/*
	This file is part of solidity.

	solidity is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	solidity is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
// SPDX-License-Identifier: GPL-3.0
/** @file SHA3.cpp
 * @author Gav Wood <i@gavwood.com>
 * @date 2014
 */

#include <libsolutil/Keccak256.h>

#include <cstdint>
#include <cstring>

namespace solidity::util
{

namespace
{

/** libkeccak-tiny
 *
 * A single-file implementation of SHA-3 and SHAKE.
 *
 * Implementor: David Leon Gil
 * License: CC0, attribution kindly requested. Blame taken too,
 * but not liability.
 */

/******** The Keccak-f[1600] permutation ********/

/*** Constants. ***/
static uint8_t const rho[24] = \
	{ 1,  3,   6, 10, 15, 21,
	28, 36, 45, 55,  2, 14,
	27, 41, 56,  8, 25, 43,
	62, 18, 39, 61, 20, 44};
static uint8_t const pi[24] = \
	{10,  7, 11, 17, 18, 3,
	5, 16,  8, 21, 24, 4,
	15, 23, 19, 13, 12, 2,
	20, 14, 22,  9, 6,  1};
static uint64_t const RC[24] = \
	{1ULL, 0x8082ULL, 0x800000000000808aULL, 0x8000000080008000ULL,
	0x808bULL, 0x80000001ULL, 0x8000000080008081ULL, 0x8000000000008009ULL,
	0x8aULL, 0x88ULL, 0x80008009ULL, 0x8000000aULL,
	0x8000808bULL, 0x800000000000008bULL, 0x8000000000008089ULL, 0x8000000000008003ULL,
	0x8000000000008002ULL, 0x8000000000000080ULL, 0x800aULL, 0x800000008000000aULL,
	0x8000000080008081ULL, 0x8000000000008080ULL, 0x80000001ULL, 0x8000000080008008ULL};

/*** Helper macros to unroll the permutation. ***/
#define rol(x, s) (((x) << s) | ((x) >> (64 - s)))
#define REPEAT6(e) e e e e e e
#define REPEAT24(e) REPEAT6(e e e e)
#define REPEAT5(e) e e e e e
#define FOR5(type, v, s, e) \
	v = 0;            \
	REPEAT5(e; v = static_cast<type>(v + s);)

/*** Keccak-f[1600] ***/
static inline void keccakf(void* state) {
	auto* a = static_cast<uint64_t*>(state);
	uint64_t b[5] = {0};

	for (int i = 0; i < 24; i++)
	{
		uint8_t x, y;
		// Theta
		FOR5(uint8_t, x, 1,
			b[x] = 0;
			FOR5(uint8_t, y, 5,
				b[x] ^= a[x + y]; ))
		FOR5(uint8_t, x, 1,
			FOR5(uint8_t, y, 5,
				a[y + x] ^= b[(x + 4) % 5] ^ rol(b[(x + 1) % 5], 1); ))
		// Rho and pi
		uint64_t t = a[1];
		x = 0;
		REPEAT24(b[0] = a[pi[x]];
				a[pi[x]] = rol(t, rho[x]);
				t = b[0];
				x++; )
		// Chi
		FOR5(uint8_t,
			y,
			5,
			FOR5(uint8_t, x, 1,
				b[x] = a[y + x];)
			FOR5(uint8_t, x, 1,
				a[y + x] = b[x] ^ ((~b[(x + 1) % 5]) & b[(x + 2) % 5]); ))
		// Iota
		a[0] ^= RC[i];
	}
}

/******** The FIPS202-defined functions. ********/

/*** Some helper macros. ***/

#define _(S) do { S } while (0)
#define FOR(i, ST, L, S) \
	_(for (size_t i = 0; i < L; i += ST) { S; })
#define mkapply_ds(NAME, S)                                          \
	static inline void NAME(uint8_t* dst,                              \
							uint8_t const* src,                        \
							size_t len) {                              \
		FOR(i, 1, len, S);                                               \
	}
#define mkapply_sd(NAME, S)                                          \
	static inline void NAME(uint8_t const* src,                        \
							uint8_t* dst,                              \
							size_t len) {                              \
		FOR(i, 1, len, S);                                               \
	}

mkapply_ds(xorin, dst[i] ^= src[i])  // xorin
mkapply_sd(setout, dst[i] = src[i])  // setout

#define P keccakf
#define Plen 200

// Fold P*F over the full blocks of an input.
#define foldP(I, L, F) \
	while (L >= rate) {  \
		F(a, I, rate);     \
		P(a);              \
		I += rate;         \
		L -= rate;         \
	}

/** The sponge-based hash construction. **/
inline void hash(
	uint8_t* out,
	size_t outlen,
	uint8_t const* in,
	size_t inlen,
	size_t rate,
	uint8_t delim
)
{
	uint8_t a[Plen] = {0};
	// Absorb input.
	foldP(in, inlen, xorin);
	// Xor in the DS and pad frame.
	a[inlen] ^= delim;
	a[rate - 1] ^= 0x80;
	// Xor in the last block.
	xorin(a, in, inlen);
	// Apply P
	P(a);
	// Squeeze output.
	foldP(out, outlen, setout);
	setout(a, out, outlen);
	memset(a, 0, 200);
}

}

h256 keccak256(bytesConstRef _input)
{
	h256 output;
	// Parameters used:
	// The 0x01 is the specific padding for keccak (sha3 uses 0x06) and
	// the way the round size (or window or whatever it was) is calculated.
	// 200 - (256 / 4) is the "rate"
	hash(output.data(), output.size, _input.data(), _input.size(), 200 - (256 / 4), 0x01);
	return output;
}

}