diff --git a/buck-tools/util.py b/buck-tools/util.py
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--- /dev/null
+++ b/buck-tools/util.py
@@ -0,0 +1,102 @@
+# Copyright (C) 2013 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.
+
+import os
+from os import path
+
+REPO_ROOTS = {
+  'GERRIT': 'http://gerrit-maven.storage.googleapis.com',
+  'GERRIT_API': 'https://gerrit-api.commondatastorage.googleapis.com/release',
+  'MAVEN_CENTRAL': 'http://repo1.maven.org/maven2',
+  'MAVEN_LOCAL': 'file://' + path.expanduser('~/.m2/repository'),
+}
+
+
+def resolve_url(url, redirects):
+  """ Resolve URL of a Maven artifact.
+
+  prefix:path is passed as URL. prefix identifies known or custom
+  repositories that can be rewritten in redirects set, passed as
+  second arguments.
+
+  A special case is supported, when prefix neither exists in
+  REPO_ROOTS, no in redirects set: the url is returned as is.
+  This enables plugins to pass custom maven_repository URL as is
+  directly to maven_jar().
+
+  Returns a resolved path for Maven artifact.
+  """
+  s = url.find(':')
+  if s < 0:
+    return url
+  scheme, rest = url[:s], url[s+1:]
+  if scheme in redirects:
+    root = redirects[scheme]
+  elif scheme in REPO_ROOTS:
+    root = REPO_ROOTS[scheme]
+  else:
+    return url
+  root = root.rstrip('/')
+  rest = rest.lstrip('/')
+  return '/'.join([root, rest])
+
+
+def hash_file(hash_obj, path):
+  """Hash the contents of a file.
+
+  Args:
+    hash_obj: an open hash object, e.g. hashlib.sha1().
+    path: path to the file to hash.
+
+  Returns:
+    The passed-in hash_obj.
+  """
+  with open(path, 'rb') as f:
+    while True:
+      b = f.read(8192)
+      if not b:
+        break
+      hash_obj.update(b)
+  return hash_obj
+
+
+def hash_bower_component(hash_obj, path):
+  """Hash the contents of a bower component directory.
+
+  This is a stable hash of a directory downloaded with `bower install`, minus
+  the .bower.json file, which is autogenerated each time by bower. Used in lieu
+  of hashing a zipfile of the contents, since zipfiles are difficult to hash in
+  a stable manner.
+
+  Args:
+    hash_obj: an open hash object, e.g. hashlib.sha1().
+    path: path to the directory to hash.
+
+  Returns:
+    The passed-in hash_obj.
+  """
+  if not os.path.isdir(path):
+    raise ValueError('Not a directory: %s' % path)
+
+  path = os.path.abspath(path)
+  for root, dirs, files in os.walk(path):
+    dirs.sort()
+    for f in sorted(files):
+      if f == '.bower.json':
+        continue
+      p = os.path.join(root, f)
+      hash_obj.update(p[len(path)+1:])
+      hash_file(hash_obj, p)
+
+  return hash_obj