How to reverse an array is assembly? - arrays

Question

I'm trying to write a simple program that reverses an array. It almost works, well it works for the first half of the array anyway. The term in the middle is always "0" and then it returns to the pattern. For example, if I input: 1,2,3,4,5,6,7,8,9,10, the output will be 10,9,8,7,6,0,6,5,4,3. The order of the program is basically this:
Call to ReverseArray:
INVOKE ReverseArray,
LENGTHOF array, SIZEOF array, TYPE array, OFFSET array
ReverseArray procedure (loops through the array and calls mSwap32):
ReverseArray PROC,
len:DWORD, s:DWORD, increment:DWORD,address:DWORD
mov edx, OFFSET revArray
call WriteString
mov edi, address
mov esi, address
add esi, s
sub esi, TYPE array
mov ecx, len
shr ecx, 1
L2:
mSwap32 edi, esi
add edi, increment
sub esi, increment
loop L2
ret
ReverseArray endp
mSwap32 Macro (is given two addresses to swap):
mSwap32 MACRO address1:REQ, address2:REQ
mov edi, address1
mov esi, address2
mov eax, [esi]
push eax
mov eax, [edi]
mov [esi], eax
pop eax
mov [edi], eax
ENDM
I'm fairly certain that the error is in mSwap32...I'm sure it is some small logical error I'm missing, but no matter how much I toy with it I can not figure it out. ??

Answer 1

it's a WORD array
With this crucial piece of information we can solve the problems. LENGTHOF will be 10 (as before), SIZEOF will now be 20 and TYPE will now be 2.
ReverseArray PROC,
len:DWORD, s:DWORD, increment:DWORD,address:DWORD
mov edx, OFFSET revArray
call WriteString
mov edi, address
mov esi, address
add esi, s
sub esi, increment ;Better not refer to the actual array here!
mov ecx, len
shr ecx, 1
L2:
mSwap32 edi, esi
add edi, increment
sub esi, increment
loop L2
ret
ReverseArray endp
and the macro:
mSwap32 MACRO address1:REQ, address2:REQ
mov edi, address1
mov esi, address2
mov ax, [esi]
push eax
mov ax, [edi]
mov [esi], ax
pop eax
mov [edi], ax
ENDM
Shorter and still using a macro:
mSwap32 MACRO address1:REQ, address2:REQ
mov edi, address1
mov esi, address2
mov ax, [esi]
xchg ax, [edi]
mov [esi], ax
ENDM