- static const char *codes =
- 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
-
- static const unsigned char map[256] = {
- 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 253, 255,
- 255, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 255, 253, 255, 255, 255,
- 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
- 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255,
- 255, 254, 255, 255, 255, 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, 255, 255, 255, 255, 255,
- 255, 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, 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, 255,
- 255, 255, 255, 255 };
-
- int base64_encode(const unsigned char *in, unsigned long len,
- unsigned char *out)
- {
- unsigned long i, len2, leven;
- unsigned char *p;
- /* valid output size ? */
- len2 = 4 * ((len + 2) / 3);
- p = out;
- leven = 3*(len / 3);
- for (i = 0; i < leven; i += 3) {
- *p++ = codes[in[0] >> 2];
- *p++ = codes[((in[0] & 3) << 4) + (in[1] >> 4)];
- *p++ = codes[((in[1] & 0xf) << 2) + (in[2] >> 6)];
- *p++ = codes[in[2] & 0x3f];
- in += 3;
- }
- /* Pad it if necessary... */
- if (i < len) {
- unsigned a = in[0];
- unsigned b = (i+1 < len) ? in[1] : 0;
- unsigned c = 0;
-
- *p++ = codes[a >> 2];
- *p++ = codes[((a & 3) << 4) + (b >> 4)];
- *p++ = (i+1 < len) ? codes[((b & 0xf) << 2) + (c >> 6)] : '=';
- *p++ = '=';
- }
-
- /* append a NULL byte */
- *p = '\0';
-
- return p - out;
- }
-
- int base64_decode(const unsigned char *in, unsigned char *out)
- {
- unsigned long t, x, y, z;
- unsigned char c;
- int g = 3;
-
- for (x = y = z = t = 0; in[x]!=0;) {
- c = map[in[x++]];
- if (c == 255) return -1;
- if (c == 253) continue;
- if (c == 254) { c = 0; g--; }
- t = (t<<6)|c;
- if (++y == 4) {
- // if (z + g > *outlen) { return CRYPT_BUFFER_OVERFLOW; }
- out[z++] = (unsigned char)((t>>16)&255);
- if (g > 1) out[z++] = (unsigned char)((t>>8)&255);
- if (g > 2) out[z++] = (unsigned char)(t&255);
- y = t = 0;
- }
- }
- // if (y != 0) {
- // return -1;
- // }
- return z;
- }
Base64编码基本上理解为:将二进制数据转变为可见的ASCII码字符串(反之亦然)。这个很有用,比如向数据库里面写东西,如果是二进制(如图片)的话,转变成字符串就会很方便的存入。 该编码的好处是:速度快,编码为ASCII码后体积增加三分之一左右。
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