Add input content checking to some build scripts

build/android/gyp/jar.py

 #!/usr/bin/env python
 #
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import fnmatch
 import optparse
 import os
 import sys
 
+from util import md5_check
+
+BUILD_ANDROID_DIR = os.path.join(os.path.dirname(__file__), '..')
+sys.path.append(BUILD_ANDROID_DIR)
+
 from pylib import build_utils
 
 
 def DoJar(options):
   class_files = build_utils.FindInDirectory(options.classes_dir, '*.class')
   for exclude in build_utils.ParseGypList(options.excluded_classes):
     class_files = filter(
         lambda f: not fnmatch.fnmatch(f, exclude), class_files)
 
   jar_path = os.path.abspath(options.jar_path)
 
   # The paths of the files in the jar will be the same as they are passed in to
   # the command. Because of this, the command should be run in
   # options.classes_dir so the .class file paths in the jar are correct.
   jar_cwd = options.classes_dir
-  class_files = [os.path.relpath(f, jar_cwd) for f in class_files]
-  jar_cmd = ['jar', 'cf0', jar_path] + class_files
-  build_utils.CheckCallDie(jar_cmd, cwd=jar_cwd)
+  class_files_rel = [os.path.relpath(f, jar_cwd) for f in class_files]
+  jar_cmd = ['jar', 'cf0', jar_path] + class_files_rel
+
+
+  md5_stamp = '%s.md5' % options.jar_path
+  md5_checker = md5_check.Md5Checker(
+      stamp=md5_stamp, inputs=class_files, command=jar_cmd)
+  if md5_checker.IsStale():
+    build_utils.CheckCallDie(jar_cmd, cwd=jar_cwd)
+  else:
+    build_utils.Touch(options.jar_path)
+  md5_checker.Write()
 
 
 def main(argv):
   parser = optparse.OptionParser()
   parser.add_option('--classes-dir', help='Directory containing .class files.')
   parser.add_option('--jar-path', help='Jar output path.')
   parser.add_option('--excluded-classes',
       help='List of .class file patterns to exclude from the jar.')
   parser.add_option('--stamp', help='Path to touch on success.')
 
   # TODO(newt): remove this once http://crbug.com/177552 is fixed in ninja.
   parser.add_option('--ignore', help='Ignored.')
 
   options, _ = parser.parse_args()
 
   DoJar(options)
 
   if options.stamp:
     build_utils.Touch(options.stamp)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))