How to resolve the algorithm String append step by step in the AArch64 Assembly programming language

Published on 12 May 2024 09:40 PM
#Aarch64 assembly

How to resolve the algorithm String append step by step in the AArch64 Assembly programming language

Table of Contents

Problem Statement

Most languages provide a way to concatenate two string values, but some languages also provide a convenient way to append in-place to an existing string variable without referring to the variable twice.

Create a string variable equal to any text value. Append the string variable with another string literal in the most idiomatic way, without double reference if your language supports it. Show the contents of the variable after the append operation.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm String append step by step in the AArch64 Assembly programming language

Source code in the aarch64 programming language

/* ARM assembly AARCH64 Raspberry PI 3B */
/*  program appendstr64.s   */

/*******************************************/
/* Constantes file                         */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"
 
.equ BUFFERSIZE,          100
/*******************************************/
/* Initialized data                        */
/*******************************************/
.data
szMessString:            .asciz "String :\n"
szString1:              .asciz "Alphabet : "
sComplement:            .fill BUFFERSIZE,1,0
szString2:              .asciz "abcdefghijklmnopqrstuvwxyz"
 
szCarriageReturn:       .asciz "\n"
/*******************************************/
/* UnInitialized data                      */
/*******************************************/
.bss 
/*******************************************/
/*  code section                           */
/*******************************************/
.text
.global main 
main: 
 
    ldr x0,qAdrszMessString               // display message
    bl affichageMess
    ldr x0,qAdrszString1                  // display begin string
    bl affichageMess
    ldr x0,qAdrszCarriageReturn           // display return line
    bl affichageMess
    ldr x0,qAdrszString1
    ldr x1,qAdrszString2
    bl append                             // append sting2 to string1
    ldr x0,qAdrszMessString
    bl affichageMess
    ldr x0,qAdrszString1                  // display string
    bl affichageMess 
    ldr x0,qAdrszCarriageReturn
    bl affichageMess
 
100:                                      // standard end of the program
    mov x0,0                              // return code
    mov x8,EXIT                           // request to exit program
    svc 0                                 // perform system call
qAdrszMessString:         .quad szMessString
qAdrszString1:            .quad szString1
qAdrszString2:            .quad szString2
qAdrszCarriageReturn:     .quad szCarriageReturn
/**************************************************/
/*     append two strings                         */ 
/**************************************************/
/* x0 contains the address of the string1 */
/* x1 contains the address of the string2 */
append:
    stp x1,lr,[sp,-16]!            // save  registers
    mov x2,#0                      // counter byte string 1
1:
    ldrb w3,[x0,x2]                // load byte string 1
    cmp x3,#0                      // zero final ?
    add x4,x2,1
    csel x2,x4,x2,ne               // if x3 not equal 0, x2 = X2 +1 else x2
    bne 1b                         // no -> loop
    mov x4,#0                      // counter byte string 2
2:
    ldrb w3,[x1,x4]                // load byte string 2
    strb w3,[x0,x2]                // store byte string 1
    cbz x3,100f                    // zero final ?
    add x2,x2,1                    // no -> increment counter 1
    add x4,x4,1                    // no -> increment counter 2
    b 2b                           // no -> loop
100:

    ldp x1,lr,[sp],16              // restaur  2 registers
    ret                            // return to address lr x30
/********************************************************/
/*        File Include fonctions                        */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"

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