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collapseos/apps/basic/buf.asm
2019-11-24 14:26:32 -05:00

183 lines
3.9 KiB
NASM

; *** Consts ***
; maximum number of lines (line number maximum, however, is always 0xffff)
.equ BUF_MAXLINES 0x100
; Size of the string pool
.equ BUF_POOLSIZE 0x1000
; *** Variables ***
; A pointer to the first free line
.equ BUF_LFREE BUF_RAMSTART
; A pointer to the first free byte in the pool
.equ BUF_PFREE @+2
; The line index. Each record consists of 4 bytes: 2 for line number,
; 2 for pointer to string in pool. Kept in order of line numbers.
.equ BUF_LINES @+2
; The line pool. A list of null terminated strings. BUF_LINES records point
; to those strings.
.equ BUF_POOL @+BUF_MAXLINES*4
.equ BUF_RAMEND @+BUF_POOLSIZE
bufInit:
ld hl, BUF_LINES
ld (BUF_LFREE), hl
ld hl, BUF_POOL
ld (BUF_PFREE), hl
cp a ; ensure Z
ret
; Add line at (HL) with line number DE to the buffer. The string at (HL) should
; not contain the line number prefix or the whitespace between the line number
; and the comment.
; Note that an empty string is *not* an error. It will be saved as a line.
; Z for success.
; Error conditions are:
; * not enough space in the pool
; * not enough space in the line index
bufAdd:
; Check whether we have enough pool space. This is done in all cases.
call strlen
inc a ; strlen doesn't include line termination
exx ; preserve HL and DE
ld hl, (BUF_PFREE)
call addHL
ld de, BUF_RAMEND
sbc hl, de
exx ; restore
; no carry? HL >= BUF_RAMEND, error. Z already unset
ret nc
; Check the kind of operation we make: add, insert or replace?
call bufFind
jr z, .replace ; exact match, replace
call c, .insert ; near match, insert
; do we have enough index space?
exx ; preserve HL and DE
ld hl, (BUF_LFREE)
ld de, BUF_POOL-4
or a ; reset carry
sbc hl, de
exx ; restore
; no carry? HL >= BUF_POOL, error. Z already unset
ret nc
; We have enough space.
; set line index data
push de ; --> lvl 1
ld (ix), e
ld (ix+1), d
ld de, (BUF_PFREE)
ld (ix+2), e
ld (ix+3), d
; Increase line index size
ld de, (BUF_LFREE)
inc de \ inc de \ inc de \ inc de
ld (BUF_LFREE), de
; Fourth step: copy string to pool
ld de, (BUF_PFREE)
call strcpyM
ld (BUF_PFREE), de
pop de ; <-- lvl 1
ret
; No need to add a new line, just replace the current one.
.replace:
ld (ix), e
ld (ix+1), d
push de
ld de, (BUF_PFREE)
ld (ix+2), e
ld (ix+3), d
call strcpyM
ld (BUF_PFREE), de
pop de
ret
; An insert is exactly like an add, except that lines following insertion point
; first.
.insert:
push hl
push de
push bc
; We want a LDDR that moves from (BUF_LFREE)-1 to (BUF_LFREE)+3
; for a count of (BUF_LFREE)-BUF_LINES
ld hl, (BUF_LFREE)
ld de, BUF_LINES
or a ; clear carry
sbc hl, de
ld b, h
ld c, l
ld hl, (BUF_LFREE)
ld d, h
ld e, l
dec hl
inc de \ inc de \ inc de
lddr
pop bc
pop de
pop hl
ret
; Set IX to point to the beginning of the pool.
; Z set if (IX) is a valid line, unset if the pool is empty.
bufFirst:
ld ix, BUF_LINES
jp bufEOF
; Given a valid line record in IX, move IX to the next line.
; This routine doesn't check that IX is valid. Ensure IX validity before
; calling.
bufNext:
inc ix \ inc ix \ inc ix \ inc ix
jp bufEOF
; Returns whether line index at IX is past the end of file, that is,
; whether IX == (BUF_LFREE)
; Z is set when not EOF, unset when EOF.
bufEOF:
push hl
push de
push ix \ pop hl
or a ; clear carry
ld de, (BUF_LFREE)
sbc hl, de
jr z, .empty
cp a ; ensure Z
.end:
pop de
pop hl
ret
.empty:
call unsetZ
jr .end
; Given a line index in (IX), set HL to its associated string pointer.
bufStr:
ld l, (ix+2)
ld h, (ix+3)
ret
; Browse lines looking for number DE. Set IX to point to one of these :
; 1 - an exact match
; 2 - the first found line to have a higher line number
; 3 - EOF
; Set Z on an exact match, C on a near match, NZ and NC on EOF.
bufFind:
call bufFirst
ret nz
.loop:
ld a, d
cp (ix+1)
ret c ; D < (IX+1), situation 2
jr nz, .next
ld a, e
cp (ix)
ret c ; E < (IX), situation 2
ret z ; exact match!
.next:
call bufNext
ret nz
jr .loop