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

/* Constantes    */
.equ STDOUT, 1                           @ Linux output console
.equ EXIT,   1                           @ Linux syscall
.equ WRITE,  4                           @ Linux syscall

.equ BUFFERSIZE,          100

/* Initialized data */
.data
szMessStartPgm:            .asciz "Program start \n"
szMessEndPgm:              .asciz "Program normal end.\n"
szMessColorRed:            .asciz "Color red.\n"
szCodeInit:                .asciz "\033[0m"                    @ color reinit
szCodeRed:                 .asciz "\033[31m"                   @ color red
szMessBlue:                .asciz "\033[34mColor Blue\n"       @ color blue
szMessTwoColor:            .asciz "\033[32mColor Green \033[35m Color Velvet\n"
szMessTest:                .asciz "\033[33m\033[1mMessage yellow bold\n"

szCarriageReturn:          .asciz "\n"

/* UnInitialized data */
.bss

/*  code section */
.text
.global main
main:

    ldr r0,iAdrszMessStartPgm                   @ display start message
    bl affichageMess
    ldr r0,iAdrszCodeRed                        @ color red
    bl affichageMess
    ldr r0,iAdrszMessColorRed
    bl affichageMess
    ldr r0,iAdrszMessBlue                       @ message color blue
    bl affichageMess
    ldr r0,iAdrszMessTwoColor                   @ message two colors
    bl affichageMess
    ldr r0,iAdrszMessTest
    bl affichageMess
    ldr r0,iAdrszCodeInit                       @ color reinitialize
    bl affichageMess
    ldr r0,iAdrszMessEndPgm                     @ display end message
    bl affichageMess

100:                                            @ standard end of the program
    mov r0, #0                                  @ return code
    mov r7, #EXIT                               @ request to exit program
    svc 0                                       @ perform system call
iAdrszMessStartPgm:        .int szMessStartPgm
iAdrszMessEndPgm:          .int szMessEndPgm
iAdrszCodeInit:            .int szCodeInit
iAdrszCodeRed:             .int szCodeRed
iAdrszMessBlue:            .int szMessBlue
iAdrszMessColorRed:        .int szMessColorRed
iAdrszMessTwoColor:        .int szMessTwoColor
iAdrszMessTest:            .int szMessTest
iAdrszCarriageReturn:      .int szCarriageReturn

/******************************************************************/
/*     display text with size calculation                         */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                       @ save  registers
    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 system
    pop {r0,r1,r2,r7,lr}                        @ restaur registers
    bx lr                                       @ return