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150 lines
4.1 KiB
C++
150 lines
4.1 KiB
C++
/*****************************************************************************
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Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
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Copyright (c) 2017, 2019, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
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*****************************************************************************/
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/**************************************************************//**
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@file include/ut0rnd.ic
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Random numbers and hashing
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Created 5/30/1994 Heikki Tuuri
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*******************************************************************/
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#define UT_HASH_RANDOM_MASK 1463735687
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#define UT_HASH_RANDOM_MASK2 1653893711
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#ifndef UNIV_INNOCHECKSUM
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/*******************************************************//**
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The following function generates a hash value for a ulint integer
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to a hash table of size table_size, which should be a prime
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or some random number for the hash table to work reliably.
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@return hash value */
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UNIV_INLINE
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ulint
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ut_hash_ulint(
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/*==========*/
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ulint key, /*!< in: value to be hashed */
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ulint table_size) /*!< in: hash table size */
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{
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ut_ad(table_size);
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key = key ^ UT_HASH_RANDOM_MASK2;
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return(key % table_size);
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}
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/*************************************************************//**
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Folds a 64-bit integer.
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@return folded value */
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UNIV_INLINE
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ulint
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ut_fold_ull(
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/*========*/
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ib_uint64_t d) /*!< in: 64-bit integer */
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{
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return(ut_fold_ulint_pair((ulint) d & ULINT32_MASK,
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(ulint) (d >> 32)));
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}
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/*************************************************************//**
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Folds a character string ending in the null character.
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@return folded value */
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UNIV_INLINE
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ulint
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ut_fold_string(
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/*===========*/
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const char* str) /*!< in: null-terminated string */
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{
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ulint fold = 0;
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ut_ad(str);
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while (*str != '\0') {
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fold = ut_fold_ulint_pair(fold, (ulint)(*str));
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str++;
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}
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return(fold);
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}
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#endif /* !UNIV_INNOCHECKSUM */
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/*************************************************************//**
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Folds a pair of ulints.
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@return folded value */
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UNIV_INLINE
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ulint
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ut_fold_ulint_pair(
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/*===============*/
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ulint n1, /*!< in: ulint */
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ulint n2) /*!< in: ulint */
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{
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return(((((n1 ^ n2 ^ UT_HASH_RANDOM_MASK2) << 8) + n1)
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^ UT_HASH_RANDOM_MASK) + n2);
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}
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/*************************************************************//**
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Folds a binary string.
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@return folded value */
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UNIV_INLINE
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ulint
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ut_fold_binary(
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/*===========*/
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const byte* str, /*!< in: string of bytes */
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ulint len) /*!< in: length */
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{
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ulint fold = 0;
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const byte* str_end = str + (len & 0xFFFFFFF8);
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ut_ad(str || !len);
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while (str < str_end) {
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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}
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switch (len & 0x7) {
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case 7:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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/* fall through */
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case 6:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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/* fall through */
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case 5:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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/* fall through */
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case 4:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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/* fall through */
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case 3:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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/* fall through */
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case 2:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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/* fall through */
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case 1:
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fold = ut_fold_ulint_pair(fold, (ulint)(*str++));
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}
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return(fold);
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}
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