File:  [gforth] / gforth / objects.fs
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Tue Dec 8 22:02:48 1998 UTC (21 years, 11 months ago) by anton
Branches: MAIN
CVS tags: v0-4-0, HEAD
updated dates in copyright messages
inserted copyright messages in most files that did not have them
removed outdated files engine/32bit.h engine/strsig.c

    1: \ yet another Forth objects extension
    2: 
    3: \ written by Anton Ertl 1996-1998
    4: \ public domain; NO WARRANTY
    5: 
    6: \ This (in combination with compat/struct.fs) is in ANS Forth (with an
    7: \ environmental dependence on case insensitivity; convert everything
    8: \ to upper case for state sensitive systems).
    9: 
   10: \ compat/struct.fs and this file together use the following words:
   11: 
   12: \ from CORE :
   13: \ : 1- + swap invert and ; DOES> @ immediate drop Create rot dup , >r
   14: \ r> IF ELSE THEN over chars aligned cells 2* here - allot execute
   15: \ POSTPONE ?dup 2dup move Variable 2@ 2! ! ['] >body = 2drop ' r@ +!
   16: \ Constant recurse 1+ BEGIN 0= UNTIL negate Literal ." .
   17: \ from CORE-EXT :
   18: \ tuck pick nip true <> 0> erase Value :noname compile, 
   19: \ from BLOCK-EXT :
   20: \ \ 
   21: \ from DOUBLE :
   22: \ 2Constant 
   23: \ from EXCEPTION :
   24: \ throw catch 
   25: \ from EXCEPTION-EXT :
   26: \ abort" 
   27: \ from FILE :
   28: \ ( 
   29: \ from FLOAT :
   30: \ faligned floats 
   31: \ from FLOAT-EXT :
   32: \ dfaligned dfloats sfaligned sfloats 
   33: \ from LOCAL :
   34: \ TO 
   35: \ from MEMORY :
   36: \ allocate resize free 
   37: \ from SEARCH :
   38: \ get-order set-order wordlist get-current set-current 
   39: 
   40: \ needs struct.fs
   41: 
   42: \ helper words
   43: 
   44: s" gforth" environment? [if]
   45:     2drop
   46: [else]
   47: 
   48: : -rot ( a b c -- c a b )
   49:     rot rot ;
   50: 
   51: : perform ( ... addr -- ... )
   52:     @ execute ;
   53: 
   54: : ?dup-if ( compilation: -- orig ; run-time: n -- n|  )
   55:     POSTPONE ?dup POSTPONE if ; immediate
   56: 
   57: : save-mem	( addr1 u -- addr2 u ) \ gforth
   58:     \ copy a memory block into a newly allocated region in the heap
   59:     swap >r
   60:     dup allocate throw
   61:     swap 2dup r> -rot move ;
   62: 
   63: : resize ( a-addr1 u -- a-addr2 ior ) \ gforth
   64:     over
   65:     if
   66: 	resize
   67:     else
   68: 	nip allocate
   69:     then ;
   70: 
   71: : extend-mem	( addr1 u1 u -- addr addr2 u2 )
   72:     \ extend memory block allocated from the heap by u aus
   73:     \ the (possibly reallocated) piece is addr2 u2, the extension is at addr
   74:     over >r + dup >r resize throw
   75:     r> over r> + -rot ;
   76: 
   77: : \g ( -- )
   78:     postpone \ ; immediate
   79: [then]
   80: 
   81: \ data structures
   82: 
   83: struct
   84:     cell% field object-map
   85: end-struct object%
   86: 
   87: struct
   88:     cell% 2* field interface-map
   89:     cell%    field interface-map-offset \ aus
   90:       \ difference between where interface-map points and where
   91:       \ object-map points (0 for non-classes)
   92:     cell%    field interface-offset \ aus
   93:       \ offset of interface map-pointer in class-map (0 for classes)
   94: end-struct interface%
   95: 
   96: interface%
   97:     cell%    field class-parent
   98:     cell%    field class-wordlist \ inst-vars and other protected words
   99:     cell% 2* field class-inst-size ( class -- addr ) \ objects- objects
  100:     \g used as @code{class-inst-size 2@ ( class -- align size )},
  101:     \g gives the size specification for an instance (i.e. an object)
  102:     \g of @code{class}.
