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, sys, threading
  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
  20 download_fetching = "fetching"  # In progress
  21 download_complete = "complete"  # Downloaded and cached OK
  22 download_failed = "failed"
  23
  24 # NB: duplicated in _download_child.py
  25 RESULT_OK = 0
  26 RESULT_FAILED = 1
  27 RESULT_NOT_MODIFIED = 2
  28
  29 import gobject; gobject.threads_init()
  30
  31 class DownloadError(SafeException):
  32         """Download process failed."""
  33         pass
  34
  35 class DownloadAborted(DownloadError):
  36         """Download aborted because of a call to L{Download.abort}"""
  37         def __init__(self, message = None):
  38                 SafeException.__init__(self, message or _("Download aborted at user's request"))
  39
  40 class Download(object):
  41         """A download of a single resource to a temporary file.
  42         @ivar url: the URL of the resource being fetched
  43         @type url: str
  44         @ivar tempfile: the file storing the downloaded data
  45         @type tempfile: file
  46         @ivar status: the status of the download
  47         @type status: (download_starting | download_fetching | download_failed | download_complete)
  48         @ivar expected_size: the expected final size of the file
  49         @type expected_size: int | None
  50         @ivar downloaded: triggered when the download ends (on success or failure)
  51         @type downloaded: L{tasks.Blocker}
  52         @ivar hint: hint passed by and for caller
  53         @type hint: object
  54         @ivar aborted_by_user: whether anyone has called L{abort}
  55         @type aborted_by_user: bool
  56         @ivar unmodified: whether the resource was not modified since the modification_time given at construction
  57         @type unmodified: bool
  58         """
  59         __slots__ = ['url', 'tempfile', 'status', 'expected_size', 'downloaded',
  60                      'hint', '_final_total_size', 'aborted_by_user',
  61                      'modification_time', 'unmodified']
  62
  63         def __init__(self, url, hint = None, modification_time = None):
  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_starting}."""
  70                 self.url = url
  71                 self.status = download_starting
  72                 self.hint = hint
  73                 self.aborted_by_user = False
  74                 self.modification_time = modification_time
  75                 self.unmodified = False
  76
  77                 self.tempfile = None            # Stream for result
  78                 self.downloaded = None
  79
  80                 self.expected_size = None       # Final size (excluding skipped bytes)
  81                 self._final_total_size = None   # Set when download is finished
  82
  83         def start(self):
  84                 """Create a temporary file and begin the download.
  85                 @precondition: L{status} == L{download_starting}"""
  86                 assert self.status == download_starting
  87                 assert self.downloaded is None
  88
  89                 self.status = download_fetching
  90                 self.tempfile = tempfile.TemporaryFile(prefix = 'injector-dl-data-')
  91
  92                 task = tasks.Task(self._do_download(), "download " + self.url)
  93                 self.downloaded = task.finished
  94
  95         def _do_download(self):
  96                 """Will trigger L{downloaded} when done (on success or failure)."""
  97                 from ._download_child import download_in_thread
  98
  99                 result = []
 100                 thread_blocker = tasks.Blocker("wait for thread " + self.url)
 101                 def notify_done(status, ex = None):
 102                         result.append(status)
 103                         def wake_up_main():
 104                                 thread_blocker.trigger(ex)
 105                                 return False
 106                         gobject.idle_add(wake_up_main)
 107                 child = threading.Thread(target = lambda: download_in_thread(self.url, self.tempfile, self.modification_time, notify_done))
 108                 child.daemon = True
 109                 child.start()
 110
 111                 # Wait for child to complete download.
 112                 yield thread_blocker
 113
 114                 # Download is complete...
 115                 child.join()
 116
 117                 assert self.status is download_fetching
 118                 assert self.tempfile is not None
 119
 120                 status, = result
 121
 122                 if status == RESULT_NOT_MODIFIED:
 123                         debug("%s not modified", self.url)
 124                         self.tempfile = None
 125                         self.unmodified = True
 126                         self.status = download_complete
 127                         self._final_total_size = 0
 128                         self.downloaded.trigger()
 129                         return
 130
 131                 self._final_total_size = self.get_bytes_downloaded_so_far()
 132
 133                 self.tempfile = None
 134
 135                 if self.aborted_by_user:
 136                         assert self.downloaded.happened
 137                         raise DownloadAborted()
 138
 139                 try:
 140
 141                         tasks.check(thread_blocker)
 142
 143                         assert status == RESULT_OK
 144
 145                         # Check that the download has the correct size, if we know what it should be.
 146                         if self.expected_size is not None:
 147                                 if self._final_total_size != self.expected_size:
 148                                         raise SafeException(_('Downloaded archive has incorrect size.\n'
 149                                                         'URL: %(url)s\n'
 150                                                         'Expected: %(expected_size)d bytes\n'
 151                                                         'Received: %(size)d bytes') % {'url': self.url, 'expected_size': self.expected_size, 'size': self._final_total_size})
 152                 except:
 153                         self.status = download_failed
 154                         _unused, ex, tb = sys.exc_info()
 155                         self.downloaded.trigger(exception = (ex, tb))
 156                 else:
 157                         self.status = download_complete
 158                         self.downloaded.trigger()
 159
 160         def abort(self):
 161                 """Signal the current download to stop.
 162                 @postcondition: L{aborted_by_user}"""
 163                 self.status = download_failed
 164
 165                 if self.tempfile is not None:
 166                         info(_("Aborting download of %s"), self.url)
 167                         # TODO: we currently just close the output file; the thread will end when it tries to
 168                         # write to it. We should try harder to stop the thread immediately (e.g. by closing its
 169                         # socket when known), although we can never cover all cases (e.g. a stuck DNS lookup).
 170                         # In any case, we don't wait for the child to exit before notifying tasks that are waiting
 171                         # on us.
 172                         self.aborted_by_user = True
 173                         self.tempfile.close()
 174                         self.tempfile = None
 175                         self.downloaded.trigger((DownloadAborted(), None))
 176
 177         def get_current_fraction(self):
 178                 """Returns the current fraction of this download that has been fetched (from 0 to 1),
 179                 or None if the total size isn't known.
 180                 @return: fraction downloaded
 181                 @rtype: int | None"""
 182                 if self.status is download_starting:
 183                         return 0
 184                 if self.tempfile is None:
 185                         return 1
 186                 if self.expected_size is None:
 187                         return None             # Unknown
 188                 current_size = self.get_bytes_downloaded_so_far()
 189                 return float(current_size) / self.expected_size
 190
 191         def get_bytes_downloaded_so_far(self):
 192                 """Get the download progress. Will be zero if the download has not yet started.
 193                 @rtype: int"""
 194                 if self.status is download_starting:
 195                         return 0
 196                 elif self.status is download_fetching:
 197                         return os.fstat(self.tempfile.fileno()).st_size
 198                 else:
 199                         return self._final_total_size or 0
 200
 201         def __str__(self):
 202                 return _("<Download from %s>") % self.url