#!/usr/bin/python2.4
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"""Download a file from a URL to a file on disk.

This module supports username and password with basic authentication.
"""

import base64
import os
import urllib2


def _CreateDirectory(path):
  """Create a directory tree, ignore if it's already there."""
  try:
    os.makedirs(path)
    return True
  except os.error:
    return False


def HttpDownload(url, target, username=None, password=None):
  """Download a file from a remote server.

  Args:
    url: A URL to download from.
    target: Filename to write download to.
    username: Optional username for download.
    password: Optional password for download (ignored if no username).
  """

  headers = [('Accept', '*/*')]
  if username:
    if password:
      auth_code = base64.b64encode(username + ':' + password)
    else:
      auth_code = base64.b64encode(username)
    headers.append(('Authorization', 'Basic ' + auth_code))
  opener = urllib2.build_opener()
  opener.addheaders = headers
  urllib2.install_opener(opener)
  src = urllib2.urlopen(url)
  data = src.read()
  src.close()

  _CreateDirectory(os.path.split(target)[0])
  fh = open(target, 'wb')
  fh.write(data)
  fh.close()