Hw4

; Sources:	http://www.programming.msjc.edu/asm/help/  
TITLE Miles Per Gallon calculator				(main.asm)
; Program Description:	Reverses elements in an array.
; Author:				Tom Bernard
; Date;					3/11/2015

INCLUDE Irvine32.inc

.data
	ary		DWORD	1, 2, 3, 4, 5, 6, 7, 8, 9;	
						
.code
main PROC	

	mov		esi,	OFFSET ary								;moves distance in bytes of ary into index register(source) esi 
	mov		edi,	OFFSET ary + sizeof ary					;moves distance in byte of ary into index reg(destination) edi 
	mov		eax,	LENGTHOF ary							;temporarily use eax to hold # elements in array.
	cdq
	mov		ebx, 2											 
	div		ebx												;div ary/2 and store divisor into e 
	
	mov		ecx, eax										;mov contents of eax into ecx(4 in this case so it will print 4 times for each register)
	
	sub		edi, 4											;remove 4 since 'OFFSET ary + sizeof ary' points you to the end of the last node(this moves it to front of node)
L1:

	mov		eax, [esi]										;move first half of ary(from index reg esi) into eax		(character by character!)
	mov		ebx, [edi]										;move last half of ary (from index reg edi) in bl(lower part of ebx reg) 
	mov		[edi], eax										;move first index(now in al) to edi(destination index reg)
	mov		[esi], ebx										;move last index(now in bl) to esi(source index reg)
	add		esi, 4											;increment in dword chunks (does first half of aray start at 1st and go forward 'ecx' times)
	sub		edi, 4											;decrement in dword chunks (start at last element and work you way back )
	LOOP	L1												;this method refers to ecx register to know how many times to loop

	mov		ecx, lengthof ary								;move entire length of array in so you loop 'ecx' (whatever value stored in ecx) # of times	
	mov		ebx, type ary
	mov		esi, offset ary									;reset esi pointer register from middle to begining

	call	dumpmem
;L2:
;	mov		eax, [esi]
;	call	writeint										;write what is in eax reg
	;add		esi, 4											;increment in dword chunks to iterate through each element of the aray
	;Loop	L2												;loop as many times as stored into the ecx register

	
	exit
main ENDP
END main