add rbp, 8
}
+;; The following macro generates the dictionary header. It updates the
+;; initial_latest_entry variable, which is used as the initial value of the
+;; latest_entry variable that is made available at runtime.
+;;
+;; The header contains a link to the previous entry, the length of the name of
+;; the word and the word itself as a string literal.
+;;
+;; This macro also defines a label LABEL_entry.
+initial_latest_entry = 0
+macro header label, name {
+ local .string_end
+
+label#_entry:
+ dq initial_latest_entry
+ db .string_end - ($ + 1)
+ db name
+ .string_end:
+label:
+
+initial_latest_entry = label#_entry
+}
+
+;; Define a Forth word that is implemented in assembly. See 'header' for details.
+macro forth_asm label, name {
+ header label, name
+ dq .start
+.start:
+}
+
+;; Define a Forth word that is implemented in Forth. (The body will be a list of
+;; 'dq' statements.)
+macro forth label, name {
+ header label, name
+ dq docol
+}
+
+
+
segment readable executable
+entry main
+
+include "impl.asm"
+
main:
cld ; Clear direction flag so LODSQ does the right thing.
mov rbp, return_stack_top ; Initialize return stack
- mov rsi, program
- next
+ mov rax, MAIN
+ jmp qword [rax]
program: dq MAIN
;; This word is called at the end of a Forth definition. It just needs to
;; restore the old value of RSI (saved by 'docol') and resume execution.
-EXIT:
- dq .start
-.start:
+forth_asm EXIT, 'EXIT'
popr rsi
next
;; LIT is a special word that reads the next "word pointer" and causes it to be
;; placed on the stack rather than executed.
-LIT:
- dq .start
-.start:
+forth_asm LIT, 'LIT'
lodsq
push rax
next
+;; Given a string (a pointer following by a size), return the location of the
+;; dictionary entry for that word. If no such word exists, return 0.
+forth_asm FIND, 'FIND'
+ mov [.rsi], rsi
+
+ pop [find.search_length]
+ pop [find.search_buffer]
+ mov rsi, [latest_entry] ; Start with the last added word
+ call find
+ push rsi
+
+ mov rsi, [.rsi]
+ next
+ push rsi
+
+ mov rsi, [.rsi]
+ next
+
+;; Given an entry in the dictionary, return a pointer to the codeword of that
+;; entry.
+forth_asm TCFA, '>CFA'
+ pop rax
+ add rax, 8 ; [rax] = length of name
+ movzx rbx, byte [rax]
+ inc rax
+ add rax, rbx ; [rax] = codeword
+ push rax
+ next
+
;; BRANCH is the fundamental mechanism for branching. BRANCH reads the next word
;; as a signed integer literal and jumps by that offset.
-BRANCH:
- dq .start
-.start:
+forth_asm BRANCH, 'BRANCH'
add rsi, [rsi] ; [RSI], which is the next word, contains the offset; we add this to the instruction pointer.
next ; Then, we can just continue execution as normal
;; 0BRANCH is like BRANCH, but it jumps only if the top of the stack is zero.
-ZBRANCH:
- dq .start
-.start:
+forth_asm ZBRANCH, '0BRANCH'
;; Compare top of stack to see if we should branch
pop rax
cmp rax, 0
add rsi, 8 ; We need to skip over the next word, which contains the offset.
next
+;; Duplicate the top of the stack.
+forth_asm DUP_, 'DUP'
+ push qword [rsp]
+ next
+
+;; Execute the codeword at the given address.
+forth_asm EXEC, 'EXEC'
+ pop rax
+ jmp qword [rax]
+
;; Expects a character on the stack and prints it to standard output.
-EMIT:
- dq .start
-.start:
+forth_asm EMIT, 'EMIT'
pushr rsi
pushr rax
mov rax, 1
next
;; Prints a newline to standard output.
-NEWLINE:
- dq docol
+forth NEWLINE, 'NEWLINE'
dq LIT, $A
dq EMIT
dq EXIT
+;; Prints a space to standard output.
+forth SPACE, 'SPACE'
+ dq LIT, ' '
+ dq EMIT
+ dq EXIT
+
;; 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_WORD: ; 400170
- dq .start
-.start:
+forth_asm READ_WORD, 'READ-WORD'
mov [.rsi], rsi
- mov [.rax], rax
-.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
-
- cmp [.char_buffer], ' '
- je .skip_whitespace
- cmp [.char_buffer], $A
- je .skip_whitespace
-
-.alpha:
- ;; We got a character that wasn't whitespace. Now read the actual word.
- mov [.length], 0
-
-.read_alpha:
- mov al, [.char_buffer]
- movzx rbx, [.length]
- mov rsi, .buffer
- add rsi, rbx
- mov [rsi], al
- inc [.length]
-
- mov rax, 0
- mov rdi, 0
- mov rsi, .char_buffer
- mov rdx, 1
- syscall
+ call read_word
+ push rdi ; Buffer
+ push rdx ; Length
- cmp [.char_buffer], ' '
- je .end
- cmp [.char_buffer], $A
- jne .read_alpha
+ mov rsi, [.rsi]
+ next
-.end:
- push .buffer
- movzx rax, [.length]
- push rax
+;; Takes a string on the stack and replaces it with the decimal number that the
+;; string represents.
