functions.asm

; functions.asm

sys_exit		equ 1
sys_read		equ 3
sys_write		equ 4
stdin			equ 0
stdout			equ 1
stderr			equ 3
sys_open        equ 5
sys_close       equ 6
O_RDONLY        equ 0
O_RDWR          equ 1
sys_creat       equ 8
sys_sync        equ 36

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; function string length (strlen) ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

strlen:
    push ebx            ;save the value of ebx in the stack
    mov ebx, eax        

nextchar:
    cmp byte[eax], 0    ; compare eax with 0
    jz finish           ; if 0 jump to finish
    inc EAX             ; increment in 1 eax
    jmp nextchar        ; goes back

finish:
    sub eax, ebx        ; substract initial value
    pop ebx             ; brings back ebx 
    ret                 ; return to where the function was called
 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; function string print (sprint) ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
sprint:
    push edx            ; save values to stack
    push ecx
    push ebx
    push eax
    call strlen         ; get string length (stored in eax)
    mov edx, eax        ; move length to edx
    pop eax             ; restore eax
    mov ecx, eax        ; move eax (message) to ecx
    mov ebx, stdout      
    mov eax, sys_write  ; sys_write
    int 80h             ; execute
    pop ebx             ; restore other values
    pop ecx
    pop edx
    ret                 ; return to where the function was called


;; uses sprint and adds a new line at the end
sprintLF:
	call sprint 	
 	push EAX 	
 	mov EAX, 0xA
 	push EAX
 	mov EAX, ESP 	
 	call sprint 
 	pop EAX	
 	pop EAX
 	ret 			


;; uses iprint and adds a new line at the end
iprintLF:
	call iprint
 	push EAX 		
 	mov EAX, 0xA	
 	push EAX	
 	mov EAX, ESP 
 	call sprint 	
 	pop EAX		
 	pop EAX	
 	ret 			


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; function to print              ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

iprint:
	push eax		; save register values to the stack
	push ecx
	push edx
	push esi
	mov ecx, 0 		; initialize the counter

divloop:
	inc ecx;		; increment (will be used to print later)
	mov edx, 0		
	mov esi, 10
	idiv esi 
	add edx, 48
	push edx
	cmp eax, 0
	jnz divloop

printloop:
	dec ecx
	mov eax, esp
	call sprint		; call print function
	pop eax			; restore eax after print
	cmp ecx, 0		; keep printing until the end
	jnz printloop	; jump back if not zero
	pop esi			; restore values
	pop edx
	pop ecx
	pop eax
	ret


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;function to convert ascii to int;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
atoi:
	push ebx		; save registers to the stack
	push ecx
	push edx
	push esi

	mov esi, eax	; number to convert in eax
	mov eax, 0		; initialize with 0
	mov ecx, 0

	multcycle:			; multiplication cycle
	xor ebx, ebx		
	mov bl, [esi+ecx]
	cmp bl, 48
	jl finished
	cmp bl, 57
	jg finished
	cmp bl, 10
	je finished
	cmp bl, 0
	jz finished
	sub bl, 48
	add eax, ebx
	mov ebx, 10
	mul ebx
	inc ecx
	jmp multcycle

	finished:
	mov ebx, 10			; decimal value 10 to ebx
	div ebx				; eax/10
	pop esi				; restore the values
	pop edx
	pop ecx
	pop ebx
	ret



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; rceives integer converts it to text;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
itoa:
	push ebx		; save registers to the stack
	push ecx
	push edx
	push esi

    mov ebx, 10
    mov ecx, 0
    push ecx
    inc ecx

.dividir:
    inc ecx
    mov edx, 0
    idiv ebx
    add edx,0x30
    push edx
    cmp eax, 0
    je .fuera
    jmp .dividir

.fuera:
    mov ebx, 0

.guardar:
    pop eax
    mov byte[esi+ebx], al
    inc ebx
    cmp ebx, ecx
    jne .guardar

    pop esi
    pop edx
    pop ecx
    pop ebx 
    ret



;; receives value in EDI and calculates it's square root
isqrt32:

    mov ebx, edi
    xor eax, eax

    .while:
    cmp eax, ebx
    jnb .endwhile

    add ebx, eax
    shr ebx, 1
    mov eax, edi
    xor edx, edx
    div ebx

    jmp .while

    .endwhile:
    mov eax, ebx
    ret

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; farenheit to celsius function  ;;;
;;; receives farenheit in eax	   ;;;
;;; C = ((F-32)*5)/9			   ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ftoc:
	sub eax, 32		
	imul eax, 5
	push edx			; save to stack
	mov edx, 0
	push ebx			; save to stack
	mov ebx, 9
	div ebx
	pop ebx				; restore values
	pop edx				; restore values
	ret

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; celsius to farenheit function  ;;;
;;; receives farenheit in eax	   ;;;
;;; F = (C*9/5) + 32			   ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ctof:
	imul eax, 9

	push ebx			; save to stack
	push edx
	mov edx, 0
	mov ebx, 5
   	div ebx

	add eax, 32		

	pop ebx				; restore values
	pop edx				; restore values

	ret

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Function to print string from array ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
copystring:
	push ecx			; save and clear registers
	push ebx
	mov ebx, 0
	mov ecx, 0
	mov ebx, eax

.sigcar:
	mov bl, byte[eax]
    cmp bl, 0xA
    je .salto
	mov byte[esi+ecx], bl	; moves a char to esi
	cmp byte[eax],0  		; checks if it's done
	jz .finalizar

.salto:
	inc eax				; next letter
	inc ecx				; so it doesn't rewrite a char
    jmp .sigcar
    
.finalizar:				; restore values
	pop ebx
	pop ecx
	ret

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Function to print string from array ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
stringcopy:
	push ecx			; save and clear registers
	push ebx
	mov ebx, 0
	mov ecx, 0
	mov ebx, eax

.sigcar:
	mov bl, byte[eax]
	mov byte[esi+ecx], bl	; moves a char to esi
	cmp byte[eax],0  		; checks if it's done
	jz .finalizar
	inc eax				; next letter
	inc ecx				; so it doesn't rewrite a char
	jmp .sigcar

.finalizar:				; restore values
	pop ebx
	pop ecx
	ret

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; function to read from user ;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ReadText:
    mov eax, sys_read
    mov ebx, stdin
    int 0x80
    ret
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; sequence to exit the program   ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

quit:
    mov eax, sys_exit          ; exit program
    int 0x80