section .data
        ;; static
hellow: db "Hello World!"
hellow_len:     equ $ - hellow
        section .bss

        common  stdinbuf        1048576:1
        common  stdinbuf_size   1:8
        common  stdinbuf_seek   1:8
        common  stdoutbuf       1048576:1
        common  stdoutbuf_size  1:8
        
        section .text
        global _start
_start:
        call    readstdin
        call    setupstdout

        mov     rdi,    hellow
        mov     rsi,    hellow_len
        call    putStrLn
        
        call    writestdout        
        mov     rax,    60
        mov     rdi,    0
        syscall
        ret

readstdin:
        mov     rax,    0
        mov     rdi,    0
        mov     rsi,    stdinbuf
        mov     rdx,    1048576
        syscall
        mov     [stdinbuf_size],        rax
        mov     rax,    0
        mov     [stdinbuf_seek],        rax
        ret
        
setupstdout:
        mov     rax,    0
        mov     [stdoutbuf_size], rax
        ret

writestdout:
        mov     rax,    1
        mov     rdi,    1
        mov     rsi,    stdoutbuf
        mov     rdx,    [stdoutbuf_size]
        syscall
        ret

;;; rdi : dest
;;; rsi : src
;;; rdx : size
strncpy:
        cmp     rdx,    0
        jne     strncpy_L1
        ret
strncpy_L1:     
        mov     al,    [rsi]
        mov     [rdi],  al
        add     rsi,    1       
        add     rdi,    1
        sub     rdx,    1
        jne     strncpy_L1
        ret

;;; dil char
putChar:
        mov     rax,    stdoutbuf
        add     rax,    [stdoutbuf_size]
        mov     [rax],  dil
        mov     rax,    [stdoutbuf_size]
        add     rax,    1
        mov     [stdoutbuf_size],       rax
        ret
        
;;; rdi str
;;; rsi size 
putStr:
        cmp     rsi,    0
        jne     putStr_L1
        ret
putStr_L1:
        mov     rax,    stdoutbuf
        add     rax,    [stdoutbuf_size]
        mov     rdx,    [stdoutbuf_size]
        add     rdx,    rsi
        mov     [stdoutbuf_size], rdx
putStr_L2:      
        mov     dl,     [rdi]
        mov     [rax],  dl
        add     rax,    1
        add     rdi,    1
        sub     rsi,    1
        jne     putStr_L2
        ret
        
;;; rdi str
;;; rsi size 
putStrLn:
        push    rdi
        push    rsi
        call    putStr
        pop     rsi
        pop     rdi
        mov     dil,    10
        call    putChar
        ret