/* +----------------------------------------------------------------------+ | 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))) #define RAND_RANGE(__n, __min, __max, __tmax) \ (__n) = php_mt_rand_range((__min), (__max)) #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 */