177 lines
3.9 KiB
C
177 lines
3.9 KiB
C
/*
|
|
* Empire - A multi-player, client/server Internet based war game.
|
|
* Copyright (C) 1986-2016, Dave Pare, Jeff Bailey, Thomas Ruschak,
|
|
* Ken Stevens, Steve McClure, Markus Armbruster
|
|
*
|
|
* Empire 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 3 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, see <http://www.gnu.org/licenses/>.
|
|
*
|
|
* ---
|
|
*
|
|
* See files README, COPYING and CREDITS in the root of the source
|
|
* tree for related information and legal notices. It is expected
|
|
* that future projects/authors will amend these files as needed.
|
|
*
|
|
* ---
|
|
*
|
|
* chance.c: Roll dice
|
|
*
|
|
* Known contributors to this file:
|
|
* Markus Armbruster, 2006-2012
|
|
*/
|
|
|
|
#include <config.h>
|
|
|
|
#include <fcntl.h>
|
|
#include <math.h>
|
|
#include <stdlib.h>
|
|
#include <sys/time.h>
|
|
#include <unistd.h>
|
|
#include "chance.h"
|
|
#include "mt19937ar.h"
|
|
|
|
/*
|
|
* Return non-zero with probability D.
|
|
*/
|
|
int
|
|
chance(double d)
|
|
{
|
|
return d > genrand_real2();
|
|
}
|
|
|
|
/*
|
|
* Return non-zero with probability @pct%.
|
|
*/
|
|
int
|
|
pct_chance(int pct)
|
|
{
|
|
return roll(100) <= pct;
|
|
}
|
|
|
|
static unsigned
|
|
round_up_to_pow2(unsigned val)
|
|
{
|
|
val--;
|
|
val |= val >> 1;
|
|
val |= val >> 2;
|
|
val |= val >> 4;
|
|
val |= val >> 8;
|
|
val |= val >> 16;
|
|
val++;
|
|
return val;
|
|
}
|
|
|
|
/*
|
|
* Return a random number in [0..N-1].
|
|
* N must be in [1..2^31-1].
|
|
*/
|
|
int
|
|
roll0(int n)
|
|
{
|
|
unsigned pow2 = round_up_to_pow2(n);
|
|
int r;
|
|
|
|
do
|
|
r = genrand_int32() & (pow2 - 1);
|
|
while (r >= n);
|
|
return r;
|
|
}
|
|
|
|
/*
|
|
* Return a random number in [1..N].
|
|
* N must be in [0..2^31-1].
|
|
*/
|
|
int
|
|
roll(int n)
|
|
{
|
|
return 1 + roll0(n);
|
|
}
|
|
|
|
/*
|
|
* Round @val to nearest integer (on the average).
|
|
* @val's fractional part is chance to round up.
|
|
*/
|
|
int
|
|
roundavg(double val)
|
|
{
|
|
double flr = floor(val);
|
|
return (int)(flr + chance(val - flr));
|
|
}
|
|
|
|
/*
|
|
* Seed the pseudo-random number generator with @seed.
|
|
* The sequence of pseudo-random numbers is repeatable by seeding it
|
|
* with the same value.
|
|
*/
|
|
void
|
|
seed_prng(unsigned seed)
|
|
{
|
|
init_genrand(seed);
|
|
}
|
|
|
|
/*
|
|
* Note: this is DJB's hash function when unsigned is 32 bits and hash
|
|
* is initially 5381.
|
|
*/
|
|
static unsigned
|
|
djb_hash(unsigned hash, void *buf, size_t sz)
|
|
{
|
|
unsigned char *bp;
|
|
|
|
for (bp = buf; bp < (unsigned char *)buf + sz; bp++)
|
|
hash = hash * 33 ^ *bp;
|
|
|
|
return hash;
|
|
}
|
|
|
|
/*
|
|
* Pick a reasonably random seed for the pseudo-random number generator.
|
|
*/
|
|
unsigned
|
|
pick_seed(void)
|
|
{
|
|
int fd;
|
|
unsigned seed;
|
|
int got_seed = 0;
|
|
struct timeval tv;
|
|
pid_t pid;
|
|
|
|
/*
|
|
* Modern systems provide random number devices, but the details
|
|
* vary. On many systems, /dev/random blocks when the kernel
|
|
* entropy pool has been depleted, while /dev/urandom doesn't.
|
|
* The former should only be used for generating long-lived
|
|
* cryptographic keys. On other systems, both devices behave
|
|
* exactly the same, or only /dev/random exists.
|
|
*
|
|
* Try /dev/urandom first, and if it can't be opened, blindly try
|
|
* /dev/random.
|
|
*/
|
|
fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK);
|
|
if (fd < 0)
|
|
fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
|
|
if (fd >= 0) {
|
|
got_seed = read(fd, &seed, sizeof(seed)) == sizeof(seed);
|
|
close(fd);
|
|
}
|
|
|
|
if (!got_seed) {
|
|
/* Kernel didn't provide, fall back to hashing time and PID */
|
|
gettimeofday(&tv, NULL);
|
|
seed = djb_hash(5381, &tv, sizeof(tv));
|
|
pid = getpid();
|
|
seed = djb_hash(seed, &pid, sizeof(pid));
|
|
}
|
|
|
|
return seed;
|
|
}
|