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collapseos/apps/zasm/symbol.asm
Virgil Dupras 7ca54d179d lib/expr: make EXPR_PARSE "tail" HL
Things are now much simpler.
2019-12-30 19:24:53 -05:00

341 lines
8.0 KiB
NASM

; Manages both constants and labels within a same namespace and registry.
;
; Local Labels
;
; Local labels during the "official" first pass are ignored. To register them
; in the global registry during that pass would be wasteful in terms of memory.
;
; What we do instead is set up a separate register for them and have a "second
; first pass" whenever we encounter a new context. That is, we wipe the local
; registry, parse the code until the next global symbol (or EOF), then rewind
; and continue second pass as usual.
;
; What is a symbol name? The accepted characters for a symbol are A-Z, a-z, 0-9
; dot (.) and underscore (_).
; This unit doesn't disallow symbols starting with a digit, but in effect, they
; aren't going to work because parseLiteral is going to get that digit first.
; So, make your symbols start with a letter or dot or underscore.
; *** Constants ***
; Size of each record in registry
.equ SYM_RECSIZE 3
.equ SYM_REGSIZE ZASM_REG_BUFSZ+1+ZASM_REG_MAXCNT*SYM_RECSIZE
.equ SYM_LOC_REGSIZE ZASM_LREG_BUFSZ+1+ZASM_LREG_MAXCNT*SYM_RECSIZE
; Maximum name length for a symbol
.equ SYM_NAME_MAXLEN 0x20
; *** Variables ***
; A registry has three parts: record count (byte) record list and names pool.
; A record is a 3 bytes structure:
; 1b - name length
; 2b - value associated to symbol
;
; We know we're at the end of the record list when we hit a 0-length one.
;
; The names pool is a list of strings, not null-terminated, associated with
; the value.
;
; It is assumed that the registry is aligned in memory in that order:
; names pool, rec count, reclist
; Global labels registry
.equ SYM_GLOB_REG SYM_RAMSTART
.equ SYM_LOC_REG @+SYM_REGSIZE
.equ SYM_CONST_REG @+SYM_LOC_REGSIZE
; Area where we parse symbol names into
.equ SYM_TMPNAME @+SYM_REGSIZE
.equ SYM_RAMEND @+SYM_NAME_MAXLEN+1
; *** Registries ***
; A symbol registry is a 5 bytes record with points to the name pool then the
; records list of the register and then the max record count.
SYM_GLOBAL_REGISTRY:
.dw SYM_GLOB_REG, SYM_GLOB_REG+ZASM_REG_BUFSZ
.db ZASM_REG_MAXCNT
SYM_LOCAL_REGISTRY:
.dw SYM_LOC_REG, SYM_LOC_REG+ZASM_LREG_BUFSZ
.db ZASM_LREG_MAXCNT
SYM_CONST_REGISTRY:
.dw SYM_CONST_REG, SYM_CONST_REG+ZASM_REG_BUFSZ
.db ZASM_REG_MAXCNT
; *** Code ***
symInit:
ld ix, SYM_GLOBAL_REGISTRY
call symClear
ld ix, SYM_LOCAL_REGISTRY
call symClear
ld ix, SYM_CONST_REGISTRY
jp symClear
; Sets Z according to whether label in (HL) is local (starts with a dot)
symIsLabelLocal:
ld a, '.'
cp (hl)
ret
symRegisterGlobal:
push ix
ld ix, SYM_GLOBAL_REGISTRY
call symRegister
pop ix
ret
symRegisterLocal:
push ix
ld ix, SYM_LOCAL_REGISTRY
call symRegister
pop ix
ret
symRegisterConst:
push ix
ld ix, SYM_CONST_REGISTRY
call symRegister
pop ix
ret
; Register label in (HL) (minus the ending ":") into the symbol registry in IX
; and set its value in that registry to the value specified in DE.
; If successful, Z is set. Otherwise, Z is unset and A is an error code (ERR_*).
symRegister:
push hl ; --> lvl 1. it's the symbol to add
call _symIsFull
jr z, .outOfMemory
; First, let's get our strlen
call strlen
ld c, a ; save that strlen for later
call _symFind
jr z, .duplicateError
; Is our new name going to make us go out of bounds?
push hl ; --> lvl 2
push de ; --> lvl 3
ld d, 0
ld e, c
add hl, de ; if carry set here, sbc will carry too
ld e, (ix+2) ; DE --> pointer to record list, which is also
ld d, (ix+3) ; the end of names pool
; DE --> names end
sbc hl, de ; compares hl and de destructively
pop de ; <-- lvl 3
pop hl ; <-- lvl 2
jr nc, .outOfMemory ; HL >= DE
; Success. At this point, we have:
; HL -> where we want to add the string
; IY -> target record where the value goes
; DE -> value to register
; SP -> string to register
; Let's start with the record
ld (iy), c ; strlen
ld (iy+1), e
ld (iy+2), d
; Good! now, the string. Destination is in HL, source is in SP
ex de, hl ; dest is in DE
pop hl ; <-- lvl 1. string to register
; Copy HL into DE until we reach null char
call strcpyM
; Last thing: increase record count
ld l, (ix+2)
ld h, (ix+3)
inc (hl)
xor a ; sets Z
ret
.outOfMemory:
pop hl ; <-- lvl 1
ld a, ERR_OOM
jp unsetZ
.duplicateError:
pop hl ; <-- lvl 1
ld a, ERR_DUPSYM
jp unsetZ ; return
; Assuming that IX points to a registry, find name HL in its names and make IY
; point to the corresponding record. If it doesn't find anything, IY will
; conveniently point to the next record after the last, and HL to the next
; name insertion point.
