Permalink
Switch branches/tags
Find file
Fetching contributors…
Cannot retrieve contributors at this time
76 lines (67 sloc) 3.15 KB
/*
+----------------------------------------------------------------------+
| PHP Version 7 |
+----------------------------------------------------------------------+
| Copyright (c) 1997-2018 The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: Rasmus Lerdorf <rasmus@php.net> |
| Zeev Suraski <zeev@zend.com> |
| Pedro Melo <melo@ip.pt> |
| Sterling Hughes <sterling@php.net> |
| |
| Based on code from: Shawn Cokus <Cokus@math.washington.edu> |
+----------------------------------------------------------------------+
*/
/* $Id$ */
#ifndef PHP_RAND_H
#define PHP_RAND_H
#include "php_lcg.h"
#include "php_mt_rand.h"
/* System Rand functions */
#ifndef RAND_MAX
#define RAND_MAX PHP_MT_RAND_MAX
#endif
#define PHP_RAND_MAX PHP_MT_RAND_MAX
/*
* A bit of tricky math here. We want to avoid using a modulus because
* that simply tosses the high-order bits and might skew the distribution
* of random values over the range. Instead we map the range directly.
*
* We need to map the range from 0...M evenly to the range a...b
* Let n = the random number and n' = the mapped random number
*
* Then we have: n' = a + n(b-a)/M
*
* We have a problem here in that only n==M will get mapped to b which
# means the chances of getting b is much much less than getting any of
# the other values in the range. We can fix this by increasing our range
# artificially and using:
#
# n' = a + n(b-a+1)/M
*
# Now we only have a problem if n==M which would cause us to produce a
# number of b+1 which would be bad. So we bump M up by one to make sure
# this will never happen, and the final algorithm looks like this:
#
# n' = a + n(b-a+1)/(M+1)
*
* -RL
*/
#define RAND_RANGE_BADSCALING(__n, __min, __max, __tmax) \
(__n) = (__min) + (zend_long) ((double) ( (double) (__max) - (__min) + 1.0) * ((__n) / ((__tmax) + 1.0)))
#ifdef PHP_WIN32
#define GENERATE_SEED() (((zend_long) (time(0) * GetCurrentProcessId())) ^ ((zend_long) (1000000.0 * php_combined_lcg())))
#else
#define GENERATE_SEED() (((zend_long) (time(0) * getpid())) ^ ((zend_long) (1000000.0 * php_combined_lcg())))
#endif
PHPAPI void php_srand(zend_long seed);
PHPAPI zend_long php_rand(void);
#endif /* PHP_RAND_H */