// SPDX-License-Identifier: LGPL-3.0-or-later

#include "impl.h"

#define rotl(v, x) (((v) << (x)) | ((v) >> (64 - (x))))

#define ROUND do { \
	v0 += v1; \
	v2 += v3; \
	v1 = rotl(v1, 13); \
	v3 = rotl(v3, 16); \
	v1 ^= v0; \
	v3 ^= v2; \
	v0 = rotl(v0, 32); \
	v2 += v1; \
	v0 += v3; \
	v1 = rotl(v1, 17); \
	v3 = rotl(v3, 21); \
	v1 ^= v2; \
	v3 ^= v0; \
	v2 = rotl(v2, 32); \
} while(0)

uint64_t hkvs_hash(const char *hk, const char *data, size_t data_size) {
	uint64_t hk0 = hkvs_read_u64(hk + 0);
	uint64_t hk1 = hkvs_read_u64(hk + 8);
	uint64_t v0 = (uint64_t)0x736f6d6570736575 ^ hk0;
	uint64_t v1 = (uint64_t)0x646f72616e646f6d ^ hk1;
	uint64_t v2 = (uint64_t)0x6c7967656e657261 ^ hk0;
	uint64_t v3 = (uint64_t)0x7465646279746573 ^ hk1;
	uint64_t last = (uint64_t)data_size << 56;
	while(data_size >= 8) {
		uint64_t m = hkvs_read_u64(data);
		v3 ^= m;
		ROUND;
		v0 ^= m;
		data += 8;
		data_size -= 8;
	}

	switch(data_size) {
		case 7:
			last |= (uint64_t)(uint8_t)data[6] << 48;
			HKVS_FALLTHROUGH;
		case 6:
			last |= (uint64_t)(uint8_t)data[5] << 40;
			HKVS_FALLTHROUGH;
		case 5:
			last |= (uint64_t)(uint8_t)data[4] << 32;
			HKVS_FALLTHROUGH;
		case 4:
			last |= (uint64_t)(uint8_t)data[3] << 24;
			HKVS_FALLTHROUGH;
		case 3:
			last |= (uint64_t)(uint8_t)data[2] << 16;
			HKVS_FALLTHROUGH;
		case 2:
			last |= (uint64_t)(uint8_t)data[1] << 8;
			HKVS_FALLTHROUGH;
		case 1:
			last |= (uint64_t)(uint8_t)data[0];
			HKVS_FALLTHROUGH;
		case 0:
			break;
		default:
			__builtin_unreachable();
	}

	v3 ^= last;
	ROUND;
	v0 ^= last;

	v2 ^= 0xff;
	ROUND;
	ROUND;
	ROUND;
	return v0 ^ v1 ^ v2 ^ v3;
}