1 files changed, 89 insertions, 0 deletions
diff --git a/src/libs/math/random2.c b/src/libs/math/random2.c
new file mode 100644
index 0000000..9d354b4
--- /dev/null
+++ b/src/libs/math/random2.c
@@ -0,0 +1,89 @@
+/*
+ *  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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+// This file contains variants of the random functions in random.c
+// that store the state of the RNG in a context, allowing for multiple
+// independant RNGs to be used simultaneously.
+// The RNG behavior itself is the same.
+
+#include "libs/compiler.h"
+
+#define RANDOM2_INTERNAL
+#include "random.h"
+
+#include "libs/memlib.h"
+
+
+#define A 16807 /* a relatively prime number -- also M div Q */
+#define M 2147483647 /* 0xFFFFFFFF / 2 */
+#define Q 127773 /* M div A */
+#define R 2836 /* M mod A */
+
+RandomContext *
+RandomContext_New (void)
+{
+	RandomContext *result = (RandomContext *) HMalloc (sizeof (RandomContext));
+	result->seed = 12345;
+	return result;
+}
+
+void
+RandomContext_Delete (RandomContext *context)
+{
+	HFree ((void *) context);
+}
+
+RandomContext *
+RandomContext_Copy (const RandomContext *source)
+{
+	RandomContext *result = (RandomContext *) HMalloc (sizeof (RandomContext));
+	*result = *source;
+	return result;
+}
+
+DWORD
+RandomContext_Random (RandomContext *context)
+{
+	context->seed = A * (context->seed % Q) - R * (context->seed / Q);
+	if (context->seed > M) {
+		context->seed -= M;
+	} else if (context->seed == 0)
+		context->seed = 1;
+
+	return context->seed;
+}
+
+DWORD
+RandomContext_SeedRandom (RandomContext *context, DWORD new_seed)
+{
+	DWORD old_seed;
+
+	/* coerce the seed to be in the range 1..M */
+	if (new_seed == 0) /* 0 becomes 1 */
+		new_seed = 1;
+	else if (new_seed > M) /* and less than M */
+		new_seed -= M;
+
+	old_seed = context->seed;
+	context->seed = new_seed;
+	return old_seed;
+}
+
+DWORD
+RandomContext_GetSeed (RandomContext *context)
+{
+	return context->seed;
+}