ref: ca455597fd9acdc4f1b86e1cb62ee294a4c3bde9
dir: /softwords/oo.fr/
\ ** ficl/softwords/oo.fr
\ ** F I C L O - O E X T E N S I O N S
\ ** john sadler aug 1998
.( loading ficl O-O extensions ) cr
17 ficl-vocabulary oop
also oop definitions
\ Design goals:
\ 0. Traditional OOP: late binding by default for safety.
\ Early binding if you ask for it.
\ 1. Single inheritance
\ 2. Object aggregation (has-a relationship)
\ 3. Support objects in the dictionary and as proxies for
\ existing structures (by reference):
\ *** A ficl object can wrap a C struct ***
\ 4. Separate name-spaces for methods - methods are
\ only visible in the context of a class / object
\ 5. Methods can be overridden, and subclasses can add methods.
\ No limit on number of methods.
\ General info:
\ Classes are objects, too: all classes are instances of METACLASS
\ All classes are derived (by convention) from OBJECT. This
\ base class provides a default initializer and superclass
\ access method
\ A ficl object binds instance storage (payload) to a class.
\ object ( -- instance class )
\ All objects push their payload address and class address when
\ executed. All objects have this footprint:
\ cell 0: first payload cell
\ A ficl class consists of a parent class pointer, a wordlist
\ ID for the methods of the class, and a size for the payload
\ of objects created by the class. A class is an object.
\ The NEW method creates and initializes an instance of a class.
\ Classes have this footprint:
\ cell 0: parent class address
\ cell 1: wordlist ID
\ cell 2: size of instance's payload
\ Methods expect an object couple ( instance class )
\ on the stack.
\ Overridden methods must maintain the same stack signature as
\ their predecessors. Ficl has no way of enforcing this, though.
user current-class
0 current-class !
\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ ** L A T E B I N D I N G
\ Compile the method name, and code to find and
\ execute it at run-time...
\ parse-method compiles the method name so that it pushes
\ the string base address and count at run-time.
\
: parse-method \ name run: ( -- c-addr u )
parse-word
postpone sliteral
; compile-only
: lookup-method ( class c-addr u -- class xt )
2dup
local u
local c-addr
end-locals
2 pick cell+ @ ( -- class c-addr u wid )
search-wordlist ( -- class 0 | xt 1 | xt -1 )
0= if
c-addr u type ." not found in "
body> >name type
cr abort
endif
;
: exec-method ( instance class c-addr u -- <method-signature> )
lookup-method execute
;
: find-method-xt \ name ( class -- class xt )
parse-word lookup-method
;
\ Method lookup operator takes a class-addr and instance-addr
\ and executes the method from the class's wordlist if
\ interpreting. If compiling, bind late.
\
: --> ( instance class -- ??? )
state @ 0= if
find-method-xt execute
else
parse-method postpone exec-method
endif
; immediate
\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ ** E A R L Y B I N D I N G
\ Early binding operator compiles code to execute a method
\ given its class at compile time. Classes are immediate,
\ so they leave their cell-pair on the stack when compiling.
\ Example:
\ : get-wid metaclass => .wid @ ;
\ Usage
\ my-class get-wid ( -- wid-of-my-class )
\
: => \ c:( class meta -- ) run: ( -- ??? ) invokes compiled method
drop find-method-xt compile, drop
; immediate compile-only
\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ ** I N S T A N C E V A R I A B L E S
\ Instance variables (IV) are represented by words in the class's
\ private wordlist. Each IV word contains the offset
\ of the IV it represents, and runs code to add that offset
\ to the base address of an instance when executed.
\ The metaclass SUB method, defined below, leaves the address
\ of the new class's offset field and its initial size on the
\ stack for these words to update. When a class definition is
\ complete, END-CLASS saves the final size in the class's size
\ field, and restores the search order and compile wordlist to
\ prior state. Note that these words are hidden in their own
\ wordlist to prevent accidental use outside a SUB END-CLASS pair.
\
1 ficl-named-wordlist instance-vars
instance-vars @ constant instance-vars
instance-vars dup >search ficl-set-current
: do-instance-var
does> ( instance class addr[offset] -- addr[field] )
nip @ +
;
: addr-units: ( offset size "name" -- offset' )
create over , +
do-instance-var
;
: chars: \ ( offset nCells "name" -- offset' ) Create n char member.
chars addr-units: ;
: char: \ ( offset nCells "name" -- offset' ) Create 1 char member.
1 chars: ;
: cells: ( offset nCells "name" -- offset' )
cells >r aligned r> addr-units:
;
: cell: ( offset nCells "name" -- offset' )
1 cells: ;
\ Aggregate an object into the class...
