1 "

     2  COPYRIGHT (c) 1993 by Claus Gittinger

     3               All Rights Reserved

     4 

     5  This software is furnished under a license and may be used

     6  only in accordance with the terms of that license and with the

     7  inclusion of the above copyright notice.   This software may not

     8  be provided or otherwise made available to, or used by, any

     9  other person.  No title to or ownership of the software is

    10  hereby transferred.

    11 "

    12 

    13 Object subclass:#Registry

    14        instanceVariableNames:'registeredObjects phantoms'

    15        classVariableNames:''

    16        poolDictionaries:''

    17        category:'System-Support'

    18 !

    19 

    20 Registry comment:'

    21 

    22 COPYRIGHT (c) 1993 by Claus Gittinger

    23               All Rights Reserved

    24 

    25 %W% %E%

    26 written jun 93 by claus

    27 '!

    28 

    29 !Registry class methodsFor:'documentation'!

    30 

    31 documentation

    32 "

    33 Registries provide an easy interface to using ShadowArrays. 

    34 A class, which wants to be informed of instance-death, can put a created object

    35 into a registry. The registry will create a copy of the object, and

    36 watch out for death of the registered object. When it dies, the copy will

    37 be sent the message >>disposed.

    38 The trick with the shallow copy is especially nice, you can think of it as

    39 beeing the original object which died.

    40 

    41 All objects, which keep external resources (such as fileDescriptors, fonts, 

    42 colormap-entries etc.) should be registered, so that the underlying resource

    43 can be freed when the object goes away.

    44 

    45 Of course, you too can use it to do whatever you need to do in case of the

    46 death of an object.

    47 "

    48 ! !

    49 

    50 !Registry methodsFor:'dispose handling'!

    51 

    52 informDispose

    53     "an instance has been destroyed - look which one it was"

    54 

    55     |phantom|

    56 

    57     1 to:phantoms size do:[:index |

    58         (registeredObjects at:index) isNil ifTrue:[

    59             (phantoms at:index) notNil ifTrue:[

    60                 phantom := phantoms at:index.

    61                 phantoms at:index put:nil.

    62                 phantom disposed

    63             ]

    64         ]

    65     ]

    66 ! !

    67 

    68 !Registry methodsFor:'enumeration'!

    69 

    70 contentsDo:aBlock

    71     "evaluate aBlock for each registered object"

    72 

    73     registeredObjects notNil ifTrue:[

    74         registeredObjects do:[:o |

    75             o notNil ifTrue:[

    76                 aBlock value:o

    77             ]

    78         ]

    79     ]

    80 ! !

    81 

    82 !Registry methodsFor:'accessing'!

    83 

    84 contents

    85     "return the collection of registered objects"

    86 

    87     ^ registeredObjects

    88 !

    89 

    90 changed:anObject

    91     "a registered object has changed, create a new phantom"

    92 

    93     |index|

    94 

    95     index := registeredObjects identityIndexOf:anObject ifAbsent:[0].

    96     index ~~ 0 ifTrue:[

    97         phantoms at:index put:anObject shallowCopy.

    98     ]

    99 !

   100 

   101 register:anObject

   102     "register anObject, so that a copy of it gets the disposed message

   103      when anObject dies (somewhere in the future)"

   104 

   105     |phantom newColl count p index|

   106 

   107     phantom := anObject shallowCopy.

   108 

   109     registeredObjects isNil ifTrue:[

   110         registeredObjects := ShadowArray new:10.

   111         registeredObjects watcher:self.

   112         registeredObjects at:1 put:anObject.

   113         phantoms := VariableArray with:phantom.

   114         ^ self

   115     ].

   116 

   117     index := registeredObjects identityIndexOf:anObject ifAbsent:[0].

   118     index ~~ 0 ifTrue:[

   119 	self error:'bad register'.

   120 	phantoms at:index put:phantom.

   121 	^ self

   122     ].

   123 

   124     "search for a free slot, on the fly look for leftovers"

   125     count := phantoms size.

   126     1 to:count do:[:index |

   127         (registeredObjects at:index) isNil ifTrue:[

   128             "is there a leftover ?"

   129             (phantoms at:index) notNil ifTrue:[

   130                 p := phantoms at:index.

   131                 phantoms at:index put:nil.

   132                 p disposed

   133             ].

   134             (phantoms at:index) isNil ifTrue:[

   135                 registeredObjects at:index put:anObject.

   136                 phantoms at:index put:phantom.

   137                 ^ self

   138             ]

   139         ]

   140     ].

   141 

   142     "no free slot, add at the end"

   143 

   144     newColl := ShadowArray new:(count * 2).

   145     newColl replaceFrom:1 to:count with:registeredObjects.

   146     registeredObjects := newColl.

   147     registeredObjects watcher:self.

   148 

   149     registeredObjects at:(count + 1) put:anObject.

   150     phantoms add:phantom

   151 !

   152 

   153 unregister:anObject

   154     "remove registration of anObject, without telling the phantom;

   155      should be sent, if we are no more interrested in destruction of

   156      anObject (i.e. it no longer holds external resources)."

   157 

   158     |index|

   159 

   160     index := registeredObjects identityIndexOf:anObject ifAbsent:[0].

   161     index ~~ 0 ifTrue:[

   162         phantoms at:index put:nil.

   163         registeredObjects at:index put:nil

   164     ]

   165 ! !