Расшифровка шестнадцатеричного кода в masm (проблема с нулевыми байтами)

Я пытаюсь декодировать шестнадцатеричную двоичную строку в masm, сначала я попробовал htodw, но это не декодировало ее правильно, поэтому я попробовал hex2bin, и этот, кажется, декодирует нормально, но у меня проблема с нулевыми байтами. Строка в шестнадцатеричной кодировке будет завершена первым нулевым байтом (0x00).

Вот мой пример кода:

.486
.model  flat, stdcall
option  casemap :none

include \masm32\include\windows.inc
include \masm32\include\masm32.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\masm32.lib
includelib \masm32\lib\user32.lib

.data
; this string is "test(NULL BYTE)test", but the messagebox only shows "test"
var_hex db "746573740074657374",0 

multitable \
    db 0,0,0,0,0,0,0,0,0,0,2,0,0,2,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 2,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0
    db 1,1,1,1,1,1,1,1,1,1,0,3,0,0,0,0
    db 0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

    ; 0 = unacceptable character
    ; 1 = acceptable characters   (0 to 9, A to F, a to f)
    ; 2 = ignored characters      (space, minus and CRLF)
    ; 3 = comment character       ( ; )

    ; 1st offset table
    db 00h,10h,20h,30h,40h,50h,60h,70h,80h,90h,0,0,0,0,0,0      ; 63
    db 00h,0A0h,0B0h,0C0h,0D0h,0E0h,0F0h,0,0,0,0,0,0,0,0,0      ; 79
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0                          ; 95
    db 00h,0A0h,0B0h,0C0h,0D0h,0E0h,0F0h

    ; 2nd offset table
    db 00h,01h,02h,03h,04h,05h,06h,07h,08h,09h,0,0,0,0,0,0      ; 63
    db 00h,0Ah,0Bh,0Ch,0Dh,0Eh,0Fh,0,0,0,0,0,0,0,0,0            ; 79
    db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0                          ; 95
    db 00h,0Ah,0Bh,0Ch,0Dh,0Eh,0Fh

    ; add 256 for allowable character table
    ; sub 48 from 1st offset table
    ; add 7 for the second BYTE

.data?
var dd ?

.code
main:
    Invoke hex2bin, addr var_hex, addr var

    Invoke MessageBoxA,0,addr var,0,0

    invoke ExitProcess, 0


    ; hex2bin
    align 4

    hex2bin proc src:DWORD,dst:DWORD

    comment * ---------------------------------
            EAX and EBX are unused in loop code
            --------------------------------- *

        push ebx
        push esi
        push edi
        push ebp

        mov esi, src
        mov edi, dst

        xor ebp, ebp

        jmp h2b                             ; mispredicted only once

      align 4
      stripcomment:
        add esi, 1
        cmp BYTE PTR [esi], 10
        jb zerofound                        ; < 10 = 0
        jne stripcomment                    ; loop if not 10
      align 4
      pre:
        add esi, 1
      align 4
      h2b:
        movzx ebp, BYTE PTR [esi]           ; zero extend 1st byte into EBP
        cmp BYTE PTR [ebp+multitable], 2    ; 1st compare short circuit on ignored characters
        je pre                              ; predicted backwards
        movzx edx, BYTE PTR [esi+1]         ; zero extend 2nd BYTE into EDX
        ja stripcomment                     ; predicted backwards

        mov cl, [ebp+multitable+208]        ; load 1st character into CL from 2nd table
        add cl, [edx+multitable+263]        ; add value of second character from 3rd table
        cmp BYTE PTR [ebp+multitable], 0    ; exit on error or ZERO
        je error1                           ; mispredicted only once

        mov [edi], cl                       ; write BYTE to output buffer
        add esi, 2
        add edi, 1
        cmp BYTE PTR [edx+multitable], 1    ; test if second byte is allowable character
        je h2b                              ; predicted backwards

      error2:
        mov ecx, 2                          ; error 2 = illegal character
        jmp exitproc
      error1:
        test ebp, ebp                       ; test if byte is terminator
        jz zerofound
        mov ecx, 1                          ; error 1 = non matching hex character pairs
        jmp exitproc
      zerofound:
        xor ecx, ecx                        ; no error 0

      exitproc:

        pop ebp                             ; restore EBP before using stack parameter
        sub edi, dst
        mov eax, edi

        pop edi
        pop esi
        pop ebx

        ret

    hex2bin endp

end main

Как я могу декодировать любой тип строки в шестнадцатеричной кодировке, независимо от того, какие символы она содержит?