  103: end-struct class%
  104: 
  105: struct
  106:     cell% field selector-offset \ the offset within the (interface) map
  107:     cell% field selector-interface \ the interface offset
  108: end-struct selector%
  109: 
  110: \ maps are not defined explicitly; they have the following structure:
  111: 
  112: \ pointers to interface maps (for classes) <- interface-map points here
  113: \ interface%/class% pointer                <- (object-)map  points here
  114: \ xts of methods 
  115: 
  116: 
  117: \ code
  118: 
  119: \ selectors and methods
  120: 
  121: variable current-interface ( -- addr ) \ objects- objects
  122: \g this variable contains the class or interface currently being
  123: \g defined.
  124: 
  125: 
  126: 
  127: : no-method ( -- )
  128:     true abort" no method defined for this object/selector combination" ;
  129: 
  130: : do-class-method ( -- )
  131: does> ( ... object -- ... )
  132:     ( object selector-body )
  133:     selector-offset @ over object-map @ + ( object xtp ) perform ;
  134: 
  135: : do-interface-method ( -- )
  136: does> ( ... object -- ... )
  137:     ( object selector-body )
  138:     2dup selector-interface @ ( object selector-body object interface-offset )
  139:     swap object-map @ + @ ( object selector-body map )
  140:     swap selector-offset @ + perform ;
  141: 
  142: : method ( xt "name" -- ) \ objects- objects
  143:     \g @code{name} execution: @code{... object -- ...}@*
  144:     \g creates selector @code{name} and makes @code{xt} its method in
  145:     \g the current class.
  146:     create
  147:     current-interface @ interface-map 2@ ( xt map-addr map-size )
  148:     dup current-interface @ interface-map-offset @ - ,
  149:     1 cells extend-mem current-interface @ interface-map 2! ! ( )
  150:     current-interface @ interface-offset @ dup ,
  151:     ( 0<> ) if
  152: 	do-interface-method
  153:     else
  154: 	do-class-method
  155:     then ;
  156: 
  157: : selector ( "name" -- ) \ objects- objects
  158:     \g @code{name} execution: @code{... object -- ...}@*
  159:     \g creates selector @code{name} for the current class and its
  160:     \g descendents; you can set a method for the selector in the
  161:     \g current class with @code{overrides}.
  162:     ['] no-method method ;
  163: 
  164: : interface-override! ( xt sel-xt interface-map -- )
  165:     \ xt is the new method for the selector sel-xt in interface-map
  166:     swap >body ( xt map selector-body )
  167:     selector-offset @ + ! ;
  168: 
  169: : class->map ( class -- map ) \ objects- objects
  170:     \g @code{map} is the pointer to @code{class}'s method map; it
  171:     \g points to the place in the map to which the selector offsets
  172:     \g refer (i.e., where @code{object-map}s point to).
  173:     dup interface-map 2@ drop swap interface-map-offset @ + ;
  174: 
  175: : unique-interface-map ( class-map offset -- )
  176:     \ if the interface at offset in class map is the same as its parent,
  177:     \ copy it to make it unique; used for implementing a copy-on-write policy
  178:     over @ class-parent @ class->map ( class-map offset parent-map )
  179:     over + @ >r  \ the map for the interface for the parent
  180:     + dup @ ( interface-mapp interface-map )
  181:     dup r> =
  182:     if
  183: 	dup @ interface-map 2@ nip save-mem drop	
  184: 	swap !
  185:     else
  186: 	2drop
  187:     then ;
  188: 
  189: : class-override! ( xt sel-xt class-map -- ) \ objects- objects
  190:     \g @code{xt} is the new method for the selector @code{sel-xt} in
  191:     \g @code{class-map}.
  192:     over >body ( xt sel-xt class-map selector-body )
  193:     selector-interface @ ( xt sel-xt class-map offset )
  194:     ?dup-if \ the selector is for an interface
  195: 	2dup unique-interface-map
  196: 	+ @
  197:     then
  198:     interface-override! ;
  199: 
  200: : overrides ( xt "selector" -- ) \ objects- objects
  201:     \g replace default method for @code{selector} in the current class
  202:     \g with @code{xt}. @code{overrides} must not be used during an
  203:     \g interface definition.
