collapseos/apps/forth/util.asm

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; *** 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.
; make Z the opposite of what it is now
toggleZ:
jp z, unsetZ
cp a
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.
strcpyM:
ld a, (hl)
ld (de), a
inc hl
inc de
or a
jr nz, strcpyM
ret
; Like strcpyM, but preserve HL and DE
strcpy:
push hl
push de
call strcpyM
pop de
pop hl
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
; Borrowed from Tasty Basic by Dimitri Theulings (GPL).
; Divide HL by DE, placing the result in BC and the remainder in HL.
divide:
push hl ; --> lvl 1
ld l, h ; divide h by de
ld h, 0
call .dv1
ld b, c ; save result in b
ld a, l ; (remainder + l) / de
pop hl ; <-- lvl 1
ld h, a
.dv1:
ld c, 0xff ; result in c
.dv2:
inc c ; dumb routine
call .subde ; divide using subtract and count
jr nc, .dv2
add hl, de
ret
.subde:
ld a, l
sub e ; subtract de from hl
ld l, a
ld a, h
sbc a, d
ld h, a
ret
; DE * BC -> DE (high) and HL (low)
multDEBC:
ld hl, 0
ld a, 0x10
.loop:
add hl, hl
rl e
rl d
jr nc, .noinc
add hl, bc
jr nc, .noinc
inc de
.noinc:
dec a
jr nz, .loop
ret
; Parse the hex char at A and extract it's 0-15 numerical value. Put the result
; in A.
;
; On success, the carry flag is reset. On error, it is set.
parseHex:
; First, let's see if we have an easy 0-9 case
add a, 0xc6 ; maps '0'-'9' onto 0xf6-0xff
sub 0xf6 ; maps to 0-9 and carries if not a digit
ret nc
and 0xdf ; converts lowercase to uppercase
add a, 0xe9 ; map 0x11-x017 onto 0xFA - 0xFF
sub 0xfa ; map onto 0-6
ret c
; we have an A-F digit
add a, 10 ; C is clear, map back to 0xA-0xF
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)
; 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.
parseDecimalSkip: ; enter here to skip parsing the first digit
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
; Parse string at (HL) as a hexadecimal value without the "0x" prefix and
; return value in DE.
; HL is advanced to the character following the last successfully read char.
; Sets Z on success.
parseHexadecimal:
ld a, (hl)
call parseHex ; before "ret c" is "sub 0xfa" in parseHex
; so carry implies not zero
ret c ; we need at least one char
push bc
ld de, 0
ld b, d
ld c, d
; The idea here is that the 4 hex digits of the result can be represented "bdce",
; where each register holds a single digit. Then the result is simply
; e = (c << 4) | e, d = (b << 4) | d
; However, the actual string may be of any length, so when loading in the most
; significant digit, we don't know which digit of the result it actually represents
; To solve this, after a digit is loaded into a (and is checked for validity),
; all digits are moved along, with e taking the latest digit.
.loop:
dec b
inc b ; b should be 0, else we've overflowed
jr nz, .end ; Z already unset if overflow
ld b, d
ld d, c
ld c, e
ld e, a
inc hl
ld a, (hl)
call parseHex
jr nc, .loop
ld a, b
add a, a \ add a, a \ add a, a \ add a, a
or d
ld d, a
ld a, c
add a, a \ add a, a \ add a, a \ add a, a
or e
ld e, a
xor a ; ensure z
.end:
pop bc
ret
; Parse string at (HL) as a binary value (010101) without the "0b" prefix and
; return value in E. D is always zero.
; HL is advanced to the character following the last successfully read char.
; Sets Z on success.
parseBinaryLiteral:
ld de, 0
.loop:
ld a, (hl)
add a, 0xff-'1'
sub 0xff-1
jr c, .end
rlc e ; sets carry if overflow, and affects Z
ret c ; Z unset if carry set, since bit 0 of e must be set
add a, e
ld e, a
inc hl
jr .loop
.end:
; HL is properly set
xor a ; ensure Z
ret
; Parses the string at (HL) and returns the 16-bit value in DE. The string
; can be a decimal literal (1234), a hexadecimal literal (0x1234) or a char
; literal ('X').
; HL is advanced to the character following the last successfully read char.
;
; As soon as the number doesn't fit 16-bit any more, parsing stops and the
; number is invalid. If the number is valid, Z is set, otherwise, unset.
parseLiteral:
ld de, 0 ; pre-fill
ld a, (hl)
cp 0x27 ; apostrophe
jr z, .char
; inline parseDecimalDigit
add a, 0xc6 ; maps '0'-'9' onto 0xf6-0xff
sub 0xf6 ; maps to 0-9 and carries if not a digit
ret c
; a already parsed so skip first few instructions of parseDecimal
jp nz, parseDecimalSkip
; maybe hex, maybe binary
inc hl
ld a, (hl)
inc hl ; already place it for hex or bin
cp 'x'
jr z, parseHexadecimal
cp 'b'
jr z, parseBinaryLiteral
; nope, just a regular decimal
dec hl \ dec hl
jp parseDecimal
; Parse string at (HL) and, if it is a char literal, sets Z and return
; corresponding value in E. D is always zero.
