Add instructions for running on real hardware

[rrq/jonasforth.git] / impl.asm

diff --git a/impl.asm b/impl.asm
index c713036c82afb2743c45a547e4b315ac4bf41ba4..ea6c04ebd42155a2dd5f495ac57874308ad2fbe4 100644 (file)
--- a/impl.asm
+++ b/impl.asm
@@ -1,16 +1,14 @@
 ;; vim: syntax=fasm
 
-segment readable executable
+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
+  sys_print_string
 
   sub rsp, 8
   pop rsi
@@ -25,12 +23,6 @@ macro print msg {
   printlen msg, msg#.len
 }
 
-macro exit code {
-  mov rax, $3C
-  mov rdi, code
-  syscall
-}
-
 struc string bytes {
   . db bytes
   .len = $ - .
@@ -88,11 +80,8 @@ find:
 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], ' '
@@ -112,11 +101,8 @@ read_word:
   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
@@ -142,11 +128,44 @@ 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:
+  ;; Finally, we want to skip one whitespace character after the word.
+  inc rsi
+  dec rcx
 
   ret
 
@@ -210,9 +229,9 @@ parse_number:
   pop rdi
   printlen rdi, [.length]
   newline
-  exit 100
+  sys_terminate 100
 
-segment readable writable
+section '.data' readable writable
 
 find.search_length dq ?
 find.search_buffer dq ?