diff --git a/include/common/buf.h b/include/common/buf.h
index 294deb7..6d1a8c0 100644
--- a/include/common/buf.h
+++ b/include/common/buf.h
@@ -311,6 +311,17 @@
 	b->o += count;
 }
 
+/* b_set_data() : sets the buffer's length */
+static inline void b_set_data(struct buffer *b, size_t len)
+{
+	if (len >= b->o)
+		b->i = len - b->o;
+	else {
+		b->o = len;
+		b->i = 0;
+	}
+}
+
 
 #endif /* _COMMON_BUF_H */