diff --git a/applypatch/main.c b/applypatch/main.c
new file mode 100644
index 0000000..e08f5c1
--- /dev/null
+++ b/applypatch/main.c
@@ -0,0 +1,60 @@
+/*
+ * 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.
+ */
+
+#include <stdio.h>
+
+extern int applypatch(int argc, char** argv);
+
+// This program applies binary patches to files in a way that is safe
+// (the original file is not touched until we have the desired
+// replacement for it) and idempotent (it's okay to run this program
+// multiple times).
+//
+// - if the sha1 hash of <tgt-file> is <tgt-sha1>, does nothing and exits
+//   successfully.
+//
+// - otherwise, if the sha1 hash of <src-file> is <src-sha1>, applies the
+//   bsdiff <patch> to <src-file> to produce a new file (the type of patch
+//   is automatically detected from the file header).  If that new
+//   file has sha1 hash <tgt-sha1>, moves it to replace <tgt-file>, and
+//   exits successfully.  Note that if <src-file> and <tgt-file> are
+//   not the same, <src-file> is NOT deleted on success.  <tgt-file>
+//   may be the string "-" to mean "the same as src-file".
+//
+// - otherwise, or if any error is encountered, exits with non-zero
+//   status.
+//
+// <src-file> (or <file> in check mode) may refer to an MTD partition
+// to read the source data.  See the comments for the
+// LoadMTDContents() function above for the format of such a filename.
+
+int main(int argc, char** argv) {
+  int result = applypatch(argc, argv);
+  if (result == 2) {
+    printf(
+            "usage: %s <src-file> <tgt-file> <tgt-sha1> <tgt-size> "
+            "[<src-sha1>:<patch> ...]\n"
+            "   or  %s -c <file> [<sha1> ...]\n"
+            "   or  %s -s <bytes>\n"
+            "   or  %s -l\n"
+            "\n"
+            "Filenames may be of the form\n"
+            "  MTD:<partition>:<len_1>:<sha1_1>:<len_2>:<sha1_2>:...\n"
+            "to specify reading from or writing to an MTD partition.\n\n",
+            argv[0], argv[0], argv[0], argv[0]);
+  }
+  return result;
+}