\ Needs the class of the instance to create
\ Example: object obj: m_obj
\
: do-aggregate
does> ( instance class pfa -- a-instance a-class )
2@ ( inst class a-class a-offset )
2swap drop ( a-class a-offset inst )
+ swap ( a-inst a-class )
;
: obj: ( offset class meta "name" -- offset' )
locals| meta class offset |
create offset , class ,
class meta --> get-size offset +
do-aggregate
;
\ Aggregate an array of objects into a class
\ Usage example:
\ 3 my-class array: my-array
\ Makes an instance variable array of 3 instances of my-class
\ named my-array.
\
: array: ( offset n class meta "name" -- offset' )
locals| meta class nobjs offset |
create offset , class ,
class meta --> get-size nobjs * offset +
do-aggregate
;
\ Aggregate a pointer to an object: REF is a member variable
\ whose class is set at compile time. This is useful for wrapping
\ data structures in C, where there is only a pointer and the type
\ it refers to is known. If you want polymorphism, see c_ref
\ in classes.fr. REF is only useful for pre-initialized structures,
\ since there's no supported way to set one.
: ref: ( offset class meta "name" -- offset' )
locals| meta class offset |
create offset , class ,
offset cell+
does> ( inst class pfa -- ptr-inst ptr-class )
2@ ( inst class ptr-class ptr-offset )
2swap drop + @ swap
;
\ END-CLASS terminates construction of a class by storing
\ the size of its instance variables in the class's size field
\ ( -- old-wid addr[size] 0 )
\
: end-class ( old-wid addr[size] size -- )
swap ! set-current
search> drop \ pop struct builder wordlist
;
\ See resume-class (a metaclass method) below for usage
\ This is equivalent to end-class for now, but that will change
\ when we support vtable bindings.
: suspend-class ( old-wid addr[size] size -- ) end-class ;
set-current previous
\ E N D I N S T A N C E V A R I A B L E S
\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ D O - D O - I N S T A N C E
\ Makes a class method that contains the code for an
\ instance of the class. This word gets compiled into
\ the wordlist of every class by the SUB method.
\ PRECONDITION: current-class contains the class address
\ why use a state variable instead of the stack?
\ >> Stack state is not well-defined during compilation (there are
\ >> control structure match codes on the stack, of undefined size
\ >> easiest way around this is use of this thread-local variable
\
: do-do-instance ( -- )
s" : .do-instance does> [ current-class @ ] literal ;"
evaluate
;
\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ ** M E T A C L A S S
\ Every class is an instance of metaclass. This lets
\ classes have methods that are different from those
\ of their instances.
\ Classes are IMMEDIATE to make early binding simpler
\ See above...
\
:noname
wordlist
create
immediate
0 , \ NULL parent class
dup , \ wid
3 cells , \ instance size
ficl-set-current
does> dup
; execute metaclass
\ now brand OBJECT's wordlist (so that ORDER can display it by name)
metaclass drop cell+ @ brand-wordlist
metaclass drop current-class !
do-do-instance
\
\ C L A S S M E T H O D S
\
instance-vars >search
create .super ( class metaclass -- parent-class )
0 cells , do-instance-var
create .wid ( class metaclass -- wid ) \ return wid of class
1 cells , do-instance-var
create .size ( class metaclass -- size ) \ return class's payload size
2 cells , do-instance-var
previous
: get-size metaclass => .size @ ;
: get-wid metaclass => .wid @ ;
: get-super metaclass => .super @ ;
\ create an uninitialized instance of a class, leaving
\ the address of the new instance and its class
\
: instance ( class metaclass "name" -- instance class )
locals| meta parent |
create
here parent --> .do-instance \ ( inst class )
parent meta metaclass => get-size
allot \ allocate payload space
;
\ create an uninitialized array
: array ( n class metaclass "name" -- n instance class )
locals| meta parent nobj |
create nobj
here parent --> .do-instance \ ( nobj inst class )
parent meta metaclass => get-size
nobj * allot \ allocate payload space
;
\ create an initialized instance
\
: new \ ( class metaclass "name" -- )
metaclass => instance --> init
;
\ create an initialized array of instances
: new-array ( n class metaclass "name" -- )
metaclass => array
--> array-init
;
\ Create an anonymous initialized instance from the heap
: alloc \ ( class metaclass -- instance class )
locals| meta class |
class meta metaclass => get-size allocate ( -- addr fail-flag )
abort" allocate failed " ( -- addr )
class 2dup --> init
;
\ Create an anonymous array of initialized instances from the heap
: alloc-array \ ( n class metaclass -- instance class )
locals| meta class nobj |
class meta metaclass => get-size
nobj * allocate ( -- addr fail-flag )
abort" allocate failed " ( -- addr )
nobj over class --> array-init
class
;
\ create a proxy object with initialized payload address given
: ref ( instance-addr class metaclass "name" -- )
drop create , ,
does> 2@
;
\ suspend-class and resume-class help to build mutually referent classes.
