download.py file for nacl_sdk

download.py

# Copyright (c) 2012 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
import sys
# when pylint runs the third_party module is the one from depot_tools
# pylint: disable=E0611
from third_party import fancy_urllib
import urllib2


SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))


def UrlOpen(url):
  return urllib2.urlopen(url) 


def MakeProgressFunction(file_size):
  # An inner function can only read nonlocal variables, not assign them. We can
  # work around this by using a list of one element.
  dots = [0]
  def ShowKnownProgress(progress):
    '''Returns a progress function based on a known file size'''
    if progress == 0:
      sys.stdout.write('|%s|\n' % ('=' * 48))
    elif progress == -1:
      sys.stdout.write('\n')
    else:
      new_dots = progress * 50 / file_size - dots[0]
      sys.stdout.write('.' * new_dots)
      dots[0] += new_dots
    sys.stdout.flush()

  return ShowKnownProgress


def DownloadAndComputeHash(from_stream, to_stream=None, progress_func=None):
  '''Read from from-stream and generate sha1 and size info.

  Args:
    from_stream:   An input stream that supports read.
    to_stream:     [optional] the data is written to to_stream if it is
                   provided.
    progress_func: [optional] A function used to report download progress. If
                   provided, progress_func is called with progress=0 at the
                   beginning of the download, periodically with progress>0
                   (== number of bytes read do far) during the download, and
                   progress=-1 at the end or if the download was aborted.

  Return
    A tuple (sha1, size) where sha1 is a sha1-hash for the archive data and
    size is the size of the archive data in bytes.'''
  # Use a no-op progress function if none is specified.
  def progress_no_op(progress):
    pass
  if not progress_func:
    progress_func = progress_no_op

  sha1_hash = hashlib.sha1()
  size = 0
  try:
    progress_func(progress=0)
    while True:
      data = from_stream.read(32768)
      if not data:
        break
      sha1_hash.update(data)
      size += len(data)
      if to_stream:
        to_stream.write(data)
      progress_func(size)
  finally:
    progress_func(progress=-1)
  return sha1_hash.hexdigest(), size