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-rw-r--r--storage/innobase/include/ut0rnd.h69
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