--- gforth/objects.fs	1997/03/11 16:00:40	1.2
+++ gforth/objects.fs	1997/06/06 17:27:57	1.3
@@ -1,6 +1,6 @@
 \ yet another Forth objects extension
 
-\ written by Anton Ertl 1996
+\ written by Anton Ertl 1996, 1997
 \ public domain
 
 \ This (in combination with compat/struct.fs) is in ANS Forth (with an
@@ -11,15 +11,16 @@
 \ compat/struct.fs and this file together use the following words:
 
 \ from CORE :
-\ : 1- + swap invert and ; Create >r rot r@ dup , r> DOES> @ chars
-\ cells 2* here - allot drop over execute 2dup move 2! 2@ ! ['] >body
-\ ' Variable POSTPONE immediate ." . cr Constant +!
+\ : 1- + swap invert and ; DOES> @ immediate drop Create >r rot r@ dup
+\ , IF ELSE THEN r> chars cells 2* here - allot over execute POSTPONE
+\ ?dup 2dup move 2! Variable 2@ ! ['] >body = 2drop ' +! Constant
+\ recurse 1+ BEGIN 0= UNTIL negate Literal ." .
 \ from CORE-EXT :
-\ tuck :noname compile, true 
+\ tuck nip true <> 0> erase Value :noname compile, 
 \ from BLOCK-EXT :
 \ \ 
 \ from DOUBLE :
-\ 2Constant 2VARIABLE 
+\ 2Constant 
 \ from EXCEPTION :
 \ throw catch 
 \ from EXCEPTION-EXT :
@@ -30,10 +31,12 @@
 \ floats 
 \ from FLOAT-EXT :
 \ dfloats sfloats 
+\ from LOCAL :
+\ TO 
 \ from MEMORY :
-\ allocate resize 
-\ from TOOLS-EXT :
-\ [IF] [THEN]
+\ allocate resize free 
+\ from SEARCH :
+\ get-order set-order wordlist get-current set-current 
 
 \ ---------------------------------------
 \ MANUAL:
@@ -99,6 +102,46 @@
 \ this:
 
 \ bind' <class> <method>
+
+
+\ An interface is defined like this:
+
+\ interface
+\   selector <name>
+\ : noname ( ... object -- ... )
+\     ... ;
+\ method <name>
+\   ...
+\ end-interface <name>
+
+\ You can only define new selectors in an interface definition, no
+\ fields or instance variables. If you define a selector with
+\ 'method', the corresponding method becomes the default method for
+\ this selector.
+
+\ An interface is used like this:
+
+\ <parent> class
+\   <interface> implementation
+\   <interface> implementation
+
+\ :noname ( ... -- ... )
+\     ... ;
+\ overrides <selector>
+
+\ end-class name
+
+\ a class inherits all interfaces of its parent. An 'implementation'
+\ means that the class also implements the specified interface (If the
+\ interface is already implemented by the parent class, an
+\ 'implementation' phrase resets the methods to the defaults.
+
+\ 'overrides' can also be used to override interface methods. It has
+\ to be used after announcing the 'implementation' of the
+\ interface. Apart from this, 'implementation' can be freely mixed
+\ with the other stuff (but I recommend to put all 'implementation'
+\ phrases at the beginning of the class definition).
+
 \ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
 
 \ needs struct.fs
@@ -108,15 +151,29 @@
 : -rot ( a b c -- c a b )
     rot rot ;
 
+: under+ ( a b c -- a+b c )
+    rot + swap ;
+
 : perform ( ... addr -- ... )
     @ execute ;
 
+: ?dup-if ( compilation: -- orig ; run-time: n -- n|  )
+    POSTPONE ?dup POSTPONE if ; immediate
+
 : save-mem	( addr1 u -- addr2 u ) \ gforth
     \ copy a memory block into a newly allocated region in the heap
     swap >r
     dup allocate throw
     swap 2dup r> -rot move ;
 
+: resize ( a-addr1 u -- a-addr2 ior ) \ gforth
+    over
+    if
+	resize
+    else
+	nip allocate
+    then ;
+
 : extend-mem	( addr1 u1 u -- addr addr2 u2 )
     \ extend memory block allocated from the heap by u aus
     \ the (possibly reallocated piece is addr2 u2, the extension is at addr )
@@ -126,164 +183,357 @@
 : 2,	( w1 w2 -- ) \ gforth
     here 2 cells allot 2! ;
 
