base64　加密解密函数

最新推荐文章于 2023-12-20 14:47:31 发布

原创最新推荐文章于 2023-12-20 14:47:31 发布 · 1.3k 阅读

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CC 4.0 BY-SA版权

文章标签：

#解密 #加密 #table #delete #null #byte

博客给出了Base64编码和解码的C++实现代码。编码函数将输入字符串按规则转换为Base64编码字符串，解码函数则将Base64编码字符串还原为原始字符串。代码中定义了编码和解码表，通过位运算和循环处理字节数据。

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CString Base64Encode(LPCTSTR lpszSrc)
{
ASSERT(lpszSrc != NULL && AfxIsValidString(lpszSrc));
const char BASE64_ENCODE_TABLE[64] = {
  65, 66, 67, 68, 69, 70, 71, 72, // 00 - 07
   73, 74, 75, 76, 77, 78, 79, 80, // 08 - 15
   81, 82, 83, 84, 85, 86, 87, 88, // 16 - 23
   89, 90, 97, 98, 99, 100, 101, 102, // 24 - 31
   103, 104, 105, 106, 107, 108, 109, 110, // 32 - 39
   111, 112, 113, 114, 115, 116, 117, 118, // 40 - 47
   119, 120, 121, 122, 48, 49, 50, 51, // 48 - 55
   52, 53, 54, 55, 56, 57, 43, 47 };// 56 - 63

unsigned int iTest;

LPCTSTR pInBuffer=lpszSrc;

  int nSize = (int)_tcslen(lpszSrc);
  char* pOutBuffer=new char[nSize/3*4+5];
  ZeroMemory(pOutBuffer,nSize/3*4+5);

  for(UINT i=0;i<_tcslen(lpszSrc) / 3;i++)
  {
   iTest = (unsigned char) *pInBuffer++;
   iTest = iTest << 8;

iTest = iTest | (unsigned char) *pInBuffer++;
iTest = iTest << 8;

iTest = iTest | (unsigned char) *pInBuffer++;

   //以4 byte倒序写入输出缓冲
   pOutBuffer[3] = BASE64_ENCODE_TABLE[iTest & 0x3F];
   iTest = iTest >> 6;
   pOutBuffer[2] = BASE64_ENCODE_TABLE[iTest & 0x3F];
   iTest = iTest >> 6;
   pOutBuffer[1] = BASE64_ENCODE_TABLE[iTest & 0x3F];
   iTest = iTest >> 6;
   pOutBuffer[0] = BASE64_ENCODE_TABLE[iTest];
   pOutBuffer+=4;
  }

  //设置尾部
  switch (_tcslen(lpszSrc) % 3)
  {
  case 0:
   break;
  case 1:
   iTest = (unsigned char) *pInBuffer;
   iTest = iTest << 4;
   pOutBuffer[1] = BASE64_ENCODE_TABLE[iTest & 0x3F];
   iTest = iTest >> 6;
   pOutBuffer[0] = BASE64_ENCODE_TABLE[iTest];
   pOutBuffer[2] = '='; //用'='也就是64码填充剩余部分
   pOutBuffer[3] = '=';
   break;
  case 2:
   iTest = (unsigned char) *pInBuffer++;
   iTest = iTest << 8;
   iTest = iTest | (unsigned char) *pInBuffer;
   iTest = iTest << 2;
   pOutBuffer[2] = BASE64_ENCODE_TABLE[iTest & 0x3F];
   iTest = iTest >> 6;
   pOutBuffer[1] = BASE64_ENCODE_TABLE[iTest & 0x3F];
   iTest = iTest >> 6;
   pOutBuffer[0] = BASE64_ENCODE_TABLE[iTest];
   pOutBuffer[3] = '='; // Fill remaining byte.
   break;
  }
  pOutBuffer-=nSize/3*4;
  CString strEncode=pOutBuffer;
  delete [] pOutBuffer;
  pOutBuffer=NULL;
  return strEncode;
}

