1                 : /*
       2                 :    +----------------------------------------------------------------------+
       3                 :    | PHP Version 5                                                        |
       4                 :    +----------------------------------------------------------------------+
       5                 :    | Copyright (c) 1997-2009 The PHP Group                                |
       6                 :    +----------------------------------------------------------------------+
       7                 :    | This source file is subject to version 3.01 of the PHP license,      |
       8                 :    | that is bundled with this package in the file LICENSE, and is        |
       9                 :    | available through the world-wide-web at the following url:           |
      10                 :    | http://www.php.net/license/3_01.txt                                  |
      11                 :    | If you did not receive a copy of the PHP license and are unable to   |
      12                 :    | obtain it through the world-wide-web, please send a note to          |
      13                 :    | license@php.net so we can mail you a copy immediately.               |
      14                 :    +----------------------------------------------------------------------+
      15                 :    | Author: Sascha Schumann <sascha@schumann.cx>                         |
      16                 :    +----------------------------------------------------------------------+
      17                 : */
      18                 : 
      19                 : /* $Id: lcg.c 272370 2008-12-31 11:15:49Z sebastian $ */
      20                 : 
      21                 : #include "php.h"
      22                 : #include "php_lcg.h"
      23                 : 
      24                 : #if HAVE_UNISTD_H
      25                 : #include <unistd.h>
      26                 : #endif
      27                 : 
      28                 : #ifdef PHP_WIN32
      29                 : #include "win32/time.h"
      30                 : #else
      31                 : #include <sys/time.h>
      32                 : #endif
      33                 : 
      34                 : #ifdef ZTS
      35                 : int lcg_globals_id;
      36                 : #else
      37                 : static php_lcg_globals lcg_globals;
      38                 : #endif
      39                 : 
      40                 : #ifdef PHP_WIN32
      41                 : #include <process.h>
      42                 : #endif
      43                 : 
      44                 : /*
      45                 :  * combinedLCG() returns a pseudo random number in the range of (0, 1).
      46                 :  * The function combines two CGs with periods of
      47                 :  * 2^31 - 85 and 2^31 - 249. The period of this function
      48                 :  * is equal to the product of both primes.
      49                 :  */
      50                 : 
      51                 : #define MODMULT(a, b, c, m, s) q = s/a;s=b*(s-a*q)-c*q;if(s<0)s+=m
      52                 : 
      53                 : static void lcg_seed(TSRMLS_D);
      54                 : 
      55                 : PHPAPI double php_combined_lcg(TSRMLS_D) /* {{{ */
      56             780 : {
      57                 :         php_int32 q;
      58                 :         php_int32 z;
      59                 : 
      60             780 :         if (!LCG(seeded)) {
      61             261 :                 lcg_seed(TSRMLS_C);
      62                 :         }
      63                 : 
      64             780 :         MODMULT(53668, 40014, 12211, 2147483563L, LCG(s1));
      65             780 :         MODMULT(52774, 40692, 3791, 2147483399L, LCG(s2));
      66                 : 
      67             780 :         z = LCG(s1) - LCG(s2);
      68             780 :         if (z < 1) {
      69             336 :                 z += 2147483562;
      70                 :         }
      71                 : 
      72             780 :         return z * 4.656613e-10;
      73                 : }
      74                 : /* }}} */
      75                 : 
      76                 : static void lcg_seed(TSRMLS_D) /* {{{ */
      77             261 : {
      78                 :         struct timeval tv;
      79                 : 
      80             261 :         if (gettimeofday(&tv, NULL) == 0) {
      81             261 :                 LCG(s1) = tv.tv_sec ^ (~tv.tv_usec);
      82                 :         } else {
      83               0 :                 LCG(s1) = 1;
      84                 :         }
      85                 : #ifdef ZTS
      86                 :         LCG(s2) = (long) tsrm_thread_id();
      87                 : #else
      88             261 :         LCG(s2) = (long) getpid();
      89                 : #endif
      90                 : 
      91             261 :         LCG(seeded) = 1;
      92             261 : }
      93                 : /* }}} */
      94                 : 
      95                 : static void lcg_init_globals(php_lcg_globals *lcg_globals_p TSRMLS_DC) /* {{{ */
      96           17633 : {
      97           17633 :         LCG(seeded) = 0;
      98           17633 : }
      99                 : /* }}} */
     100                 : 
     101                 : PHP_MINIT_FUNCTION(lcg) /* {{{ */
     102           17633 : {
     103                 : #ifdef ZTS
     104                 :         ts_allocate_id(&lcg_globals_id, sizeof(php_lcg_globals), (ts_allocate_ctor) lcg_init_globals, NULL);
     105                 : #else
     106           17633 :         lcg_init_globals(&lcg_globals);
     107                 : #endif
     108           17633 :         return SUCCESS;
     109                 : }
     110                 : /* }}} */
     111                 : 
     112                 : /* {{{ proto float lcg_value()
     113                 :    Returns a value from the combined linear congruential generator */
     114                 : PHP_FUNCTION(lcg_value)
     115             102 : {
     116             102 :         RETURN_DOUBLE(php_combined_lcg(TSRMLS_C));
     117                 : }
     118                 : /* }}} */
     119                 : 
     120                 : /*
     121                 :  * Local variables:
     122                 :  * tab-width: 4
     123                 :  * c-basic-offset: 4
     124                 :  * End:
     125                 :  * vim600: sw=4 ts=4 fdm=marker
     126                 :  * vim<600: sw=4 ts=4
     127                 :  */