Add argument parsing

wtfstopw.asm

 
 	ts_sleep:
 		tv_sleep_s dq 0
-		tv_sleep_us dq 10000000
+		tv_sleep_us dq 10000000 ; set for 4 digits bellow seconds
 
 	;; 1/2s sleep
 	;ts_sleep:
 	db 0xA
 	startmsglen: equ $ - startmsg
 
+	usage_pre: db "Usage : "
+	usage_prelen: equ $ - usage_pre
+
+	usage_post: db " [-h] [-r NDIGITS]", 0xA
+		db "Options :", 0xA
+		db 0x9, "-h print this help and exit", 0xA
+		db 0x9, "-r Number of digits bellow seconds, between [1..8]"
+		db 0xA
+	usage_postlen: equ $ - usage_post
+
+	badarg_msg: db "Unexpected argument : "
+	badarg_msglen: equ $ - badarg_msg
+
+	badval_msg: db "Value for -r should be in [1..8] but got "
+	badval_msglen: equ $ - badval_msg
+
 	hours: db "000000000"
 	timestr: db ":00:00.0           ", 0x0a
 	timestrlen: equ $ - timestr
 
-	time_res: dq 3 ; 3 digits bellow seconds
+	time_res: dq 4 ; 4 digits bellow seconds
 
 	nl: db 0x0A
 	buf: db 0
 global _start
 _start:
 
+; parse arguments and set time_res value
+jmp arg_parse
+arg_ok:
+
 ; set stdin non blocking
 xor rdx, rdx
 xor rdi, rdi
 	xor rdi, rdi
 	syscall
 
+;
+;	Argument parsing
+;
+arg_parse:
+	; Checking argument count
+	mov rax, [rsp]
+	cmp rax, 3
+	je parse_r
+	cmp rax, 1
+	je arg_ok
+	; If 1 argument only it can only be -h
+	arg_err: ; badval & badarg jmp here too
+		mov rax, [rsp+8] ; argv[0] program name
+		mov rdi, -1 ; return status
+		jmp usage
+	parse_r:
+	mov rax, [rsp+16] ; 1st arg should be "-r"
+	mov bl, [rax]
+	cmp bl, '-'
+	jne badarg
+	mov bl, [rax+1]
+	cmp bl, 'h' ; -h given with another argument
+	je arg_err
+	cmp bl, 'r'
+	jne badarg
+	mov bl, [rax+2]
+	cmp bl, 0
+	; the 1st argument is -r the second must be a 1 digit integer in [1..8]
+	mov rax, [rsp+24]
+	xor rbx, rbx
+	mov bl, [rax]
+	cmp bl, '1'
+	jl badval
+	cmp bl, '8'
+	jg badval
+	sub bl, '0'
+	dbg1:
+	mov [time_res], rbx
+	jmp arg_ok
+
+badval: ; print an error message, usage and exit
+	mov rsi, badval_msg
+	mov rdx, badval_msglen
+	mov rax, [rsp+24]
+	jmp arg_strerr
+
+badarg: ; print an error message, usage and exit
+	mov rsi, badarg_msg
+	mov rdx, badarg_msglen
+	mov rax, [rsp+16]
+	jmp arg_strerr
+
+arg_strerr: ; rsi msg ptr, rdx msg len, rax arg ptr
+	mov r8, rax
+	mov rax, 1
+	mov rdi, 1
+	syscall
+	mov rsi, r8
+	mov rax, r8
+	call strlen
+	mov rax, 1
+	syscall
+	mov rax, 1
+	mov rsi, nl
+	mov rdx, 1
+	syscall
+	syscall
+	jmp arg_err
+
+;
+; Print usage and exit
+; 	Except rax to point on programm name and rdi to be the return code
+;
+usage:
+	push rdi
+	push rax
+
+	mov rax, 1 ; write
+	mov rdi, 1 ; stdout
+	mov rsi, usage_pre
+	mov rdx, usage_prelen
+	syscall
+
+	pop rsi
+	mov rax, rsi
+	call strlen
+	mov rax, 1
+	syscall
+
+	mov rax, 1
+	mov rsi, usage_post
+	mov rdx, usage_postlen
+	syscall
+
+	mov rax, 60
+	pop rdi
+	syscall
+
+; With rax pointing on the string, the result will be in rdx
+strlen:
+	mov r8, rax
+	mov r9, r8
+	sub r9, 1
+	strlen_loop:
+		add r9, 1
+		mov al, [r9]
+		cmp al, 0
+		jne strlen_loop
+	sub r9, r8
+	mov rdx, r9
+	ret
+
 .end: