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    size_t n = s.size();
26    if ((n % 4) != 0) {
27        return NULL;
28    }
29
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    // We divide first to avoid overflow. It's OK to do this because we
44    // already made sure that n % 4 == 0.
45    size_t outLen = (n / 4) * 3 - padding;
46
47    sp<ABuffer> buffer = new ABuffer(outLen);
48
49    uint8_t *out = buffer->data();
50    if (out == NULL || buffer->size() < outLen) {
51        return NULL;
52    }
53    size_t j = 0;
54    uint32_t accum = 0;
55    for (size_t i = 0; i < n; ++i) {
56        char c = s.c_str()[i];
57        unsigned value;
58        if (c >= 'A' && c <= 'Z') {
59            value = c - 'A';
60        } else if (c >= 'a' && c <= 'z') {
61            value = 26 + c - 'a';
62        } else if (c >= '0' && c <= '9') {
63            value = 52 + c - '0';
64        } else if (c == '+') {
65            value = 62;
66        } else if (c == '/') {
67            value = 63;
68        } else if (c != '=') {
69            return NULL;
70        } else {
71            if (i < n - padding) {
72                return NULL;
73            }
74
75            value = 0;
76        }
77
78        accum = (accum << 6) | value;
79
80        if (((i + 1) % 4) == 0) {
81            out[j++] = (accum >> 16);
82
83            if (j < outLen) { out[j++] = (accum >> 8) & 0xff; }
84            if (j < outLen) { out[j++] = accum & 0xff; }
85
86            accum = 0;
87        }
88    }
89
90    return buffer;
91}
92
93static char encode6Bit(unsigned x) {
94    if (x <= 25) {
95        return 'A' + x;
96    } else if (x <= 51) {
97        return 'a' + x - 26;
98    } else if (x <= 61) {
99        return '0' + x - 52;
100    } else if (x == 62) {
101        return '+';
102    } else {
103        return '/';
104    }
105}
106
107void encodeBase64(
108        const void *_data, size_t size, AString *out) {
109    out->clear();
110
111    const uint8_t *data = (const uint8_t *)_data;
112
113    size_t i;
114    for (i = 0; i < (size / 3) * 3; i += 3) {
115        uint8_t x1 = data[i];
116        uint8_t x2 = data[i + 1];
117        uint8_t x3 = data[i + 2];
118
119        out->append(encode6Bit(x1 >> 2));
120        out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
121        out->append(encode6Bit((x2 << 2 | x3 >> 6) & 0x3f));
122        out->append(encode6Bit(x3 & 0x3f));
123    }
124    switch (size % 3) {
125        case 0:
126            break;
127        case 2:
128        {
129            uint8_t x1 = data[i];
130            uint8_t x2 = data[i + 1];
131            out->append(encode6Bit(x1 >> 2));
132            out->append(encode6Bit((x1 << 4 | x2 >> 4) & 0x3f));
133            out->append(encode6Bit((x2 << 2) & 0x3f));
134            out->append('=');
135            break;
136        }
137        default:
138        {
139            uint8_t x1 = data[i];
140            out->append(encode6Bit(x1 >> 2));
141            out->append(encode6Bit((x1 << 4) & 0x3f));
142            out->append("==");
143            break;
144        }
145    }
146}
147
148}  // namespace android
149