/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

/*
 * 32 bit Fowler/Noll/Vo FNV-1a hash code with modification for BIND
 */

#include <stdbool.h>
#include <stddef.h>
#include <inttypes.h>
#if defined(WIN32) || defined(WIN64)
#include <malloc.h>
#endif

#include "isc/hash.h" // IWYU pragma: keep
#include "isc/likely.h"
#include "isc/once.h"
#include "isc/random.h"
#include "isc/result.h"
#include "isc/types.h"
#include "isc/util.h"
#include "isc/siphash.h"
#include "isc/string.h"

#include "entropy_private.h"

static uint8_t isc_hash_key[16];
static bool hash_initialized = false;
static isc_once_t isc_hash_once = ISC_ONCE_INIT;

static void
isc_hash_initialize(void) {
	uint64_t key[2] = { 0, 1 };
#if FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
	/*
	 * Set a constant key to help in problem reproduction should
	 * fuzzing find a crash or a hang.
	 */
#else
	isc_entropy_get(key, sizeof(key));
#endif
	memmove(isc_hash_key, key, sizeof(isc_hash_key));
	hash_initialized = true;
}

static uint8_t maptolower[] = {
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
	0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
	0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
	0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
	0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
	0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
	0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
	0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
	0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
	0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
	0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
	0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
	0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
	0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
	0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
	0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
	0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
	0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
	0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff
};

const void *
isc_hash_get_initializer(void) {
	if (ISC_UNLIKELY(!hash_initialized)) {
		RUNTIME_CHECK(isc_once_do(&isc_hash_once,
					  isc_hash_initialize)
			      == ISC_R_SUCCESS);
	}

	return (isc_hash_key);
}

void
isc_hash_set_initializer(const void *initializer) {
	REQUIRE(initializer != NULL);

	/*
	 * Ensure that isc_hash_initialize() is not called after
	 * isc_hash_set_initializer() is called.
	 */
	if (ISC_UNLIKELY(!hash_initialized)) {
		RUNTIME_CHECK(isc_once_do(&isc_hash_once,
					  isc_hash_initialize)
			      == ISC_R_SUCCESS);
	}

	memmove(isc_hash_key, initializer, sizeof(isc_hash_key));
}

uint64_t
isc_hash_function(const void *data,
		  const size_t length,
		  const bool case_sensitive)
{
	uint64_t hval;

	REQUIRE(length == 0 || data != NULL);

	RUNTIME_CHECK(isc_once_do(&isc_hash_once,
				  isc_hash_initialize) == ISC_R_SUCCESS);

	if (case_sensitive) {
		isc_siphash24(isc_hash_key, data, length, (uint8_t *)&hval);
	} else {
		uint8_t input[1024];
		REQUIRE(length <= 1024);
		for (unsigned int i = 0; i < length; i++) {
			input[i] = maptolower[((const uint8_t *)data)[i]];
		}
		isc_siphash24(isc_hash_key, input, length, (uint8_t *)&hval);
	}

	return (hval);
}
