; WTFStopW : a simple stopwatch
; Copyright (C) 2018 Weber Yann
; 
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 3 of the License, or
; any later version.
; 
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; 
; You should have received a copy of the GNU General Public License
; along with this program.  If not, see <http://www.gnu.org/licenses/>.

;
; A simple precise stopwatch
; Build : nasm -felf64 wtfstopw.asm && ld -s -melf_x86_64 wtfstopw.o -o wtfstopw
; Build Debug : nasm -felf64 -l wtfstopw.lst wtfstopw.asm && ld -melf_x86_64 wtfstopw.o -o wtfstopw
;
; Usage : ./wtfstopw
;	press enter to exit
;	send SIGINT (with kill -2 or ctrl + c) for new lap on stdout
;

[bits 64]

STRUC TIMESPEC_STRUC
	.tv_sec: resq 1
	.tv_nsec: resq 1
ENDSTRUC


%macro TIMESPEC 1
	%1: ISTRUC TIMESPEC_STRUC
		at TIMESPEC_STRUC.tv_sec, dq 0
		at TIMESPEC_STRUC.tv_nsec, dq 0
	IEND
	%define %1.tv_sec %1+TIMESPEC_STRUC.tv_sec
	%define %1.tv_nsec %1+TIMESPEC_STRUC.tv_nsec
%endmacro

STRUC SIGACTION_STRUC
	.sa_handler:      resq      1
	.sa_flags:        resq      1
	.sa_restorer:     resq      1
	.sa_mask:         resb      128
ENDSTRUC

section .data

	sigaction: ISTRUC SIGACTION_STRUC
		at  SIGACTION_STRUC.sa_handler, dq 0
		at  SIGACTION_STRUC.sa_flags, dq 0
		at  SIGACTION_STRUC.sa_restorer, dq 0
		at  SIGACTION_STRUC.sa_mask, times 128 db 0
	IEND
	%define sigaction.sa_handler sigaction+SIGACTION_STRUC.sa_handler
	%define sigaction.sa_flags sigaction+SIGACTION_STRUC.sa_flags
	%define sigaction.sa_restorer sigaction+SIGACTION_STRUC.sa_restorer
	%define sigaction.sa_mask sigaction+SIGACTION_STRUC.sa_mask

	TIMESPEC ts_start
	TIMESPEC ts_cur

	ts_sleep:
		tv_sleep_s dq 0
		tv_sleep_us dq 10000000

	;; 1/2s sleep
	;ts_sleep:
	;	tv_sleep_s dq 0
	;	tv_sleep_us dq 500000000


	faultmsg: db "Fault !", 0xA
	faultmsglen: equ $ - faultmsg

	startmsg: db "Press Enter or ctrl+d to exit and ctrl+c for new lap."
	db 0xA
	startmsglen: equ $ - startmsg

	hours: db "000000000"
	timestr: db ":00:00.0000    ", 0x0a
	timestrlen: equ $ - timestr

	nl: db 0x0A
	buf: db 0

	lapsmsg: db 0x0d, "Lap : "
	lapsmsglen: equ $ - lapsmsg

	lapcount: db "00000000"
	lapcountlen: equ $ - lapcount
	laplen: dq 2

	fcntl_flag: dq 0

section .text
global _start
_start:

; set stdin non blocking
xor rdx, rdx
xor rdi, rdi
mov rax, 72 ; fcntl
mov rsi, 3 ; F_GETFL
syscall
mov [fcntl_flag], rax
mov rdx, rax
or rdx, 0x800 ; O_NONBLOCK
mov rax, 72 ; fcntl
mov rsi, 4 ; F_SETFL
syscall
cmp rax, 0
jne fault

; initializing lapptr

; preparing SIGINT catch
mov rax, proc_lap_handler
mov qword [sigaction.sa_handler], rax
mov eax, 0x14000000 ; SA_RESTART | SA_RESTORER
mov dword [sigaction.sa_flags], eax
mov rax, sig_restorer
mov qword [sigaction.sa_restorer], rax

mov rax, 13 ; sys_rt_sigaction
mov rdi, 2 ; SIGINT
mov rsi, sigaction
mov rdx, 0 ; NULL
mov r10, 8 ; sig_size
syscall
cmp rax, 0
jne fault

mov rax, 228 ; clock_gettime
mov rdi, 0 ; CLOCK_REALTIME
mov rsi, ts_start
syscall

mov rax, 1 ; write
mov rdi, 2 ; stderr
mov rsi, startmsg
mov rdx, startmsglen
syscall

main_loop:
	push 2 ; stderr
	push 0x0D ; \r
	call proc_print_time

	; Attempt to read from stdin
	; if something read, enter has been pressed
	mov rax, 0
	mov rdi, 0
	mov rsi, buf
	mov rdx, 1
	syscall
	cmp rax, 0
	jge flush_stdin ; flush stdin and exit

	mov rax, 35 ; nanosleep
	mov rdi, ts_sleep
	mov rsi, 0
	syscall

jmp main_loop ; main_loop

flush_stdin:
	mov rax, 0
	mov rdi, 0
	mov rsi, buf
	mov rdx, 1
	syscall
	cmp rax, 0
	je newline_exit
	jg flush_stdin

mov rdi, 0 ; EXIT OK
;
; Expect rdi to be the return code
;
exit:
	push rdi
	; restoring stdin state
	mov rax, 72 ; fcntl
	xor rdi, rdi
	mov rsi, 4 ; F_SETFL
	mov rdx, [fcntl_flag]
	syscall
	cmp rax, 0
	je exit_end
	pop rdi ; failed to restore
	push 1 ; exit FAIL

