TITLE Swap Procedure Example                 (Swap.asm)

; Demonstration of the Swap procedure, using
; PROTO, PROC, and INVOKE.
; Chapter 5 example. Last update: 07/22/01

INCLUDE Irvine32.inc

Swap PROTO,        ; procedure prototype
    pValX:PTR DWORD,
    pValY:PTR DWORD

.data
Array  DWORD  10000h,20000h

.code
main PROC
    ; Display the array before the exchange:
    mov  esi,OFFSET Array
    mov  ecx,2        ; count = 2
    mov  ebx,TYPE Array
    call DumpMem        ; dump the array values

    INVOKE Swap,ADDR Array, ADDR [Array+4]

    ; Display the array after the exchange:
    call DumpMem

    exit
main ENDP

;-------------------------------------------------------
Swap PROC USES eax esi edi,
    pValX:PTR DWORD,    ; pointer to first integer
    pValY:PTR DWORD    ; pointer to second integer
;
; Exchange the values of two 32-bit integers
; Returns: nothing
;-------------------------------------------------------
    mov esi,pValX    ; get pointers
    mov edi,pValY
    mov eax,[esi]    ; get first integer
    xchg eax,[edi]    ; exchange with second
    mov [esi],eax    ; replace first integer
    ret
Swap ENDP

END main