-segment readable executable
+;; vim: syntax=fasm
+
+section '.text' code 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
+ call os_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 = $ - .
.found:
ret
-;; Read a word from standard input. Returns pointer to string containing word as
-;; well as length.
+;; Read a word from a buffer. Returns the buffer without the word, as well as
+;; the word that was read (including lengths).
;;
-;; Results:
-;; * rdx = Length of string
-;; * rdi = Pointer to string buffer
+;; Inputs:
+;; * rsi = Input buffer
+;; * rcx = Length of buffer
;;
-;; Clobbers pretty much everything.
-read_word:
+;; Outputs:
+;; * rsi = Updated buffer
+;; * rcx = Length of updated buffer
+;; * rdi = Word buffer
+;; * rdx = Length of word buffer
+pop_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
-
- ;; We consider newlines and spaces to be whitespace.
- cmp [.char_buffer], ' '
- je .skip_whitespace
- cmp [.char_buffer], $A
- je .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 [.length], 0
+ mov rdi, rsi ; This is where the word starts
+ mov rdx, 1 ; Length of word
.read_alpha:
- mov al, [.char_buffer]
- movzx rbx, [.length]
- mov rsi, .buffer
- add rsi, rbx
- mov [rsi], al
- inc [.length]
-
- mov rax, 0
- mov rdi, 0
- mov rsi, .char_buffer
- mov rdx, 1
- syscall
-
- cmp [.char_buffer], ' '
+ ;; 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
- cmp [.char_buffer], $A
- jne .read_alpha
+
+ ;; It wasn't whitespace; add it to word buffer
+ inc rdx
+ jmp .read_alpha
.end:
- mov rdi, .buffer
- movzx rdx, [.length]
+ ;; Finally, we want to skip one whitespace character after the word.
+ inc rsi
+ dec rcx
ret
pop rdi
printlen rdi, [.length]
newline
- exit 100
+ mov rax, 100
+ call os_terminate
-segment readable writable
+section '.data' readable writable
find.search_length dq ?
find.search_buffer dq ?
-read_word.max_size = $FF
-read_word.buffer rb read_word.max_size
-read_word.length db ?
-read_word.char_buffer db ?
-
parse_number.length dq ?
parse_number.error_msg string "Invalid number: "