collapseos/forth/forth.asm
2020-03-27 19:53:28 -04:00

1272 lines
24 KiB
NASM

; Collapse OS' Forth
;
; Unlike other assembler parts of Collapse OS, this unit is one huge file.
;
; I do this because as Forth takes a bigger place, assembler is bound to take
; less and less place. I am thus consolidating that assembler code in one
; place so that I have a better visibility of what to minimize.
;
; I also want to reduce the featureset of the assembler so that Collapse OS
; self-hosts in a more compact manner. File include is a big part of the
; complexity in zasm. If we can get rid of it, we'll be more compact.
; *** ABI STABILITY ***
;
; This unit needs to have some of its entry points stay at a stable offset.
; These have a comment over them indicating the expected offset. These should
; not move until the Grand Bootstrapping operation has been completed.
;
; When you see random ".fill" here and there, it's to ensure that stability.
; *** Defines ***
; GETC: address of a GetC routine
; PUTC: address of a PutC routine
;
; Those GetC/PutC routines are hooked through defines and have this API:
;
; GetC: Blocks until a character is read from the device and return that
; character in A.
;
; PutC: Write character specified in A onto the device.
;
; *** Const ***
; Base of the Return Stack
.equ RS_ADDR 0xf000
; Number of bytes we keep as a padding between HERE and the scratchpad
.equ PADDING 0x20
; Buffer where WORD copies its read word to.
.equ WORD_BUFSIZE 0x20
; Allocated space for sysvars (see comment above SYSVCNT)
.equ SYSV_BUFSIZE 0x10
; Flags for the "flag field" of the word structure
; IMMEDIATE word
.equ FLAG_IMMED 7
; *** Variables ***
.equ INITIAL_SP RAMSTART
; wordref of the last entry of the dict.
.equ CURRENT @+2
; Pointer to the next free byte in dict.
.equ HERE @+2
; Interpreter pointer. See Execution model comment below.
.equ IP @+2
; Global flags
; Bit 0: whether the interpreter is executing a word (as opposed to parsing)
.equ FLAGS @+2
; Pointer to the system's number parsing function. It points to then entry that
; had the "(parse)" name at startup. During stage0, it's out builtin PARSE,
; but at stage1, it becomes "(parse)" from core.fs. It can also be changed at
; runtime.
.equ PARSEPTR @+2
; Pointer to the word executed by "C<". During stage0, this points to KEY.
; However, KEY ain't very interactive. This is why we implement a readline
; interface in Forth, which we plug in during init. If "(c<)" exists in the
; dict, CINPTR is set to it. Otherwise, we set KEY
.equ CINPTR @+2
; Pointer to (emit) word
.equ EMITPTR @+2
; Pointer to (print) word
.equ PRINTPTR @+2
.equ WORDBUF @+2
; Sys Vars are variables with their value living in the system RAM segment. We
; need this mechanisms for core Forth source needing variables. Because core
; Forth source is pre-compiled, it needs to be able to live in ROM, which means
; that we can't compile a regular variable in it. SYSVNXT points to the next
; free space in SYSVBUF. Then, at the word level, it's a regular sysvarWord.
.equ SYSVNXT @+WORD_BUFSIZE
.equ SYSVBUF @+2
.equ RAMEND @+SYSV_BUFSIZE
; (HERE) usually starts at RAMEND, but in certain situations, such as in stage0,
; (HERE) will begin at a strategic place.
.equ HERE_INITIAL RAMEND
; EXECUTION MODEL
; After having read a line through readline, we want to interpret it. As
; a general rule, we go like this:
;
; 1. read single word from line
; 2. Can we find the word in dict?
; 3. If yes, execute that word, goto 1
; 4. Is it a number?
; 5. If yes, push that number to PS, goto 1
; 6. Error: undefined word.
;
; EXECUTING A WORD
;
; At it's core, executing a word is having the wordref in IY and call
; EXECUTE. Then, we let the word do its things. Some words are special,
; but most of them are of the compiledWord type, and that's their execution that
; we describe here.
;
; First of all, at all time during execution, the Interpreter Pointer (IP)
; points to the wordref we're executing next.
;
; When we execute a compiledWord, the first thing we do is push IP to the Return
; Stack (RS). Therefore, RS' top of stack will contain a wordref to execute
; next, after we EXIT.
