| 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 >= 0 && 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 |