; compute string length
; assembly X86 window
; download and install visual studio 2022 free site microsoft
; search and open  X64 native tools command prompt
; compil and link program with this command :
; ml64  lenString.asm  /link /ENTRY:main /SUBSYSTEM:console kernel32.lib user32.lib Shell32.lib
; this program respects the 64-bit calling convention :
; registers arguments : rcx rdx r8 r9 and stack
; registers saved : rbx,rbp,rdi,rsi, r12-r15
; ATTENTION les registres rax,rcx,rdx,r8-r11 peuvent être
; perdus lors d'un appel de fonction
;*********************************
; constantes
;*********************************
STD_OUTPUT_HANDLE equ -11
BUFFERSIZE        equ 200
;*********************************
; macros
;*********************************
;for this file, see task include a file for X86-64 language
include macrosInclude.asm

;*********************************
; user data
;*********************************
.data
szMesslength    db "The lenght of string ",0
LGMESSLEN       equ $ - szMesslength - 1
szMesslength1   db " is ",0
LGMESSLEN1       equ $ - szMesslength1 - 1

szCarriageReturn  db 10,0

szString1      db "Apple",0
LGSTRING1      equ $ - szString1 - 1
szString2      db "Orange",0
LGSTRING2      equ $ - szString2 - 1

align 8

hConsole       dq 0
sConvArea      db 24 dup (0)
sBuffer        db BUFFERSIZE dup (' ')
;*********************************
; user code fonction principale
;*********************************
.code

extern WriteFile : proc, GetStdHandle : proc, ExitProcess : proc
extern GetLastError : proc

main PROC public
    displayLib "Program X86-64 start."
	
	mov rcx, offset szMesslength
	mov rdx,LGMESSLEN
	call afficherConsole
	mov rcx, offset szString1
	mov rdx,LGSTRING1
	call afficherConsole
	mov rcx, offset szMesslength1
	mov rdx,LGMESSLEN1
	call afficherConsole	
    mov rcx, offset szString1
    call lenString                 ; compute length
    mov rcx,rax
    mov rdx, offset sConvArea
    call conversion10
	mov rdx,rax                    ; result size
    mov rcx, offset sConvArea
	call afficherConsole
	mov rcx, offset szCarriageReturn
    mov rdx,1
    call afficherConsole

	mov rcx, offset szMesslength
	mov rdx,LGMESSLEN
	call afficherConsole
	mov rcx, offset szString1
	mov rdx,LGSTRING1
	call afficherConsole
	mov rcx, offset szMesslength1
	mov rdx,LGMESSLEN1
	call afficherConsole	
	mov rcx, offset szString1
    call lenString2                  ; other compute methode
    mov rcx,rax
    mov rdx, offset sConvArea
    call conversion10
	mov rdx,rax                ; result size
    mov rcx, offset sConvArea
	call afficherConsole
	mov rcx, offset szCarriageReturn
    mov rdx,1
    call afficherConsole
	
	
	mov rcx, offset szMesslength
	mov rdx,LGMESSLEN
	call afficherConsole
	mov rcx, offset szString1
	mov rdx,LGSTRING1
	call afficherConsole
	mov rcx, offset szMesslength1
	mov rdx,LGMESSLEN1
	call afficherConsole
	mov rcx,LGSTRING1            ; direct value for static string
    mov rdx, offset sConvArea
    call conversion10
	mov rdx,rax                ; result size
    mov rcx, offset sConvArea
	call afficherConsole
    mov rcx, offset szCarriageReturn
    mov rdx,1
    call afficherConsole

	mov rcx, offset szMesslength
	mov rdx,LGMESSLEN
	call afficherConsole
	mov rcx, offset szString2
	mov rdx,LGSTRING2
	call afficherConsole
	mov rcx, offset szMesslength1
	mov rdx,LGMESSLEN1
	call afficherConsole	
    mov rcx, offset szString2
    call lenString                 ; compute length
    mov rcx,rax
    mov rdx, offset sConvArea
    call conversion10
	mov rdx,rax                    ; result size
    mov rcx, offset sConvArea
	call afficherConsole
	mov rcx, offset szCarriageReturn
    mov rdx,1
    call afficherConsole

finProgramme:
    displayLib "Program end."
    sub rsp,28h
    mov rcx,0                ; return code
    call ExitProcess
main ENDP

;***************************************************
;compute string length
;****************************************************
; rcx  : string address
lenString PROC
	mov rax,0                ;  counter init
@B1:
    mov dl,[rax+rcx]         ; load one byte of string
	cmp dl,0                 ; zero final ?
	je  @B2                  ; yes -> end
	inc rax                  ; increment counter
	jmp @B1                  ; and loop
@B2:	
    ret
lenString ENDP
;***************************************************
;compute string length other method
;****************************************************
; rcx  : string address
lenString2 PROC
    push rdi
	xor rax,rax        ; raz rax
	mov rdi,rcx        ; move string address
	mov rcx,-1         ; init rcx
	cld                ; direction flag to zero
    repne  scasb       ; repeat comparaison one character
	not rcx            ; ???
	dec rcx            ; ???
	mov rax,rcx        ; return result 	
    pop rdi
    ret
lenString2 ENDP


;for this file, see task include a file for X86-64 language
include routinesInclude.asm

end