Question

CONVERT THE FOLLOWING FUNCTION IN MARS SIMULATOR (MIPS)

This FUNCTION should be Runnable on MARS (MIPS Assembler and Runtime Simulator) IDE

C FUNCTION WHICH NEEDS TO BE CONVERTED (ONLY USE MARS)

void decrypt(int numberOfChar, int key, char * cipherText, char * plainText)

{

int j = 0;

int i =0;

int k = 0;

int reverseOrderedKey[4];

int n =4;

int c =0;

int d =0;

int orderedKey[4] = {0,0,0,0};  

while(key)

{

reverseOrderedKey[k] = key %10;

key /= 10;

k++;

}

for (c = n - 1, d = 0; c >= 0; c--, d++)

orderedKey[d] = reverseOrderedKey[c];

  

for ( j=0; j <= 4; j++)

{

for( i=0; i<numberOfChar; i++)

{{

plainText[i] = cipherText[i] - orderedKey[j];

}

j += 1;

if (j %4 == 0) j = 0;

  

}

  

if (i == strlen(cipherText)) break;

  

}

  

}

Answer 1

.file   1 ""
        .section .mdebug.abi32
        .previous
        .nan    legacy
        .module fp=32
        .module nooddspreg
        .abicalls
        .text
        .align  2
        .globl  decrypt
        .set    nomips16
        .set    nomicromips
        .ent    decrypt
        .type   decrypt, @function
decrypt:
        .frame  $sp,88,$31              # vars= 32, regs= 8/0, args= 16, gp= 8
        .mask   0x807f0000,-4
        .fmask  0x00000000,0
        .set    noreorder
        .cpload $25
        .set    nomacro
        addiu   $sp,$sp,-88
        .cprestore      16
        sw      $21,76($sp)
        sw      $20,72($sp)
        sw      $17,60($sp)
        movz    $31,$31,$0
        sw      $31,84($sp)
        sw      $22,80($sp)
        sw      $19,68($sp)
        sw      $18,64($sp)
        sw      $16,56($sp)
        move    $20,$4
        move    $21,$6
        beq     $5,$0,$L4
        move    $17,$7

        li      $2,10                   # 0xa
        bne     $2,$0,1f
        div     $0,$5,$2
        break   7
1:
        mfhi    $3
        mflo    $4
        beq     $4,$0,$L4
        sw      $3,40($sp)

        li      $3,100                  # 0x64
        bne     $2,$0,1f
        div     $0,$4,$2
        break   7
1:
        mfhi    $4
        nop
        nop
        bne     $3,$0,1f
        div     $0,$5,$3
        break   7
1:
        mflo    $3
        beq     $3,$0,$L4
        sw      $4,44($sp)

        li      $4,1000                 # 0x3e8
        bne     $2,$0,1f
        div     $0,$3,$2
        break   7
1:
        mfhi    $3
        nop
        nop
        bne     $4,$0,1f
        div     $0,$5,$4
        break   7
1:
        mflo    $5
        beq     $5,$0,$L4
        sw      $3,48($sp)

        bne     $2,$0,1f
        div     $0,$5,$2
        break   7
1:
        mfhi    $5
        sw      $5,52($sp)
$L4:
        lw      $2,52($sp)
        move    $16,$0
        sw      $2,24($sp)
        lw      $2,48($sp)
        addu    $19,$21,$20
        sw      $2,28($sp)
        lw      $2,44($sp)
        addiu   $18,$sp,24
        sw      $2,32($sp)
        lw      $2,40($sp)
        nop
        sw      $2,36($sp)
$L3:
        blez    $20,$L10
        move    $22,$0

        move    $2,$21
        move    $5,$17
$L7:
        sll     $4,$16,2
        addu    $4,$18,$4
        lbu     $3,0($2)
        lw      $4,0($4)
        addiu   $16,$16,1
        subu    $3,$3,$4
        andi    $4,$16,0x3
        bne     $4,$0,$L6
        sb      $3,0($5)

        move    $16,$0
$L6:
        addiu   $2,$2,1
        bne     $19,$2,$L7
        addiu   $5,$5,1

        move    $22,$20
$L10:
        lw      $25,%call16(strlen)($28)
        nop
        .reloc  1f,R_MIPS_JALR,strlen
1:      jalr    $25
        move    $4,$21

        lw      $28,16($sp)
        beq     $2,$22,$L1
        addiu   $16,$16,1

        slt     $2,$16,5
        bne     $2,$0,$L3
        nop

$L1:
        lw      $31,84($sp)
        lw      $22,80($sp)
        lw      $21,76($sp)
        lw      $20,72($sp)
        lw      $19,68($sp)
        lw      $18,64($sp)
        lw      $17,60($sp)
        lw      $16,56($sp)
        j       $31
        addiu   $sp,$sp,88

        .set    macro
        .set    reorder
        .end    decrypt
        .size   decrypt, .-decrypt
        .ident  "GCC: (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609"