diff --git a/codelength.h b/codelength.h
new file mode 100644
index 0000000..dcb6868
--- /dev/null
+++ b/codelength.h
@@ -0,0 +1,24 @@
+/* $Id$ */
+/* Project : miniupnp
+ * Author : Thomas BERNARD
+ * copyright (c) 2005-2008 Thomas Bernard
+ * This software is subjet to the conditions detailed in the
+ * provided LICENCE file. */
+#ifndef __CODELENGTH_H__
+#define __CODELENGTH_H__
+
+/* Encode length by using 7bit per Byte :
+ * Most significant bit of each byte specifies that the
+ * following byte is part of the code */
+#define DECODELENGTH(n, p) n = 0; \
+                           do { n = (n << 7) | (*p & 0x7f); } \
+                           while(*(p++)&0x80);
+
+#define CODELENGTH(n, p) if(n>=268435456) *(p++) = (n >> 28) | 0x80; \
+                         if(n>=2097152) *(p++) = (n >> 21) | 0x80; \
+                         if(n>=16384) *(p++) = (n >> 14) | 0x80; \
+                         if(n>=128) *(p++) = (n >> 7) | 0x80; \
+                         *(p++) = n & 0x7f;
+
+#endif
+