diff options
Diffstat (limited to 'storage/innobase/include/ut0rnd.h')
| -rw-r--r-- | storage/innobase/include/ut0rnd.h | 69 |
1 files changed, 41 insertions, 28 deletions
diff --git a/storage/innobase/include/ut0rnd.h b/storage/innobase/include/ut0rnd.h index e8604ffa1c3..9af8687bfd0 100644 --- a/storage/innobase/include/ut0rnd.h +++ b/storage/innobase/include/ut0rnd.h @@ -1,6 +1,7 @@ /***************************************************************************** Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved. +Copyright (c) 2019, MariaDB Corporation. 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 @@ -27,37 +28,49 @@ Created 1/20/1994 Heikki Tuuri #define ut0rnd_h #include "ut0byte.h" +#include <my_sys.h> #ifndef UNIV_INNOCHECKSUM -/** The 'character code' for end of field or string (used -in folding records */ -#define UT_END_OF_FIELD 257 +/** Seed value of ut_rnd_gen() */ +extern int32 ut_rnd_current; + +/** @return a pseudo-random 32-bit number */ +inline uint32_t ut_rnd_gen() +{ + /* This is a Galois linear-feedback shift register. + https://en.wikipedia.org/wiki/Linear-feedback_shift_register#Galois_LFSRs + The generating primitive Galois Field polynomial is the Castagnoli + polynomial that was made popular by CRC-32C: + x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+ + x^19+x^18+x^14+x^13+x^11+x^10+x^9+x^8+x^6+1 */ + const uint32_t crc32c= 0x1edc6f41; + + uint32_t rnd= my_atomic_load32_explicit(&ut_rnd_current, + MY_MEMORY_ORDER_RELAXED); + + if (UNIV_UNLIKELY(rnd == 0)) + { + rnd= static_cast<uint32_t>(my_interval_timer()); + if (!rnd) rnd= 1; + } + else + { + bool lsb= rnd & 1; + rnd>>= 1; + if (lsb) + rnd^= crc32c; + } + + my_atomic_store32_explicit(&ut_rnd_current, rnd, MY_MEMORY_ORDER_RELAXED); + return rnd; +} + +/** @return a random number between 0 and n-1, inclusive */ +inline ulint ut_rnd_interval(ulint n) +{ + return n > 1 ? static_cast<ulint>(ut_rnd_gen() % n) : 0; +} -/********************************************************//** -This is used to set the random number seed. */ -UNIV_INLINE -void -ut_rnd_set_seed( -/*============*/ - ulint seed); /*!< in: 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 */ -/*********************************************************//** -The following function generates 'random' ulint integers which -enumerate the value space (let there be N of them) of ulint integers -in a pseudo-random fashion. Note that the same integer is repeated -always after N calls to the generator. -@return the 'random' number */ -UNIV_INLINE -ulint -ut_rnd_gen_ulint(void); -/*==================*/ /*******************************************************//** 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 |