;; 'dq' statements.)
macro forth label, name {
header label, name
- dq docol
+ dq DOCOL
}
-
-
segment readable executable
entry main
;; The codeword is the code that will be executed at the beginning of a forth
;; word. It needs to save the old RSI and update it to point to the next word to
;; execute.
-docol:
+header DOCOL, 'DOCOL'
pushr rsi ; Save old value of RSI on return stack; we will continue execution there after we are done executing this word
lea rsi, [rax + 8] ; RAX currently points to the address of the codeword, so we want to continue at RAX+8
next ; Execute word pointed to by RSI
;; 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.
+;; restore the old value of RSI (saved by 'DOCOL') and resume execution.
forth_asm EXIT, 'EXIT'
popr rsi
next
dq NEWLINE
dq EXIT
+;; Duplicate a pair of elements.
+forth_asm PAIRDUP, '2DUP'
+ pop rbx
+ pop rax
+ push rax
+ push rbx
+ push rax
+ push rbx
+ next
+
+;; Swap the top two elements on the stack.
+forth_asm SWAP, 'SWAP'
+ pop rax
+ pop rbx
+ push rax
+ push rbx
+ next
+
+;; Remove the top element from the stack.
+forth_asm DROP, 'DROP'
+ add rsp, 8
+ next
+
;; 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'
+ ;; Read word
dq READ_WORD
- dq FIND
+ dq PAIRDUP
+ ;; Stack is (word length word length).
+ dq FIND ; Try to find word
+ dq DUP_
+ dq ZBRANCH, 8 * 8 ; Check if word is found
+
+ ;; Word is found, execute it
dq TCFA
+ ;; Stack is (word length addr)
+ dq SWAP, DROP
+ dq SWAP, DROP
+ ;; Stack is (addr)
dq EXEC
dq EXIT
+ ;; No word is found, assume it is an integer literal
+ ;; Stack is (word length addr)
+ dq DROP
+ dq PARSE_NUMBER
+ dq EXIT
+
;; .U prints the value on the stack as an unsigned integer in hexadecimal.
forth_asm DOTU, '.U'
mov [.length], 0
push rax
next
+;; Add two integers on the stack.
+forth_asm PLUS, '+'
+ pop rax
+ pop rbx
+ add rax, rbx
+ push rax
+ next
+
+;; Calculate difference between two integers on the stack. The second number is
+;; subtracted from the first.
+forth_asm MINUS, '-'
+ pop rax
+ pop rbx
+ sub rbx, rax
+ push rbx
+ next
+
;; Get the location of the STATE variable. It can be set with '!' and read with
;; '@'.
forth STATE, 'STATE'
dq LIT, var_STATE
dq EXIT
+;; Get the location of the LATEST variable. It can be set with '!' and read with
+;; '@'.
+forth LATEST, 'LATEST'
+ dq LIT, latest_entry
+ dq EXIT
+
+;; Get the location at which compiled words are expected to be added. This
+;; pointer is usually modified automatically when calling ',', but we can also
+;; read it manually with 'HERE'.
+forth HERE, 'HERE'
+ dq LIT, here
+ dq EXIT
+
+forth COMMA, ','
+ dq HERE, GET, PUT ; Set the memory at the address pointed to by HERE
+ dq HERE, GET, LIT, 8, PLUS ; Calculate new address for HERE to point to
+ dq HERE, PUT ; Update HERE to point to the new address
+ dq EXIT
+
+;; Read user 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.
+forth_asm READ_STRING, 'S"'
+ push rsi
+
+ mov [.length], 0
+
+.read_char:
+ mov rax, 0
+ mov rdi, 0
+ mov rsi, .char_buffer
+ mov rdx, 1
+ syscall
+
+ mov al, [.char_buffer]
+ cmp al, '"'
+ je .done
+
+ mov rdx, .buffer
+ add rdx, [.length]
+ mov [rdx], al
+ inc [.length]
+ jmp .read_char
+
+.done:
+ pop rsi
+
+ push .buffer
+ push [.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.
+;;
+;; It takes the name of the word as a string (address length) on the stack.
+forth_asm CREATE, 'CREATE'
+ pop rcx ; Word string length
+ pop rdx ; Word string pointer
+
+ mov rdi, [here] ; rdi = Address at which to insert this entry
+ mov rax, [latest_entry] ; rax = Address of the previous entry
+ mov [rdi], rax ; Insert link to previous entry
+ mov [latest_entry], rdi ; Update LATEST to point to this word
+
+ add rdi, 8
+ mov [rdi], rcx ; Insert length
+
+ ;; Insert word string
+ add rdi, 1
+
+ push rsi
+ mov rsi, rdx ; rsi = Word string pointer
+ rep movsb
+ pop rsi
+
+ ;; Update HERE
+ mov [here], rdi
+
+ next
+
forth MAIN, 'MAIN'
dq HELLO
dq INTERPRET
segment readable writable
+;; The LATEST variable holds a pointer to the word that was last added to the
+;; dictionary. This pointer is updated as new words are added, and its value is
+;; used by FIND to look up words.
latest_entry dq initial_latest_entry
;; The STATE variable is 0 when the interpreter is executing, and non-zero when
READ_WORD.rsi dq ?
READ_WORD.rbp dq ?
+READ_STRING.char_buffer db ?
+READ_STRING.buffer rb $FF
+READ_STRING.length 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 ?
+;; Reserve space for compiled words, accessed through HERE.
+here dq here_top
+here_top rq $2000
+
;; Return stack
rq $2000
return_stack_top:
projects / rrq / jonasforth.git / blobdiff