--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libnumdb/check_nanp.c	Wed Dec 13 00:53:04 2023 +0000
@@ -0,0 +1,47 @@
+/*
+ * The library function implemented in this module consults ThemWi number db
+ * to see if a given NANP number is owned by us or not.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <themwi/nanp/number_db_v2.h>
+#include <themwi/nanp/number_lookup.h>
+#include <themwi/nanp/number_utils.h>
+
+extern struct numdb_file_hdr numdb_hdr;
+extern struct owned_number_rec *numdb_owned_numbers;
+
+static int compare_owned_num(const void *p1v, const void *p2v)
+{
+	const uint16_t *p1 = p1v, *p2 = p2v;
+
+	if (p1[0] < p2[0])
+		return(-1);
+	if (p1[0] > p2[0])
+		return(1);
+	if (p1[1] < p2[1])
+		return(-1);
+	if (p1[1] > p2[1])
+		return(1);
+	if (p1[2] < p2[2])
+		return(-1);
+	if (p1[2] > p2[2])
+		return(1);
+	return(0);
+}
+
+const struct owned_number_rec *numdb_lookup_nanp(const char *numstr)
+{
+	uint16_t key[3];
+
+	if (!numdb_owned_numbers || !numdb_hdr.owned_number_count)
+		return(0);
+	key[0] = digits3_to_uint16(numstr);
+	key[1] = digits3_to_uint16(numstr + 3);
+	key[2] = digits4_to_uint16(numstr + 6);
+	return bsearch(key, numdb_owned_numbers, numdb_hdr.owned_number_count,
+			sizeof(struct owned_number_rec), compare_owned_num);
+}