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 Constants
  23 import error
  24 import gobject
  25 import straw.defs
  26
  27 STATUS_IMAGE_WAITING = None
  28 STATUS_IMAGE_BROKEN = None
  29
  30 class CacheEntry(object):
  31     def __init__(self, image, count, pollstopper = None, restore = False):
  32         self._image = image
  33         self._count = count
  34         self._pollstopper = pollstopper
  35         if not restore:
  36             self._save_count()
  37
  38     @apply
  39     def image():
  40         doc="The image object that is associated with this class"
  41         def fget(self):
  42             return self._image
  43         def fset(self, image):
  44             self._image = image
  45         return property(**locals())
  46
  47     @apply
  48     def count():
  49         doc="image ref count"
  50         def fget(self):
  51             return self._count
  52         def fset(self, count):
  53             self._count = count
  54             self._save_count()
  55         return property(**locals())
  56
  57     @apply
  58     def pollstopper():
  59         doc="the stopper object for this cache entry"
  60         def fget(self):
  61             return self._pollstopper
  62         def fset(self, pollstopper):
  63             self._pollstopper = pollstopper
  64             if pollstopper:
  65                 pollstopper.connect('stopped', self._polling_stopped)
  66         return property(**locals())
  67
  68     def incr_count(self): self._count += 1
  69     def decr_count(self): self._count -= 1
  70
  71     def _polling_stopped(self, poller):
  72         self._pollstopper = None
  73
  74     def _save_count(self):
  75         pass
  76         #ItemStore.get_instance().set_image_count(self._image.url, self._count)
  77
  78
  79 class Cache(gobject.GObject):
  80     """Image cache with explicit reference counting."""
  81
  82     __gsignals__ = {
  83         'image-updated' : (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE,
  84                            (gobject.TYPE_STRING, gobject.TYPE_PYOBJECT))
  85         }
  86
  87     def __init__(self):
  88         gobject.GObject.__init__(self)
  89         # self.__cache contains items of the form [Image, refcount]
  90         self.__cache = dict()
  91
  92     def __getitem__(self, key):
  93         print "got getitem for %s" % key
  94         print "cache is %s" %  self.__cache
  95         return self.__cache[key].image
  96
  97     def add_refer(self, key, restore = False, item = None):
  98         if key not in self.__cache:
  99             if not restore:
 100                 # fetch image
 101                 image = Image(key, Image.WAITING)
 102                 ic = ImageConsumer(image)
 103                 headers = {}
 104                 stopper = None
 105                 if item and item.feed:
 106                     headers['Referer'] = item.feed.location
 107                 try:
 108                     stopper = URLFetch.get_instance().request(
 109                         key, ic,
 110                         priority=Constants.PRIORITY_IMAGE,
 111                         headers=headers)
 112                 #except URLFetch.RequestSchemeException, e:
 113                 #    ic.http_failed(e)
 114                 except Exception, e:
 115                     error.logtb("ImageCache.add_refer:  ", str(e))
 116                     ic.http_failed(e)
 117                 self.__cache[key] = CacheEntry(
 118                     image, 1, PollManager.PollStopper(stopper, image), restore=restore)
 119             else:
 120                 image = Image(key, Image.DATA_IN_DB)
 121                 self.__cache[key] = CacheEntry(image, 1, pollstopper=None, restore=restore)
 122         elif key in self.__cache and not restore:
 123             self.__cache[key].incr_count()
 124
 125     def remove_refer(self, key):
 126         if self.__cache.has_key(key):
 127             entry = self.__cache[key]
 128             entry.decr_count()
 129             if entry.count == 0:
 130                 del self.__cache[key]
 131                 ItemStore.get_instance().update_image(key, None)
 132                 self.emit('image-updated', key, None)
 133
 134     def image_updated(self, url, data):
 135         self.__cache[url].pollstopper = None
 136         self.set_image(url,data)
 137         ItemStore.get_instance().update_image(url,data)
 138         self.emit('image-updated', url, data)
 139
 140     def set_image(self, url, image):
 141         if self.__cache.has_key(url):
 142             self.__cache[url].incr_count()
 143         else:
 144             self.__cache[url] = CacheEntry(image, 1)
 145
 146     def set_image_with_count(self, url, image, count, restore=False):
 147         self.__cache[url] = CacheEntry(image, count, restore=restore)
 148
 149     def stop_transfer(self, url):
 150         image = self.__cache.get(url, None)
 151         if image and image.pollstopper:
 152             self.__cache[url].pollstopper.stop()
 153             self.__cache[url].pollstopper = None
 154
 155 class Image:
 156     WAITING = 1
 157     DATA_IN_DB = 2
 158     FAILED = 3
 159
 160     def __init__(self, url, status = DATA_IN_DB):
 161         self.url = url
 162         self.status = status
 163
 164     def get_data(self):
 165         if self.status == self.WAITING:
 166             return STATUS_IMAGE_WAITING
 167         elif self.status == self.DATA_IN_DB:
 168             data = self.read_data()
 169             if data is None:
 170                 self.status = self.FAILED
 171                 return STATUS_IMAGE_BROKEN
 172             return data
 173         else:
 174             self.status = self.FAILED
 175             return STATUS_IMAGE_BROKEN
 176
 177     def set_data(self, data):
 178         cache.image_updated(self.url, data)
 179         self.status = self.DATA_IN_DB
 180
 181     def set_failed(self):
 182         self.status = self.FAILED
 183
 184     def read_data(self):
 185         istore = ItemStore.get_instance()
 186         return istore.read_image(self.url)
 187
 188     def _return_id(self):
 189         return "%d %s" % (id(self), self.url)
 190
 191 cache = Cache()
 192
 193 class ImageConsumer:
 194     def __init__(self, imobj):
 195         self._imobj = imobj
 196
 197     def http_results(self, status, data):
 198         if status[1] == 200:
 199             self._imobj.set_data(data)
 200         else:
 201             self._imobj.set_failed()
 202
 203     def http_failed(self, exception):
 204         self._imobj.set_failed()
 205
 206     def operation_stopped(self):
 207         # XXX operation stopped is not really failed
 208         self._imobj.set_failed()
 209
 210 def initialize():
 211     global STATUS_IMAGE_WAITING
 212     global STATUS_IMAGE_BROKEN
 213     STATUS_IMAGE_WAITING = open(
 214         straw.defs.STRAW_DATA_DIR + "/image-loading.svg").read()
 215     STATUS_IMAGE_BROKEN = open(
 216         straw.defs.STRAW_DATA_DIR + "/image-missing.svg").read()