  204:     ' current-interface @ class->map class-override! ;
  205: 
  206: \ interfaces
  207: 
  208: \ every interface gets a different offset; the latest one is stored here
  209: variable last-interface-offset 0 last-interface-offset !
  210: 
  211: : interface ( -- ) \ objects- objects
  212:     \g starts an interface definition.
  213:     interface% %allot >r
  214:     r@ current-interface !
  215:     current-interface 1 cells save-mem r@ interface-map 2!
  216:     -1 cells last-interface-offset +!
  217:     last-interface-offset @ r@ interface-offset !
  218:     0 r> interface-map-offset ! ;
  219: 
  220: : end-interface-noname ( -- interface ) \ objects- objects
  221:     \g ends an interface definition. The resulting interface is
  222:     \g @code{interface}.
  223:     current-interface @ ;
  224: 
  225: : end-interface ( "name" -- ) \ objects- objects
  226:     \g @code{name} execution: @code{-- interface}@*
  227:     \g ends an interface definition. The resulting interface is
  228:     \g @code{interface}.
  229:     end-interface-noname constant ;
  230: 
  231: \ classes
  232: 
  233: : add-class-order ( n1 class -- wid1 ... widn n+n1 )
  234:     dup >r class-parent @
  235:     ?dup-if
  236: 	recurse \ first add the search order for the parent class
  237:     then
  238:     r> class-wordlist @ swap 1+ ;
  239: 
  240: : push-order ( class -- ) \ objects- objects
  241:     \g add @code{class}'s wordlists to the search-order (in front)
  242:     >r get-order r> add-class-order set-order ;
  243: 
  244: : class ( parent-class -- align offset ) \ objects- objects
  245:     \g start a new class definition as a child of
  246:     \g @code{parent-class}. @code{align offset} are for use by
  247:     \g @code{field} etc.
  248:     class% %allot >r
  249:     dup interface-map 2@ save-mem r@ interface-map 2!
  250:     dup interface-map-offset @ r@ interface-map-offset !
  251:     r@ dup class->map !
  252:     0 r@ interface-offset !
  253:     dup r@ class-parent !
  254:     wordlist r@ class-wordlist !
  255:     r@ current-interface !
  256:     r> push-order
  257:     class-inst-size 2@ ;
  258: 
  259: : remove-class-order ( wid1 ... widn n+n1 class -- n1 )
  260:     \ note: no checks, whether the wordlists are correct
  261:     begin
  262: 	>r nip 1-
  263: 	r> class-parent @ dup 0=
  264:     until
  265:     drop ;
  266: 
  267: : drop-order ( class -- ) \ objects- objects
  268:     \g drops @code{class}'s wordlists from the search order. No
  269:     \g checking is made whether @code{class}'s wordlists are actually
  270:     \g on the search order.
  271:     >r get-order r> remove-class-order set-order ;
  272: 
  273: : end-class-noname ( align offset -- class ) \ objects- objects
  274:     \g ends a class definition. The resulting class is @code{class}.
  275:     current-interface @ dup drop-order class-inst-size 2!
  276:     end-interface-noname ;
  277: 
  278: : end-class ( align offset "name" -- ) \ objects- objects
  279:     \g @code{name} execution: @code{-- class}@*
  280:     \g ends a class definition. The resulting class is @code{class}.
  281:     \ name execution: ( -- class )
  282:     end-class-noname constant ;
  283: 
  284: \ visibility control
  285: 
  286: variable public-wordlist
  287: 
  288: : protected ( -- ) \ objects- objects
  289:     \g set the compilation wordlist to the current class's wordlist
  290:     current-interface @ class-wordlist @
  291:     dup get-current <>
  292:     if \ we are not protected already
  293: 	get-current public-wordlist !
  294:     then
  295:     set-current ;
  296: 
  297: : public ( -- ) \ objects- objects
  298:     \g restore the compilation wordlist that was in effect before the
  299:     \g last @code{protected} that actually changed the compilation
  300:     \g wordlist.
