ENUM example and request for ideas.

[hutch--]

I have on and off been looking for a method of duplicating the "typedef enum" data structures in C as it would make a number of extra structures available.

I found a posting by Ultrano from 2007 that has a useful if undocumented technique for MASM where you can use a structure to hold sequential values. Now the test piece below show the experiments done with this technique but as it has been many years since I used an "enum" data structure, I wonder if the method used in the example below is of any real use. If you load the structure members without allocating a structure in either the .DATA section or as a LOCAL variable, the order is treated like a sequence of constants if the structure uses BYTE sized members.

This is the test piece.

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IF 0  ; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
                      Build this template with "CONSOLE ASSEMBLE AND LINK"
ENDIF ; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

    include \masm32\include\masm32rt.inc

    ENUM TEXTEQU <STRUCT>

    BIDI_TYPE ENUM
      BIDI_NULL     db ?    ; = 0
      BIDI_INT      db ?    ; = 1
      BIDI_FLOAT    db ?    ; = 2
      BIDI_BOOL     db ?    ; = 3
      BIDI_STRING   db ?    ; = 4
      BIDI_TEXT     db ?    ; = 5
      BIDI_ENUM     db ?    ; = 6
      BIDI_BLOB     db ?    ; = 7
    BIDI_TYPE ENDS

    MYSTRUCT STRUCT
      bidi BIDI_TYPE <>
      var1 dd ?
      var2 dd ?
    MYSTRUCT ENDS

    .code

start:
   
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

    call main
    inkey
    exit

; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

main proc

    LOCAL mstr  :MYSTRUCT

    mov mstr.var1, 1234
    print ustr$(mstr.var1),13,10,13,10

    mov mstr.bidi.BIDI_NULL, MYSTRUCT.bidi.BIDI_NULL    ; copy constant to memory
    movzx eax, BYTE PTR mstr.bidi.BIDI_NULL

    print ustr$(eax),13,10,13,10

    print ustr$(MYSTRUCT.bidi.BIDI_TEXT),13,10,13,10

    print ustr$(BIDI_TYPE.BIDI_NULL),13,10
    print ustr$(BIDI_TYPE.BIDI_INT),13,10
    print ustr$(BIDI_TYPE.BIDI_FLOAT),13,10
    print ustr$(BIDI_TYPE.BIDI_BOOL),13,10
    print ustr$(BIDI_TYPE.BIDI_STRING),13,10
    print ustr$(BIDI_TYPE.BIDI_TEXT),13,10
    print ustr$(BIDI_TYPE.BIDI_ENUM),13,10
    print ustr$(BIDI_TYPE.BIDI_BLOB),13,10

    ret

main endp


; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

end start


[dedndave]

my understanding of enumerations is that they are like having a structure of EQUates
defining them as data bytes (or words or dwords) doesn't seem to quite fill the bill
and, it takes up data space   :P

at any rate, they are often parameters in INVOKE, so DB isn't good without first expanding them

[hutch--]

If you look at the line of code,

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    mov mstr.bidi.BIDI_NULL, MYSTRUCT.bidi.BIDI_NULL    ; copy constant to memory


You will see that its not the case. "mstr.bidi.BIDI_NULL" is a memory operand where the direct structure reference "MYSTRUCT.bidi.BIDI_NULL" functions as an immediate.

[MichaelW]

Yes, the enumeration functionality does not depend on there being any data allocated.

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include \masm32\include\masm32rt.inc

ENUM STRUCT
    _NULL     db ?    ; = 0
    _INT      db ?    ; = 1
    _FLOAT    db ?    ; = 2
    _BOOL     db ?    ; = 3
    _STRING   db ?    ; = 4
    _TEXT     db ?    ; = 5
    _ENUM     db ?    ; = 6
    _BLOB     db ?    ; = 7
ENUM ENDS

.code
start:

    print ustr$(ENUM._NULL),13,10
    print ustr$(ENUM._INT),13,10
    print ustr$(ENUM._FLOAT),13,10
    print ustr$(ENUM._BOOL),13,10
    print ustr$(ENUM._STRING),13,10
    print ustr$(ENUM._TEXT),13,10
    print ustr$(ENUM._ENUM),13,10
    print ustr$(ENUM._BLOB),13,10
   
    inkey
    exit
end start


But this still seems like a clumsy way to do it. Is there some other benefit to having the structure definition that I'm just not seeing?

[hutch--]

I am trying to get them going because of the number of structures that include a "typedef enum" member.

The unallocated ENUM clearly works as a constant.

Code Select Expand



    LOCAL mstr  :MYSTRUCT

    mov al, MYSTRUCT.bidi.BIDI_BLOB
    movzx ecx, al
    print ustr$(ecx)," written to a BYTE sized register",13,10

    mov ax, MYSTRUCT.bidi.BIDI_BLOB
    movzx ecx, ax
    print ustr$(ecx)," written to a WORD sized register",13,10

    mov ecx, MYSTRUCT.bidi.BIDI_BLOB
    print ustr$(ecx)," written to a DWORD sized register",13,10,13,10

    mov mstr.bidi.BIDI_NULL, MYSTRUCT.bidi.BIDI_NULL    ; copy constant to memory
    movzx eax, BYTE PTR mstr.bidi.BIDI_NULL

    print ustr$(eax),13,10,13,10

    print ustr$(MYSTRUCT.bidi.BIDI_TEXT),13,10,13,10