From 23ea2ecc2a43d850bc9482068201ece5da36a448 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Tue, 6 Aug 2013 15:44:49 +0800
Subject: [PATCH] qemu-iotests: add poke_file utility function

The new poke_file function sets bytes at an offset in a file given a
printf-style format string.  It can be used to corrupt an image file for
test coverage of error paths.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 tests/qemu-iotests/common.rc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index e9ba3586b5..5e077c3573 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -34,6 +34,12 @@ dd()
    fi
 }
 
+# poke_file 'test.img' 512 '\xff\xfe'
+poke_file()
+{
+    printf "$3" | dd "of=$1" bs=1 "seek=$2" conv=notrunc &>/dev/null
+}
+
 # we need common.config
 if [ "$iam" != "check" ]
 then