;
; At the end of every compiledWord is an EXIT. This pops RS, sets IP to it, and
; continues.
; *** Stable ABI ***
; Those jumps below are supposed to stay at these offsets, always. If they
; change bootstrap binaries have to be adjusted because they rely on them.
; We're at 0 here
jp forthMain
.fill 0x08-$
JUMPTBL:
jp sysvarWord
jp cellWord
jp compiledWord
jp pushRS
jp popRS
jp nativeWord
jp next
jp chkPS
NUMBER:
.dw numberWord
LIT:
.dw litWord
; *** Code ***
forthMain:
; STACK OVERFLOW PROTECTION:
; To avoid having to check for stack underflow after each pop operation
; (which can end up being prohibitive in terms of costs), we give
; ourselves a nice 6 bytes buffer. 6 bytes because we seldom have words
; requiring more than 3 items from the stack. Then, at each "exit" call
; we check for stack underflow.
push af \ push af \ push af
ld (INITIAL_SP), sp
ld ix, RS_ADDR
; LATEST is a label to the latest entry of the dict. This can be
; overridden if a binary dict has been grafted to the end of this
; binary
ld hl, LATEST
ld (CURRENT), hl
ld hl, HERE_INITIAL
ld (HERE), hl
; Set up PARSEPTR
ld hl, .parseName
call find
ld (PARSEPTR), de
; Set up EMITPTR
ld hl, .emitName
call find
ld (EMITPTR), de
; Set up PRINTPTR
ld hl, .printName
call find
ld (PRINTPTR), de
; Set up CINPTR
; do we have a (c<) impl?
ld hl, .cinName
call find
jr z, .skip
; no? then use KEY
ld hl, .keyName
call find
.skip:
ld (CINPTR), de
; Set up SYSVNXT
ld hl, SYSVBUF
ld (SYSVNXT), hl
ld hl, BEGIN
push hl
jp EXECUTE+2
.parseName:
.db "(parse)", 0
.cinName:
.db "(c<)", 0
.emitName:
.db "(emit)", 0
.printName:
.db "(print)", 0
.keyName:
.db "KEY", 0
BEGIN:
.dw compiledWord
.dw LIT
.db "(c<$)", 0
.dw FIND_
.dw NOT
.dw CSKIP
.dw EXECUTE
.dw INTERPRET
INTERPRET:
.dw compiledWord
.dw LIT
.db "INTERPRET", 0
.dw FIND_
.dw DROP
.dw EXECUTE
.fill 13
; *** Collapse OS lib copy ***
; In the process of Forth-ifying Collapse OS, apps will be slowly rewritten to
; Forth and the concept of ASM libs will become obsolete. To facilitate this
; transition, I make, right now, a copy of the routines actually used by Forth's
; native core. This also has the effect of reducing binary size right now and
; give us an idea of Forth's compactness.
; These routines below are copy/paste from apps/lib and stdio.
; copy (HL) into DE, then exchange the two, utilising the optimised HL instructions.
; ld must be done little endian, so least significant byte first.
intoHL:
push de
ld e, (hl)
inc hl
ld d, (hl)
ex de, hl
pop de
ret
; add the value of A into HL
; affects carry flag according to the 16-bit addition, Z, S and P untouched.
addHL:
push de
ld d, 0
ld e, a
add hl, de
pop de
ret
; Copy string from (HL) in (DE), that is, copy bytes until a null char is
; encountered. The null char is also copied.
; HL and DE point to the char right after the null char.
; B indicates the length of the copied string, including null-termination.
strcpy:
ld b, 0
.loop:
ld a, (hl)
ld (de), a
inc hl
inc de
inc b
or a
jr nz, .loop
ret
; Compares strings pointed to by HL and DE until one of them hits its null char.
; If equal, Z is set. If not equal, Z is reset. C is set if HL > DE
strcmp:
push hl
push de
.loop:
ld a, (de)
cp (hl)
jr nz, .end ; not equal? break early. NZ is carried out
; to the caller
or a ; If our chars are null, stop the cmp
inc hl
inc de
jr nz, .loop ; Z is carried through
.end:
pop de
pop hl
; Because we don't call anything else than CP that modify the Z flag,
; our Z value will be that of the last cp (reset if we broke the loop
; early, set otherwise)
ret
; Given a string at (HL), move HL until it points to the end of that string.
strskip:
push bc
ex af, af'
xor a ; look for null char
ld b, a
ld c, a
cpir ; advances HL regardless of comparison, so goes one too far
dec hl
ex af, af'
pop bc
ret
; Parse string at (HL) as a decimal value and return value in DE.
