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/*
random.c - implementation of all random number related functions
Copyright (C) 2001, 2002, 2004 Arthur de Jong
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 Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <limits.h>
#include "rl.h"
#include "random.h"
#if defined(USE_RAND_RNG)
/* initialize the random number generator with a sensible value
this calls srand() so rand() can be used */
void
randomize()
{
struct timeval tv;
gettimeofday(&tv,NULL);
srand(((unsigned int)(tv.tv_usec))^((unsigned int)getpid()));
}
/* returns a random number x where 0 <= x < max */
int
random_below(int max)
{
int i;
int j;
i=RAND_MAX/max;
/* there realy should be a better way for this */
/* TODO: fix with something smart so that this even works for large values
(on systems with a low RAND_MAX maybe two calls
to rand() could be used) */
/* TODO: add range checking 0<max<RAND_MAX */
do
{
j=rand()/i;
}
while (j>=max);
return j;
}
#elif defined(USE_DEV_RNG)
#define RANDOM_DEVICE "/dev/urandom"
/* the file pointer that is used to read from the random device */
static FILE *random_fp;
/* open random device for reading */
void
randomize()
{
random_fp=fopen(RANDOM_DEVICE,"rb");
}
/* returns a random number x where 0 <= x < max */
int
random_below(int max)
{
int i;
int j;
int r;
i=INT_MAX/max;
/* TODO: check same problems as above */
do
{
if (fread(&r,sizeof(int),1,random_fp)!=1)
{
fprintf(stderr,_("Error reading from %s\n"),RANDOM_DEVICE);
exit(1);
}
j=(r&INT_MAX)/i;
}
while (j>=max);
return j;
}
#else
#error invalid random number generator selected
#endif
/* thow the dice and return true (1)
with a chance of x/y (false=0) */
int
random_draw(int x,int y)
{
return random_below(y)<x;
}
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