[Zope-dev] delete feature to z3c.extfile

[Jayarajan Jn]

Hi Jürgen,

First of all thank you for your reply....
hmm you are right too... And i am comfortable with the explicit delete. But
in my prototype for i have also added webDAV interface for managing
extfile.... Then when a user deletes the extfile object through webDAV
interface, the file remains there.... coz i don't know where to put my codes
to call delete() in that case... And in my project there wont be more than
one extfiles refering to same file! so in my case its ok to go for implicit
delete! but its now working!

But form a general perspective you are correct.... may be HashDir will have
to evolve to add reference counting feture just like python do!

On Wed, Sep 24, 2008 at 11:34 AM, Jürgen kartnaller <
juergen.kartnaller at gmail.com> wrote:

> 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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