+;; vim: syntax=fasm
+
segment readable executable
macro printlen msg, len {
push rsi
add rsp, 8
- mov rsi, msg
+ mov rcx, msg
mov rdx, len
- mov rax, 1
- mov rdi, 1
- syscall
+ sys_print_string
sub rsp, 8
pop rsi
printlen msg, msg#.len
}
-macro exit code {
- mov rax, $3C
- mov rdi, code
- syscall
-}
-
struc string bytes {
. db bytes
.len = $ - .
read_word:
.skip_whitespace:
;; Read characters into .char_buffer until one of them is not whitespace.
- mov rax, 0
- mov rdi, 0
mov rsi, .char_buffer
- mov rdx, 1
- syscall
+ sys_read_char
;; We consider newlines and spaces to be whitespace.
cmp [.char_buffer], ' '
mov [rsi], al
inc [.length]
- mov rax, 0
- mov rdi, 0
mov rsi, .char_buffer
- mov rdx, 1
- syscall
+ sys_read_char
cmp [.char_buffer], ' '
je .end
ret
+;; Read a word from a buffer. Returns the buffer without the word, as well as
+;; the word that was read (including lengths).
+;;
+;; Inputs:
+;; * rsi = Input buffer
+;; * rcx = Length of buffer
+;;
+;; Outputs:
+;; * rsi = Updated buffer
+;; * rcx = Length of updated buffer
+;; * rdi = Word buffer
+;; * rdx = Length of word buffer
+pop_word:
+.skip_whitespace:
+ mov al, [rsi]
+ cmp al, ' '
+ je .got_whitespace
+ cmp al, $A
+ je .got_whitespace
+ jmp .alpha
+.got_whitespace:
+ ;; The buffer starts with whitespace; discard the first character from the buffer.
+ inc rsi
+ dec rcx
+ jmp .skip_whitespace
+
+.alpha:
+ ;; We got a character that wasn't whitespace. Now read the actual word.
+ mov rdi, rsi ; This is where the word starts
+ mov rdx, 1 ; Length of word
+
+.read_alpha:
+ ;; Extract character from original buffer:
+ inc rsi
+ dec rcx
+
+ ;; When we hit whitespace, we are done with this word
+ mov al, [rsi]
+ cmp al, ' '
+ je .end
+ cmp al, $A
+ je .end
+
+ ;; It wasn't whitespace; add it to word buffer
+ inc rdx
+ jmp .read_alpha
+
+.end:
+ ;; Finally, we want to skip one whitespace character after the word.
+ inc rsi
+ dec rcx
+
+ ret
+
;; Parses a string.
;;
;; Parameters:
pop rdi
printlen rdi, [.length]
newline
- exit 100
+ sys_terminate 100
segment readable writable