Added Nitfol and Frotz source code.

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

diff --git a/interpreters/frotz/random.c b/interpreters/frotz/random.c
new file mode 100644 (file)
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+++ b/interpreters/frotz/random.c
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+/* random.c - Z-machine random number generator
+ *     Copyright (c) 1995-1997 Stefan Jokisch
+ *
+ * This file is part of Frotz.
+ *
+ * Frotz 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.
+ *
+ * Frotz 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include "frotz.h"
+
+static long A = 1;
+
+static int interval = 0;
+static int counter = 0;
+
+/*
+ * seed_random
+ *
+ * Set the seed value for the random number generator.
+ *
+ */
+
+void seed_random (int value)
+{
+
+    if (value == 0) {          /* ask interface for seed value */
+       A = os_random_seed ();
+       interval = 0;
+    } else if (value < 1000) { /* special seed value */
+       counter = 0;
+       interval = value;
+    } else {                   /* standard seed value */
+       A = value;
+       interval = 0;
+    }
+
+}/* seed_random */
+
+/*
+ * z_random, store a random number or set the random number seed.
+ *
+ *     zargs[0] = range (positive) or seed value (negative)
+ *
+ */
+
+void z_random ()
+{
+
+    if ((short) zargs[0] <= 0) {       /* set random seed */
+
+       seed_random (- (short) zargs[0]);
+       store (0);
+
+    } else {                           /* generate random number */
+
+       zword result;
+
+       if (interval != 0) {            /* ...in special mode */
+           result = counter++;
+           if (counter == interval) counter = 0;
+       } else {                        /* ...in standard mode */
+           A = 0x015a4e35L * A + 1;
+           result = (A >> 16) & 0x7fff;
+       }
+
+       store ((zword) (result % zargs[0] + 1));
+
+    }
+
+}/* z_random */