GarbageCollector.py

##Copyright 2008-2014 Thomas Paviot (tpaviot@gmail.com)
##
##This file is part of pythonOCC.
##
##pythonOCC is free software: you can redistribute it and/or modify
##it under the terms of the GNU Lesser General Public License as published by
##the Free Software Foundation, either version 3 of the License, or
##(at your option) any later version.
##
##pythonOCC is distributed in the hope that it will be useful,
##but WITHOUT ANY WARRANTY; without even the implied warranty of
##MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##GNU Lesser General Public License for more details.
##
##You should have received a copy of the GNU Lesser General Public License
##along with pythonOCC.  If not, see <http://www.gnu.org/licenses/>.

# Init logging system
from collections import deque

class GarbageCollector(object):
    """ Garbage collector for OCC objects
    """
    def __init__(self):
        #self._collected_objects = []
        self._handles = deque()
        self._transients = deque()
        self._misc = deque()

        # The list for the prevented objects
        self._prevent = deque()

        # define contexts lists
        self._handles_contexts = deque()
        self._transients_contexts = deque
        self._misc_contexts = deque()

    def prevent_object(self, obj):
        ''' Prevent an object from being deleted. This object is temporary
        stored in a list to increase its refecount.
        '''
        self._prevent.append(obj)

    def push_context(self):
        ''' Create a new context. When the push context method is called,
        objects are collected in this new context. When the context is popped,
        erase the content of the context.
        '''
        # store the current objects in the contexts list
        self._handles_contexts.append(self._handles)
        self._transients_contexts.append(self._transients)
        self._misc_contexts.append(self._misc)
        # Then erase the content of the current lists
        self._handles = deque()
        self._transients = deque()
        self._misc = deque()

    def pop_context(self):
        self._handles = self._handles_contexts.pop()
        self._transients = self._transients_contexts.pop()
        self._misc = self._misc_contexts.pop()

    def collect_object(self, obj_deleted):
        ''' This method is called whenever a pythonOCC instance is deleted.'''
        if hasattr(obj_deleted, 'was_purged'):
            return False
        if obj_deleted.__class__.__name__.startswith('Handle'):
            self._handles.append(obj_deleted)
        elif hasattr(obj_deleted, "GetHandle"):
            self._transients.append(obj_deleted)
        else:
            self._misc.append(obj_deleted)

    def smart_purge(self):
        # TODO: need to reverse the lists first in order
        # to start with the olders objects?
        # Remove Handles
        while len(self._handles) > 0:
            handle = self._handles.pop()
            handle.Nullify()  # decrement ref counting_kill_pointed()
            # after that, the reference counting of transients objects
            # in the garbage should be 0
            handle.was_purged = True
        # Remove Transients
        for transient in self._transients:
            transient_must_be_purged = False
            if transient.GetRefCount() == 0:
                transient_must_be_purged = True
            if transient_must_be_purged:
                transient._kill_pointed()
                transient.was_purged = True
                self._transients.remove(transient)
        # Remove other objects
        while len(self._misc) > 0:
            misc = self._misc.pop()
            misc._kill_pointed()
            misc.was_purged = True

garbage = GarbageCollector()