\ Example:
\ object subclass c-akbar
\ suspend-class ( put akbar on hold while we define jeff )
\ object subclass c-jeff
\ c-akbar ref: .akbar
\ ( and whatever else comprises this class )
\ end-class ( done with c-jeff )
\ c-akbar --> resume-class
\ c-jeff ref: .jeff
\ ( and whatever else goes in c-akbar )
\ end-class ( done with c-akbar )
\
: resume-class { 2this -- old-wid addr[size] size }
this --> .wid @ ficl-set-current ( old-wid )
this --> .size dup @ ( old-wid addr[size] size )
instance-vars >search
;
\ create a subclass
\ This method leaves the stack and search order ready for instance variable
\ building. Pushes the instance-vars wordlist onto the search order,
\ and sets the compilation wordlist to be the private wordlist of the
\ new class. The class's wordlist is deliberately NOT in the search order -
\ to prevent methods from getting used with wrong data.
: sub ( class metaclass "name" -- old-wid addr[size] size )
wordlist
locals| wid meta parent |
parent meta metaclass => get-wid
wid wid-set-super \ set superclass
create immediate \ get the subclass name
wid brand-wordlist \ label the subclass wordlist
here current-class ! \ prep for do-do-instance
parent , \ save parent class
wid , \ save wid
here parent meta --> get-size dup , ( addr[size] size )
metaclass => .do-instance
wid ficl-set-current -rot
do-do-instance
instance-vars >search \ push struct builder wordlist
;
\ OFFSET-OF returns the offset of an instance variable
\ from the instance base address. If the next token is not
\ the name of in instance variable method, you get garbage
\ results -- there is no way at present to check for this error.
: offset-of ( class metaclass "name" -- offset )
drop find-method-xt nip >body @ ;
\ ID returns the string name cell-pair of its class
: id ( class metaclass -- c-addr u )
drop body> >name ;
\ list methods of the class
: methods \ ( class meta -- )
locals| meta class |
begin
class body> >name type ." methods:" cr
class meta --> get-wid >search words cr previous
class meta metaclass => get-super
dup to class
0= until cr
;
\ list class's ancestors
: pedigree ( class meta -- )
locals| meta class |
begin
class body> >name type space
class meta metaclass => get-super
dup to class
0= until cr
;
\ decompile a method
: see ( class meta -- )
metaclass => get-wid >search see previous ;
set-current
\ E N D M E T A C L A S S
\ META is a nickname for the address of METACLASS...
metaclass drop
constant meta
\ SUBCLASS is a nickname for a class's SUB method...
\ Subclass compilation ends when you invoke end-class
\ This method is late bound for safety...
: subclass --> sub ;
\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ ** O B J E C T
\ Root of all classes
:noname
wordlist
create immediate
0 , \ NULL parent class
dup , \ wid
0 , \ instance size
ficl-set-current
does> meta
; execute object
\ now brand OBJECT's wordlist (so that ORDER can display it by name)
object drop cell+ @ brand-wordlist
object drop current-class !
do-do-instance
\ O B J E C T M E T H O D S
\ Convert instance cell-pair to class cell-pair
\ Useful for binding class methods from an instance
: class ( instance class -- class metaclass )
nip meta ;
\ default INIT method zero fills an instance
: init ( instance class -- )
meta
metaclass => get-size ( inst size )
erase ;
\ Apply INIT to an array of NOBJ objects...
\
: array-init ( nobj inst class -- )
0 dup locals| &init &next class inst |
\
\ bind methods outside the loop to save time
\
class s" init" lookup-method to &init
s" next" lookup-method to &next
drop
0 ?do
inst class 2dup
&init execute
&next execute drop to inst
loop
;
\ free storage allocated to a heap instance by alloc or alloc-array
\ NOTE: not protected against errors like FREEing something that's
\ really in the dictionary.
: free \ ( instance class -- )
drop free
abort" free failed "
;
\ Instance aliases for common class methods
\ Upcast to parent class
: super ( instance class -- instance parent-class )
meta metaclass => get-super ;
: pedigree ( instance class -- )
object => class
metaclass => pedigree ;
: size ( instance class -- sizeof-instance )
object => class
metaclass => get-size ;
: methods ( instance class -- )
object => class
metaclass => methods ;
\ Array indexing methods...
\ Usage examples:
\ 10 object-array --> index
\ obj --> next
\
: index ( n instance class -- instance[n] class )
locals| class inst |
inst class
object => class
metaclass => get-size * ( n*size )
inst + class ;
: next ( instance[n] class -- instance[n+1] class )
locals| class inst |
inst class
object => class
metaclass => get-size
inst +
class ;
: prev ( instance[n] class -- instance[n-1] class )
locals| class inst |
inst class
object => class
metaclass => get-size
inst swap -
class ;
set-current
\ E N D O B J E C T
previous definitions