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
22namespace android {
23
24sp<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            if (n >= 3 && s.c_str()[n - 3] == '=') {
38                padding = 3;
39            }
40        }
41    }
42
43    size_t outLen = 3 * s.size() / 4 - padding;
44
45    sp<ABuffer> buffer = new ABuffer(outLen);
46
47    uint8_t *out = buffer->data();
48    size_t j = 0;
49    uint32_t accum = 0;
50    for (size_t i = 0; i < n; ++i) {
51        char c = s.c_str()[i];
52        unsigned value;
53        if (c >= 'A' && c <= 'Z') {
54            value = c - 'A';
55        } else if (c >= 'a' && c <= 'z') {
56            value = 26 + c - 'a';
57        } else if (c >= '0' && c <= '9') {
58            value = 52 + c - '0';
59        } else if (c == '+') {
60            value = 62;
61        } else if (c == '/') {
62            value = 63;
63        } else if (c != '=') {
64            return NULL;
65        } else {
66            if (i < n - padding) {
67                return NULL;
68            }
69
70            value = 0;
71        }
72
73        accum = (accum << 6) | value;
74
75        if (((i + 1) % 4) == 0) {
76            out[j++] = (accum >> 16);
77
78            if (j < outLen) { out[j++] = (accum >> 8) & 0xff; }
79            if (j < outLen) { out[j++] = accum & 0xff; }
80
81            accum = 0;
82        }
83    }
84
85    return buffer;
86}
87
88static char encode6Bit(unsigned x) {
89    if (x <= 25) {
90        return 'A' + x;
91    } else if (x <= 51) {
92        return 'a' + x - 26;
93    } else if (x <= 61) {
94        return '0' + x - 52;
95    } else if (x == 62) {
96        return '+';
97    } else {
98        return '/';
99    }
100}
101
102void encodeBase64(
103        const void *_data, size_t size, AString *out) {
104    out->clear();
105
106    const uint8_t *data = (const uint8_t *)_data;
107
108    size_t i;
109    for (i = 0; i < (size / 3) * 3; i += 3) {
110        uint8_t x1 = data[i];
111        uint8_t x2 = data[i + 1];
112        uint8_t x3 = data[i + 2];
113
114        out->append(encode6Bit(x1 >> 2));
115        out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
116        out->append(encode6Bit((x2 << 2 | x3 >> 6) & 0x3f));
117        out->append(encode6Bit(x3 & 0x3f));
118    }
119    switch (size % 3) {
120        case 0:
121            break;
122        case 2:
123        {
124            uint8_t x1 = data[i];
125            uint8_t x2 = data[i + 1];
126            out->append(encode6Bit(x1 >> 2));
127            out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
128            out->append(encode6Bit((x2 << 2) & 0x3f));
129            out->append('=');
130            break;
131        }
132        default:
133        {
134            uint8_t x1 = data[i];
135            out->append(encode6Bit(x1 >> 2));
136            out->append(encode6Bit((x1 << 4) & 0x3f));
137            out->append("==");
138            break;
139        }
140    }
141}
142
143}  // namespace android
144