Make mojob.py test succeed on Windows.

mojo/tools/mopy/transitive_hash.py

 # Copyright 2014 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 logging
+import platform
 import subprocess
 import sys
 
 # pylint: disable=E0611
 from hashlib import sha256
 # pylint: enable=E0611
 from os.path import basename, realpath
 
 _logging = logging.getLogger()
 
 # pylint: disable=C0301
 # Based on/taken from
 #   http://code.activestate.com/recipes/578231-probably-the-fastest-memoization-decorator-in-the-/
 # (with cosmetic changes).
 # pylint: enable=C0301
 def _memoize(f):
   """Memoization decorator for a function taking a single argument."""
   class Memoize(dict):
     def __missing__(self, key):
       rv = self[key] = f(key)
       return rv
   return Memoize().__getitem__
 
 @_memoize
 def _file_hash(filename):
   """Returns a string representing the hash of the given file."""
   _logging.debug("Hashing %s ...", filename)
-  rv = subprocess.check_output(['sha256sum', '-b', filename]).split(None, 1)[0]
-  _logging.debug("  => %s", rv)
-  return rv
+  with open(filename, mode='rb') as f:

[viettrungluu, 2014/11/11 18:35:38]

What's the performance of this versus running sha256sum?

[jam, 2014/11/11 20:09:32]

it's about 10% faster. probably because it doesn't have to launch an external
program.

+    m = hashlib.sha256()
+    while True:
+      block = f.read(4096)
+      if not block:
+        break
+  _logging.debug("  => %s", m.hexdigest())
+  return m.hexdigest()
 
 @_memoize
 def _get_dependencies(filename):
   """Returns a list of filenames for files that the given file depends on."""
+  if platform.system() == 'Windows':
+    # There's no ldd on Windows. We can try to bundle or require depends, but
+    # given that we're not supporting component build this seems low priority.
+    return []
   _logging.debug("Getting dependencies for %s ...", filename)
   lines = subprocess.check_output(['ldd', filename]).splitlines()
   rv = []
   for line in lines:
     i = line.find('/')
     if i < 0:
       _logging.debug("  => no file found in line: %s", line)
       continue
     rv.append(line[i:].split(None, 1)[0])
   _logging.debug("  => %s", rv)
@@ skipping 34 matching lines @@
   for filename in argv[1:]:
     try:
       print transitive_hash(filename), filename
     except subprocess.CalledProcessError:
       print "ERROR", filename
       rv = 1
   return rv
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))