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 | #ifndef FLUTTER_FML_BASE32_H_ |
6 | #define FLUTTER_FML_BASE32_H_ |
7 | |
8 | #include <string_view> |
9 | #include <utility> |
10 | |
11 | #include "flutter/fml/logging.h" |
12 | |
13 | namespace fml { |
14 | |
15 | template <int from_length, int to_length, int buffer_length> |
16 | class BitConverter { |
17 | public: |
18 | void Append(int bits) { |
19 | FML_DCHECK(bits < (1 << from_length)); |
20 | FML_DCHECK(CanAppend()); |
21 | lower_free_bits_ -= from_length; |
22 | buffer_ |= (bits << lower_free_bits_); |
23 | } |
24 | |
25 | int Extract() { |
26 | FML_DCHECK(CanExtract()); |
27 | int result = Peek(); |
28 | buffer_ = (buffer_ << to_length) & mask_; |
29 | lower_free_bits_ += to_length; |
30 | return result; |
31 | } |
32 | |
33 | int Peek() const { return (buffer_ >> (buffer_length - to_length)); } |
34 | int BitsAvailable() const { return buffer_length - lower_free_bits_; } |
35 | bool CanAppend() const { return lower_free_bits_ >= from_length; } |
36 | bool CanExtract() const { return BitsAvailable() >= to_length; } |
37 | |
38 | private: |
39 | static_assert(buffer_length >= 2 * from_length); |
40 | static_assert(buffer_length >= 2 * to_length); |
41 | static_assert(buffer_length < sizeof(int) * 8); |
42 | |
43 | static constexpr int mask_ = (1 << buffer_length) - 1; |
44 | |
45 | int buffer_ = 0; |
46 | int lower_free_bits_ = buffer_length; |
47 | }; |
48 | |
49 | using Base32DecodeConverter = BitConverter<5, 8, 16>; |
50 | using Base32EncodeConverter = BitConverter<8, 5, 16>; |
51 | |
52 | std::pair<bool, std::string> Base32Encode(std::string_view input); |
53 | std::pair<bool, std::string> Base32Decode(const std::string& input); |
54 | |
55 | } // namespace fml |
56 | |
57 | #endif // FLUTTER_FML_BASE32_H_ |
58 |