; If we find something, Z is set, otherwise unset.
_symFind:
push de
push bc
call strlen
ld c, a ; save strlen
ex de, hl ; easier if needle is in DE
; IY --> records
ld l, (ix+2)
ld h, (ix+3)
; first byte is count
ld b, (hl)
inc hl ; first record
push hl \ pop iy
; HL --> names
ld l, (ix)
ld h, (ix+1)
; do we have an empty reclist?
xor a
cp b
jr z, .nothing ; zero count? nothing
.loop:
ld a, (iy) ; name len
cp c
jr nz, .skip ; different strlen, can't possibly match. skip
call strncmp
jr z, .end ; match! Z already set, IY and HL placed.
.skip:
; ok, next!
push de ; --> lvl 1
ld de, 0x0003
add iy, de ; faster and shorter than three inc's
ld e, (iy-3) ; offset is also compulsory, so no extra bytes used
; (iy-3) holds the name length of the string just processed
add hl, de ; advance HL by (iy-3) characters
pop de ; <-- lvl 1
djnz .loop
; end of the chain, nothing found
.nothing:
call unsetZ
.end:
pop bc
pop de
ret
; For a given symbol name in (HL), find it in the appropriate symbol register
; and return its value in DE. If (HL) is a local label, the local register is
; searched. Otherwise, the global one. It is assumed that this routine is
; always called when the global registry is selected. Therefore, we always
; reselect it afterwards.
symFindVal:
push ix
call symIsLabelLocal
jr z, .local
; global. Let's try consts first, then symbols
push hl ; --> lvl 1. we'll need it again if not found.
ld ix, SYM_CONST_REGISTRY
call _symFind
pop hl ; <-- lvl 1
jr z, .found
ld ix, SYM_GLOBAL_REGISTRY
call _symFind
jr nz, .end
.found:
; Found! let's fetch value
ld e, (iy+1)
ld d, (iy+2)
jr .end
.local:
ld ix, SYM_LOCAL_REGISTRY
call _symFind
jr z, .found
; continue to end
.end:
pop ix
ret
; Clear registry at IX
symClear:
push af
push hl
ld l, (ix+2)
ld h, (ix+3)
; HL --> reclist count
xor a
ld (hl), a
pop hl
pop af
ret
; Returns whether register in IX has reached its capacity.
; Sets Z if full, unset if not.
_symIsFull:
push hl
ld l, (ix+2)
ld h, (ix+3)
ld l, (hl) ; record count
ld a, (ix+4) ; max record count
cp l
pop hl
ret
; Parse string (HL) as far as it can for a valid symbol name (see definition in
; comment at top) for a maximum of SYM_NAME_MAXLEN characters. Puts the parsed
; symbol, null-terminated, in SYM_TMPNAME. Make DE point to SYM_TMPNAME.
; HL is advanced to the character following the last successfully read char.
; Z for success.
; Error conditions:
; 1 - No character parsed.
; 2 - name too long.
symParse:
ld de, SYM_TMPNAME
push bc
; +1 because we want to loop one extra time to see if the char is good
; or bad. If it's bad, then fine, proceed as normal. If it's good, then
; its going to go through djnz and we can return an error then.
ld b, SYM_NAME_MAXLEN+1
.loop:
ld a, (hl)
; Set it directly, even if we don't know yet if it's good
ld (de), a
or a ; end of string?
jr z, .end ; easy ending, Z set, HL set
; Check special symbols first
cp '.'
jr z, .good
cp '_'
jr z, .good
; lowercase
or 0x20
cp '0'
jr c, .bad
cp '9'+1
jr c, .good
cp 'a'
jr c, .bad
cp 'z'+1
jr nc, .bad
.good:
; character is valid, continue!
inc hl
inc de
djnz .loop
; error: string too long
; NZ is already set from cp 'z'+1
; HL is one char too far
dec hl
jr .end
.bad:
; invalid char, stop where we are.
; In all cases, we want to null-terminate that string
xor a
ld (de), a
; HL is good. Now, did we succeed? to know, let's see where B is.
ld a, b
cp SYM_NAME_MAXLEN+1
; Our result is the invert of Z
call toggleZ
.end:
ld de, SYM_TMPNAME
pop bc
ret