dolphin/Source/Core/DiscIO/LaggedFibonacciGenerator.h

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// SPDX-License-Identifier: CC0-1.0
#pragma once
#include <array>
#include <cstddef>
#include "Common/CommonTypes.h"
namespace DiscIO
{
class LaggedFibonacciGenerator
{
public:
static constexpr size_t SEED_SIZE = 17;
// Reconstructs a seed and writes it to seed_out, then returns the number of bytes which can
// be reconstructed using that seed. Can return any number between 0 and size, inclusive.
// data - data_offset must be 4-byte aligned.
static size_t GetSeed(const u8* data, size_t size, size_t data_offset, u32 seed_out[SEED_SIZE]);
// SetSeed must be called before using the functions below
void SetSeed(const u32 seed[SEED_SIZE]);
void SetSeed(const u8 seed[SEED_SIZE * sizeof(u32)]);
// Outputs a number of bytes and advances the internal state by the same amount.
void GetBytes(size_t count, u8* out);
u8 GetByte();
// Advances the internal state like GetBytes, but without outputting data. O(N), like GetBytes.
void Forward(size_t count);
private:
static bool GetSeed(const u32* data, size_t size, size_t data_offset,
LaggedFibonacciGenerator* lfg, u32 seed_out[SEED_SIZE]);
void Forward();
void Backward(size_t start_word = 0, size_t end_word = LFG_K);
bool Reinitialize(u32 seed_out[SEED_SIZE]);
bool Initialize(bool check_existing_data);
static constexpr size_t LFG_K = 521;
static constexpr size_t LFG_J = 32;
std::array<u32, LFG_K> m_buffer{};
size_t m_position_bytes = 0;
};
} // namespace DiscIO