tproc.txt

TPROC.EXE

Tproc is a jump table creation tool that has code replication capacity for
each code block. At its simplest it produces code of the following type
without the error prone problems of manually typing the table and matching
labels.

It will normally produce a procedure that takes a single numeric argument
which indicates which block of code is executed. The numeric range would
normally be sequential to avoid redundant code that it not used in the
procedure. You have the option of adding additional arguments if your
jump table design requires it.

The tool is used to produce procedures that will branch to a very large
number of diferent labels without having to sequentially compare them to
get the correct value first.

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align 4

default proc value:DWORD

  .data
    align 4
    deftbl \
      dd l0,l1,l2,l3
  .code

    mov eax, value
    cmp eax, 3
    ja error
    jmp DWORD PTR [deftbl+eax*4]

  align 4
  error:
    mov eax, -1
    jmp quit_default

  align 4
  l0:
    mov eax, 0
    jmp quit_default

  align 4
  l1:
    mov eax, 1
    jmp quit_default

  align 4
  l2:
    mov eax, 2
    jmp quit_default

  align 4
  l3:
    mov eax, 3
    jmp quit_default

  quit_default:

    ret

default endp

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It has input range control so that if a number beyond the range of the table is
passed to the procedure, it returns -1.

Within code of the following type the content between the start label and
the jump to the exit label is user defined and can be written in the edit
window of TPROC.

  l0:
  ; -----------------------
  ; user defined code goes here.
  ; -----------------------
    jmp quit_default

The default code when the tool opens is,

    mov eax, {num}

The only available variable in the code replication process is the label number
which can be inserted at any location in the user defined code by using the notation
{num}. The tool will replace {num} with the label number of the preceding label.

If the label number is 155, the inserted code with the default is,

    mov eax, 155

You can write any code you like in the edit control on the interface that will
work with the rest of the procedure and it will be replicated for every label
within the range of labels set in the interface. If your user defined code needs
to use any of EBX ESI or EDI, you can preserve any of the three registers from
the check boxes on the interface.

You can add additional parameters to the default "value" in normal MASM proc syntax
which you can use with your user defined code to make more complex procedures
automatically. You can treat the extra parameters as normal procedure parameters
and use them in your user defined code.

You can routinely include data in the user defined code and use the {num} variable
to make unique names for each data item.

; ----------------------------------------
    .data
      dat1{num} db "text1{num}",0
      dat2{num} db "text2{num}",0
      dat3{num} db "text3{num}",0
      dat4{num} db "text4{num}",0
      arr(num} dd dat1{num},dat2{num},dat3{num},dat4{num}
    .code
    mov eax, arr{num}
; ----------------------------------------

Code of this type will return the address of an array of zero terminated
strings that is unique for every label in the jump table.

This general technique gives very high speed access to what can be a very large
range of variables (thousands) with only the overhead of a single jump to the
label.