Write a procedure named CountNearMatches that receives pointers to two arrays of

Question

Write a procedure named CountNearMatches that receives pointers to two arrays of signed doublewords, a parameter that indicates the length of the two arrays, and a parameter that indicates the maximum allowed difference (called diff) between any two matching elements. For each element x(i) in the rst array, if the difference between it and the corresponding y(i) in the second array is less than or equal to diff, increment a count. At the end, return a count of the number of nearly matching array elements in EAX. Display this value.

Write a test program that calls CountNearMatches and passes pointers to two different pairs of arrays. Use the INVOKE statement to call your procedure and pass stack parameters. Create a PROTO declaration for CountMatches. Save and restore any registers (other than EAX) changed by your procedure.

Explanation / Answer

CountNearMatches PROTO, ptrArray1:PTR SDWORD, ptrArray2:PTR SDWORD, szArray:DWORD, diff:DWORD

    .data
    array1a SDWORD 1,2,3,4
    array1b SDWORD 5,7,8,7
    array2a SDWORD 5,6,7,5,
    array2b SDWORD 8,2,5,4
    cnt DWORD ?,0
    dif1 DWORD 11
    dif2 DWORD 0

    .code
    main PROC      
            INVOKE CountNearMatches, ADDR array1a, ADDR array1b, LENGTHOF array1a, dif1
            call WriteInt
            call Crlf
            INVOKE CountNearMatches, ADDR array2a, ADDR array2b, LENGTHOF array2a, dif2
            call WriteInt
            call Crlf
            exit
            main ENDP

    CountNearMatches PROC USES edx ebx edi esi ecx, ptrArray1:PTR SDWORD, ptrArray2:PTR SDWORD, szArray:DWORD, diff:DWORD
            mov esi,ptrArray1
            mov edi,ptrArray2
            mov ecx,szArray
; Loop L1:
; compare sets
    mov ebx,0
    mov ebx,[esi]
    mov edx,0
    mov edx,[edi]
    .IF ebx > edx
            mov eax,ebx
            sub eax,edx
    .ELSE
            mov eax,edx
            sub eax,ebx
    .ENDIF
    .IF (eax <= diff)
            inc cnt
    .ENDIF
    add esi, SIZEOF SDWORD
    add edi, SIZEOF SDWORD
    loop L1
; increment count
    mov eax,0
    mov eax,cnt
    mov cnt,0
    ret
    CountNearMatches ENDP
    END main

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