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|
/*
+----------------------------------------------------------------------+
| Copyright (c) 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. |
+----------------------------------------------------------------------+
| Author: Sascha Schumann <sascha@schumann.cx> |
+----------------------------------------------------------------------+
*/
#include "php.h"
#include "php_lcg.h"
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef PHP_WIN32
#include "win32/time.h"
#else
#include <sys/time.h>
#endif
#ifdef ZTS
int lcg_globals_id;
#else
static php_lcg_globals lcg_globals;
#endif
#ifdef PHP_WIN32
#include <process.h>
#endif
/*
* combinedLCG() returns a pseudo random number in the range of (0, 1).
* The function combines two CGs with periods of
* 2^31 - 85 and 2^31 - 249. The period of this function
* is equal to the product of both primes.
*/
#define MODMULT(a, b, c, m, s) q = s/a;s=b*(s-a*q)-c*q;if(s<0)s+=m
static void lcg_seed(void);
PHPAPI double php_combined_lcg(void) /* {{{ */
{
int32_t q;
int32_t z;
if (!LCG(seeded)) {
lcg_seed();
}
MODMULT(53668, 40014, 12211, 2147483563L, LCG(s1));
MODMULT(52774, 40692, 3791, 2147483399L, LCG(s2));
z = LCG(s1) - LCG(s2);
if (z < 1) {
z += 2147483562;
}
return z * 4.656613e-10;
}
/* }}} */
static void lcg_seed(void) /* {{{ */
{
struct timeval tv;
if (gettimeofday(&tv, NULL) == 0) {
LCG(s1) = tv.tv_sec ^ (tv.tv_usec<<11);
} else {
LCG(s1) = 1;
}
#ifdef ZTS
LCG(s2) = (zend_long) tsrm_thread_id();
#else
LCG(s2) = (zend_long) getpid();
#endif
/* Add entropy to s2 by calling gettimeofday() again */
if (gettimeofday(&tv, NULL) == 0) {
LCG(s2) ^= (tv.tv_usec<<11);
}
LCG(seeded) = 1;
}
/* }}} */
static void lcg_init_globals(php_lcg_globals *lcg_globals_p) /* {{{ */
{
LCG(seeded) = 0;
}
/* }}} */
PHP_MINIT_FUNCTION(lcg) /* {{{ */
{
#ifdef ZTS
ts_allocate_id(&lcg_globals_id, sizeof(php_lcg_globals), (ts_allocate_ctor) lcg_init_globals, NULL);
#else
lcg_init_globals(&lcg_globals);
#endif
return SUCCESS;
}
/* }}} */
/* {{{ proto float lcg_value()
Returns a value from the combined linear congruential generator */
PHP_FUNCTION(lcg_value)
{
ZEND_PARSE_PARAMETERS_NONE();
RETURN_DOUBLE(php_combined_lcg());
}
/* }}} */
|
