diff --git a/tools/applypatch/imgdiff.h b/tools/applypatch/imgdiff.h
new file mode 100644
index 0000000..7ec45c5
--- /dev/null
+++ b/tools/applypatch/imgdiff.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Image patch chunk types
+#define CHUNK_NORMAL 0
+#define CHUNK_GZIP   1
+
+// The gzip header size is actually variable, but we currently don't
+// support gzipped data with any of the optional fields, so for now it
+// will always be ten bytes.  See RFC 1952 for the definition of the
+// gzip format.
+#define GZIP_HEADER_LEN   10
+
+// The gzip footer size really is fixed.
+#define GZIP_FOOTER_LEN   8