plusplus.txt

汇编编程艺术

MASM++ OVERVIEW:

MASM++ is a methodology used to make Microsoft (c) Macro Assembler 6.00
behave as if it supported object oriented programming (OOP).   MASM was
chosen for this project because, regardless of its shortcomings, MASM
is going to be around for a long time.  It is also a well funded project,
that has received many important upgrades.  One particularly useful
advantage that MASM 6.00 has, is local identifiers.

Local identifiers within procedures and structures is much of what
makes MASM++ possible.  Though this might not seem like much to the
assembly language programmer, this feature is crucial to the success
of OOP.  

Some of the object oriented features that we currently support are:

- virtual functions
- inheritance
- data and method encapsulation
- name overloading

As we know, assembly language has not traditionally been thought of
as a target for OOP, but there really is no reason that it shouldn't
be.  It only requires that the programmer use a little restraint to
avoid defeating the features of object oriented programming. 

The real key to the system is the .a files.  These are similar to 
the .h files of C++, in that they contain the class specification,
but not the class implementation.   A typical MASM++ file will look 
something like this:

include  c:\stdlib\stdlib.a

;
; sample : baseobj	A MASM++ object that explains .a files
;			Written by Michael A. Griffith
;
; Modification List:
;
; 26 Oct 91  Michael A. Griffith:
;	     Created.
;


sample__methods		STRUC
			new		DW	PROC PTR sample__new
			constructor	DW	PROC PTR sample__constructor
			destructor	DW	PROC PTR sample__destructor
			delete		DW	PROC PTR baseobj__delete
			printself	DW	PROC PTR sample__print
			name		DW	PROC PTR sample__name
			; Keep these in the same order as in baseobj.
			; All classes need this primative set of operations.
			; Add additional methods here.
			addedmethod1	DW	PROC PTR sample__addedmethod1
			addedmethod2	DW	PROC PTR sample__addedmethod2
sample__methods		ENDS

sample__data		STRUC
			; Add any class data objects here
			; 
			data1		DB	?
			data2		DB	?
			data3		DB	?
sample__data		ENDS

sample			STRUC
			methods		sample__methods	
			data		sample__data
			parent		baseobj__data
sample			ENDS


All MASM++ requires the stdlib package for assembly, available via
anonymous ftp from ucrmath.ucr.edu.  We include the header for
it in all files. 

The methods STRUC contains PROC PTRs to each of the functions in the
class.   Note that all objects have the minimal set of methods that
are defined in baseobj.a.  The order must be the same for all classes,
so it is best to just copy the baseobj.a file and add to it as necessary.
We can either write methods for the class, as we did with new,
or inherit them as we did with delete.  The name with the underscores
is the real name of the function, as it is written, while the
shorter name is the virtual name which it is called with.

The data STRUC contains all of the class data.  Three examples have
been included.

The object STRUCT defines what the object looks like.  It has three
components for all objects, regardless of what they do:

- methods
- data
- parent information

The order is important due to the ways that we do virtual functions,
and inheritance.

Assume that we have the .a file written as above.  We would still
need to write the methods in our .asm file.  A trivial example would
contain:

.
.
.
Sample__addedmethod1	PROC
			ret
Sample__addedmethod1	ENDP


Sample__addedmethod2	PROC
			ret
Sample__addedmethod2	ENDP
.
.
.

At least minimal functions would have to be written (or inherited) for
all methods defined in the .a file.  Assuming that we had completed that,
we would be ready to use our object:


_EXPRESSD	SEGMENT PARA PUBLIC 'DATA'
		sobjptr		DWORD PTR	;Pointer to object
		sobj		sample		;Static object
_EXPRESSD	ENDS

_EXPRESSC	SEGMENT PARA PUBLIC 'CODE'

		les	di, sobj		;Static example
		call	es:di.constructor
		.
		.
		.
		call	es:di.name
		call	es:di.addedmethod1
		.
		.
		.
		call	es:di.destructor



		les	di, sobjptr
		call	sample__new		;Dynamic example
		call	es:di.constructor
		.
		.
		.
		call	es:di.name
		call	es:di.addedmethod1
		.
		.
		.
		call	es:di.destructor
		call	es:di.delete
	
_EXPRESSC	ENDS