+forth_asm PARSE_NUMBER, 'PARSE-NUMBER'
+ pop [parse_number.length] ; Length
+ pop [parse_number.buffer] ; String pointer
- mov rsi, [.rsi]
- mov rax, [.rax]
+ push rsi
+ call parse_number
+ pop rsi
+ push rax ; Result
next
+forth READ_NUMBER, 'READ-NUMBER'
+ dq READ_WORD
+ dq PARSE_NUMBER
+ dq EXIT
+
;; Takes a string (in the form of a pointer and a length on the stack) and
;; prints it to standard output.
-TELL:
- dq .start
-.start:
+forth_asm TELL, 'TELL'
mov rbx, rsi
mov rcx, rax
next
;; Exit the program cleanly.
-TERMINATE:
- dq .start
-.start:
+forth_asm TERMINATE, 'TERMINATE'
mov rax, $3C
mov rdi, 0
syscall
-PUSH_HELLO_CHARS:
- dq docol
- dq LIT, $A
- dq LIT, 'o'
- dq LIT, 'l'
- dq LIT, 'l'
- dq LIT, 'e'
- dq LIT, 'H'
- dq EXIT
-
-PUSH_YOU_TYPED:
- dq .start
-.start:
- push you_typed_string
- push you_typed_string.length
- next
-
-HELLO:
- dq docol
+forth HELLO, 'HELLO'
dq LIT, 'H', EMIT
dq LIT, 'e', EMIT
dq LIT, 'l', EMIT
dq NEWLINE
dq EXIT
-MAIN:
- dq docol
- dq HELLO
+;; The INTERPRET word reads and interprets user input. It's behavior depends on
+;; the current STATE. It provides special handling for integers. (TODO)
+forth INTERPRET, 'INTERPRET'
dq READ_WORD
- dq LIT, you_typed_string
- dq LIT, you_typed_string.length
- dq TELL
- dq TELL
- dq NEWLINE
- dq BRANCH, -72
+ dq FIND
+ dq TCFA
+ dq EXEC
+ dq EXIT
+
+;; .U prints the value on the stack as an unsigned integer in hexadecimal.
+forth_asm DOTU, '.U'
+ mov [.length], 0
+ mov [.printed_length], 1
+ pop rax ; RAX = value to print
+ push rsi ; Save value of RSI
+
+ ;; We start by constructing the buffer to print in reverse
+
+.loop:
+ mov rdx, 0
+ mov rbx, $10
+ div rbx ; Put remainer in RDX and quotient in RAX
+
+ ;; Place the appropriate character in the buffer
+ mov rsi, .chars
+ add rsi, rdx
+ mov bl, [rsi]
+ mov rdi, .rbuffer
+ add rdi, [.length]
+ mov [rdi], bl
+ inc [.length]
+
+ ;; .printed_length is the number of characters that we ulitmately want to
+ ;; print. If we have printed a non-zero character, then we should update
+ ;; .printed_length.
+ cmp bl, '0'
+ je .skip_updating_real_length
+ mov rbx, [.length]
+ mov [.printed_length], rbx
+.skip_updating_real_length:
+
+ cmp [.length], 16
+ jle .loop
+
+ ;; Flip buffer around, since it is currently reversed
+ mov rcx, [.printed_length]
+.flip:
+ mov rsi, .rbuffer
+ add rsi, rcx
+ dec rsi
+ mov al, [rsi]
+
+ mov rdi, .buffer
+ add rdi, [.printed_length]
+ sub rdi, rcx
+ mov [rdi], al
+
+ loop .flip
+
+ ;; Print the buffer
+ mov rax, 1
+ mov rdi, 1
+ mov rsi, .buffer
+ mov rdx, [.printed_length]
+ syscall
+
+ ;; Restore RSI and continue execution
+ pop rsi
+ next
+
+forth MAIN, 'MAIN'
dq HELLO
+ dq INTERPRET
+ dq BRANCH, -8 * 2
dq TERMINATE
segment readable writable
-you_typed_string db 'You typed: '
-.length = $ - you_typed_string
+latest_entry dq initial_latest_entry
+
+FIND.rsi dq ?
READ_WORD.rsi dq ?
-READ_WORD.rax dq ?
-READ_WORD.max_size = $FF
-READ_WORD.buffer rb READ_WORD.max_size
-READ_WORD.length db ?
-READ_WORD.char_buffer db ?
+READ_WORD.rbp dq ?
+
+DOTU.chars db '0123456789ABCDEF'
+DOTU.buffer rq 16 ; 64-bit number has no more than 16 digits in hex
+DOTU.rbuffer rq 16
+DOTU.length dq ?
+DOTU.printed_length dq ?
;; Return stack
rq $2000
projects / rrq / jonasforth.git / blobdiff