; Reads as many digits as it can and stop when:
; 1 - A non-digit character is read
; 2 - The number overflows from 16-bit
; HL is advanced to the character following the last successfully read char.
; Error conditions are:
; 1 - There wasn't at least one character that could be read.
; 2 - Overflow.
; Sets Z on success, unset on error.
parseDecimal:
; First char is special: it has to succeed.
ld a, (hl)
cp '-'
jr z, .negative
; Parse the decimal char at A and extract it's 0-9 numerical value. Put the
; result in A.
; On success, the carry flag is reset. On error, it is set.
add a, 0xff-'9' ; maps '0'-'9' onto 0xf6-0xff
sub 0xff-9 ; maps to 0-9 and carries if not a digit
ret c ; Error. If it's C, it's also going to be NZ
; During this routine, we switch between HL and its shadow. On one side,
; we have HL the string pointer, and on the other side, we have HL the
; numerical result. We also use EXX to preserve BC, saving us a push.
exx ; HL as a result
ld h, 0
ld l, a ; load first digit in without multiplying
.loop:
exx ; HL as a string pointer
inc hl
ld a, (hl)
exx ; HL as a numerical result
; same as other above
add a, 0xff-'9'
sub 0xff-9
jr c, .end
ld b, a ; we can now use a for overflow checking
add hl, hl ; x2
sbc a, a ; a=0 if no overflow, a=0xFF otherwise
ld d, h
ld e, l ; de is x2
add hl, hl ; x4
rla
add hl, hl ; x8
rla
add hl, de ; x10
rla
ld d, a ; a is zero unless there's an overflow
ld e, b
add hl, de
adc a, a ; same as rla except affects Z
; Did we oveflow?
jr z, .loop ; No? continue
; error, NZ already set
exx ; HL is now string pointer, restore BC
; HL points to the char following the last success.
ret
.end:
push hl ; --> lvl 1, result
exx ; HL as a string pointer, restore BC
pop de ; <-- lvl 1, result
cp a ; ensure Z
ret
.negative:
inc hl
call parseDecimal
ret nz
push hl ; --> lvl 1
or a ; clear carry
ld hl, 0
sbc hl, de
ex de, hl
pop hl ; <-- lvl 1
xor a ; set Z
ret
; *** Support routines ***
; Find the entry corresponding to word where (HL) points to and sets DE to
; point to that entry.
; Z if found, NZ if not.
find:
push bc
push hl
; First, figure out string len
ld bc, 0
xor a
cpir
; C has our length, negative, -1
ld a, c
neg
dec a
; special case. zero len? we never find anything.
jr z, .fail
ld c, a ; C holds our length
; Let's do something weird: We'll hold HL by the *tail*. Because of our
; dict structure and because we know our lengths, it's easier to
; compare starting from the end. Currently, after CPIR, HL points to
; char after null. Let's adjust
; Because the compare loop pre-decrements, instead of DECing HL twice,
; we DEC it once.
dec hl
ld de, (CURRENT)
.inner:
; DE is a wordref. First step, do our len correspond?
push hl ; --> lvl 1
push de ; --> lvl 2
dec de
ld a, (de)
and 0x7f ; remove IMMEDIATE flag
cp c
jr nz, .loopend
; match, let's compare the string then
dec de \ dec de ; skip prev field. One less because we
; pre-decrement
ld b, c ; loop C times
.loop:
; pre-decrement for easier Z matching
dec de
dec hl
ld a, (de)
cp (hl)
jr nz, .loopend
djnz .loop
.loopend:
; At this point, Z is set if we have a match. In all cases, we want
; to pop HL and DE
pop de ; <-- lvl 2
pop hl ; <-- lvl 1
jr z, .end ; match? we're done!
