) {strEncode+="\r\n";LineLength=0;}
	}

	//對剩余數據進行編碼
	int Mod=DataByte % 3;
	if(Mod==1)
	{
        Tmp[1] = *Data++;
        strEncode+= EncodeTable[(Tmp[1] & 0xFC) >> 2];
        strEncode+= EncodeTable[((Tmp[1] & 0x03) << 4)];
        strEncode+= "==";
	}
	else if(Mod==2)
	{
		Tmp[1] = *Data++;
		Tmp[2] = *Data++;
		strEncode+= EncodeTable[(Tmp[1] & 0xFC) >> 2];
		strEncode+= EncodeTable[((Tmp[1] & 0x03) << 4) | ((Tmp[2] & 0xF0) >> 4)];
		strEncode+= EncodeTable[((Tmp[2] & 0x0F) << 2)];
		strEncode+= "=";
	}
	
	return strEncode;
}

string ZBase64::Decode(const char* Data,int DataByte,int& OutByte)
{
	//解碼表
	const char DecodeTable[] =
	{
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		62, // '+'
		0, 0, 0,
		63, // '/'
		52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // '0'-'9'
		0, 0, 0, 0, 0, 0, 0,
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
		13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // 'A'-'Z'
		0, 0, 0, 0, 0, 0,
		26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
		39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // 'a'-'z'
	};

	//返回值
	string strDecode;

    int nValue;
    int i= 0;
 
    while (i < DataByte)
    {
        if (*Data != '\r' && *Data!='\n')
        {
            nValue = DecodeTable[*Data++] << 18;
            nValue += DecodeTable[*Data++] << 12;
			strDecode+=(nValue & 0x00FF0000) >> 16;
            OutByte++;
 
            if (*Data != '=')
            {
                nValue += DecodeTable[*Data++] << 6;
				strDecode+=(nValue & 0x0000FF00) >> 8;
                OutByte++;
 
                if (*Data != '=')
                {
                    nValue += DecodeTable[*Data++];
					strDecode+=nValue & 0x000000FF;
                    OutByte++;
                }
            }
            i += 4;
        }
        else// 回車換行,跳過
        {
            Data++;
            i++;
        }
     }
	return strDecode;
}