--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libutil/decimal_str.c	Sun Mar 14 05:42:37 2021 +0000
@@ -0,0 +1,41 @@
+/*
+ * This module implements some functions for initial parsing of decimal
+ * string arguments, intended for implementation of commands like
+ * write-iccid and write-imsi.
+ */
+
+#include <sys/types.h>
+#include <ctype.h>
+#include <stdio.h>
+
+parse_decimal_string_arg(arg, dest, maxdigits)
+	char *arg;
+	u_char *dest;
+	unsigned maxdigits;
+{
+	unsigned n, ndig;
+
+	if (!*arg) {
+		fprintf(stderr,
+			"error: empty argument given for decimal string\n");
+		return(-1);
+	}
+	for (n = 0; *arg; ) {
+		if (!isdigit(*arg)) {
+			fprintf(stderr,
+			"error: non-digit char in decimal string argument\n");
+			return(-1);
+		}
+		if (n >= maxdigits) {
+			fprintf(stderr,
+			"error: decimal string exceeds limit of %u digits\n",
+				maxdigits);
+			return(-1);
+		}
+		dest[n++] = *arg++ - '0';
+	}
+	ndig = n;
+	while (n < maxdigits)
+		dest[n++] = 0xF;
+	return ndig;
+}