/* ARM assembly Raspberry PI  */
/*  program forfunction.s   */

/* Constantes    */
.equ STDOUT, 1     @ Linux output console
.equ EXIT,   1     @ Linux syscall
.equ WRITE,  4     @ Linux syscall
/* Initialized data */
.data
szString: .asciz "Hello word\n"

/* UnInitialized data */
.bss

/*  code section */
.text
.global main
main:                            @ entry of program
    push {fp,lr}                 @ saves registers

    ldr r0,iAdrszString          @ string address
    bl strdup                    @ call function C
                                 @ return new pointer
    bl affichageMess             @ display dup string
    bl free                      @ free heap

100:                             @ standard end of the program */
    mov r0, #0                   @ return code
    pop {fp,lr}                  @restaur 2 registers
    mov r7, #EXIT                @ request to exit program
    swi 0                        @ perform the system call
iAdrszString:      .int szString

/******************************************************************/
/*     display text with size calculation                         */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                          @ save  registres
    mov r2,#0                                      @ counter length
1:                                                 @ loop length calculation
    ldrb r1,[r0,r2]                                @ read octet start position + index
    cmp r1,#0                                      @ if 0 its over
    addne r2,r2,#1                                 @ else add 1 in the length
    bne 1b                                         @ and loop
                                                   @ so here r2 contains the length of the message
    mov r1,r0                                      @ address message in r1
    mov r0,#STDOUT                                 @ code to write to the standard output Linux
    mov r7, #WRITE                                 @ code call system "write"
    svc #0                                         @ call systeme
    pop {r0,r1,r2,r7,lr}                           @ restaur des  2 registres */
    bx lr                                          @ return