collapseos/apps/ed/buf.asm

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; buf - manage line buffer
;
; Lines in edited file aren't loaded in memory, their offsets is referenced to
; in this buffer.
;
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; About scratchpad and offsets. There are two scratchpads: file and memory.
; The file one is the contents of the active blkdev. The second one is
; in-memory, for edits. We differentiate between the two with a
; "scatchpad mask". When the high bits of the offset match the mask, then we
; know that this offset is from the scratchpad.
;
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; *** Consts ***
;
; Maximum number of lines allowed in the buffer.
.equ BUF_MAXLINES 0x800
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; Size of our scratchpad
.equ BUF_PADMAXLEN 0x1000
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; Scratchpad mask (only applies on high byte)
.equ BUF_SCRATCHPAD_MASK 0b11110000
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; *** Variables ***
; Number of lines currently in the buffer
.equ BUF_LINECNT BUF_RAMSTART
; List of words pointing to scratchpad offsets
.equ BUF_LINES BUF_LINECNT+2
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; Points to the end of the scratchpad
.equ BUF_PADEND BUF_LINES+BUF_MAXLINES*2
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; The in-memory scratchpad
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.equ BUF_PAD BUF_PADEND+2
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.equ BUF_RAMEND BUF_PAD+BUF_PADMAXLEN
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; *** Code ***
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; On initialization, we read the whole contents of target blkdev and add lines
; as we go.
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bufInit:
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ld hl, BUF_PAD
ld (BUF_PADEND), hl
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ld ix, BUF_LINES
ld bc, 0 ; line count
.loop:
call blkTell ; --> HL
call blkGetC
jr nz, .loopend
ld (ix), l
inc ix
ld (ix), h
inc ix
inc bc
call ioGetLine
jr .loop
.loopend:
ld (BUF_LINECNT), bc
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ret
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; transform line index HL into its corresponding memory address in BUF_LINES
; array.
bufLineAddr:
push de
ex de, hl
ld hl, BUF_LINES
add hl, de
add hl, de ; twice, because two bytes per line
pop de
ret
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; Read line number specified in HL and loads the I/O buffer with it.
; Like ioGetLine, sets HL to line buffer pointer.
; Sets Z on success, unset if out of bounds.
bufGetLine:
push de
ld de, (BUF_LINECNT)
call cpHLDE
jr nc, .outOfBounds ; HL > (BUF_LINECNT)
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call bufLineAddr
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; HL now points to seek offset in memory
ld e, (hl)
inc hl
ld d, (hl)
; DE has seek offset
ex de, hl
pop de
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; is it a scratchpad offset?
ld a, h
and BUF_SCRATCHPAD_MASK
cp BUF_SCRATCHPAD_MASK
jr z, .fromScratchpad
; not from scratchpad
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cp a ; ensure Z
jp ioGetLine ; preserves AF
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.fromScratchpad:
; remove scratchpad mask
ld a, BUF_SCRATCHPAD_MASK
xor 0xff
and h
ld h, a
; HL is now a mask-less offset to BUF_PAD
push de ; --> lvl 1
ld de, BUF_PAD
add hl, de
pop de ; <-- lvl 1
ret
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.outOfBounds:
pop de
jp unsetZ
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; Given line indexes in HL and DE where HL < DE < CNT, move all lines between
; DE and CNT by an offset of DE-HL. Also, adjust BUF_LINECNT by DE-HL.
; WARNING: no bounds check. The only consumer of this routine already does
; bounds check.
bufDelLines:
; Let's start with setting up BC, which is (CNT-DE) * 2
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push hl ; --> lvl 1
ld hl, (BUF_LINECNT)
scf \ ccf
sbc hl, de
; mult by 2 and we're done
sla l \ rl h
push hl \ pop bc
pop hl ; <-- lvl 1
; Good! BC done. Now, let's adjust BUF_LINECNT by DE-HL
push hl ; --> lvl 1
scf \ ccf
sbc hl, de ; HL -> nb of lines to delete, negative
push de ; --> lvl 2
ld de, (BUF_LINECNT)
add hl, de ; adding DE to negative HL
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ld (BUF_LINECNT), hl
pop de ; <-- lvl 2
pop hl ; <-- lvl 1
; Line count updated!
; let's have invert HL and DE to match LDIR's signature
ex de, hl
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; At this point we have higher index in HL, lower index in DE and number
; of bytes to delete in BC. It's convenient because it's rather close
; to LDIR's signature! The only thing we need to do now is to translate
; those HL and DE indexes in memory addresses, that is, multiply by 2
; and add BUF_LINES
push hl ; --> lvl 1
ex de, hl
call bufLineAddr
ex de, hl
pop hl ; <-- lvl 1
call bufLineAddr
; Both HL and DE are translated. Go!
ldir
ret
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; Insert string where DE points to memory scratchpad, then insert that line
; at index HL, offsetting all lines by 2 bytes.
bufInsertLine:
push de ; --> lvl 1, scratchpad offset
push hl ; --> lvl 2, insert index
; The logic below is mostly copy-pasted from bufDelLines, but with a
; LDDR logic (to avoid overwriting). I learned, with some pain involved,
; that generalizing this code wasn't working very well. I don't repeat
; the comments, refer to bufDelLines
ex de, hl ; line index now in DE
ld hl, (BUF_LINECNT)
scf \ ccf
sbc hl, de
; mult by 2 and we're done
sla l \ rl h
push hl \ pop bc
; From this point, we don't need our line index in DE any more because
; LDDR will start from BUF_LINECNT-1 with count BC. We'll only need it
; when it's time to insert the line in the space we make.
ld hl, (BUF_LINECNT)
call bufLineAddr
push hl \ pop de
dec hl
dec hl
; HL = BUF_LINECNT-1, DE = BUF_LINECNT, BC is set. We're good!
lddr
; We still need to increase BUF_LINECNT
ld hl, (BUF_LINECNT)
inc hl
ld (BUF_LINECNT), hl
; A space has been opened at line index HL. Let's fill it with our
; inserted line.
pop hl ; <-- lvl 2, insert index
call bufLineAddr
pop de ; <-- lvl 1, scratchpad offset
ld (hl), e
inc hl
ld (hl), d
ret
; copy string that HL points to to scratchpad and return its seek offset, in HL.
bufScratchpadAdd:
push de
ld de, (BUF_PADEND)
push de ; --> lvl 1
call strcpyM
ld (BUF_PADEND), de
pop hl ; <-- lvl 1
; we have a memory offset in HL, but it's not what we want! we want a
; seek offset stamped with the "scratchpad mask"
ld de, BUF_PAD
scf \ ccf
sbc hl, de
ld a, h
or BUF_SCRATCHPAD_MASK
ld h, a
; now we're good...
pop de
ret