-: const-field ( size1 align1 -- size2 align2 )
-    1 cells: field
-does> ( addr -- w )
-    @ + @ ;
+\ data structures
 
 struct
     1 cells: field object-map
 end-struct object-struct
 
 struct
-    2 cells: field class-map
-    const-field class-instance-size \ aus
-    const-field class-instance-align \ aus
+    2 cells: field interface-map
+    1 cells: field interface-map-offset \ aus
+      \ difference between where interface-map points and where
+      \ object-map points (0 for non-classes)
+    1 cells: field interface-offset \ aus
+      \ offset of interface map-pointer in class-map (0 for classes)
+end-struct interface-struct
+
+interface-struct
+    1 cells: field class-parent
+    1 cells: field class-wordlist \ instance variables and other private words
+    2 cells: field class-inst-size \ size and alignment
 end-struct class-struct
 
-2variable current-map \ address and size (in aus) of the current map
+struct
+    1 cells: field selector-offset \ the offset within the (interface) map
+    1 cells: field selector-interface \ the interface offset
+end-struct selector-struct
+
+\ maps are not defined explicitly; they have the following structure:
 
-: class ( class -- size align )
-    dup class-map 2@ save-mem current-map 2!
-    dup class-instance-size
-    swap class-instance-align ;
+\ pointers to interface maps (for classes) <- interface-map points here
+\ interface/class-struct pointer           <- (object-)map  points here
+\ xts of methods 
 
-: end-class ( size align "name" -- )
-    create
-    current-map 2@ 2,
-    swap , , ;
+
+\ code
+
+\ selectors and methods
+
+variable current-interface
 
 : no-method ( -- )
-    abort" no method defined" ;
+    true abort" no method defined for this object/selector combination" ;
 
-: method ( xt "name" -- )
-    \ define method and selector
-    current-map 2@ ( xt map-addr map-size )
-    create dup ,
-    1 cells extend-mem current-map 2!
-    !
+: do-class-method ( -- )
+does> ( ... object -- ... )
+    ( object )
+    selector-offset @ over object-map @ + ( object xtp ) perform ;
+
+: do-interface-method ( -- )
 does> ( ... object -- ... )
-    ( object addr )
-    @ over ( object-map ) @ + ( object xtp ) perform ;
+    ( object selector-body )
+    2dup selector-interface @ ( object selector-body object interface-offset )
+    swap object-map @ + @ ( object selector-body map )
+    swap selector-offset @ + perform ;
+
+: method ( xt "name" -- )
+    \ define selector with method xt
+    create
+    current-interface @ interface-map 2@ ( xt map-addr map-size )
+    dup current-interface @ interface-map-offset @ - ,
+    1 cells extend-mem current-interface @ interface-map 2! ! ( )
+    current-interface @ interface-offset @ dup ,
+    ( 0<> ) if
+	do-interface-method
+    else
+	do-class-method
+    then ;
 
 : selector ( "name" -- )
     \ define a method selector for later overriding in subclasses
     ['] no-method method ;
 
-: override! ( xt method-xt -- )
-    >body @ current-map 2@ drop + ! ;
+: interface-override! ( xt sel-xt interface-map -- )
+    \ xt is the new method for the selector sel-xt in interface-map
+    swap >body ( xt map selector-body )
+    selector-offset @ + ! ;
+
+: class->map ( class -- map )
+    \ compute the (object-)map for the class
+    dup interface-map 2@ drop swap interface-map-offset @ + ;
+
+: unique-interface-map ( class-map offset -- )
+    \ if the interface at offset in class map is the same as its parent,
+    \ copy it to make it unique; used for implementing a copy-on-write policy
+    over @ class-parent @ class->map ( class-map offset parent-map )
+    over + @ >r  \ the map for the interface for the parent
+    + dup @ ( mapp map )
+    dup r> =
+    if
+	@ interface-map 2@ save-mem drop
+	swap !
+    else
+	2drop
+    then ;
+
+: class-override! ( xt sel-xt class-map -- )
+    \ xt is the new method for the selector sel-xt in class-map
+    over >body ( xt sel-xt class-map selector-body )
+    selector-interface @ ( xt sel-xt class-map offset )
+    ?dup-if \ the selector is for an interface
+	2dup unique-interface-map
+	+ @
+    then
+    interface-override! ;
 
