TITLE AsmBinarySearch Procedure (AsmBinarySearch.asm)

    .586
    .model flat,C
    INCLUDE \Irvine\Irvine32.inc
    AsmBinarySearch PROTO, searchValue:DWORD, arrayPTR:PTR DWORD, count:DWORD

    .data
    first DWORD ?
    last DWORD ?
    mid DWORD ?
    .code
    ;----------------------------------------------------------
    AsmBinarySearch PROC USES edi, searchValue:DWORD, arrayPTR:PTR DWORD, count:DWORD
    ;
    ; Performs a binary search for a 32 - bit integer
    ; in an array of integers. Returns the value of the subscript
    ; of the matching array element in EAX, or -1 in EAX if the
    ; search value was not found in the array.
    ; ----------------------------------------------------------

    mov eax, 0              ;FIRST VAR
    mov ebx, count      ;LAST VAR
    dec ebx
    mov ecx, searchValue    ;comparison VAR
    mov edi, arrayPTR       ;array pointer

    .WHILE eax <= ebx
        mov esi, ebx
        add esi, eax        ;middle = (last+first/2)
        shr esi, 1          ;esi has middle VAR
        mov edx, [edi+esi*4]    ;current value of array[mid] NOTE COULD INCREASE SPEED BY SHIFTING RIGHT INSTEAD OF MULT

        .IF edx < ecx
            mov eax, esi
            inc eax
        .ELSEIF edx > ecx
            mov ebx, esi
            dec ebx
        .ELSE
            mov eax, esi
            ret
        .ENDIF
    .ENDW

    mov eax,-1      ; Set the return value to indicate that
    ret         ; return

AsmBinarySearch ENDP
END