src/lib/ImageCache.py

   1 """ ImageCache.py
   2
   3 Module for handling images
   4 """
   5 __copyright__ = "Copyright (c) 2002-2005 Free Software Foundation, Inc."
   6 __license__ = """
   7 Straw is free software; you can redistribute it and/or modify it under the
   8 terms of the GNU General Public License as published by the Free Software
   9 Foundation; either version 2 of the License, or (at your option) any later
  10 version.
  11
  12 Straw is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  14 A PARTICULAR PURPOSE. See the GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License along with
  17 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  18 Place - Suite 330, Boston, MA 02111-1307, USA. """
  19
  20 import NetworkConstants
  21 import URLFetch
  22 import PollManager
  23 import ItemStore
  24 import utils
  25 import error
  26 import Config
  27 import gobject
  28
  29 STATUS_IMAGE_WAITING = None
  30 STATUS_IMAGE_BROKEN = None
  31
  32 class CacheEntry(object):
  33     def __init__(self, image, count, pollstopper = None, restore = False):
  34         self._image = image
  35         self._count = count
  36         self._pollstopper = pollstopper
  37         if not restore:
  38             self._save_count()
  39
  40     @apply
  41     def image():
  42         doc="The image object that is associated with this class"
  43         def fget(self):
  44             return self._image
  45         def fset(self, image):
  46             self._image = image
  47         return property(**locals())
  48
  49     @apply
  50     def count():
  51         doc="image ref count"
  52         def fget(self):
  53             return self._count
  54         def fset(self, count):
  55             self._count = count
  56             self._save_count()
  57         return property(**locals())
  58
  59     @apply
  60     def pollstopper():
  61         doc="the stopper object for this cache entry"
  62         def fget(self):
  63             return self._pollstopper
  64         def fset(self, pollstopper):
  65             self._pollstopper = pollstopper
  66             if pollstopper:
  67                 pollstopper.connect('stopped', self._polling_stopped)
  68         return property(**locals())
  69
  70     def incr_count(self): self._count += 1
  71     def decr_count(self): self._count -= 1
  72
  73     def _polling_stopped(self, poller):
  74         self._pollstopper = None
  75
  76     def _save_count(self):
  77         ItemStore.get_instance().set_image_count(self._image.url, self._count)
  78
  79
  80 class Cache(gobject.GObject):
  81     """Image cache with explicit reference counting."""
  82
  83     __gsignals__ = {
  84         'image-updated' : (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE,
  85                            (gobject.TYPE_STRING, gobject.TYPE_PYOBJECT))
  86         }
  87
  88     def __init__(self):
  89         gobject.GObject.__init__(self)
  90         # self.__cache contains items of the form [Image, refcount]
  91         self.__cache = dict()
  92
  93     def __getitem__(self, key):
  94         return self.__cache[key].image
  95
  96     def add_refer(self, key, restore = False, item = None):
  97         if key not in self.__cache:
  98             if not restore:
  99                 # fetch image
 100                 image = Image(key, Image.WAITING)
 101                 ic = ImageConsumer(image)
 102                 headers = {}
 103                 stopper = None
 104                 if item and item.feed:
 105                     headers['Referer'] = item.feed.location
 106                 try:
 107                     stopper = URLFetch.get_instance().request(
 108                         key, ic,
 109                         priority=NetworkConstants.PRIORITY_IMAGE,
 110                         headers=headers)
 111                 except URLFetch.RequestSchemeException, e:
 112                     ic.http_failed(e)
 113                 except Exception, e:
 114                     error.logtb("ImageCache.add_refer:  ", str(e))
 115                     ic.http_failed(e)
 116                 self.__cache[key] = CacheEntry(
 117                     image, 1, PollManager.PollStopper(stopper, image), restore=restore)
 118             else:
 119                 image = Image(key, Image.DATA_IN_DB)
 120                 self.__cache[key] = CacheEntry(image, 1, pollstopper=None, restore=restore)
 121         elif key in self.__cache and not restore:
 122             self.__cache[key].incr_count()
 123
 124     def remove_refer(self, key):
 125         if self.__cache.has_key(key):
 126             entry = self.__cache[key]
 127             entry.decr_count()
 128             if entry.count == 0:
 129                 del self.__cache[key]
 130                 self.emit('image-updated', url, None)
 131
 132     def image_updated(self, url, data):
 133         self.__cache[url].pollstopper = None
 134         self.emit('image-updated', url, data)
 135
 136     def set_image(self, url, image):
 137         if self.__cache.has_key(url):
 138             self.__cache[url].incr_count()
 139         else:
 140             self.__cache[url] = CacheEntry(image, 1)
 141
 142     def set_image_with_count(self, url, image, count, restore=False):
 143         self.__cache[url] = CacheEntry(image, count, restore=restore)
 144
 145     def stop_transfer(self, url):
 146         image = self.__cache.get(url, None)
 147         if image and image.pollstopper:
 148             self.__cache[url].pollstopper.stop()
 149             self.__cache[url].pollstopper = None
 150
 151 class Image:
 152     WAITING = 1
 153     DATA_IN_DB = 2
 154     FAILED = 3
 155
 156     def __init__(self, url, status = DATA_IN_DB):
 157         self.url = url
 158         self.status = status
 159
 160     def get_data(self):
 161         if self.status == self.WAITING:
 162             return STATUS_IMAGE_WAITING
 163         elif self.status == self.DATA_IN_DB:
 164             data = self.read_data()
 165             if data is None:
 166                 self.status = self.FAILED
 167                 return STATUS_IMAGE_BROKEN
 168             return data
 169         else:
 170             self.status = self.FAILED
 171             return STATUS_IMAGE_BROKEN
 172
 173     def set_data(self, data):
 174         cache.image_updated(self.url, data)
 175         self.status = self.DATA_IN_DB
 176
 177     def set_failed(self):
 178         self.status = self.FAILED
 179
 180     def read_data(self):
 181         istore = ItemStore.get_instance()
 182         return istore.read_image(self.url)
 183
 184     def _return_id(self):
 185         return "%d %s" % (id(self), self.url)
 186
 187 cache = Cache()
 188
 189 class ImageConsumer:
 190     def __init__(self, imobj):
 191         self._imobj = imobj
 192
 193     def http_results(self, status, data):
 194         if status[1] == 200:
 195             self._imobj.set_data(data)
 196         else:
 197             self._imobj.set_failed()
 198
 199     def http_failed(self, exception):
 200         self._imobj.set_failed()
 201
 202     def operation_stopped(self):
 203         # XXX operation stopped is not really failed
 204         self._imobj.set_failed()
 205
 206 def initialize():
 207     global STATUS_IMAGE_WAITING
 208     global STATUS_IMAGE_BROKEN
 209     libdir = utils.find_image_dir()
 210     STATUS_IMAGE_WAITING = open(
 211         libdir + "/image-loading.svg").read()
 212     STATUS_IMAGE_BROKEN = open(
 213         libdir + "/image-missing.svg").read()