openssl 中base64编解码的c语言实现

来源：互联网发布：苏州科达算法笔试题编辑：程序博客网时间：2024/06/09 20:57
openssl 中base64编解码的c语言实现，比较简洁。理论上base64 编码后的长度会变成编码前长度的4/3倍。
#define B64_WS0xE0#define B64_ERROR       0xFF#define B64_NOT_BASE64(a)(((a)|0x13) == 0xF3)#define conv_bin2ascii(a)   (data_bin2ascii[(a)&0x3f])  #define conv_ascii2bin(a)   (data_ascii2bin[(a)&0x7f])static const unsigned char data_bin2ascii[65] =  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";    static const unsigned char data_ascii2bin[128] =  { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xE0, 0xF0, 0xFF, 0xFF,          0xF1, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,          0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xE0, 0xFF, 0xFF, 0xFF, 0xFF,          0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x3E, 0xFF, 0xF2, 0xFF, 0x3F, 0x34,          0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0xFF, 0xFF, 0xFF,          0x00, 0xFF, 0xFF, 0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,          0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13,          0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,          0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25,          0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31,          0x32, 0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, };      /* Base64 Encode */  int EVP_EncodeBlock(unsigned char *t, const unsigned char *f, int dlen)  {      int i, ret = 0;      unsigned long l;        for (i = dlen; i > 0; i -= 3)      {          if (i >= 3)          {              l = (((unsigned long) f[0]) << 16L) | (((unsigned long) f[1]) << 8L) | f[2];              *(t++) = conv_bin2ascii(l>>18L);              *(t++) = conv_bin2ascii(l>>12L);              *(t++) = conv_bin2ascii(l>> 6L);              *(t++) = conv_bin2ascii(l );          }          else          {              l = ((unsigned long) f[0]) << 16L;              if (i == 2)                  l |= ((unsigned long) f[1] << 8L);                *(t++) = conv_bin2ascii(l>>18L);              *(t++) = conv_bin2ascii(l>>12L);              *(t++) = (i == 1) ? '=' : conv_bin2ascii(l>> 6L);              *(t++) = '=';          }          ret += 4;          f += 3;      }        *t = '\0';      return (ret);  } /* Base64 Decode */int EVP_DecodeBlock(unsigned char *t, const unsigned char *f, int n){int i, ret = 0, a, b, c, d;unsigned long l;/* trim white space from the start of the line. */while ((conv_ascii2bin(*f) == B64_WS) && (n > 0)){f++;n--;}/* strip off stuff at the end of the line * ascii2bin values B64_WS, B64_EOLN, B64_EOLN and B64_EOF */while ((n > 3) && (B64_NOT_BASE64(conv_ascii2bin(f[n-1]))))n--;if (n % 4 != 0)return (-1);for (i = 0; i < n; i += 4){a = conv_ascii2bin(*(f++));b = conv_ascii2bin(*(f++));c = conv_ascii2bin(*(f++));d = conv_ascii2bin(*(f++));if ((a & 0x80) || (b & 0x80) || (c & 0x80) || (d & 0x80))return (-1);l = ((((unsigned long) a) << 18L) | (((unsigned long) b) << 12L)| (((unsigned long) c) << 6L) | (((unsigned long) d)));*(t++) = (unsigned char) (l >> 16L) & 0xff;*(t++) = (unsigned char) (l >> 8L) & 0xff;*(t++) = (unsigned char) (l) & 0xff;ret += 3;}return (ret);}
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