note description: "[ Utility class to traverse object graphs starting at a root object. When traversing a graph the class distinguishes four different types of references: (1) Normal references (2) References with copy-semantics, which are usually seen when attaching an expanded object to an ANY reference (3) User-defined expanded objects, embedded inside another object. Semantically this is a special case of a copy-semantics reference. (4) Language-defined expanded objects (INTEGER, POINTER etc) embedded inside another object. Semantically, this is a special case of a copy-semantics reference. This class will follow all reference types except (4). During traversal the agent on_processing_object_action will be called for each object and the agent on_processing_reference_action for each reference, if present. This includes references to objects that have already been processed. The algorighm has two output values: visited_objects and visited_types: Any standard object without copy-semantics (i.e. reference type (1)) will be stored by aliasing inside visited_object. For references of type (2) and (3) a copy will be stored. The visited_types hash table contains the dynamic type id of all types encountered during traversal. The key and value in the hashtable are the same. Setting is_skip_copy_semantics_reference to true means that references of (2) and (3) will not be stored in visited_types. Note that this is the only effect of this setting - i.e. the traversal algorithm will still follow the references, the agents will be called, and the visited_types array will be extended anyway. NOTE: Due to a limitation in the reflection library, references of type (2) and (3) within TUPLE and references of type (3) within SPECIAL cannot be handled without causing a copy. This is problematic for agents, especially when they want to change the object. Therefore the algorithm will raise an exception when an agent is attached. In read-only situations it may be acceptable to use a copy of an object. Therefore to disable the exception behaviour you can set is_exception_on_copy_suppressed to True. NOTE: To maintain backwards compatibility the traversal algorithm will silently ignore any kind of exception and just return normally, with traversed_objects set to whatever value it had before invoking traverse. In order to get exceptions you need to set is_exception_propagated to True. ]" library: "Free implementation of ELKS library" legal: "See notice at end of class." status: "See notice at end of class." author: "Stephanie Balzer" date: "$Date: 2017-03-23 19:18:26 +0000 (Thu, 23 Mar 2017) $" revision: "$Revision: 100033 $" deferred class OBJECT_GRAPH_TRAVERSABLE feature -- Access root_object: detachable ANY -- Starting point of graph traversing on_processing_object_action: detachable PROCEDURE [REFLECTED_OBJECT] -- Action called on every object in the object graph. -- Note: The argument is reused later for a different object. Do not alias it. on_processing_reference_action: detachable PROCEDURE [REFLECTED_OBJECT, REFLECTED_OBJECT] -- Action called on every reference in the object graph. -- Note: The arguments are reused later for different objects. Do not alias them. object_action: detachable PROCEDURE [separate ANY] -- Action called on every object in object graph visited_objects: detachable ARRAYED_LIST [separate ANY] -- List referencing objects of object graph that have been visited in traverse. visited_types: detachable HASH_TABLE [INTEGER_32, INTEGER_32] -- List of all types encountered during traversal feature -- Status report has_failed: BOOLEAN -- Was the last traversal successful? is_root_object_set: BOOLEAN -- Is starting point of graph traversing set? do Result := root_object /= Void end is_object_action_set: BOOLEAN -- Is procedure to call on every object set? do Result := object_action /= Void end has_reference_with_copy_semantics: BOOLEAN -- Does the traversed graph of objects contain reference with copy semantics? is_skip_transient: BOOLEAN -- Do we skip transient attribute during traversal? is_skip_copy_semantics_reference: BOOLEAN -- Do we skip copy semantics reference from visited_objects during traversal? is_exception_on_copy_suppressed: BOOLEAN -- Do we suppress an exception when object_action is called on a copied object? -- A copy happens when encountering tuples containing copy-semantics references -- or with SPECIAL[XX], where XX is a user-defined expanded type. is_exception_propagated: BOOLEAN -- Does the algorithm propagate any exceptions to the user? feature -- Element change set_root_object (an_object: like root_object) -- Set root_object with 'an_object'. require an_object_not_void: an_object /= Void do root_object := an_object ensure root_object_set: root_object = an_object and is_root_object_set end set_on_processing_object_action (an_action: like on_processing_object_action) -- Set on_processing_object_action with an_action require an_action_not_void: an_action /= Void do on_processing_object_action := an_action ensure on_processing_object_action_set: on_processing_object_action = an_action end set_on_processing_reference_action (an_action: like on_processing_reference_action) -- Set on_processing_object_action with an_action require an_action_not_void: an_action /= Void do on_processing_reference_action := an_action ensure on_processing_reference_action_set: on_processing_reference_action = an_action end set_object_action (an_object_action: like object_action) obsolete "Use set_on_processing_object_action to read and manipulate objects via REFLECTED_OBJECT. [2017-05-31]" -- Set object_action with an_object_action. require an_object_action_not_void: an_object_action /= Void do object_action := an_object_action ensure an_object_action_set: object_action = an_object_action and is_object_action_set end set_is_skip_transient (v: like is_skip_transient) -- Set is_skip_transient with v. do is_skip_transient := v ensure is_skip_transient_set: is_skip_transient = v end set_is_skip_copy_semantics_reference (v: like is_skip_copy_semantics_reference) -- Set is_skip_copy_semantics_reference with v. do is_skip_copy_semantics_reference := v ensure is_skip_copy_semantics_reference_set: is_skip_copy_semantics_reference = v end set_is_exception_on_copy_suppressed (v: like is_exception_on_copy_suppressed) -- Set set_is_exception_on_copy_suppressed with v. do is_exception_on_copy_suppressed := v ensure is_exception_on_copy_suppressed_set: is_exception_on_copy_suppressed = v end set_is_exception_propagated (v: like is_exception_propagated) -- Set is_exception_propagated with v. do is_exception_propagated := v ensure is_exception_propagated_set: is_exception_propagated = v end feature -- Basic operations frozen traverse -- Traverse object structure starting at 'root_object' and call object_action -- on every object in the graph. require root_object_available: is_root_object_set local l_marker: detachable OBJECT_GRAPH_MARKER l_has_lock: BOOLEAN l_retried: BOOLEAN do if not l_retried and then attached root_object as l_root then create l_marker l_marker.lock_marking l_has_lock := True internal_traverse (l_root) l_marker.unlock_marking has_failed := False end rescue l_retried := True has_failed := True if l_has_lock and then l_marker /= Void then l_marker.unlock_marking end if not is_exception_propagated then retry end end wipe_out -- Clear current to default values do visited_objects := Void visited_types := Void object_action := Void root_object := Void ensure visited_objects_reset: visited_objects = Void object_action_not_set: not is_object_action_set root_object_not_set: not is_root_object_set end feature {NONE} -- Implementation new_dispenser: DISPENSER [separate ANY] -- New dispenser to use for storing visited objects. deferred ensure new_dispenser_not_void: Result /= Void end Default_size: INTEGER_32 = 200 -- Default size for containers used during object traversal internal_traverse (a_root_object: ANY) -- Traverse object structure starting at 'root_object' and call object_action -- on every object in the graph. local i, nb: INTEGER_32 l_object: separate ANY l_field: like {TUPLE}.reference_item l_field_type: INTEGER_32 l_marker: OBJECT_GRAPH_MARKER l_objects_to_visit: like new_dispenser l_visited: like visited_objects l_visited_types: like visited_types l_action: like object_action l_on_processing_object_action: like on_processing_object_action l_spec: like visited_objects.area l_reflected_reference_object: REFLECTED_REFERENCE_OBJECT l_reflected_object: REFLECTED_OBJECT l_has_reference_with_copy_semantics: BOOLEAN l_on_processing_reference_action: like on_processing_reference_action l_referee_object_cache: REFLECTED_REFERENCE_OBJECT l_referee_object: REFLECTED_OBJECT do from create l_marker create l_reflected_reference_object.make (a_root_object) l_marker.mark (a_root_object) create l_visited.make (Default_size) create l_visited_types.make (Default_size) l_objects_to_visit := new_dispenser l_objects_to_visit.put (a_root_object) l_action := object_action l_on_processing_object_action := on_processing_object_action l_on_processing_reference_action := on_processing_reference_action create l_referee_object_cache.make (a_root_object) until l_objects_to_visit.is_empty loop l_object := l_objects_to_visit.item l_objects_to_visit.remove if attached {REFLECTED_OBJECT} l_object as l_copy_semantics_object then check embedded_or_copy_semantics: attached {REFLECTED_COPY_SEMANTICS_OBJECT} l_copy_semantics_object or (attached {REFLECTED_REFERENCE_OBJECT} l_copy_semantics_object as l_ref_obj and then l_ref_obj.physical_offset /= 0) end l_has_reference_with_copy_semantics := True l_reflected_object := l_copy_semantics_object if not is_skip_copy_semantics_reference then l_visited.extend (l_copy_semantics_object.object) end else l_reflected_reference_object.set_object (l_object) l_reflected_object := l_reflected_reference_object if l_reflected_reference_object.is_expanded then l_has_reference_with_copy_semantics := True if