Update from NeXT-ppp-2.2-0.4.6

[ppp.git] / NeXT / random.c

diff --git a/NeXT/random.c b/NeXT/random.c
new file mode 100644 (file)
index 0000000..1c44fa1
--- /dev/null
+++ b/NeXT/random.c
@@ -0,0 +1,52 @@
+/*
+ * Because the standard library random number
+ * functions are not availble at the kernel level
+ * I wrote this simple random number generator.
+ *
+ * It uses the multiplicative congruential method.
+ * See pg 263 of Banks and Carson "Discrete-Event
+ * System Simulation".
+ *
+ */
+
+#include "random.h"
+
+static unsigned x0=123457;     /* seed */
+static unsigned a=16807;       /* constant multiplier */
+static unsigned c=0;           /* increment */
+static unsigned m=2147483647;  /* modulus */
+
+/*
+ * Set the seed to the argument.
+ */
+
+void srand(unsigned i)
+{
+  x0 = i;
+}
+
+
+/*
+ * Use Linear Congruential Method to Generate
+ * sequence.  Return either int or float...
+ */
+  
+unsigned rand(void)
+{
+  unsigned tmpseed;
+
+  tmpseed = (a*x0+c) % m;
+  x0 = tmpseed;
+  return (unsigned) x0;
+}
+
+
+
+float frand(void)
+{
+  unsigned tmpseed;
+
+  tmpseed = (a*x0+c) % m;
+  x0 = tmpseed;
+  return (x0/(float)m);
+}