Implement POP-WORD

[rrq/jonasforth.git] / impl.asm

diff --git a/impl.asm b/impl.asm
index f8093d0653a43534971fd1a91cb590317019583b..070ad2a70561899ab567d4ec92796e68a588dc9a 100644 (file)
--- a/impl.asm
+++ b/impl.asm
@@ -1,5 +1,41 @@
+;; vim: syntax=fasm
+
 segment readable executable
 
+macro printlen msg, len {
+  push rsi
+  add rsp, 8
+
+  mov rsi, msg
+  mov rdx, len
+  mov rax, 1
+  mov rdi, 1
+  syscall
+
+  sub rsp, 8
+  pop rsi
+}
+
+macro newline {
+  push $A
+  printlen rsp, 1
+}
+
+macro print msg {
+  printlen msg, msg#.len
+}
+
+macro exit code {
+  mov rax, $3C
+  mov rdi, code
+  syscall
+}
+
+struc string bytes {
+  . db bytes
+  .len = $ - .
+}
+
 ;; Find the given word in the dictionary of words. If no such word exists,
 ;; return 0.
 ;;
@@ -15,12 +51,12 @@ segment readable executable
 find:
   ;; RSI contains the entry we are currently looking at
 .loop:
-  movzx rcx, byte [rsi + 8]     ; Length of word being looked at
+  movzx rcx, byte [rsi + 8 + 1]    ; Length of word being looked at
   cmp rcx, [.search_length]
   jne .next    ; If the words don't have the same length, we have the wrong word
 
   ;; Otherwise, we need to compare strings
-  lea rdx, [rsi + 8 + 1]        ; Location of character being compared in entry
+  lea rdx, [rsi + 8 + 1 + 1]    ; Location of character being compared in entry
   mov rdi, [.search_buffer]     ; Location of character being compared in search buffer
 .compare_char:
   mov al, [rdx]
@@ -93,11 +129,62 @@ read_word:
 
   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:
+
+  ret
+
 ;; Parses a string.
 ;;
 ;; Parameters:
-;;   * [.length] = Length of string
-;;   * [.buffer] = Pointer to string buffer
+;;   * rcx = Length of string
+;;   * rdi = Pointer to string buffer
 ;;
 ;; Results:
 ;;   * rax = Value
@@ -108,7 +195,7 @@ parse_number:
 
   ;; Add (10^(rcx-1) * parse_char(rdi[length - rcx])) to the accumulated value
   ;; for each rcx.
-  mov rcx, [.length]
+  mov [.length], rcx
 .loop:
   ;; First, calcuate 10^(rcx - 1)
   mov rax, 1
@@ -125,12 +212,15 @@ parse_number:
   ;; 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
@@ -144,6 +234,13 @@ parse_number:
   mov rax, r8
   ret
 
+.error:
+  push rdi
+  print parse_number.error_msg
+  pop rdi
+  printlen rdi, [.length]
+  newline
+  exit 100
 
 segment readable writable
 
@@ -155,6 +252,6 @@ read_word.buffer rb read_word.max_size
 read_word.length db ?
 read_word.char_buffer db ?
 
-parse_number.buffer dq ?
 parse_number.length dq ?
+parse_number.error_msg string "Invalid number: "