--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libnumutil/digit_groups.c	Tue Dec 12 23:52:50 2023 +0000
@@ -0,0 +1,31 @@
+/*
+ * In version 2 of ThemWi owned number database, NANP numbers are stored as 3
+ * uint16_t words: NPA, exchange and prefix, each uint16_t encoding a group of
+ * 3 or 4 digits of the full telephone number.  This library module provides
+ * functions for turning groups of 3 or 4 digits into uint16_t words.
+ */
+
+#include <stdint.h>
+
+#include <themwi/nanp/number_utils.h>
+
+uint16_t digits3_to_uint16(const char *str)
+{
+	int acc;
+
+	acc = (str[0] - '0') * 100;
+	acc += (str[1] - '0') * 10;
+	acc += str[2] - '0';
+	return acc;
+}
+
+uint16_t digits4_to_uint16(const char *str)
+{
+	int acc;
+
+	acc = (str[0] - '0') * 1000;
+	acc += (str[1] - '0') * 100;
+	acc += (str[2] - '0') * 10;
+	acc += str[3] - '0';
+	return acc;
+}