[Zope-dev] delete feature to z3c.extfile

[Jürgen kartnaller]

Hi jayaraj,
it is definitely not a good idea to implicitily delete files.

What if two ExtFile objects reference the same file ?

Jürgen

On Wed, Sep 24, 2008 at 4:37 AM, Jayarajan Jn <jayarajan at musmo.com> wrote:

> Hi,
> i am now doing some prototypes for my projects which will be dealing with
> tones of files. After a little scouting i decided to try z3c.extfile. Every
> thing works fine. But i found it strange that there is no delete feature in
> z3c.extfile. ie, even if i can delete a ExtFile object, the file in the hash
> directory is not getting deleted! and it keeps on accumulating...
>
> So i  thought i 'll add a delete feature... but  my  __del__() approach
> doesn't  work for me. but i added an additional delete() function too which
> can be invoked explicitly to delete the file before trying to delete ExtFile
> object.
>
> i made following  changes to the source...
> inside  z3c.extfile.file.file.ExtFile,
>
>
> ----------------------------------------------------------------------------------------------
> class ExtFile(Persistent):
>
>     """A zope file implementation based on z3c.extfile"""
>
>     interface.implements(IExtFile)
>     data = ExtBytesProperty('data')
>
>     def __init__(self, data='', contentType=''):
>         self.data = data
>         self.contentType = contentType
>
>     # added the following lines#
>
> *    def __del__(self):   # <- this is not being invoked when i try to
> delete an extfile object
>         del self.data
>         #print "deleted data via destructor"
>
>     def delete(self):     # <- added this to be able to manually able to
> delete files
>         del self.data
>         #print "deleted data via delete()"
>
>     # # # # # # #  # # # # # # #  #
> *
>     def getSize(self):
>         return len(self.data)
>
>
> ----------------------------------------------------------------------------------------------
>
> and the 'data' is a 'property'  (ExtBytesProperty)
> so i made following changes to z3c.extfile.property.ExtBytesProperty
>
>
> ----------------------------------------------------------------------------------------------
> class ExtBytesProperty(object):
>
>     """a property which's values are stored as external files"""
>
>     def __init__(self, name):
>         self.__name = name
>
>
>
>     # added the following lines#
>
> *    def __delete__(self,inst):
>         digest = inst.__dict__[self.__name]
>         self.hd.delete(digest)
>
> *    *# # # # # # #  # # # # # # #  #
>
>
>
> *    @property
>     def hd(self):
>         return component.getUtility(interfaces.IHashDir)
>
>     def __get__(self, inst, klass):
>
>         if inst is None:
>             return self
>         digest = inst.__dict__.get(self.__name, _marker)
>         if digest is _marker:
>             return None
>         return getFile(digest)
>
>     def __set__(self, inst, value):
>         # ignore if value is None
>         if value is None:
>             if inst.__dict__.has_key(self.__name):
>                 del inst.__dict__[self.__name]
>             return
>         # Handle case when value is a string
>         if isinstance(value, unicode):
>             value = value.encode('UTF-8')
>         if isinstance(value, str):
>             value = StringIO(value)
>         value.seek(0)
>         f = self.hd.new()
>         while True:
>             chunk = value.read(BLOCK_SIZE)
>             if not chunk:
>                 newDigest = f.commit()
>                 oldDigest = inst.__dict__.get(self.__name, _marker)
>                 if newDigest == oldDigest:
>                     # we have no change, so we have to seek to zero
>                     # because this is normal behaviour when setting a
>                     # new value
>                     if hasattr(_storage, 'dataManager'):
>                         if newDigest in _storage.dataManager.files:
>                             f = _storage.dataManager.files[newDigest]
>                             f.seek(0)
>                 else:
>                     inst.__dict__[self.__name] = newDigest
>                 break
>             f.write(chunk)
>
> ----------------------------------------------------------------------------------------------------
>
> and at last added the real code which delete the file in hash directory too
>
> i added following codes inside z3c.extfile.hashdir.HashDir class
> ---------------------------------------------------
> def delete(self,digest):
>         """delete the file"""
>         path=self.getPath(digest)
>         if os.path.exists(path):
>             os.remove(path)
>         return
> ----------------------------------------------------
>
> Now, everything works fine when i try to delete an ExtFile object in ZODB,
> __del__() is not being invoked!!!!!
>
> can anyone tell me how can i fix this???
>
> thanks in advance
>
> jayaraj
>
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