/*
* Empire - A multi-player, client/server Internet based war game.
- * Copyright (C) 1986-2006, Dave Pare, Jeff Bailey, Thomas Ruschak,
- * Ken Stevens, Steve McClure
+ * Copyright (C) 1986-2013, Dave Pare, Jeff Bailey, Thomas Ruschak,
+ * Ken Stevens, Steve McClure, Markus Armbruster
*
- * This program is free software; you can redistribute it and/or modify
+ * 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 2 of the License, or
+ * 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,
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* ---
*
*
* ---
*
- * chance.c: return 1 if "roll" is under the chance.
- *
+ * chance.c: Roll dice
+ *
* Known contributors to this file:
- *
+ * Markus Armbruster, 2006-2012
*/
#include <config.h>
+#include <fcntl.h>
#include <math.h>
-#include "gen.h"
+#include <stdint.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 > (random() % 32768) / 32768.0;
+ 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 + random() % n;
+ return 1 + roll0(n);
}
/*
- * round value to nearest int (on the average). E.g. rounds up
- * with a chance proportional to the size of the fractional part.
+ * 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);
+}
+
+static uint32_t
+djb_hash(uint32_t 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;
+ uint32_t 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;
+}