 : overrides ( xt "selector" -- )
-    \ replace default method "method" with xt
-    ' override! ;
+    \ replace default method "method" in the current class with xt
+    \ must not be used during an interface definition
+    ' current-interface @ class->map class-override! ;
+
+\ interfaces
+
+\ every interface gets a different offset; the latest one is stored here
+variable last-interface-offset 0 last-interface-offset !
+
+: interface ( -- )
+    interface-struct struct-allot >r
+    0 0 r@ interface-map 2!
+    -1 cells last-interface-offset +!
+    last-interface-offset @ r@ interface-offset !
+    0 r@ interface-map-offset !
+    r> current-interface ! ;
+
+: end-interface-noname ( -- interface )
+    current-interface @ ;
+
+: end-interface ( "name" -- )
+    \ name execution: ( -- interface )
+    end-interface-noname constant ;
+
+\ classes
+
+: add-class-order ( n1 class -- wid1 ... widn n+n1 )
+    dup >r class-parent @
+    ?dup-if
+	recurse \ first add the search order for the parent class
+    then
+    r> class-wordlist @ swap 1+ ;
+
+: push-order ( class -- )
+    \ add the class's wordlist to the search-order (in front)
+    >r get-order r> add-class-order set-order ;
+
+: class ( parent-class -- size align )
+    class-struct struct-allot >r
+    dup interface-map 2@ save-mem r@ interface-map 2!
+    dup interface-map-offset @ r@ interface-map-offset !
+    r@ dup class->map !
+    0 r@ interface-offset !
+    dup r@ class-parent !
+    wordlist r@ class-wordlist !
+    r@ current-interface !
+    r> push-order
+    class-inst-size 2@ ;
+
+: remove-class-order ( wid1 ... widn n+n1 class -- n1 )
+    \ note: no checks, whether the wordlists are correct
+    begin
+	>r nip 1-
+	r> class-parent @ dup 0=
+    until
+    drop ;
+
+: drop-order ( class -- )
+    \ note: no checks, whether the wordlists are correct
+    >r get-order r> remove-class-order set-order ;
+
+: end-class-noname ( size align -- class )
+    current-interface @ dup drop-order class-inst-size 2!
+    end-interface-noname ;
+
+: end-class ( size align "name" -- )
+    \ name execution: ( -- class )
+    end-class-noname constant ;
 
-: alloc-instance ( class -- object )
-    \ make a new, (almost) uninitialized instance of a class
-    dup class-instance-size allocate throw
-    swap class-map 2@ drop over ( object-map ) ! ;
+\ visibility control
+
+variable public-wordlist
+
+: private ( -- )
+    current-interface @ class-wordlist @
+    dup get-current <>
+    if \ we are not private already
+	get-current public-wordlist !
+    then
+    set-current ;
+
+: public ( -- )
+    public-wordlist @ set-current ;
+
+\ classes that implement interfaces
+
+: front-extend-mem ( addr1 u1 u -- addr addr2 u2 )
+    \ extend memory block allocated from the heap by u aus, with the
+    \ old stuff coming at the end
+    2dup + dup >r allocate throw ( addr1 u1 u addr2 ; R: u2 )
+    dup >r + >r over r> rot move ( addr1 ; R: u2 addr2 )
+    free throw
+    r> dup r> ;
+    
+: implementation ( interface -- )
+    dup interface-offset @ ( interface offset )
+    current-interface @ interface-map-offset @ negate over - dup 0>
+    if \ the interface does not fit in the present class-map
+	>r current-interface @ interface-map 2@
+	r@ front-extend-mem
+	current-interface @ interface-map 2!
+	r@ erase
+	dup negate current-interface @ interface-map-offset !
+	r>
+    then ( interface offset n )
+    drop >r
+    interface-map 2@ save-mem drop ( map )
+    current-interface @ dup interface-map 2@ drop
+    swap interface-map-offset @ + r> + ! ;
 
 \ this/self, instance variables etc.
 
-variable thisp
-: this ( -- object )
-    \ rename this into self if you are a Smalltalk fiend
-    thisp @ ;
+\ rename "this" into "self" if you are a Smalltalk fiend
+0 value this ( -- object )
+: to-this ( object -- )
+    TO this ;
+
+\ another implementation, if you don't have (fast) values
+\ variable thisp
+\ : this ( -- object )
+\     thisp @ ;
+\ : to-this ( object -- )
+\     thisp ! ;
 
 : m: ( -- xt colon-sys ) ( run-time: object -- )
     :noname 
     POSTPONE this
     POSTPONE >r
-    POSTPONE thisp
-    POSTPONE ! ;
+    POSTPONE to-this ;
 
 : ;m ( colon-sys -- ) ( run-time: -- )
     POSTPONE r>
-    POSTPONE thisp
-    POSTPONE !
+    POSTPONE to-this
     POSTPONE ; ; immediate
 
 : catch ( ... xt -- ... n )
     \ make it safe to call CATCH within a method.
     \ should also be done with all words containing CATCH.
-    this >r catch r> thisp ! ;
+    this >r catch r> to-this ;
+
+\ the following is a bit roundabout; this is caused by the standard
+\ disallowing to change the compilation wordlist between CREATE and
+\ DOES> (see RFI 3)
+
+: inst-something ( size1 align1 size align xt "name" -- size2 align2 )
+    \ xt ( -- ) typically is for a DOES>-word
+    get-current >r
+    current-interface @ class-wordlist @ set-current
+    >r create-field r> execute
+    r> set-current ;
 