  301:     public-wordlist @ set-current ;
  302: 
  303: \ classes that implement interfaces
  304: 
  305: : front-extend-mem ( addr1 u1 u -- addr addr2 u2 )
  306:     \ extend memory block allocated from the heap by u aus, with the
  307:     \ old stuff coming at the end
  308:     2dup + dup >r allocate throw ( addr1 u1 u addr2 ; R: u2 )
  309:     dup >r + >r over r> rot move ( addr1 ; R: u2 addr2 )
  310:     free throw
  311:     r> dup r> ;
  312:     
  313: : implementation ( interface -- ) \ objects- objects
  314:     \g the current class implements @code{interface}. I.e., you can
  315:     \g use all selectors of the interface in the current class and its
  316:     \g descendents.
  317:     dup interface-offset @ ( interface offset )
  318:     current-interface @ interface-map-offset @ negate over - dup 0>
  319:     if \ the interface does not fit in the present class-map
  320: 	>r current-interface @ interface-map 2@
  321: 	r@ front-extend-mem
  322: 	current-interface @ interface-map 2!
  323: 	r@ erase
  324: 	dup negate current-interface @ interface-map-offset !
  325: 	r>
  326:     then ( interface offset n )
  327:     drop >r
  328:     interface-map 2@ save-mem drop ( map )
  329:     current-interface @ dup interface-map 2@ drop
  330:     swap interface-map-offset @ + r> + ! ;
  331: 
  332: \ this/self, instance variables etc.
  333: 
  334: \ rename "this" into "self" if you are a Smalltalk fiend
  335: 0 value this ( -- object ) \ objects- objects
  336: \g the receiving object of the current method (aka active object).
  337: : to-this ( object -- ) \ objects- objects
  338:     \g sets @code{this} (used internally, but useful when debugging).
  339:     TO this ;
  340: 
  341: \ another implementation, if you don't have (fast) values
  342: \ variable thisp
  343: \ : this ( -- object )
  344: \     thisp @ ;
  345: \ : to-this ( object -- )
  346: \     thisp ! ;
  347: 
  348: : m: ( -- xt colon-sys; run-time: object -- ) \ objects- objects
  349:     \g start a method definition; @code{object} becomes new @code{this}.
  350:     :noname 
  351:     POSTPONE this
  352:     POSTPONE >r
  353:     POSTPONE to-this ;
  354: 
  355: : exitm ( -- ) \ objects- objects
  356:     \g @code{exit} from a method; restore old @code{this}.
  357:     POSTPONE r>
  358:     POSTPONE to-this
  359:     POSTPONE exit ; immediate
  360: 
  361: : ;m ( colon-sys --; run-time: -- ) \ objects- objects
  362:     \g end a method definition; restore old @code{this}.
  363:     POSTPONE r>
  364:     POSTPONE to-this
  365:     POSTPONE ; ; immediate
  366: 
  367: : catch ( ... xt -- ... n ) \ exception
  368:     \ make it safe to call CATCH within a method.
  369:     \ should also be done with all words containing CATCH.
  370:     this >r catch r> to-this ;
  371: 
  372: \ the following is a bit roundabout; this is caused by the standard
  373: \ disallowing to change the compilation wordlist between CREATE and
  374: \ DOES> (see RFI 3)
  375: 
  376: : inst-something ( align1 size1 align size xt "name" -- align2 size2 )
  377:     \ xt ( -- ) typically is for a DOES>-word
  378:     get-current >r
  379:     current-interface @ class-wordlist @ set-current
  380:     >r create-field r> execute
  381:     r> set-current ;
  382: 
  383: : do-inst-var ( -- )
  384: does> \ name execution: ( -- addr )
  385:     ( addr1 ) @ this + ;
  386: 
  387: : inst-var ( align1 offset1 align size "name" -- align2 offset2 ) \ objects- objects
  388:     \g @code{name} execution: @code{-- addr}@*
  389:     \g @code{addr} is the address of the field @code{name} in
  390:     \g @code{this} object.
  391:     ['] do-inst-var inst-something ;
  392: 
  393: : do-inst-value ( -- )
  394: does> \ name execution: ( -- w )
  395:     ( addr1 ) @ this + @ ;
  396: 
  397: : inst-value ( align1 offset1 "name" -- align2 offset2 ) \ objects- objects
  398:     \g @code{name} execution: @code{-- w}@*
  399:     \g @code{w} is the value of the field @code{name} in @code{this}
  400:     \g object.
  401:     cell% ['] do-inst-value inst-something ;
  402: 
  403: : <to-inst> ( w xt -- ) \ objects- objects
  404:     \g store @code{w} into the field @code{xt} in @code{this} object.
