| 140 | |
| 141 | |
| 142 | static size_t base64_encode(const char* src, |
| 143 | size_t slen, |
| 144 | char* dst, |
| 145 | size_t dlen) { |
| 146 | // We know how much we'll write, just make sure that there's space. |
| 147 | assert(dlen >= base64_encoded_size(slen) && |
| 148 | "not enough space provided for base64 encode"); |
| 149 | |
| 150 | dlen = base64_encoded_size(slen); |
| 151 | |
| 152 | unsigned a; |
| 153 | unsigned b; |
| 154 | unsigned c; |
| 155 | unsigned i; |
| 156 | unsigned k; |
| 157 | unsigned n; |
| 158 | |
| 159 | static const char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" |
| 160 | "abcdefghijklmnopqrstuvwxyz" |
| 161 | "0123456789+/"; |
| 162 | |
| 163 | i = 0; |
| 164 | k = 0; |
| 165 | n = slen / 3 * 3; |
| 166 | |
| 167 | while (i < n) { |
| 168 | a = src[i + 0] & 0xff; |
| 169 | b = src[i + 1] & 0xff; |
| 170 | c = src[i + 2] & 0xff; |
| 171 | |
| 172 | dst[k + 0] = table[a >> 2]; |
| 173 | dst[k + 1] = table[((a & 3) << 4) | (b >> 4)]; |
| 174 | dst[k + 2] = table[((b & 0x0f) << 2) | (c >> 6)]; |
| 175 | dst[k + 3] = table[c & 0x3f]; |
| 176 | |
| 177 | i += 3; |
| 178 | k += 4; |
| 179 | } |
| 180 | |
| 181 | if (n != slen) { |
| 182 | switch (slen - n) { |
| 183 | case 1: |
| 184 | a = src[i + 0] & 0xff; |
| 185 | dst[k + 0] = table[a >> 2]; |
| 186 | dst[k + 1] = table[(a & 3) << 4]; |
| 187 | dst[k + 2] = '='; |
| 188 | dst[k + 3] = '='; |
| 189 | break; |
| 190 | |
| 191 | case 2: |
| 192 | a = src[i + 0] & 0xff; |
| 193 | b = src[i + 1] & 0xff; |
| 194 | dst[k + 0] = table[a >> 2]; |
| 195 | dst[k + 1] = table[((a & 3) << 4) | (b >> 4)]; |
| 196 | dst[k + 2] = table[(b & 0x0f) << 2]; |
| 197 | dst[k + 3] = '='; |
| 198 | break; |
| 199 | } |