forth

commit c54d77850972826175e624f376825362906ece84
parent ad1ee3243fe6a83760842cbf5c6b13fcb253cc0e
Author: Christian Ermann <christianermann@gmail.com>
Date:   Sat, 16 Dec 2023 13:56:51 -0500

Add FIND

Diffstat:
M
forth.asm
 | 
58
++++++++++++++++++++++++++++++++++++++++++++++++++++++++--

1 file changed, 56 insertions(+), 2 deletions(-)
diff --git a/forth.asm b/forth.asm
@@ -279,7 +279,7 @@ macro set_program init_stack_macro, program_label {
 ;
 
 defcode "EMIT", 4, 0, EMIT
-; Print a character.
+; Print a character. 
 ;
 ; The character is temporarily stored in the `.char_buffer` local variable.
 ; `.char_buffer` is defined as a 1-byte variable in the data section at the
@@ -353,15 +353,69 @@ defcode "WORD", 4, 0, WORD_
     push rdx
     NEXT
 
+defcode "FIND", 4, 0, FIND
+    pop rcx    ; string length
+    pop rdi    ; string address
+
+    push rsi
+    mov rdx, link
+
+.match_word:
+    test rdx, rdx     ; check if null (start of dictionary / out of words)
+    je .end
+
+    movzx rax, byte [rdx + 9] ; al = name length
+    
+    ; TEMP: print current word for debugging
+    push rax
+    push rcx
+    push rdx
+    push rdi
+    lea rcx, [rdx + 10]
+    mov rdx, rax
+    call sys_print_string
+    pop rdi
+    pop rdx
+    pop rcx
+    pop rax
+
+    cmp cl, al                ; check if word lengths match
+    jne .next_word
+
+    push rdi                  ; Save word address
+    push rcx                  ; Save word length
+    lea rsi, [rdx + 10]       ; Get word name address
+
+    ; RSI = src string
+    ; RDI = dst string
+    ; RCX = # of characters to compare
+    repe cmpsb
+    pop rcx
+    pop rdi
+
+    jne .next_word
+
+.end:
+    pop rsi
+    push rdx
+    mov rax, rdx
+    NEXT
+
+.next_word:
+    mov rdx, [rdx]
+    jmp .match_word
+
+
 macro initialize_stack_s4 {
     push version_string
     push version_string.length
+    mov rdx, [link]
 }
 
 program_s4:
     dq TYPE
     dq WORD_
-    dq TYPE
+    dq FIND
 
 set_program initialize_stack_s4, program_s4