CString Base64Decode(LPCTSTR lpszSrc)
{
ASSERT(lpszSrc != NULL && AfxIsValidString(lpszSrc));
const unsigned int BASE64_DECODE_TABLE[256] = {
  255, 255, 255, 255, 255, 255, 255, 255, // 00 - 07
   255, 255, 255, 255, 255, 255, 255, 255, // 08 - 15
   255, 255, 255, 255, 255, 255, 255, 255, // 16 - 23
   255, 255, 255, 255, 255, 255, 255, 255, // 24 - 31
   255, 255, 255, 255, 255, 255, 255, 255, // 32 - 39
   255, 255, 255, 62, 255, 255, 255, 63, // 40 - 47
   52, 53, 54, 55, 56, 57, 58, 59, // 48 - 55
   60, 61, 255, 255, 255, 255, 255, 255, // 56 - 63
   255,   0,   1,   2,   3,   4,   5,   6, // 64 - 71
   7,   8,   9, 10, 11, 12, 13, 14, // 72 - 79
   15, 16, 17, 18, 19, 20, 21, 22, // 80 - 87
   23, 24, 25, 255, 255, 255, 255, 255, // 88 - 95
   255, 26, 27, 28, 29, 30, 31, 32, // 96 - 103
   33, 34, 35, 36, 37, 38, 39, 40, // 104 - 111
   41, 42, 43, 44, 45, 46, 47, 48, // 112 - 119
   49, 50, 51, 255, 255, 255, 255, 255, // 120 - 127
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255,
   255, 255, 255, 255, 255, 255, 255, 255 };

  const int nSrcCount=(int)_tcslen(lpszSrc);
  int nSize=nSrcCount/4*3;
  if(lpszSrc[nSrcCount-1]=='=')
   nSize--;
  if(lpszSrc[nSrcCount-2]=='=')
   nSize--;
  char* pOutBuffer=new char[nSize+3];
  ZeroMemory(pOutBuffer,nSize+3);
  LPCTSTR pInBuffer=lpszSrc;
  UINT iTest,iPack;
  for(int i=0;i<nSize/3 ;i++)
  {
   for(int j=0;j<4;j++)
   {
    iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
    //InPtr++;
    if (iTest == 0xFF)
    {
     j--;
     continue; //读到255非法字符
    }
    iPack = iPack << 6 ;
    iPack = iPack | iTest ;
   }
   pOutBuffer[2] = iPack;
   iPack = iPack >> 8;
   pOutBuffer[1] = iPack;
   iPack = iPack >> 8;
   pOutBuffer[0] = iPack;
   //准备写入后3位
   pOutBuffer+= 3; iPack = 0;

  }
  switch(nSize%3)
  {
  case 1:
   iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
   if (iTest != 0xFF)
   {
    iPack = iPack << 6 ;
    iPack = iPack | iTest ;
   }
   iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
   if (iTest != 0xFF)
   {
    iPack = iPack << 6 ;
    iPack = iPack | iTest ;
   }
   iPack = iPack >> 4;
   pOutBuffer[0] = iPack;
   pOutBuffer++;
   break;
  case 2:
   iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
   if (iTest != 0xFF)
   {
    iPack = iPack << 6 ;
    iPack = iPack | iTest ;
   }
   iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
   if (iTest != 0xFF)
   {
    iPack = iPack << 6 ;
    iPack = iPack | iTest ;
   }
   iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
   if (iTest != 0xFF)
   {
    iPack = iPack << 6 ;
    iPack = iPack | iTest ;
   }
   iPack = iPack >> 2;
   pOutBuffer[1] = iPack;
   iPack = iPack >> 8;
   pOutBuffer[0] = iPack;
   pOutBuffer+=2;
   break;
  default:
   break;
  }
  pOutBuffer-=nSize;
  CString strDecode=pOutBuffer;
  delete pOutBuffer;
  return strDecode;
}