; no match, go to prev and continue
push hl ; --> lvl 1
dec de \ dec de \ dec de ; prev field
push de ; --> lvl 2
ex de, hl
call intoHL
ex de, hl ; DE contains prev offset
pop hl ; <-- lvl 2
; HL is prev field's addr
; Is offset zero?
ld a, d
or e
jr z, .noprev ; no prev entry
; get absolute addr from offset
; carry cleared from "or e"
sbc hl, de
ex de, hl ; result in DE
.noprev:
pop hl ; <-- lvl 1
jr nz, .inner ; try to match again
; Z set? end of dict unset Z
.fail:
xor a
inc a
.end:
pop hl
pop bc
ret
; Checks flags Z and S and sets BC to 0 if Z, 1 if C and -1 otherwise
flagsToBC:
ld bc, 0
ret z ; equal
inc bc
ret m ; >
; <
dec bc
dec bc
ret
; Write DE in (HL), advancing HL by 2.
DEinHL:
ld (hl), e
inc hl
ld (hl), d
inc hl
ret
; *** Stack management ***
; The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
; maintained by IX. This allows us to generally use push and pop freely because
; PS is the most frequently used. However, this causes a problem with routine
; calls: because in Forth, the stack isn't balanced within each call, our return
; offset, when placed by a CALL, messes everything up. This is one of the
; reasons why we need stack management routines below. IX always points to RS'
; Top Of Stack (TOS)
;
; This return stack contain "Interpreter pointers", that is a pointer to the
; address of a word, as seen in a compiled list of words.
; Push value HL to RS
pushRS:
inc ix
inc ix
ld (ix), l
ld (ix+1), h
ret
; Pop RS' TOS to HL
popRS:
ld l, (ix)
ld h, (ix+1)
dec ix
dec ix
ret
popRSIP:
call popRS
ld (IP), hl
ret
; Verifies that SP and RS are within bounds. If it's not, call ABORT
chkRS:
push ix \ pop hl
push de ; --> lvl 1
ld de, RS_ADDR
or a ; clear carry
sbc hl, de
pop de ; <-- lvl 1
jp c, abortUnderflow
ret
chkPS:
push hl
ld hl, (INITIAL_SP)
; We have the return address for this very call on the stack and
; protected registers. Let's compensate
dec hl \ dec hl
dec hl \ dec hl
or a ; clear carry
sbc hl, sp
pop hl
ret nc ; (INITIAL_SP) >= SP? good
jp abortUnderflow
; *** Dictionary ***
; It's important that this part is at the end of the resulting binary.
; A dictionary entry has this structure:
; - Xb name. Arbitrary long number of character (but can't be bigger than
; input buffer, of course). not null-terminated
; - 2b prev offset
; - 1b size + IMMEDIATE flag
; - 2b code pointer
; - Parameter field (PF)
;
; The prev offset is the number of bytes between the prev field and the
; previous word's code pointer.
;
; The size + flag indicate the size of the name field, with the 7th bit
; being the IMMEDIATE flag.
;
; The code pointer point to "word routines". These routines expect to be called
; with IY pointing to the PF. They themselves are expected to end by jumping
; to the address at (IP). They will usually do so with "jp next".
;
; That's for "regular" words (words that are part of the dict chain). There are
; also "special words", for example NUMBER, LIT, FBR, that have a slightly
; different structure. They're also a pointer to an executable, but as for the
; other fields, the only one they have is the "flags" field.
; This routine is jumped to at the end of every word. In it, we jump to current
; IP, but we also take care of increasing it my 2 before jumping
next:
; Before we continue: are stacks within bounds?
call chkPS
call chkRS
ld de, (IP)
ld h, d
ld l, e
inc de \ inc de
ld (IP), de
; HL is an atom list pointer. We need to go into it to have a wordref
ld e, (hl)
inc hl
ld d, (hl)
push de
jp EXECUTE+2
; Execute a word containing native code at its PF address (PFA)
nativeWord:
jp (iy)
; Execute a list of atoms, which always end with EXIT.
; IY points to that list. What do we do:
; 1. Push current IP to RS
; 2. Set new IP to the second atom of the list
; 3. Execute the first atom of the list.
compiledWord:
ld hl, (IP)
call pushRS
push iy \ pop hl
inc hl
inc hl
ld (IP), hl
; IY still is our atom reference...
ld l, (iy)
ld h, (iy+1)
push hl ; argument for EXECUTE
jp EXECUTE+2
; Pushes the PFA directly
cellWord:
push iy
jp next
; Pushes the address in the first word of the PF
sysvarWord:
ld l, (iy)
ld h, (iy+1)
push hl
jp next
; The word was spawned from a definition word that has a DOES>. PFA+2 (right
; after the actual cell) is a link to the slot right after that DOES>.
