1 files changed, 82 insertions, 0 deletions
diff --git a/netem/paretonormal.c b/netem/paretonormal.c
new file mode 100644
index 0000000..c36e325
--- /dev/null
+++ b/netem/paretonormal.c
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: NIST-PD */
+/*
+ * Paretoormal distribution table generator
+ *
+ * This distribution is simply .25*normal + .75*pareto; a combination
+ * which seems to match experimentally observed distributions reasonably
+ *  well, but is computationally easy to handle.
+ * The entries represent a scaled inverse of the cumulative distribution
+ * function.
+ *
+ * Taken from the uncopyrighted NISTnet code.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <limits.h>
+#include <malloc.h>
+
+#include <linux/types.h>
+#include <linux/pkt_sched.h>
+
+#define TABLESIZE	16384
+#define TABLEFACTOR	NETEM_DIST_SCALE
+
+static double
+normal(double x, double mu, double sigma)
+{
+	return .5 + .5*erf((x-mu)/(sqrt(2.0)*sigma));
+}
+
+static const double a=3.0;
+
+static int
+paretovalue(int i)
+{
+	double dvalue;
+
+	i = 65536-4*i;
+	dvalue = (double)i/(double)65536;
+	dvalue = 1.0/pow(dvalue, 1.0/a);
+	dvalue -= 1.5;
+	dvalue *= (4.0/3.0)*(double)TABLEFACTOR;
+	if (dvalue > 32767)
+		dvalue = 32767;
+	return (int)rint(dvalue);
+}
+
+int
+main(int argc, char **argv)
+{
+	int i,n;
+	double x;
+	double table[TABLESIZE+1];
+
+	for (x = -10.0; x < 10.05; x += .00005) {
+		i = rint(TABLESIZE*normal(x, 0.0, 1.0));
+		table[i] = x;
+	}
+	printf(
+"# This is the distribution table for the paretonormal distribution.\n"
+	);
+
+	for (i = n = 0; i < TABLESIZE; i += 4) {
+		int normvalue, parvalue, value;
+
+		normvalue = (int) rint(table[i]*TABLEFACTOR);
+		parvalue = paretovalue(i);
+
+		value = (normvalue+3*parvalue)/4;
+		if (value < SHRT_MIN) value = SHRT_MIN;
+		if (value > SHRT_MAX) value = SHRT_MAX;
+
+		printf(" %d", value);
+		if (++n == 8) {
+			putchar('\n');
+			n = 0;
+		}
+	}
+
+	return 0;
+}