From: Jonas Hvid <mail@johv.dk>
Date: Sun, 8 Mar 2020 14:48:18 +0000 (+0100)
Subject: Implement POP-WORD
X-Git-Url: https://git.rrq.au/?a=commitdiff_plain;h=bb3723bbe99455e7b95d5376758047563bd72eed;p=rrq%2Fjonasforth.git

Implement POP-WORD
---

diff --git a/example.f b/example.f
index 547887f..f5215db 100644
--- a/example.f
+++ b/example.f
@@ -25,9 +25,12 @@ S" 10 FIB = " TELL
 10 FIB .U
 SPACE S" (Expected: 59)" TELL NEWLINE
 
-S" Word:" TELL NEWLINE
-SYSCODE POP-WORD TELL NEWLINE
-S" Remaining:" TELL NEWLINE
-TELL
+SYSCODE
+S" Word: " TELL POP-WORD TELL NEWLINE
+S" Word: " TELL POP-WORD TELL NEWLINE
+S" Word: " TELL POP-WORD TELL NEWLINE
+S" Word: " TELL POP-WORD TELL NEWLINE
+S" Word: " TELL POP-WORD TELL NEWLINE
+S" Word: " TELL POP-WORD TELL NEWLINE
 
 TERMINATE
diff --git a/impl.asm b/impl.asm
index c713036..070ad2a 100644
--- a/impl.asm
+++ b/impl.asm
@@ -142,11 +142,41 @@ read_word:
 ;;   * rdi = Word buffer
 ;;   * rdx = Length of word buffer
 pop_word:
-  mov rdi, rsi
-  mov rdx, 10
+.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
 
-  add rsi, 10
-  sub rcx, 10
+.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