// Copyright Low Entry. Apache License, Version 2.0.

#pragma once


#include "CoreMinimal.h"


class ULowEntryHashingSha256Library
{
private:
	const static int32 k[64];
	constexpr static int32 BLOCK_SIZE = 64;


private:
	TArray<int32> w;

	int32 h0 = 0x6a09e667;
	int32 h1 = 0xbb67ae85;
	int32 h2 = 0x3c6ef372;
	int32 h3 = 0xa54ff53a;
	int32 h4 = 0x510e527f;
	int32 h5 = 0x9b05688c;
	int32 h6 = 0x1f83d9ab;
	int32 h7 = 0x5be0cd19;

	int64 count = 0;
	TArray<uint8> buffer;


private:
	void initialize();
	void update(const TArray<uint8>& b, const int64 offset, const int64 len);
	TArray<uint8> digest();
	TArray<uint8> padBuffer();
	TArray<uint8> getResult();
	void sha(const TArray<uint8>& in, int64 offset);
	FORCEINLINE static int32 s(const int32 a, const int32 b);


public:
	static TArray<uint8> Hash(const TArray<uint8>& Bytes);
	static TArray<uint8> Hash(const TArray<uint8>& Bytes, int32 Index, int32 Length);
};