1 | // Copyright 2013 The Flutter Authors. All rights reserved. |
2 | // Use of this source code is governed by a BSD-style license that can be |
3 | // found in the LICENSE file. |
4 | |
5 | #include "flutter/fml/base32.h" |
6 | |
7 | #include <limits> |
8 | #include <string> |
9 | |
10 | namespace fml { |
11 | |
12 | static constexpr char kEncoding[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567" ; |
13 | |
14 | std::pair<bool, std::string> Base32Encode(std::string_view input) { |
15 | if (input.empty()) { |
16 | return {true, "" }; |
17 | } |
18 | |
19 | if (input.size() > std::numeric_limits<size_t>::max() / 8) { |
20 | return {false, "" }; |
21 | } |
22 | |
23 | std::string output; |
24 | const size_t encoded_length = (input.size() * 8 + 4) / 5; |
25 | output.reserve(encoded_length); |
26 | |
27 | Base32EncodeConverter converter; |
28 | converter.Append(input[0]); |
29 | size_t next_byte_index = 1; |
30 | |
31 | while (converter.CanExtract()) { |
32 | output.push_back(kEncoding[converter.Extract()]); |
33 | if (converter.CanAppend() && next_byte_index < input.size()) { |
34 | converter.Append(static_cast<uint8_t>(input[next_byte_index++])); |
35 | } |
36 | } |
37 | |
38 | if (converter.BitsAvailable() > 0) { |
39 | output.push_back(kEncoding[converter.Peek()]); |
40 | } |
41 | |
42 | return {true, output}; |
43 | } |
44 | |
45 | static constexpr signed char kDecodeMap[] = { |
46 | // starting from ASCII 50 '2' |
47 | 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, |
48 | -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, |
49 | 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25}; |
50 | |
51 | static constexpr int kDecodeMapSize = |
52 | sizeof(kDecodeMap) / sizeof(kDecodeMap[0]); |
53 | |
54 | std::pair<bool, std::string> Base32Decode(const std::string& input) { |
55 | std::string result; |
56 | Base32DecodeConverter converter; |
57 | for (char c : input) { |
58 | int map_index = c - '2'; |
59 | if (map_index < 0 || map_index >= kDecodeMapSize || |
60 | kDecodeMap[map_index] == -1) { |
61 | return {false, result}; |
62 | } |
63 | converter.Append(kDecodeMap[map_index]); |
64 | if (converter.CanExtract()) { |
65 | result.push_back(converter.Extract()); |
66 | } |
67 | } |
68 | if (converter.Peek() != 0) { |
69 | // The padding should always be zero. Return false if not. |
70 | return {false, result}; |
71 | } |
72 | return {true, result}; |
73 | } |
74 | |
75 | } // namespace fml |
76 | |