base64解码工具

个人开发的，主要供软件开发者进行base64码校对使用。

界面如下:

 

生成base64的函数代码如下：

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

int Base64Enc(const char *src, int len, char *r)
{
    unsigned char* q=(unsigned char*)src;
    char *p = r;
    for(; len >= 3; len -= 3, q += 3)
    {
        *p++ = base64[q[0] >> 2];
        *p++ = base64[((q[0] & 0x3) << 4) | (q[1] >> 4)];
        *p++ = base64[((q[1] & 0xF) << 2) | (q[2] >> 6)];
        *p++ = base64[q[2] & 0x3F];
    }

    if(len > 0)
    {
        *p++ = base64[q[0] >> 2];
        if(len == 1 )
        {
            *p++ = base64[(q[0] & 0x3) << 4];
            *p++ = '=';
        }
        else // len == 2
        {
            *p++ = base64[((q[0] & 0x3) << 4) | (q[1] >> 4)];
            *p++ = base64[(q[1] & 0xF) << 2];
        }
        *p++ = '=';
    }
    return p - r;
}

base64解码的源代码函数如下：

static int get6bits(char c)
{
  if(c >= 'A' && c <= 'Z')
    return c - 'A';
  if(c >= 'a' && c <= 'z')
    return c - 'a' + 26;
  if(c >= '0' && c <= '9')
    return c - '0' + 52;
  if(c == '+')
    return 62;
  if(c == '/')
    return 63;
  return -1;
}

int Base64Dec(const char *src, int len, char *r)
{
  char *p = r;
  int i, bits, code;
  int k = 0; // 指示当前code中的bit数
  for(i=0; i<len; i++)
  {
    bits = get6bits(src[i]);
    if(bits < 0)
      break;
    if(k == 0)
    {
      code = (bits << 2);
      k = 6;
    }
    else if(k == 6)
    {
      code |= (bits >> 4);
      *p++ = code;
      k = 4;
      code = (bits << 4);
    }
    else if(k == 4)
    {
      code |= (bits >> 2);
      *p++ = code;
      k = 2;
      code = (bits << 6);
    }
    else if(k == 2)
    {
      code |= bits;
      *p++ = code;
      k = 0;
    }
  }
  return p - r;
}