"{ Package: 'stx:libview2' }"

ValueHolder subclass:#ValueHolderWithWeakDependents

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'Interface-Support-Models'

!

!ValueHolderWithWeakDependents methodsFor:'dependents access'!

addDependent:anObject

    "make the argument, anObject be a weak dependent of the receiver"

    |wasBlocked|

    wasBlocked := OperatingSystem blockInterrupts.

    [

        |deps dep|

        deps := dependents.

        "/

        "/ store the very first dependent directly in

        "/ the dependents instVar

        "/

        (deps isNil and:[anObject isCollection not]) ifTrue:[

            dependents := WeakArray with:anObject

        ] ifFalse:[

            deps class == WeakArray ifTrue:[

                dep := deps at:1.

                dep ~~ anObject ifTrue:[

                    (dep isNil or:[dep == 0]) ifTrue:[

                        deps at:1 put:anObject

                    ] ifFalse:[

                        self dependents:(WeakIdentitySet with:dep with:anObject)

                    ]

                ]

            ] ifFalse:[

                deps add:anObject

            ]

        ]

    ] ensure:[

        wasBlocked ifFalse:[

            OperatingSystem unblockInterrupts

        ]

    ]

    "Modified: 8.1.1997 / 23:40:30 / cg"

!

dependentsDo:aBlock

    "evaluate aBlock for all of my dependents"

    |deps|

    deps := dependents.

    deps size ~~ 0 ifTrue:[

        deps do:[:d | 

                    (d notNil and:[d ~~ 0]) ifTrue:[

                        aBlock value:d

                    ]

                ]

    ].

!

removeDependent:anObject

    "make the argument, anObject be independent of the receiver"

    |wasBlocked|

    "/ must do this save from interrupts, since the dependents collection

    "/ is possibly accessed from multiple threads.

    "/ Used to use #valueUninterruptably here; inlined that code for slightly

    "/ faster execution.

    wasBlocked := OperatingSystem blockInterrupts.

    [

        |deps n d|

        deps := dependents.

        deps size ~~ 0 ifTrue:[

            "/ to save a fair amount of memory in case of

            "/ many dependencies, we store a single dependent in

            "/ a WeakArray, and switch to a WeakSet if more dependents are

            "/ added. Here we have to do the inverse ...

            deps class == WeakArray ifTrue:[

                ((d := deps at:1) == anObject 

                or:[d isNil

                or:[d == 0]]) ifTrue:[

                    dependents := nil

                ]

            ] ifFalse:[

                deps remove:anObject ifAbsent:[].

                (n := deps size) == 0 ifTrue:[

                    dependents := nil

                ] ifFalse:[

                    n == 1 ifTrue:[

                        d := deps firstIfEmpty:nil.

                        d notNil ifTrue:[

                            deps := WeakArray with:d

                        ] ifFalse:[

                            deps := nil

                        ].

                        dependents := deps.

                    ]

                ]

            ]

        ]

    ] ensure:[

        wasBlocked ifFalse:[

            OperatingSystem unblockInterrupts

        ]

    ]

    "Modified: / 26.1.1998 / 19:51:50 / cg"

! !

!ValueHolderWithWeakDependents class methodsFor:'documentation'!

version

    ^ '$Header: /cvs/stx/stx/libview2/ValueHolderWithWeakDependents.st,v 1.2 2002-02-26 12:59:22 cg Exp $'

! !