-: inst-var ( size1 align1 size align -- size2 align2 )
-    field
-does> ( -- addr )
+: do-inst-var ( -- )
+does> \ name execution: ( -- addr )
     ( addr1 ) @ this + ;
 
+: inst-var ( size1 align1 size align "name" -- size2 align2 )
+    \ name execution: ( -- addr )
+    ['] do-inst-var inst-something ;
+
+: do-inst-value ( -- )
+does> \ name execution: ( -- w )
+    ( addr1 ) @ this + @ ;
+
+: inst-value ( size1 align1 "name" -- size2 align2 )
+    \ name execution: ( -- w )
+    \ a cell-sized value-flavoured instance field
+    1 cells: ['] do-inst-value inst-something ;
+
+: <to-inst> ( w xt -- )
+    >body @ this + ! ;
+
+: to-inst ( w "name" -- )
+    ' <to-inst> ;
+
+: [to-inst] ( compile-time: "name" -- ; run-time: w -- )
+    ' >body @ POSTPONE literal
+    POSTPONE this
+    POSTPONE +
+    POSTPONE ! ; immediate
+
 \ early binding stuff
 
 \ this is not generally used, only where you want to do something like
 \ superclass method invocation (so that you don't have to name your methods)
 
-: (bind) ( class method-xt -- xt )
-    >body @ swap class-map 2@ drop + @ ;
+: <bind> ( class selector-xt -- xt )
+    >body swap class->map over selector-interface @
+    ?dup-if
+	+ @
+    then
+    swap selector-offset @ + @ ;
 
-: bind' ( "class" "method" -- xt )
-    ' >body ' (bind) ;
+: bind' ( "class" "selector" -- xt )
+    ' execute ' <bind> ;
 
-: bind ( ... object "class" "method" -- ... )
+: bind ( ... object "class" "selector" -- ... )
     bind' execute ;
 
-: [bind] ( compile-time: "class" "method" -- ; run-time: ... object -- ... )
+: [bind] ( compile-time: "class" "selector" -- ; run-time: ... object -- ... )
     bind' compile, ; immediate
 
+: [super] ( compile-time: "selector" -- ; run-time: ... object -- ... )
+    \ same as `[bind] "parent" "selector"', where "parent" is the
+    \ parent class of the current class
+    current-interface @ class-parent @ ' <bind> compile, ; immediate
+
 \ the object class
 
-0 0 save-mem current-map 2!
-object-struct \ no class to inherit from, so we have to do this manually
+\ because OBJECT has no parent class, we have to build it by hand
+\ (instead of with class)
+
+wordlist
+here current-interface !
+current-interface 1 cells save-mem 2, \ map now contains a pointer to class
+0 ,
+0 , 
+0 , \ parent
+, \ wordlist
+object-struct 2, \ instance size
+object-struct
+
 :noname ( object -- )
-    ." object:" dup . ." class:" object-map @ . ;
+    drop ;
+method construct ( ... object -- )
+
+:noname ( object -- )
+    ." object:" dup . ." class:" object-map @ @ . ;
 method print
-end-class object
 
-\ examples
-true [if]
-cr object alloc-instance print
+end-class object
 
-object class
-:noname ( object -- )
-    drop ." undefined" ;
-overrides print
-end-class nothing
-
-nothing alloc-instance constant undefined
-
-cr undefined print
-
-\ instance variables and this
-object class
-1 cells: inst-var count-n
-m: ( object -- )
-    count-n @ . ;m
-overrides print
-m: ( object -- )
-   0 count-n ! ;m
-method init
-m: ( object -- )
-    1 count-n +! ;m
-method inc
-end-class counter
-
-counter alloc-instance constant counter1
-
-cr
-counter1 init
-counter1 print
-counter1 inc
-counter1 print
-counter1 inc
-counter1 inc
-counter1 inc
-counter1 print
-counter1 print
-
-\ examples of static binding
-
-cr undefined bind object print
-: object-print ( object -- )
-    [bind] object print ;
+\ constructing objects
 
-cr undefined object-print
-[then]
+: init-object ( ... class object -- )
+    swap class->map over object-map ! ( ... object )
+    construct ;
+
+: xt-new ( ... class xt -- object )
+    \ makes a new object, using XT ( size align -- addr ) to allocate memory
+    over class-inst-size 2@ rot execute
+    dup >r init-object r> ;
+
+: dict-new ( ... class -- object )
+    \ makes a new object HERE in dictionary
+    ['] struct-allot xt-new ;
+
+: heap-new ( ... class -- object )
+    \ makes a new object in ALLOCATEd memory
+    ['] struct-alloc xt-new ;