collapseos/apps/zasm/symbol.asm
Virgil Dupras 1dec33e02a zasm: make symbol registry a bit more straightforward
Instead of strings of variable length driving the iteration of the
registry, we do so through records that keep track of lengths and
counts.
2019-07-23 15:21:42 -04:00

272 lines
6.3 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 don 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.
; *** Constants ***
; Maximum number of symbols we can have in the global and consts registry
.equ SYM_MAXCOUNT 0xff
; Maximum number of symbols we can have in the local registry
.equ SYM_LOC_MAXCOUNT 0x40
; Size of each record in registry
.equ SYM_RECSIZE 3
; Size of the symbol name buffer size. This is a pool. There is no maximum name
; length for a single symbol, just a maximum size for the whole pool.
; Global labels and consts have the same buf size
.equ SYM_BUFSIZE 0x1000
.equ SYM_REGSIZE SYM_BUFSIZE+1+SYM_MAXCOUNT*SYM_RECSIZE
; Size of the names buffer for the local context registry
.equ SYM_LOC_BUFSIZE 0x200
.equ SYM_LOC_REGSIZE SYM_LOC_BUFSIZE+1+SYM_LOC_MAXCOUNT*SYM_RECSIZE
; *** 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_GLOB_REG+SYM_REGSIZE
.equ SYM_CONST_REG SYM_LOC_REG+SYM_LOC_REGSIZE
.equ SYM_RAMEND SYM_CONST_REG+SYM_REGSIZE
; *** 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+SYM_BUFSIZE
.db SYM_MAXCOUNT
SYM_LOCAL_REGISTRY:
.dw SYM_LOC_REG, SYM_LOC_REG+SYM_LOC_BUFSIZE
.db SYM_LOC_MAXCOUNT
SYM_CONST_REGISTRY:
.dw SYM_CONST_REG, SYM_CONST_REG+SYM_BUFSIZE
.db SYM_MAXCOUNT
; *** 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 e, (ix+2) ; DE --> pointer to record list, which is also
ld d, (ix+3) ; the end of names pool
; DE --> names end
ld a, c
call addHL
call cpHLDE
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!
ld a, (iy) ; name len again
call addHL ; advance HL by A chars
inc iy \ inc iy \ inc iy
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 labels first, then consts
push hl ; --> lvl 1. we'll need it again if not found.
ld ix, SYM_GLOBAL_REGISTRY
call _symFind
pop hl ; <-- lvl 1
jr z, .found
ld ix, SYM_CONST_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