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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "base64.h"
     18 
     19 #include "ABuffer.h"
     20 #include "ADebug.h"
     21 
     22 namespace android {
     23 
     24 sp<ABuffer> decodeBase64(const AString &s) {
     25     if ((s.size() % 4) != 0) {
     26         return NULL;
     27     }
     28 
     29     size_t n = s.size();
     30     size_t padding = 0;
     31     if (n >= 1 && s.c_str()[n - 1] == '=') {
     32         padding = 1;
     33 
     34         if (n >= 2 && s.c_str()[n - 2] == '=') {
     35             padding = 2;
     36         }
     37     }
     38 
     39     size_t outLen = 3 * s.size() / 4 - padding;
     40 
     41     sp<ABuffer> buffer = new ABuffer(outLen);
     42 
     43     uint8_t *out = buffer->data();
     44     size_t j = 0;
     45     uint32_t accum = 0;
     46     for (size_t i = 0; i < n; ++i) {
     47         char c = s.c_str()[i];
     48         unsigned value;
     49         if (c >= 'A' && c <= 'Z') {
     50             value = c - 'A';
     51         } else if (c >= 'a' && c <= 'z') {
     52             value = 26 + c - 'a';
     53         } else if (c >= '0' && c <= '9') {
     54             value = 52 + c - '0';
     55         } else if (c == '+') {
     56             value = 62;
     57         } else if (c == '/') {
     58             value = 63;
     59         } else if (c != '=') {
     60             return NULL;
     61         } else {
     62             if (i < n - padding) {
     63                 return NULL;
     64             }
     65 
     66             value = 0;
     67         }
     68 
     69         accum = (accum << 6) | value;
     70 
     71         if (((i + 1) % 4) == 0) {
     72             out[j++] = (accum >> 16);
     73 
     74             if (j < outLen) { out[j++] = (accum >> 8) & 0xff; }
     75             if (j < outLen) { out[j++] = accum & 0xff; }
     76 
     77             accum = 0;
     78         }
     79     }
     80 
     81     return buffer;
     82 }
     83 
     84 static char encode6Bit(unsigned x) {
     85     if (x <= 25) {
     86         return 'A' + x;
     87     } else if (x <= 51) {
     88         return 'a' + x - 26;
     89     } else if (x <= 61) {
     90         return '0' + x - 52;
     91     } else if (x == 62) {
     92         return '+';
     93     } else {
     94         return '/';
     95     }
     96 }
     97 
     98 void encodeBase64(
     99         const void *_data, size_t size, AString *out) {
    100     out->clear();
    101 
    102     const uint8_t *data = (const uint8_t *)_data;
    103 
    104     size_t i;
    105     for (i = 0; i < (size / 3) * 3; i += 3) {
    106         uint8_t x1 = data[i];
    107         uint8_t x2 = data[i + 1];
    108         uint8_t x3 = data[i + 2];
    109 
    110         out->append(encode6Bit(x1 >> 2));
    111         out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
    112         out->append(encode6Bit((x2 << 2 | x3 >> 6) & 0x3f));
    113         out->append(encode6Bit(x3 & 0x3f));
    114     }
    115     switch (size % 3) {
    116         case 0:
    117             break;
    118         case 2:
    119         {
    120             uint8_t x1 = data[i];
    121             uint8_t x2 = data[i + 1];
    122             out->append(encode6Bit(x1 >> 2));
    123             out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
    124             out->append(encode6Bit((x2 << 2) & 0x3f));
    125             out->append('=');
    126             break;
    127         }
    128         default:
    129         {
    130             uint8_t x1 = data[i];
    131             out->append(encode6Bit(x1 >> 2));
    132             out->append(encode6Bit((x1 << 4) & 0x3f));
    133             out->append("==");
    134             break;
    135         }
    136     }
    137 }
    138 
    139 }  // namespace android
    140