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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef FLUTTER_FML_BASE32_H_
#define FLUTTER_FML_BASE32_H_
#include <string_view>
#include <utility>
#include "flutter/fml/logging.h"
namespace fml {
template <int from_length, int to_length, int buffer_length>
class BitConverter {
public:
void Append(int bits) {
FML_DCHECK(bits >= 0 && bits < (1 << from_length));
FML_DCHECK(CanAppend());
lower_free_bits_ -= from_length;
buffer_ |= (bits << lower_free_bits_);
}
int Extract() {
FML_DCHECK(CanExtract());
int result = Peek();
buffer_ = (buffer_ << to_length) & mask_;
lower_free_bits_ += to_length;
return result;
}
int Peek() const { return (buffer_ >> (buffer_length - to_length)); }
int BitsAvailable() const { return buffer_length - lower_free_bits_; }
bool CanAppend() const { return lower_free_bits_ >= from_length; }
bool CanExtract() const { return BitsAvailable() >= to_length; }
private:
static_assert(buffer_length >= 2 * from_length);
static_assert(buffer_length >= 2 * to_length);
static_assert(buffer_length < sizeof(int) * 8);
static constexpr int mask_ = (1 << buffer_length) - 1;
int buffer_ = 0;
int lower_free_bits_ = buffer_length;
};
using Base32DecodeConverter = BitConverter<5, 8, 16>;
using Base32EncodeConverter = BitConverter<8, 5, 16>;
std::pair<bool, std::string> Base32Encode(std::string_view input);
std::pair<bool, std::string> Base32Decode(const std::string& input);
} // namespace fml
#endif // FLUTTER_FML_BASE32_H_