collapseos/apps/ed/main.asm

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NASM
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; 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. Moreover, there's that whole "scratchpad
; being loaded in memory" thing that's a bit iffy.
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;
; 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
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; 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 ***
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; BLOCKDEV_SIZE
; FS_HANDLE_SIZE
; _blkGetC
; _blkPutC
; _blkSeek
; _blkTell
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; addHL
; cpHLDE
; fsFindFN
; fsOpen
; fsGetC
; fsPutC
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; intoHL
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; printstr
; printcrlf
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; stdioReadLine
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; stdioPutC
; unsetZ
;
; *** Variables ***
;
.equ ED_CURLINE ED_RAMSTART
.equ ED_RAMEND ED_CURLINE+2
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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
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call bufInit
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.mainLoop:
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ld a, ':'
call stdioPutC
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call stdioReadLine ; --> HL
; Now, process line.
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call printcrlf
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call cmdParse
jr nz, .error
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ld a, (CMD_TYPE)
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cp 'q'
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jr z, .doQuit
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; The rest of the commands need an address
call edReadAddrs
jr nz, .error
ld a, (CMD_TYPE)
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cp 'd'
jr z, .doDel
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cp 'a'
jr z, .doAppend
cp 'i'
jr z, .doInsert
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jr .doPrint
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.doQuit:
xor a
ret
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.doDel:
; bufDelLines expects an exclusive upper bound, which is why we inc DE.
inc de
call bufDelLines
jr .mainLoop
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.doAppend:
inc de
.doInsert:
call stdioReadLine ; --> HL
call bufScratchpadAdd ; --> HL
; insert index in DE, line offset in HL. We want the opposite.
ex de, hl
call bufInsertLine
call printcrlf
jr .mainLoop
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.doPrint:
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push hl
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call bufGetLine
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jr nz, .error
call printstr
call printcrlf
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pop hl
call cpHLDE
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jr z, .doPrintEnd
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inc hl
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jr .doPrint
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.doPrintEnd:
ld (ED_CURLINE), hl
jr .mainLoop
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.error:
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ld a, '?'
call stdioPutC
call printcrlf
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jr .mainLoop
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; Transform an address "cmd" in IX into an absolute address in HL.
edResolveAddr:
ld a, (ix)
cp RELATIVE
jr z, .relative
; absolute
ld l, (ix+1)
ld h, (ix+2)
ret
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.relative:
ld hl, (ED_CURLINE)
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push de
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ld e, (ix+1)
ld d, (ix+2)
add hl, de
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pop de
ret
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; 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
ex de, hl
ld hl, (BUF_LINECNT)
ex de, hl ; HL: addr2 DE: cnt
call cpHLDE
jp nc, unsetZ ; HL (addr2) >= DE (cnt). no good
ex de, hl ; DE: addr2
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