; Therefore, what we need to do push the cell addr like a regular cell, then
; follow the link from the PFA, and then continue as a regular compiledWord.
doesWord:
push iy ; like a regular cell
ld l, (iy+2)
ld h, (iy+3)
push hl \ pop iy
jr compiledWord
; This is not a word, but a number literal. This works a bit differently than
; others: PF means nothing and the actual number is placed next to the
; numberWord reference in the compiled word list. What we need to do to fetch
; that number is to play with the IP.
numberWord:
ld hl, (IP) ; (HL) is out number
ld e, (hl)
inc hl
ld d, (hl)
inc hl
ld (IP), hl ; advance IP by 2
push de
jp next
; Similarly to numberWord, this is not a real word, but a string literal.
; Instead of being followed by a 2 bytes number, it's followed by a
; null-terminated string. When called, puts the string's address on PS
litWord:
ld hl, (IP)
push hl
call strskip
inc hl ; after null termination
ld (IP), hl
jp next
; Pop previous IP from Return stack and execute it.
; ( R:I -- )
.db "EXIT"
.dw 0
.db 4
EXIT:
.dw nativeWord
call popRSIP
jp next
; ( R:I -- )
.db "QUIT"
.dw $-EXIT
.db 4
QUIT:
.dw compiledWord
.dw NUMBER
.dw 0
.dw FLAGS_
.dw STORE
.dw .private
.dw INTERPRET
.private:
.dw nativeWord
ld ix, RS_ADDR
jp next
.db "ABORT"
.dw $-QUIT
.db 5
ABORT:
.dw compiledWord
.dw .private
.dw QUIT
.private:
.dw nativeWord
; Reinitialize PS
ld sp, (INITIAL_SP)
jp next
abortUnderflow:
ld hl, .word
push hl
jp EXECUTE+2
.word:
.dw compiledWord
.dw LIT
.db "stack underfl", 0
.dw NUMBER
.dw PRINTPTR
.dw FETCH
.dw EXECUTE
.dw ABORT
.db "BYE"
.dw $-ABORT
.db 3
BYE:
.dw nativeWord
halt
; STABLE ABI
; Offset: 02aa
.out $
; ( c -- )
.db "EMIT"
.dw $-BYE
.db 4
EMIT:
.dw compiledWord
.dw NUMBER
.dw EMITPTR
.dw FETCH
.dw EXECUTE
.dw EXIT
.fill 71
.db ","
.dw $-EMIT
.db 1
WR:
.dw nativeWord
pop de
call chkPS
ld hl, (HERE)
call DEinHL
ld (HERE), hl
jp next
.fill 100
; ( addr -- )
.db "EXECUTE"
.dw $-WR
.db 7
; STABLE ABI
; Offset: 0388
.out $
EXECUTE:
.dw nativeWord
pop iy ; is a wordref
call chkPS
ld l, (iy)
ld h, (iy+1)
; HL points to code pointer
inc iy
inc iy
; IY points to PFA
jp (hl) ; go!
.fill 77
.db "DOES>"
.dw $-EXECUTE
.db 5
DOES:
.dw nativeWord
; We run this when we're in an entry creation context. Many things we
; need to do.
; 1. Change the code link to doesWord
; 2. Leave 2 bytes for regular cell variable.
; 3. Write down IP+2 to entry.
; 3. exit. we're done here.
ld hl, (CURRENT)
ld de, doesWord
call DEinHL
inc hl \ inc hl ; cell variable space
ld de, (IP)
call DEinHL
ld (HERE), hl
jp EXIT+2
.db "IMMEDIATE"
.dw $-DOES
.db 9
IMMEDIATE:
.dw nativeWord
ld hl, (CURRENT)
dec hl
set FLAG_IMMED, (hl)
jp next
.db "IMMED?"