	exit_end:
	mov rax, 60 ; sys_exit
	pop rdi ; return code
	syscall
fault:
	mov rax, 1 ; write
	mov rdi, 2 ; stderr
	mov rsi, nl
	mov rdx, 1
	syscall
	mov rax, 1
	mov rsi, faultmsg
	mov rdx, faultmsglen
	syscall

	mov rdi, 1 ; failure
	jmp exit

newline_exit:
	mov rax, 1
	mov rdi, 1
	mov rsi, nl
	mov rdx, 1
	syscall

	mov rdi, 0 ; exit OK
	jmp exit

;
; Print current time on FD and add a leading char CHR
; push FD & push CHR to set arguments
;
proc_print_time:
	; push ret addr before arguments
	pop r8
	pop r9
	pop r10
	push r8
	push r10
	push r9

	; updating ts_cur time
	mov rax, 228 ; clock_gettime
	mov rdi, 0 ; CLOCK_REALTIME
	mov rsi, ts_cur
	syscall

	; Calculating elapsed ns
	mov rax, [ts_cur.tv_nsec]
	mov rbx, [ts_start.tv_nsec]
	sub rax, rbx
	cmp rax, 0
	jge print_time_us_cont
	; negativ result
	add rax, 1000000000
	mov rbx, [ts_cur.tv_sec]
	sub rbx, 1
	mov [ts_cur.tv_sec], rbx
	print_time_us_cont:
	xor rdx, rdx
	mov rcx, 100000
	div rcx
	; set the us char in timestr
	mov r8, timestr
	add r8, 10 ; r8 points on last char before \r
	mov r9, 4 ; r9 count the number of digits
	print_time_us_loop:
		xor rdx, rdx
		mov rcx, 10
		div rcx
		add dl, 0x30
		mov [r8], dl
		sub r8, 1
		sub r9, 1
		cmp r9, 0
		jg print_time_us_loop

	; handling seconds, minutes & hours
	mov rax, [ts_cur.tv_sec]
	mov rbx, [ts_start.tv_sec]
	sub rax, rbx
	; rax now contain elapsed seconds
	; filling timestr with seconds & minutes

	xor rdx, rdx
	mov rcx, 10
	div rcx
	add dl, 0x30
	mov byte [timestr + 5], dl

	xor rdx, rdx
	mov rcx, 6
	div rcx
	push rax
	add dl, 0x30
	mov byte [timestr + 4], dl

	xor rdx, rdx
	mov rcx, 10
	div rcx
	add dl, 0x30
	mov byte [timestr + 2], dl

	pop rax
	xor rdx, rdx
	mov rcx, 6
	div rcx
	add dl, 0x30
	mov byte[timestr + 1], dl

	; filling the hours buffer
	; r8 will contain our digits counter : max is 8
	mov r8, 8
	print_time_hours_loop:
		mov rcx, 10
		xor rdx, rdx
		div rcx
		add dl, 0x30
		cmp rax, 0
		jne print_time_hours_print_mod
		cmp rdx, 0
		je print_time_hours_loop_end

		print_time_hours_print_mod:
		mov r9, hours
		add r9, r8
		mov byte [r9], dl
		cmp r8, 0
		je fault
		sub r8, 1
		cmp rax, 0
		jne print_time_hours_loop
	print_time_hours_loop_end:

	; print hours + timestr
	add r8, 1
	cmp r8, 7
	jle print_time_hours_cont
	mov r8, 7 ; maximum value for r8
	print_time_hours_cont:
	mov r9, hours
	add r9, r8
	mov rcx, 9
	sub rcx, r8 ; rcx is hours size 
	add rcx, timestrlen ; add to timestrlen

	; Set leading char
	pop r10
	mov byte [timestr+timestrlen-1], r10b

	mov rax, 1 ; write
	pop r10 ; print_time FD arg
	mov rdi, r10 ; print_time arg
	mov rsi, r9 ; start hours pointer
	mov rdx, rcx ; size to timestr end
	syscall

	ret

;
;	sig handler for SIGINT displaying lap count and time on stdout
;
proc_lap_handler:
	mov rax, 1
	mov rdi, 1
	mov rsi, lapsmsg
	mov rdx, 5 ; "Lap "
	syscall

	; increment the lapcount str directly
	mov rbx, lapcount ; first digit ptr
	add rbx, lapcountlen ; rightmost digit ptr
	sub rbx, 1
	mov r8, 1 ; counter
	lap_handler_inc_lap:
		mov r10b, [rbx]
		cmp r10b, 0x39 ; '9'
		jl lap_handler_inc_end

		add r8, 1
		cmp r8, [laplen]
		jl lap_handler_laplen_noupd
		mov [laplen], r8 ; update laplen

		lap_handler_laplen_noupd:
		mov byte [rbx], 0x30 ; set current digit to '0'
		sub rbx, 1
		cmp rbx, lapcount
		jl fault
		jmp lap_handler_inc_lap
	lap_handler_inc_end:
		add r10b, 1
		mov [rbx], r10b
	

	mov rax, 1
	mov rdi, 1
	mov rdx, [laplen]
	mov rsi, lapcount
	add rsi, lapcountlen
	sub rsi, rdx ; leftmost digit ptr
	syscall

	mov rax, 1
	mov rdi, 1
	mov rsi, lapsmsg + 4
	mov rdx, 3 ; " : "
	syscall

	push 1 ; stdout
	push 0x0A ; \n
	call proc_print_time

	ret

sig_restorer:
	mov rax, 15 ; sys_rt_sigreturn
	xor rdi, rdi
	syscall

.end: