mirror of https://github.com/hsoft/collapseos.git
128 lines
3.1 KiB
NASM
128 lines
3.1 KiB
NASM
; buf - manage line buffer
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;
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; Lines in edited file aren't loaded in memory, their offsets is referenced to
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; in this buffer.
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;
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; *** Consts ***
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;
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; Maximum number of lines allowed in the buffer.
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.equ BUF_MAXLINES 0x800
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; Size of our scratchpad
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.equ BUF_PADMAXLEN 0x1000
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; *** Variables ***
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; Number of lines currently in the buffer
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.equ BUF_LINECNT BUF_RAMSTART
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; List of words pointing to scratchpad offsets
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.equ BUF_LINES BUF_LINECNT+2
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; size of file we read in bufInit. That offset is the beginning of our
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; in-memory scratchpad.
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.equ BUF_FSIZE BUF_LINES+BUF_MAXLINES*2
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; The in-memory scratchpad
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.equ BUF_PADLEN BUF_FSIZE+2
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.equ BUF_PAD BUF_PADLEN+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
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; as we go.
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bufInit:
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ld hl, 0
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ld (BUF_PADLEN), hl
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ld ix, BUF_LINES
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ld bc, 0 ; line count
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.loop:
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call blkTell ; --> HL
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call blkGetC
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jr nz, .loopend
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ld (ix), l
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inc ix
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ld (ix), h
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inc ix
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inc bc
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call ioGetLine
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jr .loop
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.loopend:
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; HL currently has the result of the last blkTell
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ld (BUF_FSIZE), hl
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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
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; array.
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bufLineAddr:
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push de
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ex de, hl
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ld hl, BUF_LINES
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add hl, de
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add hl, de ; twice, because two bytes per line
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pop de
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ret
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; Read line number specified in HL and loads the I/O buffer with it.
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; Like ioGetLine, sets HL to line buffer pointer.
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; Sets Z on success, unset if out of bounds.
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bufGetLine:
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push de
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ld de, (BUF_LINECNT)
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call cpHLDE
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jr nc, .outOfBounds ; HL > (BUF_LINECNT)
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call bufLineAddr
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; HL now points to seek offset in memory
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ld e, (hl)
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inc hl
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ld d, (hl)
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; DE has seek offset
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ex de, hl
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; and now HL has it. We're ready to call ioGetLine!
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pop de
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cp a ; ensure Z
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jp ioGetLine ; preserves AF
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.outOfBounds:
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pop de
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jp unsetZ
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; Given line indexes in HL and DE where HL < DE < CNT, move all lines between
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; DE and CNT by an offset of DE-HL. Also, adjust BUF_LINECNT by DE-HL.
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; WARNING: no bounds check. The only consumer of this routine already does
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; bounds check.
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bufDelLines:
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; Let's start with setting up BC, which is (CNT-DE) * 2
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push hl ; --> lvl 1
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ld hl, (BUF_LINECNT)
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scf \ ccf
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sbc hl, de
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; mult by 2 and we're done
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sla l \ rl h
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push hl \ pop bc
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pop hl ; <-- lvl 1
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; Good! BC done. Now, let's adjust BUF_LINECNT by DE-HL
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push hl ; --> lvl 1
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scf \ ccf
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sbc hl, de ; HL -> nb of lines to delete, negative
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push de ; --> lvl 2
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ld de, (BUF_LINECNT)
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add hl, de ; adding DE to negative HL
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ld (BUF_LINECNT), hl
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pop de ; <-- lvl 2
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pop hl ; <-- lvl 1
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; Line count updated!
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; let's have invert HL and DE to match LDIR's signature
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ex de, hl
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; At this point we have higher index in HL, lower index in DE and number
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; of bytes to delete in BC. It's convenient because it's rather close
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; to LDIR's signature! The only thing we need to do now is to translate
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; those HL and DE indexes in memory addresses, that is, multiply by 2
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; and add BUF_LINES
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push hl ; --> lvl 1
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ex de, hl
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call bufLineAddr
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ex de, hl
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pop hl ; <-- lvl 1
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call bufLineAddr
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; Both HL and DE are translated. Go!
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ldir
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ret
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