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Editing: hookable.py
# -*- coding: utf-8 -*- # slip.util.hookable -- run hooks on changes in objects # # Copyright © 2008 Red Hat, Inc. # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program 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 General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see <http://www.gnu.org/licenses/>. # # Authors: # Nils Philippsen <nils@redhat.com> """This module contains variants of certain base types which call registered hooks on changes.""" import collections from six import with_metaclass __all__ = ["Hookable", "HookableSet"] class HookableType(type): def __new__(cls, name, bases, dct): if '_hookable_change_methods' in dct: try: base = dct["_hookable_base_class"] except KeyError: base = None for base_candidate in (x for x in bases if x != Hookable): if base: raise TypeError( "too many base classes: %s" % str(bases)) else: base = base_candidate for methodname in dct["_hookable_change_methods"]: dct[methodname] = HookableType.wrap_method(base, methodname) return type.__new__(cls, name, bases, dct) @classmethod def wrap_method(cls, base, methodname): func = getattr(base, methodname) def methodwrapper(self, *p, **k): retval = func(self, *p, **k) self._run_hooks() return retval methodwrapper.__name__ = methodname return methodwrapper class _HookEntry(object): def __init__(self, hook, args, kwargs, hookable=None): assert(isinstance(hook, collections.Callable)) assert(isinstance(hookable, Hookable)) for n, x in enumerate(args): try: hash(x) except TypeError: raise TypeError( "Positional argument %d is not hashable: %r" % (n, x)) for k, x in kwargs.items(): try: hash(x) except TypeError: raise TypeError( "Keyword argument %r is not hashable: %r" % (k, x)) if not isinstance(args, tuple): args = tuple(args) self.__hook = hook self.__args = args self.__kwargs = kwargs self.__hookable = hookable self.__hash = None def __cmp__(self, obj): return ( self.__hook == obj.__hook and self.__args == obj.__args and self.__kwargs == obj.__kwargs) def __hash__(self): if not self.__hash: self.__hash = self._compute_hash() return self.__hash def _compute_hash(self): hashvalue = hash(self.__hook) hashvalue = hash(hashvalue) ^ hash(self.__args) hashvalue = hash(hashvalue) ^ hash( tuple(sorted(self.__kwargs.items()))) return hashvalue def run(self): if self.__hookable: self.__hook(self.__hookable, *self.__args, **self.__kwargs) else: self.__hook(*self.__args, **self.__kwargs) class Hookable(with_metaclass(HookableType, object)): """An object which calls registered hooks on changes.""" @property def __hooks__(self, *p, **k): if not hasattr(self, "__real_hooks__"): self.__real_hooks__ = set() return self.__real_hooks__ def _get_hooks_enabled(self): if not hasattr(self, "__hooks_enabled__"): self.__hooks_enabled__ = True return self.__hooks_enabled__ def _set_hooks_enabled(self, enabled): self.__hooks_enabled__ = enabled hooks_enabled = property(_get_hooks_enabled, _set_hooks_enabled) def _get_hooks_frozen(self): if not hasattr(self, "__hooks_frozen__"): self.__hooks_frozen__ = False return self.__hooks_frozen__ def _set_hooks_frozen(self, freeze): if freeze == self.hooks_frozen: return self.__hooks_frozen__ = freeze if freeze: self.__hooks_frozen_entries__ = set() else: for hookentry in self.__hooks_frozen_entries__: hookentry.run() del self.__hooks_frozen_entries__ hooks_frozen = property(_get_hooks_frozen, _set_hooks_frozen) def freeze_hooks(self): self.hooks_frozen = True def thaw_hooks(self): self.hooks_frozen = False def add_hook(self, hook, *args, **kwargs): self.__add_hook(hook, None, *args, **kwargs) def add_hook_hookable(self, hook, *args, **kwargs): self.__add_hook(hook, self, *args, **kwargs) def __add_hook(self, hook, _hookable, *args, **kwargs): assert isinstance(hook, collections.Callable) assert isinstance(_hookable, Hookable) hookentry = _HookEntry(hook, args, kwargs, hookable=_hookable) self.__hooks__.add(hookentry) def remove_hook(self, hook, *args, **kwargs): self.__hooks__.remove(_HookEntry(hook, args, kwargs)) def _run_hooks(self): if self.hooks_enabled: if not self.hooks_frozen: for hookentry in self.__hooks__: hookentry.run() else: self.__hooks_frozen_entries__.update(self.__hooks__) class HookableSet(set, Hookable): """A set object which calls registered hooks on changes.""" _hookable_change_methods = ( "add", "clear", "difference_update", "discard", "intersection_update", "pop", "remove", "symmetric_difference_update", "update") def copy(self): obj = set.copy(self) obj.__real_hooks__ = set() return obj
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