collapseos/apps/ed/main.asm
2019-10-04 13:49:33 -04:00

198 lines
3.9 KiB
NASM

; ed - line editor
;
; A text editor modeled after UNIX's ed, but simpler. The goal is to stay tight
; on resources and to avoid having to implement screen management code (that is,
; develop the machinery to have ncurses-like apps in Collapse OS).
;
; ed has a mechanism to avoid having to move a lot of memory around at each
; edit. Each line is an element in an doubly-linked list and each element point
; to an offset in the "scratchpad". The scratchpad starts with the file
; contents and every time we change or add a line, that line goes to the end of
; the scratch pad and linked lists are reorganized whenever lines are changed.
; Contents itself is always appended to the scratchpad.
;
; That's on a resourceful UNIX system.
;
; That doubly linked list on the z80 would use 7 bytes per line (prev, next,
; offset, len), which is a bit much.
;
; We sacrifice speed for memory usage by making that linked list into a simple
; array of pointers to line contents in scratchpad. This means that we
; don't have an easy access to line length and we have to move a lot of memory
; around whenever we add or delete lines. Hopefully, "LDIR" will be our friend
; here...
;
; *** Requirements ***
; BLOCKDEV_SIZE
; FS_HANDLE_SIZE
; _blkGetC
; _blkPutC
; _blkSeek
; _blkTell
; addHL
; cpHLDE
; fsFindFN
; fsOpen
; fsGetC
; fsPutC
; fsSetSize
; intoHL
; printstr
; printcrlf
; stdioReadLine
; stdioPutC
; unsetZ
;
; *** Variables ***
;
.equ ED_CURLINE ED_RAMSTART
.equ ED_RAMEND ED_CURLINE+2
edMain:
; because ed only takes a single string arg, we can use HL directly
call ioInit
ret nz
; diverge from UNIX: start at first line
ld hl, 0
ld (ED_CURLINE), hl
call bufInit
.mainLoop:
ld a, ':'
call stdioPutC
call stdioReadLine ; --> HL
; Now, process line.
call printcrlf
call cmdParse
jp nz, .error
ld a, (CMD_TYPE)
cp 'q'
jr z, .doQ
cp 'w'
jr z, .doW
; The rest of the commands need an address
call edReadAddrs
jr nz, .error
ld a, (CMD_TYPE)
cp 'i'
jr z, .doI
; The rest of the commands don't allow addr == cnt
push hl ; --> lvl 1
ld hl, (BUF_LINECNT)
call cpHLDE
pop hl ; <-- lvl 1
jr z, .error
ld a, (CMD_TYPE)
cp 'd'
jr z, .doD
cp 'a'
jr z, .doA
jr .doP
.doQ:
xor a
ret
.doW:
ld a, 3 ; seek beginning
call ioSeek
ld de, 0 ; cur line
.wLoop:
push de \ pop hl
call bufGetLine ; --> buffer in (HL)
jr nz, .wEnd
call ioPutLine
jr nz, .error
inc de
jr .wLoop
.wEnd:
; Set new file size
call ioTell
call ioSetSize
; for now, writing implies quitting
; TODO: reload buffer
xor a
ret
.doD:
ld (ED_CURLINE), de
; bufDelLines expects an exclusive upper bound, which is why we inc DE.
inc de
call bufDelLines
jr .mainLoop
.doA:
inc de
.doI:
call stdioReadLine ; --> HL
call bufScratchpadAdd ; --> HL
; insert index in DE, line offset in HL. We want the opposite.
ex de, hl
ld (ED_CURLINE), hl
call bufInsertLine
call printcrlf
jr .mainLoop
.doP:
push hl
call bufGetLine
jr nz, .error
call printstr
call printcrlf
pop hl
call cpHLDE
jr z, .doPEnd
inc hl
jr .doP
.doPEnd:
ld (ED_CURLINE), hl
jp .mainLoop
.error:
ld a, '?'
call stdioPutC
call printcrlf
jp .mainLoop
; Transform an address "cmd" in IX into an absolute address in HL.
edResolveAddr:
ld a, (ix)
cp RELATIVE
jr z, .relative
cp EOF
jr z, .eof
; absolute
ld l, (ix+1)
ld h, (ix+2)
ret
.relative:
ld hl, (ED_CURLINE)
push de
ld e, (ix+1)
ld d, (ix+2)
add hl, de
pop de
ret
.eof:
ld hl, (BUF_LINECNT)
dec hl
ret
; Read absolute addr1 in HL and addr2 in DE. Also, check bounds and set Z if
; both addresses are within bounds, unset if not.
edReadAddrs:
ld ix, CMD_ADDR2
call edResolveAddr
ld de, (BUF_LINECNT)
ex de, hl ; HL: cnt DE: addr2
call cpHLDE
jp c, unsetZ ; HL (cnt) < DE (addr2). no good
ld ix, CMD_ADDR1
call edResolveAddr
ex de, hl ; HL: addr2, DE: addr1
call cpHLDE
jp c, unsetZ ; HL (addr2) < DE (addr1). no good
ex de, hl ; HL: addr1, DE: addr2
cp a ; ensure Z
ret