--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libutil/gsm7_pack.c	Sun Mar 07 07:40:33 2021 +0000
@@ -0,0 +1,22 @@
+/*
+ * This library module implements the function for packing septets into octets.
+ */
+
+#include <sys/types.h>
+
+gsm7_pack(inbuf, outbuf, noctets)
+	u_char *inbuf, *outbuf;
+	unsigned noctets;
+{
+	u_char *ip = inbuf, *op = outbuf;
+	unsigned n, c;
+
+	for (n = 0; n < noctets; n++) {
+		c = n % 7;
+		*op++ = ((ip[1] << 7) | ip[0]) >> c;
+		if (c == 6)
+			ip += 2;
+		else
+			ip += 1;
+	}
+}