not is_skip_copy_semantics_reference then l_visited.extend (l_object) end else l_visited.extend (l_object) end end l_visited_types.put (l_reflected_object.dynamic_type, l_reflected_object.dynamic_type) if l_action /= Void or l_on_processing_object_action /= Void then if not is_exception_on_copy_suppressed and then l_reflected_object.is_expanded then raise_unwanted_copy_exception else if l_action /= Void then l_action.call ([l_object]) end if attached l_on_processing_object_action then l_on_processing_object_action.call ([l_reflected_object]) end end end if l_reflected_object.is_special then if l_reflected_object.is_special_of_reference then if attached {SPECIAL [detachable ANY]} l_object as l_sp then from i := 0 nb := l_sp.count until i = nb loop if l_reflected_object.is_special_copy_semantics_item (i) then l_referee_object := l_reflected_object.special_copy_semantics_item (i) l_field := l_referee_object l_objects_to_visit.put (l_field) if attached l_on_processing_reference_action then l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) end else l_field := l_sp.item (i) if l_field /= Void and then not l_marker.is_marked (l_field) then l_marker.mark (l_field) l_objects_to_visit.put (l_field) end if attached l_on_processing_reference_action and attached l_field then l_referee_object_cache.set_object (l_field) l_referee_object := l_referee_object_cache l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) end end i := i + 1 end end elseif l_reflected_object.is_special_of_expanded then if attached {SPECIAL [ANY]} l_object as l_sp then from i := 0 nb := l_sp.count until i = nb loop l_field := l_sp.item (i) l_objects_to_visit.put (l_field) if attached l_on_processing_reference_action then if is_exception_on_copy_suppressed then l_referee_object_cache.set_object (l_field) l_referee_object := l_referee_object_cache l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) else raise_unwanted_copy_exception end end i := i + 1 end end end elseif l_reflected_object.is_tuple then if attached {TUPLE} l_object as l_tuple_obj then from i := 1 nb := l_tuple_obj.count + 1 until i = nb loop if l_tuple_obj.is_reference_item (i) then l_field := l_tuple_obj.reference_item (i) if l_field /= Void and then not l_marker.is_marked (l_field) then l_marker.mark (l_field) l_objects_to_visit.put (l_field) end if attached l_on_processing_reference_action and attached l_field then if is_exception_on_copy_suppressed then l_referee_object_cache.set_object (l_field) l_referee_object := l_referee_object_cache l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) else raise_unwanted_copy_exception end end end i := i + 1 end end else from i := 1 nb := l_reflected_object.field_count + 1 until i = nb loop l_field_type := l_reflected_object.field_type (i) if l_field_type = {REFLECTOR_CONSTANTS}.reference_type or l_field_type = {REFLECTOR_CONSTANTS}.expanded_type then if not is_skip_transient or else not l_reflected_object.is_field_transient (i) then if l_field_type = {REFLECTOR_CONSTANTS}.expanded_type then l_referee_object := l_reflected_object.expanded_field (i) l_objects_to_visit.put (l_referee_object) if attached l_on_processing_reference_action then l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) end elseif l_reflected_object.is_copy_semantics_field (i) then l_referee_object := l_reflected_object.copy_semantics_field (i) l_objects_to_visit.put (l_referee_object) if attached l_on_processing_reference_action then l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) end else l_field := l_reflected_object.reference_field (i) if l_field /= Void then if not l_marker.is_marked (l_field) then l_marker.mark (l_field) l_objects_to_visit.put (l_field) end if attached l_on_processing_reference_action then l_referee_object_cache.set_object (l_field) l_referee_object := l_referee_object_cache l_on_processing_reference_action.call ([l_reflected_object, l_referee_object]) end end end end end i := i + 1 variant nb - i end end end from i := 0 nb := l_visited.count l_spec := l_visited.area until i = nb loop l_marker.unmark (l_spec.item (i)) i := i + 1 end visited_objects := l_visited visited_types := l_visited_types has_reference_with_copy_semantics := l_has_reference_with_copy_semantics end raise_unwanted_copy_exception local l_exception: DEVELOPER_EXCEPTION do create l_exception l_exception.set_description ("An agent has been invoked on a copy of an object during object graph traversal.%NThis happens in TUPLE containing objects with copy-semantics or in SPECIAL[XX],%Nwhere XX is a user-defined expanded type.") l_exception.raise end note copyright: "Copyright (c) 1984-2017, Eiffel Software and others" license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)" source: "[ Eiffel Software 5949 Hollister Ave., Goleta, CA 93117 USA Telephone 805-685-1006, Fax 805-685-6869 Website http://www.eiffel.com Customer support http://support.eiffel.com ]" end -- class OBJECT_GRAPH_TRAVERSABLE
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