zeroinstall/injector/download.py

   1 """
   2 Handles URL downloads.
   3
   4 This is the low-level interface for downloading interfaces, implementations, icons, etc.
   5
   6 @see: L{fetch} higher-level API for downloads that uses this module
   7 """
   8
   9 # Copyright (C) 2009, Thomas Leonard
  10 # See the README file for details, or visit http://0install.net.
  11
  12 import tempfile, os
  13
  14 from zeroinstall import SafeException
  15 from zeroinstall.support import tasks
  16 from logging import info, debug
  17 from zeroinstall import _
  18
  19 download_starting = "starting"  # Waiting for UI to start it (no longer used)
  20 download_fetching = "fetching"  # In progress
  21 download_complete = "complete"  # Downloaded and cached OK
  22 download_failed = "failed"
  23
  24 RESULT_OK = 0
  25 RESULT_FAILED = 1
  26 RESULT_NOT_MODIFIED = 2
  27 RESULT_REDIRECT = 3
  28
  29 class DownloadError(SafeException):
  30         """Download process failed."""
  31         pass
  32
  33 class DownloadAborted(DownloadError):
  34         """Download aborted because of a call to L{Download.abort}"""
  35         def __init__(self, message = None):
  36                 SafeException.__init__(self, message or _("Download aborted at user's request"))
  37
  38 class Download(object):
  39         """A download of a single resource to a temporary file.
  40         @ivar url: the URL of the resource being fetched
  41         @type url: str
  42         @ivar tempfile: the file storing the downloaded data
  43         @type tempfile: file
  44         @ivar status: the status of the download
  45         @type status: (download_fetching | download_failed | download_complete)
  46         @ivar expected_size: the expected final size of the file
  47         @type expected_size: int | None
  48         @ivar downloaded: triggered when the download ends (on success or failure)
  49         @type downloaded: L{tasks.Blocker}
  50         @ivar hint: hint passed by and for caller
  51         @type hint: object
  52         @ivar aborted_by_user: whether anyone has called L{abort}
  53         @type aborted_by_user: bool
  54         @ivar unmodified: whether the resource was not modified since the modification_time given at construction
  55         @type unmodified: bool
  56         """
  57         __slots__ = ['url', 'tempfile', 'status', 'expected_size', 'downloaded',
  58                      'hint', '_final_total_size', 'aborted_by_user',
  59                      'modification_time', 'unmodified', '_aborted']
  60
  61         def __init__(self, url, hint = None, modification_time = None, expected_size = None):
  62                 """Create a new download object.
  63                 @param url: the resource to download
  64                 @param hint: object with which this download is associated (an optional hint for the GUI)
  65                 @param modification_time: string with HTTP date that indicates last modification time.
  66                   The resource will not be downloaded if it was not modified since that date.
  67                 @postcondition: L{status} == L{download_fetching}."""
  68                 self.url = url
  69                 self.hint = hint
  70                 self.aborted_by_user = False            # replace with _aborted?
  71                 self.modification_time = modification_time
  72                 self.unmodified = False
  73
  74                 self.tempfile = None            # Stream for result
  75                 self.downloaded = None
  76
  77                 self.expected_size = expected_size      # Final size (excluding skipped bytes)
  78                 self._final_total_size = None   # Set when download is finished
  79
  80                 self.status = download_fetching
  81                 self.tempfile = tempfile.TemporaryFile(prefix = 'injector-dl-data-')
  82
  83                 self._aborted = tasks.Blocker("abort " + url)
  84
  85         def _finish(self, status):
  86                 assert self.status is download_fetching
  87                 assert self.tempfile is not None
  88                 assert not self.aborted_by_user
  89
  90                 if status == RESULT_NOT_MODIFIED:
  91                         debug("%s not modified", self.url)
  92                         self.tempfile = None
  93                         self.unmodified = True
  94                         self.status = download_complete
  95                         self._final_total_size = 0
  96                         return
  97
  98                 self._final_total_size = self.get_bytes_downloaded_so_far()
  99
 100                 self.tempfile = None
 101
 102                 try:
 103                         assert status == RESULT_OK
 104
 105                         # Check that the download has the correct size, if we know what it should be.
 106                         if self.expected_size is not None:
 107                                 if self._final_total_size != self.expected_size:
 108                                         raise SafeException(_('Downloaded archive has incorrect size.\n'
 109                                                         'URL: %(url)s\n'
 110                                                         'Expected: %(expected_size)d bytes\n'
 111                                                         'Received: %(size)d bytes') % {'url': self.url, 'expected_size': self.expected_size, 'size': self._final_total_size})
 112                 except:
 113                         self.status = download_failed
 114                         raise
 115                 else:
 116                         self.status = download_complete
 117
 118         def abort(self):
 119                 """Signal the current download to stop.
 120                 @postcondition: L{aborted_by_user}"""
 121                 self.status = download_failed
 122
 123                 if self.tempfile is not None:
 124                         info(_("Aborting download of %s"), self.url)
 125                         # TODO: we currently just close the output file; the thread will end when it tries to
 126                         # write to it. We should try harder to stop the thread immediately (e.g. by closing its
 127                         # socket when known), although we can never cover all cases (e.g. a stuck DNS lookup).
 128                         # In any case, we don't wait for the child to exit before notifying tasks that are waiting
 129                         # on us.
 130                         self.aborted_by_user = True
 131                         self.tempfile.close()
 132                         self.tempfile = None
 133                         self._aborted.trigger()
 134
 135         def get_current_fraction(self):
 136                 """Returns the current fraction of this download that has been fetched (from 0 to 1),
 137                 or None if the total size isn't known.
 138                 @return: fraction downloaded
 139                 @rtype: int | None"""
 140                 if self.tempfile is None:
 141                         return 1
 142                 if self.expected_size is None:
 143                         return None             # Unknown
 144                 current_size = self.get_bytes_downloaded_so_far()
 145                 return float(current_size) / self.expected_size
 146
 147         def get_bytes_downloaded_so_far(self):
 148                 """Get the download progress. Will be zero if the download has not yet started.
 149                 @rtype: int"""
 150                 if self.status is download_fetching:
 151                         return os.fstat(self.tempfile.fileno()).st_size
 152                 else:
 153                         return self._final_total_size or 0
 154
 155         def __str__(self):
 156                 return _("<Download from %s>") % self.url