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