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/*****************************************************************************
Copyright (c) 1994, 2009, Innobase Oy. All Rights Reserved.
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; version 2 of the License.
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, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA
*****************************************************************************/
/**************************************************************//**
@file include/ut0rnd.ic
Random numbers and hashing
Created 5/30/1994 Heikki Tuuri
*******************************************************************/
#define UT_HASH_RANDOM_MASK 1463735687
#define UT_HASH_RANDOM_MASK2 1653893711
#define UT_RND1 151117737
#define UT_RND2 119785373
#define UT_RND3 85689495
#define UT_RND4 76595339
#define UT_SUM_RND2 98781234
#define UT_SUM_RND3 126792457
#define UT_SUM_RND4 63498502
#define UT_XOR_RND1 187678878
#define UT_XOR_RND2 143537923
/** Seed value of ut_rnd_gen_ulint() */
extern ulint ut_rnd_ulint_counter;
/********************************************************//**
This is used to set the random number seed. */
UNIV_INLINE
void
ut_rnd_set_seed(
/*============*/
ulint seed) /*!< in: seed */
{
ut_rnd_ulint_counter = seed;
}
/********************************************************//**
The following function generates a series of 'random' ulint integers.
@return the next 'random' number */
UNIV_INLINE
ulint
ut_rnd_gen_next_ulint(
/*==================*/
ulint rnd) /*!< in: the previous random number value */
{
ulint n_bits;
n_bits = 8 * sizeof(ulint);
rnd = UT_RND2 * rnd + UT_SUM_RND3;
rnd = UT_XOR_RND1 ^ rnd;
rnd = (rnd << 20) + (rnd >> (n_bits - 20));
rnd = UT_RND3 * rnd + UT_SUM_RND4;
rnd = UT_XOR_RND2 ^ rnd;
rnd = (rnd << 20) + (rnd >> (n_bits - 20));
rnd = UT_RND1 * rnd + UT_SUM_RND2;
return(rnd);
}
/********************************************************//**
The following function generates 'random' ulint integers which
enumerate the value space of ulint integers in a pseudo random
fashion. Note that the same integer is repeated always after
2 to power 32 calls to the generator (if ulint is 32-bit).
@return the 'random' number */
UNIV_INLINE
ulint
ut_rnd_gen_ulint(void)
/*==================*/
{
ulint rnd;
ulint n_bits;
n_bits = 8 * sizeof(ulint);
ut_rnd_ulint_counter = UT_RND1 * ut_rnd_ulint_counter + UT_RND2;
rnd = ut_rnd_gen_next_ulint(ut_rnd_ulint_counter);
return(rnd);
}
/********************************************************//**
Generates a random integer from a given interval.
@return the 'random' number */
UNIV_INLINE
ulint
ut_rnd_interval(
/*============*/
ulint low, /*!< in: low limit; can generate also this value */
ulint high) /*!< in: high limit; can generate also this value */
{
ulint rnd;
ut_ad(high >= low);
if (low == high) {
return(low);
}
rnd = ut_rnd_gen_ulint();
return(low + (rnd % (high - low + 1)));
}
/*********************************************************//**
Generates a random iboolean value.
@return the random value */
UNIV_INLINE
ibool
ut_rnd_gen_ibool(void)
/*=================*/
{
ulint x;
x = ut_rnd_gen_ulint();
if (((x >> 20) + (x >> 15)) & 1) {
return(TRUE);
}
return(FALSE);
}
/*******************************************************//**
The following function generates a hash value for a ulint integer
to a hash table of size table_size, which should be a prime
or some random number for the hash table to work reliably.
@return hash value */
UNIV_INLINE
ulint
ut_hash_ulint(
/*==========*/
ulint key, /*!< in: value to be hashed */
ulint table_size) /*!< in: hash table size */
{
key = key ^ UT_HASH_RANDOM_MASK2;
return(key % table_size);
}
/*************************************************************//**
Folds a pair of ulints.
@return folded value */
UNIV_INLINE
ulint
ut_fold_ulint_pair(
/*===============*/
ulint n1, /*!< in: ulint */
ulint n2) /*!< in: ulint */
{
return(((((n1 ^ n2 ^ UT_HASH_RANDOM_MASK2) << 8) + n1)
^ UT_HASH_RANDOM_MASK) + n2);
}
/*************************************************************//**
Folds a dulint.
@return folded value */
UNIV_INLINE
ulint
ut_fold_dulint(
/*===========*/
dulint d) /*!< in: dulint */
{
return(ut_fold_ulint_pair(ut_dulint_get_low(d),
ut_dulint_get_high(d)));
}
/*************************************************************//**
Folds a character string ending in the null character.
@return folded value */
UNIV_INLINE
ulint
ut_fold_string(
/*===========*/
const char* str) /*!< in: null-terminated string */
{
ulint fold = 0;
ut_ad(str);
while (*str != '\0') {
fold = ut_fold_ulint_pair(fold, (ulint)(*str));
str++;
}
return(fold);
}
/*************************************************************//**
Folds a binary string.
@return folded value */
UNIV_INLINE
ulint
ut_fold_binary(
/*===========*/
const byte* str, /*!< in: string of bytes */
ulint len) /*!< in: length */
{
const byte* str_end = str + len;
ulint fold = 0;
ut_ad(str || !len);
while (str < str_end) {
fold = ut_fold_ulint_pair(fold, (ulint)(*str));
str++;
}
return(fold);
}
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