#pragma once
//从ATL的base64库整理而来
//整理的目的是提供一个仅基于标准c++的base64库，提高代码的可移植性
#include <string>
namespace Crypt
{
class Base64
{
public:
enum Base64_Flag
{
ATL_BASE64_FLAG_NONE = 0, // 0000 0000 标准的编码方式（RFC2045）
ATL_BASE64_FLAG_NOPAD = 1 , // 0000 0001 没有补全（ = ）
ATL_BASE64_FLAG_NOCRLF = 2 // 0000 0010 没有换行 ( crlf )
} ;
//计算编码后的长度
static int EncodeGetRequiredLength(int nSrcLen, Base64_Flag dwFlags = ATL_BASE64_FLAG_NONE)
{
int nRet = static_cast<int>( (nSrcLen<<2) /3);
if ((dwFlags & ATL_BASE64_FLAG_NOPAD) == 0)// 需要补全 =
nRet += nSrcLen % 3;
int nOnLastLine = nRet % 76;
if (nOnLastLine)
{
if ( (nOnLastLine & 0x03) ) //nOnLastLine % 4
nRet += 4-(nOnLastLine & 0x03 );
}
if ((dwFlags & ATL_BASE64_FLAG_NOCRLF) == 0) //需要换行符
{
nRet += ((nRet / 76 + 1) << 1) ;//(nRet / 76 + 1) * 2, 回车换行个数（+1是为了取最多值），根据rfc2045，编码后一行最多76个字符（不含换行）
}
return nRet;
}
inline static int DecodeGetRequiredLength(int nSrcLen)
{
return ((nSrcLen*3)>>2)+2; //(nSrcLen*3)/4+2
}
//pbSrcData 要编码的原始数据
//nSrcLen 原始数据长度
//szDest 编码后的输出
//pnEncodeRealLen 编码后的实际长度
static bool Encode(const unsigned char *pbSrcData,int nSrcLen,char* szDest,int *pnEncodeRealLen,Base64_Flag dwFlags = ATL_BASE64_FLAG_NONE)
{
static const char *s_chBase64EncodingTable="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
if (!pbSrcData || !szDest || !pnEncodeRealLen)
{
return false;
}
int nWritten = 0 ; //编码后的长度，EncodeGetRequiredLength获得的长度通常大于实际长度
int nLen1 = (nSrcLen/3) << 2; // (nSrcLen/3)*4
int nLen2 = nLen1/76 ; //RFC2045 base64编码后，每行最多76个字符
int nLen3 = 19 ;
for (int i=0; i<=nLen2; i++)
{
if (i==nLen2)
nLen3 = (nLen1%76)/4;
for (int j=0; j<nLen3; j++)
{
unsigned long dwCurr = 0;
for (int n=0; n<3; n++)
{
dwCurr |= *pbSrcData++;
dwCurr <<= 8;
}
for (int k=0; k<4; k++)
{
unsigned char b = (unsigned char)(dwCurr>>26);
*szDest++ = s_chBase64EncodingTable[b];
dwCurr <<= 6;
}
}
nWritten+= nLen3*4;
if ((dwFlags & ATL_BASE64_FLAG_NOCRLF)==0)
{
*szDest++ = '\r';
*szDest++ = '\n';
nWritten+= 2;
}
}
if (nWritten && (dwFlags & ATL_BASE64_FLAG_NOCRLF)==0)
{
szDest-= 2;
nWritten -= 2;
}
nLen2 = (nSrcLen%3) ? (nSrcLen%3 + 1) : 0;
if (nLen2)
{
unsigned long dwCurr = 0;
for (int n=0; n<3; n++)
{
if (n<(nSrcLen%3))
dwCurr |= *pbSrcData++;
dwCurr <<= 8;
}
for (int k=0; k<nLen2; k++)
{
unsigned char b = (unsigned char)(dwCurr>>26);
*szDest++ = s_chBase64EncodingTable[b];
dwCurr <<= 6;
}
nWritten+= nLen2;
if ((dwFlags & ATL_BASE64_FLAG_NOPAD)==0)
{
nLen3 = nLen2 ? 4-nLen2 : 0;
for (int j=0; j<nLen3; j++)
{
*szDest++ = '=';
}
nWritten+= nLen3;
}
}
*pnEncodeRealLen = nWritten;
return true;
}
//szSrc 要解码的数据
//nSrcLen 要解码数据的长度
//pbDest 解码后的输出
//pnDecodeRealLen 解码后的字节长度
static bool Decode(const char* szSrc, int nSrcLen, unsigned char *pbDest, int *pnDecodeRealLen)
{
// 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
// returns -1 if the character is invalid
// or should be skipped
// otherwise, returns the 6-bit code for the character
// from the encoding table
static const int base64_decode_table[] =
{
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
-1, -1, -1, -1, -1, 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, -1, -1, -1, -1, -1, -1, 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, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};
if (szSrc == 0 || pnDecodeRealLen == 0)
{
return false;
}
const char* szSrcEnd = szSrc + nSrcLen;
int nWritten = 0;
while (szSrc < szSrcEnd &&(*szSrc) != 0)
{
unsigned long dwCurr = 0;
int i;
int nBits = 0;
for (i=0; i<4; i++)
{
if (szSrc >= szSrcEnd)
break;
int nCh = base64_decode_table[(unsigned char)(*szSrc)]; //强转为unsigned char，防止运行时抛出异常
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 = (unsigned char) ((dwCurr & 0x00ff0000) >> 16);
pbDest++;
dwCurr <<= 8;
nWritten++;
}
}
*pnDecodeRealLen = nWritten;
return true;
}
static bool Encode(const std::string & in , std::string & out,Base64_Flag dwFlags = ATL_BASE64_FLAG_NONE)
{
int len = EncodeGetRequiredLength(static_cast<int>(in.size()),dwFlags);
out.assign(len,0);
bool ret=Encode((const unsigned char*)in.c_str(),static_cast<int>(in.size()),(char*)out.c_str(),&len,dwFlags);
out.resize(static_cast<size_t>(len));
return ret;
}
static bool Encode( const unsigned char * in ,int in_len,std::string & out ,Base64_Flag dwFlags = ATL_BASE64_FLAG_NONE)
{
int len = EncodeGetRequiredLength(in_len,dwFlags);
out.assign(len,0);
bool ret=Encode(in ,in_len,(char*)out.c_str(),&len,dwFlags);
out.resize(static_cast<size_t>(len));
return ret;
}
static bool Decode(const std::string & in, std::string & out )
{
out.assign(in.size(),0);
int len=static_cast<int>(out.size());
bool ret = Decode(in.c_str(),static_cast<int>(in.size()), (unsigned char*) out.c_str() , &len);
out.resize(static_cast<size_t>(len));
return ret;
}
static bool Decode(const char * in ,int in_len , std::string & out )
{
out.assign( static_cast<size_t>(in_len),0);
int outlen=static_cast<int>(out.size());
bool ret = Decode(in ,in_len, (unsigned char*) out.c_str() , &outlen);
out.resize(static_cast<size_t>(outlen));
return ret;
}
};
}
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