straw/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 from straw import helpers
  21 import Config
  22 import NetworkConstants
  23 import URLFetch
  24 import error
  25 import gobject
  26 import straw.defs
  27
  28 STATUS_IMAGE_WAITING = None
  29 STATUS_IMAGE_BROKEN = None
  30
  31 class CacheEntry(object):
  32     def __init__(self, image, count, pollstopper = None, restore = False):
  33         self._image = image
  34         self._count = count
  35         self._pollstopper = pollstopper
  36         if not restore:
  37             self._save_count()
  38
  39     @apply
  40     def image():
  41         doc="The image object that is associated with this class"
  42         def fget(self):
  43             return self._image
  44         def fset(self, image):
  45             self._image = image
  46         return property(**locals())
  47
  48     @apply
  49     def count():
  50         doc="image ref count"
  51         def fget(self):
  52             return self._count
  53         def fset(self, count):
  54             self._count = count
  55             self._save_count()
  56         return property(**locals())
  57
  58     @apply
  59     def pollstopper():
  60         doc="the stopper object for this cache entry"
  61         def fget(self):
  62             return self._pollstopper
  63         def fset(self, pollstopper):
  64             self._pollstopper = pollstopper
  65             if pollstopper:
  66                 pollstopper.connect('stopped', self._polling_stopped)
  67         return property(**locals())
  68
  69     def incr_count(self): self._count += 1
  70     def decr_count(self): self._count -= 1
  71
  72     def _polling_stopped(self, poller):
  73         self._pollstopper = None
  74
  75     def _save_count(self):
  76         pass
  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         print "got getitem for %s" % key
  95         print "cache is %s" %  self.__cache
  96         return self.__cache[key].image
  97
  98     def add_refer(self, key, restore = False, item = None):
  99         if key not in self.__cache:
 100             if not restore:
 101                 # fetch image
 102                 image = Image(key, Image.WAITING)
 103                 ic = ImageConsumer(image)
 104                 headers = {}
 105                 stopper = None
 106                 if item and item.feed:
 107                     headers['Referer'] = item.feed.location
 108                 try:
 109                     stopper = URLFetch.get_instance().request(
 110                         key, ic,
 111                         priority=NetworkConstants.PRIORITY_IMAGE,
 112                         headers=headers)
 113                 #except URLFetch.RequestSchemeException, e:
 114                 #    ic.http_failed(e)
 115                 except Exception, e:
 116                     error.logtb("ImageCache.add_refer:  ", str(e))
 117                     ic.http_failed(e)
 118                 self.__cache[key] = CacheEntry(
 119                     image, 1, PollManager.PollStopper(stopper, image), restore=restore)
 120             else:
 121                 image = Image(key, Image.DATA_IN_DB)
 122                 self.__cache[key] = CacheEntry(image, 1, pollstopper=None, restore=restore)
 123         elif key in self.__cache and not restore:
 124             self.__cache[key].incr_count()
 125
 126     def remove_refer(self, key):
 127         if self.__cache.has_key(key):
 128             entry = self.__cache[key]
 129             entry.decr_count()
 130             if entry.count == 0:
 131                 del self.__cache[key]
 132                 ItemStore.get_instance().update_image(key, None)
 133                 self.emit('image-updated', key, None)
 134
 135     def image_updated(self, url, data):
 136         self.__cache[url].pollstopper = None
 137         self.set_image(url,data)
 138         ItemStore.get_instance().update_image(url,data)
 139         self.emit('image-updated', url, data)
 140
 141     def set_image(self, url, image):
 142         if self.__cache.has_key(url):
 143             self.__cache[url].incr_count()
 144         else:
 145             self.__cache[url] = CacheEntry(image, 1)
 146
 147     def set_image_with_count(self, url, image, count, restore=False):
 148         self.__cache[url] = CacheEntry(image, count, restore=restore)
 149
 150     def stop_transfer(self, url):
 151         image = self.__cache.get(url, None)
 152         if image and image.pollstopper:
 153             self.__cache[url].pollstopper.stop()
 154             self.__cache[url].pollstopper = None
 155
 156 class Image:
 157     WAITING = 1
 158     DATA_IN_DB = 2
 159     FAILED = 3
 160
 161     def __init__(self, url, status = DATA_IN_DB):
 162         self.url = url
 163         self.status = status
 164
 165     def get_data(self):
 166         if self.status == self.WAITING:
 167             return STATUS_IMAGE_WAITING
 168         elif self.status == self.DATA_IN_DB:
 169             data = self.read_data()
 170             if data is None:
 171                 self.status = self.FAILED
 172                 return STATUS_IMAGE_BROKEN
 173             return data
 174         else:
 175             self.status = self.FAILED
 176             return STATUS_IMAGE_BROKEN
 177
 178     def set_data(self, data):
 179         cache.image_updated(self.url, data)
 180         self.status = self.DATA_IN_DB
 181
 182     def set_failed(self):
 183         self.status = self.FAILED
 184
 185     def read_data(self):
 186         istore = ItemStore.get_instance()
 187         return istore.read_image(self.url)
 188
 189     def _return_id(self):
 190         return "%d %s" % (id(self), self.url)
 191
 192 cache = Cache()
 193
 194 class ImageConsumer:
 195     def __init__(self, imobj):
 196         self._imobj = imobj
 197
 198     def http_results(self, status, data):
 199         if status[1] == 200:
 200             self._imobj.set_data(data)
 201         else:
 202             self._imobj.set_failed()
 203
 204     def http_failed(self, exception):
 205         self._imobj.set_failed()
 206
 207     def operation_stopped(self):
 208         # XXX operation stopped is not really failed
 209         self._imobj.set_failed()
 210
 211 def initialize():
 212     global STATUS_IMAGE_WAITING
 213     global STATUS_IMAGE_BROKEN
 214     STATUS_IMAGE_WAITING = open(
 215         straw.defs.STRAW_DATA_DIR + "/image-loading.svg").read()
 216     STATUS_IMAGE_BROKEN = open(
 217         straw.defs.STRAW_DATA_DIR + "/image-missing.svg").read()