.dw $-IMMEDIATE
.db 6
ISIMMED:
.dw nativeWord
pop hl
call chkPS
dec hl
ld de, 0
bit FLAG_IMMED, (hl)
jr z, .notset
inc de
.notset:
push de
jp next
; ( n -- )
.db "LITN"
.dw $-ISIMMED
.db 4
LITN:
.dw nativeWord
ld hl, (HERE)
ld de, NUMBER
call DEinHL
pop de ; number from stack
call chkPS
call DEinHL
ld (HERE), hl
jp next
.db "SCPY"
.dw $-LITN
.db 4
SCPY:
.dw nativeWord
pop hl
ld de, (HERE)
call strcpy
ld (HERE), de
jp next
.db "(find)"
.dw $-SCPY
.db 6
; STABLE ABI
; Offset: 047c
.out $
FIND_:
.dw nativeWord
pop hl
call find
jr z, .found
; not found
push hl
ld de, 0
push de
jp next
.found:
push de
ld de, 1
push de
jp next
; This is an indirect word that can be redirected through "CINPTR"
; code: it is replaced in readln.fs.
.db "C<"
.dw $-FIND_
.db 2
CIN:
.dw compiledWord
.dw NUMBER
.dw CINPTR
.dw FETCH
.dw EXECUTE
.dw EXIT
; ( c -- f )
; 33 CMP 1 + NOT
; The NOT is to normalize the negative/positive numbers to 1 or 0.
; Hadn't we wanted to normalize, we'd have written:
; 32 CMP 1 -
.db "WS?"
.dw $-CIN
.db 3
ISWS:
.dw compiledWord
.dw NUMBER
.dw 33
.dw CMP
.dw NUMBER
.dw 1
.dw PLUS
.dw NOT
.dw EXIT
.db "NOT"
.dw $-ISWS
.db 3
NOT:
.dw nativeWord
pop hl
call chkPS
ld a, l
or h
ld hl, 0
jr nz, .skip ; true, keep at 0
; false, make 1
inc hl
.skip:
push hl
jp next
; ( -- c )
; C< DUP 32 CMP 1 - SKIP? EXIT DROP TOWORD
.db "TOWORD"
.dw $-NOT
.db 6
TOWORD:
.dw compiledWord
.dw CIN
.dw DUP
.dw ISWS
.dw CSKIP
.dw EXIT
.dw DROP
.dw TOWORD
.dw EXIT
; Read word from C<, copy to WORDBUF, null-terminate, and return, make
; HL point to WORDBUF.
.db "WORD"
.dw $-TOWORD
.db 4
; STABLE ABI
; Offset: 04f7
.out $
WORD:
.dw compiledWord
.dw NUMBER ; ( a )
.dw WORDBUF
.dw TOWORD ; ( a c )
; branch mark
.dw OVER ; ( a c a )
.dw STORE ; ( a )
.dw NUMBER ; ( a 1 )
.dw 1
.dw PLUS ; ( a+1 )
.dw CIN ; ( a c )
.dw DUP ; ( a c c )
.dw ISWS ; ( a c f )
.dw CSKIP ; ( a c )
.dw BBR
.db 20 ; here - mark
; at this point, we have ( a WS )
.dw DROP
.dw NUMBER
.dw 0
.dw SWAP ; ( 0 a )
.dw STORE ; ()
.dw NUMBER
.dw WORDBUF
.dw EXIT
.wcpy:
.dw nativeWord
ld de, WORDBUF
push de ; we already have our result
.loop:
ld a, (hl)
cp ' '+1
jr c, .loopend
ld (de), a
inc hl
inc de
jr .loop
.loopend:
; null-terminate the string.
xor a
ld (de), a
jp next
.db "(parsed)"
.dw $-WORD
.db 8
PARSED:
.dw nativeWord
pop hl
call chkPS
call parseDecimal
jr z, .success
; error
ld de, 0
push de ; dummy
push de ; flag
jp next
.success:
push de
ld de, 1 ; flag
push de
jp next
.fill 96
.db "JTBL"
.dw $-PARSED
.db 4
JTBL:
.dw sysvarWord
.dw JUMPTBL
; STABLE ABI (every sysvars)
; Offset: 05ca
.out $
.db "HERE"
.dw $-JTBL
.db 4
HERE_: ; Caution: conflicts with actual variable name
.dw sysvarWord
.dw HERE
.db "CURRENT"
.dw $-HERE_
.db 7
CURRENT_:
.dw sysvarWord
.dw CURRENT
.db "(parse*)"
.dw $-CURRENT_
.db 8
PARSEPTR_:
.dw sysvarWord
.dw PARSEPTR
.db "FLAGS"
.dw $-PARSEPTR_
.db 5
FLAGS_:
.dw sysvarWord
.dw FLAGS
.db "SYSVNXT"
.dw $-FLAGS_
.db 7
SYSVNXT_:
.dw sysvarWord
.dw SYSVNXT
; ( n a -- )
.db "!"
