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/* Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
This program 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.
This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
*/
/*!
* \brief Microsoft Toeplitz-based hash implementation
*/
#pragma once
#include <assert.h>
#include <stdint.h>
#include "libknot/endian.h"
/*!
* \brief Computes a Toeplitz hash value for given key and data.
*
* \param key Key vector
* \param key_len Length of the key vector in bytes.
* \param data Input data to compute hash from.
* \param data_len Lenght of the input data in bytes.
*
* \return A Toeplitz hash value.
*/
inline static uint32_t toeplitz_hash(const uint8_t *key, const size_t key_len,
const uint8_t *data, const size_t data_len)
{
assert(key_len >= 4 + 2 * (16 + 2));
uint32_t key32 = be32toh(*(const uint32_t *)key);
key += sizeof(uint32_t);
int ret = 0;
for (int i = 0; i < data_len; i++) {
for (int bit = 7; bit >= 0; bit--) {
if (data[i] & (1 << bit)) {
ret ^= key32;
}
key32 <<= 1;
key32 |= !!(key[0] & (1 << bit));
}
key++;
}
return ret;
}
/*!
* \brief Toeplitz hash context for divided processing.
*/
typedef struct {
const uint8_t *data;
const uint8_t *data_end;
const uint8_t *key;
uint32_t hash;
uint32_t key32;
} toeplitz_ctx_t;
inline static void toeplitz_init(toeplitz_ctx_t *ctx, uint8_t count,
const uint8_t *key, const uint8_t key_len,
const uint8_t *data, const uint8_t data_len)
{
assert(key_len >= 40);
ctx->data = data;
ctx->data_end = data + data_len;
ctx->key = key + sizeof(uint32_t);
ctx->hash = 0;
ctx->key32 = be32toh(*(const uint32_t *)key);
const uint8_t *stop = ctx->data + count;
assert(stop <= ctx->data_end);
while (ctx->data < stop) {
for (int bit = 7; bit >= 0; bit--) {
if (*ctx->data & (1 << bit)) {
ctx->hash ^= ctx->key32;
}
ctx->key32 <<= 1;
ctx->key32 |= !!(*ctx->key & (1 << bit));
}
ctx->data++;
ctx->key++;
}
}
inline static uint32_t toeplitz_finish(toeplitz_ctx_t *ctx)
{
uint32_t hash = ctx->hash;
uint32_t key32 = ctx->key32;
const uint8_t *key = ctx->key;
for (const uint8_t *in = ctx->data; in < ctx->data_end; in++) {
for (int bit = 7; bit >= 0; bit--) {
if (*in & (1 << bit)) {
hash ^= key32;
}
key32 <<= 1;
key32 |= !!(*key & (1 << bit));
}
key++;
}
return hash;
}
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