Improve README and update information about sys.f

[rrq/jonasforth.git] / main.asm

diff --git a/main.asm b/main.asm
index c9a7fc42acc1d9deb022010648f9c36c1aab30ee..a670b343e99c1a1f0154f0eab083ef6eb1e6cc1a 100644 (file)
--- a/main.asm
+++ b/main.asm
@@ -195,9 +195,14 @@ forth_asm EMIT, 'EMIT'
   popr rsi
   next
 
-;; Read a word from standard input and push it onto the stack as a pointer and a
-;; size. The pointer is valid until the next call to READ_WORD.
+;; Read a word and push it onto the stack as a pointer and a size. The pointer
+;; is valid until the next call to READ_WORD.
 forth_asm READ_WORD, 'READ-WORD'
+  ;; Are we reading from user input or from the input buffer?
+  cmp [input_buffer], 0
+  jne .from_buffer
+
+  ;; Reading user input
   mov [.rsi], rsi
 
   call read_word
@@ -207,23 +212,21 @@ forth_asm READ_WORD, 'READ-WORD'
   mov rsi, [.rsi]
   next
 
-;; Read a word from a buffer. Expects (buffer buffer-length) on the stack.
-;; Updates buffer and buffer-length, such that the word has been removed from
-;; the buffer. Appends (word-buffer word-buffer-length) to the stack.
-forth_asm POP_WORD, 'POP-WORD'
-  pushr rsi
+.from_buffer:
+  ;; Reading from buffer
+  mov [.rsi], rsi
 
-  pop rcx ; Length
-  pop rsi ; Buffer
+  mov rsi, [input_buffer]
+  mov rcx, [input_buffer_length]
 
   call pop_word
 
-  push rsi ; Updated buffer
-  push rcx ; Length of updated buffer
-  push rdi ; Word buffer
-  push rdx ; Length of word buffer
+  mov [input_buffer], rsi        ; Updated buffer
+  mov [input_buffer_length], rcx ; Length of updated buffer
+  push rdi                       ; Word buffer
+  push rdx                       ; Length of word buffer
 
-  popr rsi
+  mov rsi, [.rsi]
   next
 
 ;; Takes a string on the stack and replaces it with the decimal number that the
@@ -406,10 +409,14 @@ forth_asm TIMESMOD, '/MOD'
   push rdx                      ; a % b
   next
 
-;; Read user input until next " character is found. Push a string containing the
+;; Read input until next " character is found. Push a string containing the
 ;; input on the stack as (buffer length). Note that the buffer is only valid
-;; until the next call to S" and that no more than 255 character can be read.
+;; until the next call to S" and that no more than 255 characters can be read.
 forth_asm READ_STRING, 'S"'
+  ;; If the input buffer is set, we should read from there instead.
+  cmp [input_buffer], 0
+  jne read_string_buffer
+
   push rsi
 
   mov [.length], 0
@@ -439,6 +446,40 @@ forth_asm READ_STRING, 'S"'
 
   next
 
+read_string_buffer:
+  push rsi
+
+  ;; We borrow READ_STRING's buffer. They won't mind.
+  mov [READ_STRING.length], 0
+
+.read_char:
+  mov rbx, [input_buffer]
+  mov al, [rbx]
+  cmp al, '"'
+  je .done
+
+  mov rdx, READ_STRING.buffer
+  add rdx, [READ_STRING.length]
+  mov [rdx], al
+  inc [READ_STRING.length]
+
+  inc [input_buffer]
+  dec [input_buffer_length]
+
+  jmp .read_char
+
+.done:
+  pop rsi
+
+  ;; Skip closing "
+  inc [input_buffer]
+  dec [input_buffer_length]
+
+  push READ_STRING.buffer
+  push [READ_STRING.length]
+
+  next
+
 ;; CREATE inserts a new header in the dictionary, and updates LATEST so that it
 ;; points to the header. To compile a word, the user can then call ',' to
 ;; continue to append data after the header.
@@ -506,6 +547,8 @@ forth_asm EQL, '='
   next
 
 forth MAIN, 'MAIN'
+  dq SYSCODE
+  dq INTERPRET_STRING
   dq INTERPRET
   dq BRANCH, -8 * 2
   dq TERMINATE
@@ -529,6 +572,14 @@ forth SYSCODE, 'SYSCODE'
   dq LIT, sysf.len
   dq EXIT
 
+forth INPUT_BUFFER, 'INPUT-BUFFER'
+  dq LIT, input_buffer
+  dq EXIT
+
+forth INPUT_LENGTH, 'INPUT-LENGTH'
+  dq LIT, input_buffer_length
+  dq EXIT
+
 segment readable writable
 
 ;; The LATEST variable holds a pointer to the word that was last added to the
@@ -540,6 +591,12 @@ latest_entry dq initial_latest_entry
 ;; it is compiling.
 var_STATE dq 0
 
+;; The interpreter can read either from standard input or from a buffer. When
+;; input-buffer is set (non-null), words like READ-WORD and S" will use this
+;; buffer instead of reading user input.
+input_buffer dq 0
+input_buffer_length dq 0
+
 FIND.rsi dq ?
 
 READ_WORD.rsi dq ?