network: Add function that counts the bit length of an addres

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/libloc/private.h

@@ -94,6 +94,20 @@ static inline struct in6_addr loc_prefix_to_bitmask(const unsigned int prefix) {
 	return bitmask;
 }
 
+static inline unsigned int loc_address_bit_length(const struct in6_addr* address) {
+	unsigned int length = 128;
+
+	for (int octet = 0; octet <= 15; octet++) {
+		if (address->s6_addr[octet]) {
+			length -= __builtin_clz(address->s6_addr[octet]) - 24;
+			break;
+		} else
+			length -= 8;
+	}
+
+	return length;
+}
+
 static inline struct in6_addr loc_address_and(
 		const struct in6_addr* address, const struct in6_addr* bitmask) {
 	struct in6_addr a;

src/test-network.c

@@ -25,6 +25,7 @@
 #include <libloc/libloc.h>
 #include <libloc/database.h>
 #include <libloc/network.h>
+#include <libloc/private.h>
 #include <libloc/writer.h>
 
 int main(int argc, char** argv) {
@@ -311,6 +312,36 @@ int main(int argc, char** argv) {
 	}
 	loc_network_unref(network1);
 
+	const struct bit_length_test {
+		const char* network;
+		unsigned int bit_length;
+	} bit_length_tests[] = {
+		{ "::/0", 0 },
+		{ "2001::/128", 126 },
+		{ NULL, 0, },
+	};
+
+	for (const struct bit_length_test* t = bit_length_tests; t->network; t++) {
+		err = loc_network_new_from_string(ctx, &network1, t->network);
+		if (err) {
+			fprintf(stderr, "Could not create network %s: %m\n", t->network);
+			exit(EXIT_FAILURE);
+		}
+
+		const struct in6_addr* addr = loc_network_get_first_address(network1);
+
+		unsigned int bit_length = loc_address_bit_length(addr);
+
+		if (bit_length != t->bit_length) {
+			printf("Bit length of %s didn't match: %u != %u\n",
+				t->network, t->bit_length, bit_length);
+			loc_network_unref(network1);
+			exit(EXIT_FAILURE);
+		}
+
+		loc_network_unref(network1);
+	}
+
 	loc_unref(ctx);
 	fclose(f);