  405:     >body @ this + ! ;
  406: 
  407: : [to-inst] ( compile-time: "name" -- ; run-time: w -- ) \ objects- objects
  408:     \g store @code{w} into field @code{name} in @code{this} object.
  409:     ' >body @ POSTPONE literal
  410:     POSTPONE this
  411:     POSTPONE +
  412:     POSTPONE ! ; immediate
  413: 
  414: \ class binding stuff
  415: 
  416: : <bind> ( class selector-xt -- xt ) \ objects- objects
  417:     \g @code{xt} is the method for the selector @code{selector-xt} in
  418:     \g @code{class}.
  419:     >body swap class->map over selector-interface @
  420:     ?dup-if
  421: 	+ @
  422:     then
  423:     swap selector-offset @ + @ ;
  424: 
  425: : bind' ( "class" "selector" -- xt ) \ objects- objects
  426:     \g @code{xt} is the method for @code{selector} in @code{class}.
  427:     ' execute ' <bind> ;
  428: 
  429: : bind ( ... "class" "selector" -- ... ) \ objects- objects
  430:     \g execute the method for @code{selector} in @code{class}.
  431:     bind' execute ;
  432: 
  433: : [bind] ( compile-time: "class" "selector" -- ; run-time: ... object -- ... ) \ objects- objects
  434:     \g compile the method for @code{selector} in @code{class}.
  435:     bind' compile, ; immediate
  436: 
  437: : current' ( "selector" -- xt ) \ objects- objects
  438:     \g @code{xt} is the method for @code{selector} in the current class.
  439:     current-interface @ ' <bind> ;
  440: 
  441: : [current] ( compile-time: "selector" -- ; run-time: ... object -- ... ) \ objects- objects
  442:     \g compile the method for @code{selector} in the current class.
  443:     current' compile, ; immediate
  444: 
  445: : [parent] ( compile-time: "selector" -- ; run-time: ... object -- ... ) \ objects- objects
  446:     \g compile the method for @code{selector} in the parent of the
  447:     \g current class.
  448:     current-interface @ class-parent @ ' <bind> compile, ; immediate
  449: 
  450: \ the object class
  451: 
  452: \ because OBJECT has no parent class, we have to build it by hand
  453: \ (instead of with class)
  454: 
  455: class% %allot current-interface !
  456: current-interface 1 cells save-mem current-interface @ interface-map 2!
  457: 0 current-interface @ interface-map-offset !
  458: 0 current-interface @ interface-offset !
  459: 0 current-interface @ class-parent !
  460: wordlist current-interface @ class-wordlist !
  461: object%
  462: current-interface @ push-order
  463: 
  464: ' drop ( object -- )
  465: method construct ( ... object -- ) \ objects- objects
  466: \g initializes the data fields of @code{object}. The method for the
  467: \g class @code{object} just does nothing @code{( object -- )}.
  468: 
  469: :noname ( object -- )
  470:     ." object:" dup . ." class:" object-map @ @ . ;
  471: method print ( object -- ) \ objects- objects
  472: \g prints the object. The method for the class @code{object} prints
  473: \g the address of the object and the address of its class.
  474: 
  475: end-class object ( -- class ) \ objects- objects
  476: \g the ancestor of all classes.
  477: 
  478: \ constructing objects
  479: 
  480: : init-object ( ... class object -- ) \ objects- objects
  481:     \g initializes a chunk of memory (@code{object}) to an object of
  482:     \g class @code{class}; then performs @code{construct}.
  483:     swap class->map over object-map ! ( ... object )
  484:     construct ;
  485: 
  486: : xt-new ( ... class xt -- object ) \ objects- objects
  487:     \g makes a new object, using @code{xt ( align size -- addr )} to
  488:     \g get memory.
  489:     over class-inst-size 2@ rot execute
  490:     dup >r init-object r> ;
  491: 
  492: : dict-new ( ... class -- object ) \ objects- objects
  493:     \g @code{allot} and initialize an object of class @code{class} in
  494:     \g the dictionary.
  495:     ['] %allot xt-new ;
  496: 
  497: : heap-new ( ... class -- object ) \ objects- objects
  498:     \g @code{allocate} and initialize an object of class @code{class}.
  499:     ['] %alloc xt-new ;

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