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