CDBottomUp.mesa
Copyright © 1985, 1986 by Xerox Corporation. All rights reserved.
Jacobi, December 13, 1985 5:49:59 pm PST
Jacobi, March 21, 1986 8:32:31 pm PST
DIRECTORY
CD, Rope;
CDBottomUp: CEDAR DEFINITIONS =
BEGIN
A module which allows easy implementation of bottom up calls which cache the results.
Each independent call creates a new invocation key. Results which are created with the same invocation key are allways trusted and taken from the cache. Results with a different invocation key are re-used if all the subcells haven't changed.
Calls for each application (class) - design pair should be monitored by the client, to prevent conflicts on the cached results and which invocation is the latest.
Class: TYPE = REF --READONLY-- ClassRec;
ClassRec: TYPE = RECORD [do: PRIVATE DoProc, reUse: PRIVATE ReUseProc, key: PRIVATE REF, classData: REF];
--a class represents the application program; what analysis procedure should be called
Handle: TYPE = REF HandleRec;
HandleRec: TYPE = RECORD [class: Class, design: CD.Design, data: REF, invocation: REF, r: Rope.ROPENIL, cnt: INT𡤀];
--a handle represents one bottom up call sequence
--data, r, cnt are reserved for clients (there are never many HandleRec's arround)
DoProc: TYPE = PROC [handle: Handle, ob: CD.Object] RETURNS [val: REFNIL];
--a DoProc should not recurse directly but may call DoBottomUp to get recursion going
--if ~ob.class.inDirectory then results must NOT depend on design
--val: value which will be cached
ReUseProc: TYPE = PROC [handle: Handle, ob: CD.Object, previousVal: REF] RETURNS [shouldDoAain: BOOL�LSE];
--a ReUseProc should be fast and should not recurse directly nor call DoBottomUp
Peek: PROC [key: REF, ob: CD.Object] RETURNS [val: REF];
--Returns cached result; independent whether valid or not...
--key: as in Class registration
DoRecurse: PROC [handle: Handle, ob: CD.Object] RETURNS [val: REF, new: BOOL];
--Gets value or start recursion if value is not valid
--May be called recursively at clients own will; caches results (not slower as Peek)
--val: the result which was computed or cached
--new: whether a new result was computed this invocation (important for the engine room!)
MakeHandle: PROC [class: Class, design: CD.Design←NIL, data: REFNIL, invocation: REFNIL] RETURNS [handle: Handle];
--Creates the handle datastructure which will be passed trough the recursion.
--class: determines application (procedures to be called)
--design: for client's use
--data: reserved for the client (implementor of class)
--invocation: invocation-key; (NIL for a new invocation-key)
StartRecurse: PROC [class: Class, design: CD.Design, ob: CD.Object, data: REFNIL] RETURNS [val: REF, new: BOOL, handle: Handle];
--Short cut for DoRecurse[MakeHandle[...], ...]
Register: PROC [do: DoProc, reUse: ReUseProc←NIL, key: REFNIL, reRegistrationKey: REFNIL, classData: REFNIL] RETURNS [class: Class];
--Registers an application of CDBottomUp
--do: will be called bottom up for all objects in the directory. Do will typically
-- call DoBottomUp to get recursion going; but for objects in the
-- directory, recursive calls of DoBottomUp have been precalled and
-- the result cached.
--reUse: is called to figure out whether objects which are already handled should
-- be handled again. It is called only for objects in the directory and
-- if do is not called anyway.
--key: property used to cache previous results; a NIL value creates a new property key.
-- Clients must can not access properties directly, but may use Peek.
--reRegistrationKey: property re-registration key; a NIL value ensures a new registration.
--class: identity of application.
END.