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         @ivar mirror: an alternative URL to try if this download fails
  57         @type mirror: str | None
  58         """
  59         __slots__ = ['url', 'tempfile', 'status', 'expected_size', 'downloaded',
  60                      'hint', '_final_total_size', 'aborted_by_user', 'mirror',
  61                      'modification_time', 'unmodified', '_aborted']
  62
  63         def __init__(self, url, hint = None, modification_time = None, expected_size = None, auto_delete = True):
  64                 """Create a new download object.
  65                 @param url: the resource to download
  66                 @param hint: object with which this download is associated (an optional hint for the GUI)
  67                 @param modification_time: string with HTTP date that indicates last modification time.
  68                   The resource will not be downloaded if it was not modified since that date.
  69                 @postcondition: L{status} == L{download_fetching}."""
  70                 self.url = url
  71                 self.hint = hint
  72                 self.aborted_by_user = False            # replace with _aborted?
  73                 self.modification_time = modification_time
  74                 self.unmodified = False
  75
  76                 self.tempfile = None            # Stream for result
  77                 self.downloaded = None
  78                 self.mirror = None
  79
  80                 self.expected_size = expected_size      # Final size (excluding skipped bytes)
  81                 self._final_total_size = None   # Set when download is finished
  82
  83                 self.status = download_fetching
  84                 if auto_delete:
  85                         self.tempfile = tempfile.TemporaryFile(prefix = 'injector-dl-data-', mode = 'w+b')
  86                 else:
  87                         self.tempfile = tempfile.NamedTemporaryFile(prefix = 'injector-dl-data-', mode = 'w+b', delete = False)
  88
  89                 self._aborted = tasks.Blocker("abort " + url)
  90
  91         def _finish(self, status):
  92                 assert self.status is download_fetching
  93                 assert self.tempfile is not None
  94                 assert not self.aborted_by_user
  95
  96                 if status == RESULT_NOT_MODIFIED:
  97                         debug("%s not modified", self.url)
  98                         self.tempfile = None
  99                         self.unmodified = True
 100                         self.status = download_complete
 101                         self._final_total_size = 0
 102                         return
 103
 104                 self._final_total_size = self.get_bytes_downloaded_so_far()
 105
 106                 self.tempfile = None
 107
 108                 try:
 109                         assert status == RESULT_OK
 110
 111                         # Check that the download has the correct size, if we know what it should be.
 112                         if self.expected_size is not None:
 113                                 if self._final_total_size != self.expected_size:
 114                                         raise SafeException(_('Downloaded archive has incorrect size.\n'
 115                                                         'URL: %(url)s\n'
 116                                                         'Expected: %(expected_size)d bytes\n'
 117                                                         'Received: %(size)d bytes') % {'url': self.url, 'expected_size': self.expected_size, 'size': self._final_total_size})
 118                 except:
 119                         self.status = download_failed
 120                         raise
 121                 else:
 122                         self.status = download_complete
 123
 124         def abort(self):
 125                 """Signal the current download to stop.
 126                 @postcondition: L{aborted_by_user}"""
 127                 self.status = download_failed
 128
 129                 if self.tempfile is not None:
 130                         info(_("Aborting download of %s"), self.url)
 131                         # TODO: we currently just close the output file; the thread will end when it tries to
 132                         # write to it. We should try harder to stop the thread immediately (e.g. by closing its
 133                         # socket when known), although we can never cover all cases (e.g. a stuck DNS lookup).
 134                         # In any case, we don't wait for the child to exit before notifying tasks that are waiting
 135                         # on us.
 136                         self.aborted_by_user = True
 137                         self.tempfile.close()
 138                         if hasattr(self.tempfile, 'delete') and not self.tempfile.delete:
 139                                 os.remove(self.tempfile.name)
 140                         self.tempfile = None
 141                         self._aborted.trigger()
 142
 143         def get_current_fraction(self):
 144                 """Returns the current fraction of this download that has been fetched (from 0 to 1),
 145                 or None if the total size isn't known.
 146                 @return: fraction downloaded
 147                 @rtype: int | None"""
 148                 if self.tempfile is None:
 149                         return 1
 150                 if self.expected_size is None:
 151                         return None             # Unknown
 152                 current_size = self.get_bytes_downloaded_so_far()
 153                 return float(current_size) / self.expected_size
 154
 155         def get_bytes_downloaded_so_far(self):
 156                 """Get the download progress. Will be zero if the download has not yet started.
 157                 @rtype: int"""
 158                 if self.status is download_fetching:
 159                         return os.fstat(self.tempfile.fileno()).st_size
 160                 else:
 161                         return self._final_total_size or 0
 162
 163         def get_next_mirror_url(self):
 164                 """Return an alternative download URL to try, or None if we're out of options."""
 165                 mirror = self.mirror
 166                 self.mirror = None
 167                 return mirror
 168
 169         def __str__(self):
 170                 return _("<Download from %s>") % self.url