Changeset 6528

Timestamp:

23 Jul 2011, 02:22:13 (13 years ago)

Author:

uli

Message:

Fix imagestorage. It took ages to find out, that strange behaviour of
saved image files (content disappearing, etc.) was not due to the
imagestorage implementation, but most probably caused by some design
problem in ZODB Blob storage. Nevertheless the new implementation
seems to work properly.

File:

• main/waeup.sirp/trunk/src/waeup/sirp/imagestorage.py (modified) (6 diffs)

main/waeup.sirp/trunk/src/waeup/sirp/imagestorage.py

@@ -25 +25 @@
 import hashlib
 import os
+import transaction
+import warnings
 from StringIO import StringIO
 from ZODB.blob import Blob
 from persistent import Persistent
 from hurry.file.interfaces import IFileRetrieval
-from zope.container.contained import Contained
 from waeup.sirp.image import WAeUPImageFile
 from waeup.sirp.utils.helpers import cmp_files
@@ -45 +46 @@
     """A basket holds a set of image files with same hash.
     """
+
     def _del(self):
         """Remove temporary files associated with local blobs.
@@ -71 +73 @@
 
     def getInternalId(self, fd):
+        """Get the basket-internal id for the file stored in `fd`.
+
+        `fd` must be a file open for reading. If an (byte-wise) equal
+        file can be found in the basket, its internal id (basket id)
+        is returned, ``None`` otherwise.
+        """
+        fd.seek(0)
         for key, val in self.items():
-            fd.seek(0)
             fd_stored = val.open('r')
+            file_len = os.stat(fd_stored.name)[6]
+            if file_len == 0:
+                # Nasty workaround. Blobs seem to suffer from being emptied
+                # accidentally.
+                site = grok.getSite()
+                if site is not None:
+                    site.logger.warn(
+                        'Empty Blob detected: %s' % fd_stored.name)
+                warnings.warn("EMPTY BLOB DETECTED: %s" % fd_stored.name)
+                fd_stored.close()
+                val.open('w').write(fd.read())
+                return key
+            fd_stored.seek(0)
             if cmp_files(fd, fd_stored):
                 fd_stored.close()
@@ -82 +103 @@
     @property
     def curr_id(self):
+        """The current basket id.
+
+        An integer number which is not yet in use. If there are
+        already `maxint` entries in the basket, a :exc:`ValueError` is
+        raised. The latter is _highly_ unlikely. It would mean to have
+        more than 2**32 hash collisions, i.e. so many files with the
+        same MD5 sum.
+        """
         num = 1
         while True:
@@ -92 +121 @@
 
     def storeFile(self, fd, filename):
-        internal_id = self.getInternalId(fd)
+        """Store the file in `fd` into the basket.
+
+        The file will be stored in a Blob.
+        """
+        fd.seek(0)
+        internal_id = self.getInternalId(fd) # Moves file pointer!
         if internal_id is None:
             internal_id = self.curr_id
-            self[internal_id] = Blob(fd.read())
+            fd.seek(0)
+            self[internal_id] = Blob()
+            transaction.commit() # Urgently needed to make the Blob
+                                 # persistent. Took me ages to find
+                                 # out that solution, which makes some
+                                 # design flaw in ZODB Blobs likely.
+            self[internal_id].open('w').write(fd.read())
+            fd.seek(0)
+            self._p_changed = True
         return internal_id
 
     def retrieveFile(self, basket_id):
+        """Retrieve a file open for reading with basket id `basket_id`.
+
+        If there is no such id, ``None`` is returned. It is the
+        callers responsibility to close the open file.
+        """
         if basket_id in self.keys():
             return self[basket_id].open('r')
@@ -156 +203 @@
         if storage is None:
             raise ValueError('Cannot find an image storage')
+        result = storage.retrieveFile(data)
+        if result is None:
+            return StringIO(data)
         return storage.retrieveFile(data)