Add input content checking to some build scripts

build/android/gyp/util/md5_check.py

Index: build/android/gyp/util/md5_check.py
diff --git a/build/android/gyp/util/md5_check.py b/build/android/gyp/util/md5_check.py
new file mode 100644
index 0000000000000000000000000000000000000000..47f1ec941544d97c8ec5500013537a0a3ac05691
--- /dev/null
+++ b/build/android/gyp/util/md5_check.py
@@ -0,0 +1,52 @@
+# 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 hashlib
+import os
+
+
+def UpdateMd5ForFile(md5, path, block_size=2**16):
+  with open(path, 'rb') as infile:
+    while True:
+      data = infile.read(block_size)
+      if not data:
+        break
+      md5.update(data)
+
+
+def UpdateMd5ForDirectory(md5, dir_path):
+  for root, _, files in os.walk(dir_path):
+    for f in files:
+      UpdateMd5ForFile(md5, os.path.join(root, f))
+
+
+def UpdateMd5ForPath(md5, path):
+  if os.path.isdir(path):
+    UpdateMd5ForDirectory(md5, path)
+  else:
+    UpdateMd5ForFile(md5, path)
+
+
+class Md5Checker(object):
+  def __init__(self, stamp=None, inputs=[], command=[]):
+    self.stamp = stamp
+
+    md5 = hashlib.md5()
+    for i in inputs:
+      UpdateMd5ForPath(md5, i)
+    for s in command:
+      md5.update(s)
+    self.new_digest = md5.hexdigest()
+
+    self.old_digest = ''
+    if os.path.exists(stamp):
+      with open(stamp, 'r') as old_stamp:
+        self.old_digest = old_stamp.read()
+
+  def IsStale(self):
+    return self.old_digest != self.new_digest
+
+  def Write(self):
+    with open(self.stamp, 'w') as new_stamp:
+      new_stamp.write(self.new_digest)