-segment readable executable
+;; vim: syntax=fasm
+
+section '.text' code readable executable
+
+macro printlen msg, len {
+ push rsi
+ add rsp, 8
+
+ mov rcx, msg
+ mov rdx, len
+ sys_print_string
+
+ sub rsp, 8
+ pop rsi
+}
+
+macro newline {
+ push $A
+ printlen rsp, 1
+}
+
+macro print msg {
+ printlen msg, msg#.len
+}
+
+struc string bytes {
+ . db bytes
+ .len = $ - .
+}
;; Find the given word in the dictionary of words. If no such word exists,
;; return 0.
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:
;; Now, rax = 10^(rcx - 1).
;; We need to calulate the value of the character at rdi[length - rcx].
- mov rbx, rdi
+ mov rbx, rdi
add rbx, [.length]
sub rbx, rcx
movzx rbx, byte [rbx]
sub rbx, '0'
+ cmp rbx, 10
+ jae .error
+
;; Multiply this value by rax to get (10^(rcx-1) * parse_char(rdi[length - rcx])),
;; then add this to the result.
mul rbx
mov rax, r8
ret
+.error:
+ push rdi
+ print parse_number.error_msg
+ pop rdi
+ printlen rdi, [.length]
+ newline
+ sys_terminate 100
-segment readable writable
+section '.data' readable writable
find.search_length dq ?
find.search_buffer dq ?
read_word.char_buffer db ?
parse_number.length dq ?
+parse_number.error_msg string "Invalid number: "
projects / rrq / jonasforth.git / blobdiff