bitvec: Add bitvec_bytes_used() function

This new bitvec API function returns the number of bytes used in a given
bit-vector.

Change-Id: Id4bd7f7543f5b0f4f6f876e283bd065039c37646
diff --git a/include/osmocom/core/bitvec.h b/include/osmocom/core/bitvec.h
index c9bab39..da2d4e4 100644
--- a/include/osmocom/core/bitvec.h
+++ b/include/osmocom/core/bitvec.h
@@ -84,4 +84,13 @@
 			      unsigned int array_len, bool dry_run,
 			      unsigned int num_bits);
 
+/*! Return the number of bytes used within the bit vector */
+static inline unsigned int bitvec_used_bytes(const struct bitvec *bv)
+{
+	unsigned int bytes = bv->cur_bit/8;
+	if (bv->cur_bit%8)
+		bytes++;
+	return bytes;
+}
+
 /*! @} */