.dw $-SYSVNXT_
.db 1
; STABLE ABI
; Offset: 0610
.out $
STORE:
.dw nativeWord
pop iy
pop hl
call chkPS
ld (iy), l
ld (iy+1), h
jp next
; ( a -- n )
.db "@"
.dw $-STORE
.db 1
FETCH:
.dw nativeWord
pop hl
call chkPS
call intoHL
push hl
jp next
; ( a -- )
.db "DROP"
.dw $-FETCH
.db 4
; STABLE ABI
DROP:
.dw nativeWord
pop hl
jp next
; ( a b -- b a )
.db "SWAP"
.dw $-DROP
.db 4
SWAP:
.dw nativeWord
pop hl
call chkPS
ex (sp), hl
push hl
jp next
; ( a -- a a )
.db "DUP"
.dw $-SWAP
.db 3
DUP:
.dw nativeWord
pop hl
call chkPS
push hl
push hl
jp next
; ( a b -- a b a )
.db "OVER"
.dw $-DUP
.db 4
OVER:
.dw nativeWord
pop hl ; B
pop de ; A
call chkPS
push de
push hl
push de
jp next
.fill 31
; ( a b -- c ) A + B
.db "+"
.dw $-OVER
.db 1
PLUS:
.dw nativeWord
pop hl
pop de
call chkPS
add hl, de
push hl
jp next
.fill 18
; ( a1 a2 -- b )
.db "SCMP"
.dw $-PLUS
.db 4
SCMP:
.dw nativeWord
pop de
pop hl
call chkPS
call strcmp
call flagsToBC
push bc
jp next
; ( n1 n2 -- f )
.db "CMP"
.dw $-SCMP
.db 3
CMP:
.dw nativeWord
pop hl
pop de
call chkPS
or a ; clear carry
sbc hl, de
call flagsToBC
push bc
jp next
; Skip the compword where HL is currently pointing. If it's a regular word,
; it's easy: we inc by 2. If it's a NUMBER, we inc by 4. If it's a LIT, we skip
; to after null-termination.
.db "SKIP?"
.dw $-CMP
.db 5
; STABLE ABI
; Offset: 06ee
.out $
CSKIP:
.dw nativeWord
pop hl
call chkPS
ld a, h
or l
jp z, next ; False, do nothing.
ld hl, (IP)
ld de, NUMBER
call .HLPointsDE
jr z, .isNum
ld de, FBR
call .HLPointsDE
jr z, .isBranch
ld de, BBR
call .HLPointsDE
jr z, .isBranch
ld de, LIT
call .HLPointsDE
jr nz, .isWord
; We have a literal
inc hl \ inc hl
call strskip
inc hl ; byte after word termination
jr .end
.isNum:
; skip by 4
inc hl
; continue to isBranch
.isBranch:
; skip by 3
inc hl
; continue to isWord
.isWord:
; skip by 2
inc hl \ inc hl
.end:
ld (IP), hl
jp next
; Sets Z if (HL) == E and (HL+1) == D
.HLPointsDE:
ld a, (hl)
cp e
ret nz ; no
inc hl
ld a, (hl)
dec hl
cp d ; Z has our answer
ret
; This word's atom is followed by 1b *relative* offset (to the cell's addr) to
; where to branch to. For example, The branching cell of "IF THEN" would
; contain 3. Add this value to RS.
.db "(fbr)"
.dw $-CSKIP
.db 5
; STABLE ABI
; Offset: 073e
.out $
FBR:
.dw nativeWord
push de
ld hl, (IP)
ld a, (hl)
call addHL
ld (IP), hl
pop de
jp next
.db "(bbr)"
.dw $-FBR
.db 5
; STABLE ABI
; Offset: 0757
.out $
BBR:
.dw nativeWord
ld hl, (IP)
ld d, 0
ld e, (hl)
or a ; clear carry
sbc hl, de
ld (IP), hl
jp next
; To allow dict binaries to "hook themselves up", we always end such binary
; with a dummy, *empty* entry. Therefore, we can have a predictable place for
; getting a prev label.
.db "_bend"
.dw $-BBR
.db 5