From 678a89d5722fe9eb1f36aa6733c0f50076841615 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sebastien@milkymist.org>
Date: Thu, 8 Mar 2012 15:34:08 +0100
Subject: [PATCH] sim: fix zero encoding

---
 migen/sim/ipc.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/migen/sim/ipc.py b/migen/sim/ipc.py
index 5d9f9eb68..f463dcfff 100644
--- a/migen/sim/ipc.py
+++ b/migen/sim/ipc.py
@@ -51,11 +51,14 @@ message_classes = [MessageTick, MessageGo, MessageWrite, MessageRead, MessageRea
 #
 
 def _pack_int(v):
-	p = []
-	while v != 0:
-		p.append(v & 0xff)
-		v >>= 8
-	p.insert(0, len(p))
+	if v == 0:
+		p = [1, 0]
+	else:
+		p = []
+		while v != 0:
+			p.append(v & 0xff)
+			v >>= 8
+		p.insert(0, len(p))
 	return p
 
 def _pack_str(v):