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
10namespace fml {
11
12static constexpr char kEncoding[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
13
14std::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(requested_capacity: encoded_length);
26
27 Base32EncodeConverter converter;
28 converter.Append(bits: static_cast<uint8_t>(input[0]));
29 size_t next_byte_index = 1;
30
31 while (converter.CanExtract()) {
32 output.push_back(c: kEncoding[converter.Extract()]);
33 if (converter.CanAppend() && next_byte_index < input.size()) {
34 converter.Append(bits: static_cast<uint8_t>(input[next_byte_index++]));
35 }
36 }
37
38 if (converter.BitsAvailable() > 0) {
39 output.push_back(c: kEncoding[converter.Peek()]);
40 }
41
42 return {true, output};
43}
44
45static 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
51static constexpr int kDecodeMapSize =
52 sizeof(kDecodeMap) / sizeof(kDecodeMap[0]);
53
54std::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(bits: kDecodeMap[map_index]);
64 if (converter.CanExtract()) {
65 result.push_back(c: 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

source code of flutter_engine/flutter/fml/base32.cc