# riscv assembly raspberry pico2 rp2350
# program concatstring.s
# connexion putty com3
/*********************************************/
/*           CONSTANTES                      */
/********************************************/
/* for this file see risc-v task include a file */
.include "../../constantesRiscv.inc"
.equ BUFFERSIZE,          255
/*******************************************/
/* INITIALED DATAS                    */
/*******************************************/
.data
szMessStart:         .asciz "Program riscv start.\r\n"
szMessEndOk:         .asciz "Program riscv end OK.\r\n"
szCariageReturn:     .asciz "\r\n"

szMessFinal:   .asciz "The final string is \n"

szString1:           .asciz "Hello "
szString2:           .asciz " the world. \n"

szMessErrorSize:     .asciz "Error : size final string too small\n"

.align 2
/*******************************************/
/*  UNINITIALED DATA                    */
/*******************************************/
.bss
szFinalString:   .skip BUFFERSIZE
.align 2

/**********************************************/
/* SECTION CODE                              */
/**********************************************/
.text
.global main

main:
    call stdio_init_all        # général init
1:                             # start loop connexion
    li a0,0                    # raz argument register
    call tud_cdc_n_connected   # waiting for USB connection
    beqz a0,1b                 # return code = zero ?

    la a0,szMessStart          # message address
    call writeString           # display message
	

	la a0,szString1            # adresse string 1
	la a1,szString2            # adresse string 2
	la a2,szFinalString        # adresse string final
	li a3,BUFFERSIZE           # size area string final
    call concatString          # concat string	
	li t0,-1
    beq a0,t0,100f             # error ?
	
	la a0,szMessFinal          # message address
    call writeString           # display message
	la a0,szFinalString
    call writeString           # display message	
	la a0,szCariageReturn      # message address
    call writeString           # display message

    la a0,szMessEndOk          # message address
    call writeString           # display message
    call getchar
100:                           # final loop
    j 100b

/*********************************************/
/* add string to string                      */
/*********************************************/
/* a0 contains address String 1          */
/* a1 contains address String 2          */
/* a2 contains address String final      */
/* a3 contains string final size         */
concatString:
    addi    sp, sp, -4
    sw      ra, 0(sp)
	li t0,0                    # counter byte string 1
	
1:
    add t1,a0,t0
    lbu t2,(t1)                 # load byte string 1
	add t1,a2,t0
	sb  t2,(t1)                 # store byte final string
	beqz t2,2f                  # zero final ?
	addi t0,t0,1                # no -> increment counter
	bge t0,a3,99f               # size maxi ?
	j 1b                        # loop
2:	
    li t3, 0                    # counter byte string 2
3:
    add t4,a1,t3
    lbu t5,(t4)                 # load byte string 2
	add t1,a2,t0
	sb  t5,(t1)                 # store byte string final
    beqz t5,100f                # zero final ? -> end
	addi t3,t3,1                # increment counter
	addi t0,t0,1
	bge t0,a3,99f               # size maxi ?
	j 3b                        # end loop
99:
    la a0,szMessErrorSize
	call writeString
	li a0,-1                    # return error
100:
    lw      ra, 0(sp)
    addi    sp, sp, 4
    ret

/************************************/
/*     file include  Fonctions   */
/***********************************/
/* for this file see risc-v task include a file */
.include "../../includeFunctions.s"