Add Bocfel interpreter

[projects/chimara/chimara.git] / interpreters / bocfel / random.c

diff --git a/interpreters/bocfel/random.c b/interpreters/bocfel/random.c
new file mode 100644 (file)
index 0000000..2d15347
--- /dev/null
+++ b/interpreters/bocfel/random.c
@@ -0,0 +1,162 @@
+/*-
+ * Copyright 2010-2012 Chris Spiegel.
+ *
+ * This file is part of Bocfel.
+ *
+ * Bocfel is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version
+ * 2 or 3, as published by the Free Software Foundation.
+ *
+ * Bocfel 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 Bocfel.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <limits.h>
+#include <time.h>
+
+#include "random.h"
+#include "process.h"
+#include "zterp.h"
+
+/* Mersenne Twister. */
+static uint32_t mt[624];
+static uint32_t mt_idx = 0;
+
+static void zterp_srand(uint32_t s)
+{
+  mt[0] = s;
+  for(int i = 1; i < 624; i++)
+  {
+    mt[i] = 1812433253UL * (mt[i - 1] ^ (mt[i - 1] >> 30)) + i;
+  }
+  mt_idx = 0;
+}
+
+static void mt_gen_num(void)
+{
+  for(int i = 0; i < 624; i++)
+  {
+    uint32_t y;
+
+    y = mt[i] & 0x80000000UL;
+    y |= (mt[(i + 1) % 624]) & 0x7fffffffUL;
+
+    mt[i] = mt[(i + 397) % 624] ^ (y >> 1);
+
+    if(y % 2 == 1) mt[i] ^= 2567483615UL;
+  }
+}
+
+static uint32_t zterp_rand(void)
+{
+  uint32_t y;
+
+  if(mt_idx == 0) mt_gen_num();
+
+  y = mt[mt_idx];
+  y ^= (y >> 11);
+  y ^= (y << 7) & 2636928640UL;
+  y ^= (y << 15) & 4022730752UL;
+  y ^= (y >> 18);
+
+  mt_idx = (mt_idx + 1) % 624;
+
+  return y;
+}
+
+static int rng_interval = 0;
+static int rng_counter  = 0;
+
+/* Called with 0, seed the PRNG with either
+ * a) a user-provided seed (via -z) if available, or
+ * b) a seed read from a user-provided file/device (via -Z) if
+ *    available, or
+ * c) a seed derived from a hash of the constituent bytes of the value
+ *    returned by time(NULL)
+ *
+ * Called with a value 0 < S < 1000, generate a string of numbers 1, 2,
+ * 3, ..., S, 1, 2, 3, ... S, ... as recommended in the remarks to §2.
+ *
+ * Called with a value >= 1000, use that value as a normal seed.
+ */
+void seed_random(long value)
+{
+  if(value == 0)
+  {
+    if(options.random_seed == -1)
+    {
+      time_t t = time(NULL);
+      unsigned char *p = (unsigned char *)&t;
+      uint32_t s = 0;
+
+      /* time_t hashing based on code by Lawrence Kirby. */
+      for(size_t i = 0; i < sizeof t; i++) s = s * (UCHAR_MAX + 2U) + p[i];
+
+      if(options.random_device != NULL)
+      {
+        FILE *fp;
+        uint32_t temp;
+
+        fp = fopen(options.random_device, "r");
+        if(fp != NULL)
+        {
+          if(fread(&temp, sizeof temp, 1, fp) == 1) s = temp;
+          fclose(fp);
+        }
+      }
+
+      zterp_srand(s);
+    }
+    else
+    {
+      zterp_srand(options.random_seed);
+    }
+
+    rng_interval = 0;
+  }
+  else if(value < 1000)
+  {
+    rng_counter = 0;
+    rng_interval = value;
+  }
+  else
+  {
+    zterp_srand(value);
+    rng_interval = 0;
+  }
+}
+
+void zrandom(void)
+{
+  long v = (int16_t)zargs[0];
+
+  if(v <= 0)
+  {
+    seed_random(-v);
+    store(0);
+  }
+  else
+  {
+    uint32_t res;
+
+    if(rng_interval != 0)
+    {
+      res = rng_counter++;
+      if(rng_counter == rng_interval) rng_counter = 0;
+    }
+    else
+    {
+      res = zterp_rand();
+    }
+
+    store(res % zargs[0] + 1);
+  }
+}