; HL is advanced to the character following the last successfully read char.
;
; A valid char literal starts with ', ends with ' and has one character in the
; middle. No escape sequence are accepted, but ''' will return the apostrophe
; character.
.char:
inc hl
ld e, (hl) ; our result
inc hl
cp (hl)
; advance HL and return if good char
inc hl
ret z
; Z unset and there's an error
; In all error conditions, HL is advanced by 3. Rewind.
dec hl \ dec hl \ dec hl
; NZ already set
ret
; *** Forth-specific part ***
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; Return address of scratchpad in HL
pad:
ld hl, (HERE)
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ld a, PADDING
jp addHL
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; Advance (INPUTPOS) until a non-whitespace is met. If needed,
; call fetchline.
; Set HL to newly set (INPUTPOS)
toword:
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ld hl, (INPUTPOS)
; skip leading whitespace
dec hl ; offset leading "inc hl"
.loop:
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inc hl
ld a, (hl)
or a
; When at EOL, fetch a new line directly
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jr z, .empty
cp ' '+1
jr c, .loop
ret
.empty:
call fetchline
jr toword
; Read word from (INPUTPOS) and return, in HL, a null-terminated word.
; Advance (INPUTPOS) to the character following the whitespace ending the
; word.
; When we're at EOL, we call fetchline directly, so this call always returns
; a word.
readword:
call toword
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push hl ; --> lvl 1. that's our result
.loop:
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inc hl
ld a, (hl)
; special case: is A null? If yes, we will *not* inc A so that we don't
; go over the bounds of our input string.
or a
jr z, .noinc
cp ' '+1
jr nc, .loop
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; we've just read a whitespace, HL is pointing to it. Let's transform
; it into a null-termination, inc HL, then set (INPUTPOS).
xor a
ld (hl), a
inc hl
.noinc:
ld (INPUTPOS), hl
pop hl ; <-- lvl 1. our result
ret ; Z set from XOR A
; 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
HLPointsNUMBER:
push de
ld de, NUMBER
call HLPointsDE
pop de
ret
HLPointsLIT:
push de
ld de, LIT
call HLPointsDE
pop de
ret
HLPointsBR:
push de
ld de, FBR
call HLPointsDE
jr z, .end
ld de, BBR
call HLPointsDE
.end:
pop de
ret
; 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.
compSkip:
call HLPointsNUMBER
jr z, .isNum
call HLPointsBR
jr z, .isBranch
call HLPointsLIT
jr nz, .isWord
; We have a literal
inc hl \ inc hl
call strskip
inc hl ; byte after word termination
ret
.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
ret
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; 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 hl
push bc
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ld de, (CURRENT)
ld bc, CODELINK_OFFSET
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.inner:
; DE is a wordref, let's go to beginning of struct
push de ; --> lvl 1
or a ; clear carry
ex de, hl
sbc hl, bc
ex de, hl ; We're good, DE points to word name
ld a, NAMELEN
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call strncmp
pop de ; <-- lvl 1, return to wordref
jr z, .end ; found
call .prev
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jr nz, .inner
; Z set? end of dict unset Z
inc a
.end:
pop bc
pop hl
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ret
; For DE being a wordref, move DE to the previous wordref.
; Z is set if DE point to 0 (no entry). NZ if not.
.prev:
dec de \ dec de \ dec de ; prev field
call intoDE
; DE points to prev. Is it zero?
xor a
or d
or e
; Z will be set if DE is zero
ret
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; Write compiled data from HL into IY, advancing IY at the same time.
wrCompHL:
ld (iy), l
inc iy
ld (iy), h
inc iy
ret
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; Spit name + prev in (HERE) and adjust (HERE) and (CURRENT)
; HL points to new (HERE)
entryhead:
call readword
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ld de, (HERE)
call strcpy
ex de, hl ; (HERE) now in HL
ld de, (CURRENT)
ld a, NAMELEN
call addHL
call DEinHL
; Set word flags: not IMMED, not UNWORD, so it's 0
xor a
ld (hl), a
inc hl
ld (CURRENT), hl
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ld (HERE), hl
ret
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; Sets Z if wordref at HL is of the IMMEDIATE type
HLisIMMED:
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dec hl
bit FLAG_IMMED, (hl)
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inc hl
; We need an invert flag. We want to Z to be set when flag is non-zero.
jp toggleZ
; Sets Z if wordref at (HL) is of the IMMEDIATE type
HLPointsIMMED:
push hl
call intoHL
call HLisIMMED
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pop hl
ret
; Sets Z if wordref at HL is of the UNWORD type
HLisUNWORD:
dec hl
bit FLAG_UNWORD, (hl)
inc hl
; We need an invert flag. We want to Z to be set when flag is non-zero.
jp toggleZ
; Sets Z if wordref at (HL) is of the IMMEDIATE type
HLPointsUNWORD:
push hl
call intoHL
call HLisUNWORD
pop hl
ret
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; 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
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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
fetchline:
call printcrlf
call stdioReadLine
ld (INPUTPOS), hl
ret