mirror of https://github.com/fadden/fhpack.git
major refactor for more speed and smaller size
This commit is contained in:
Peter Ferrie
parent
7720b2c161
commit
d79ef369fd
151
LZ4FH6502.S
151
LZ4FH6502.S
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@ -18,6 +18,7 @@ tok_empty equ 253
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tok_eod equ 254
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overrun_check equ 0
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smaller equ 0
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*
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* Variable storage
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@ -59,13 +60,60 @@ entry
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lda (srcptr),y
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cmp #lz4fh_magic ;does magic match?
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beq goodmagic
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jmp fail
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fail
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jsr bell
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jmp monitor
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hi2
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inc srcptr+1
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bne nohi2
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hi3
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inc srcptr+1
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clc
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bcc nohi3
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hi4
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inc dstptr+1
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bne nohi4
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notempty
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cmp #tok_eod
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bne fail
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rts ;success!
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;* handle "special" match values (value in A)
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specialmatch
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cmp #tok_empty
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bne notempty
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DO smaller
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advsrc1
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sec
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advsrc2
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FIN
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tya ;empty match, advance srcptr
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adc srcptr ; past and jump to main loop
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sta srcptr
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bcc mainloop
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inc srcptr+1
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bne mainloop
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DO smaller
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ELSE
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hi5
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inc srcptr+1
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clc
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bcc nohi5
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FIN
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goodmagic
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inc srcptr
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bne :nohi
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bne mainloop
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inc srcptr+1
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:nohi
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mainloop
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* Get the mixed-length byte and handle the literal.
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@ -81,12 +129,10 @@ mainloop
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bne shortlit
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inc srcptr
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bne :nohi
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inc srcptr+1
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:nohi
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beq hi2
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nohi2
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lda (srcptr),y ;get length extension
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clc
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adc #15 ;add 15 - will not exceed 255
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adc #14 ;(carry set) add 15 - will not exceed 255
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* At this point, srcptr holds the address of the "mix"
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* word or the length extension, and dstptr holds the
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@ -107,21 +153,18 @@ shortlit sta savlen
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bne :litloop ;3 -> 16 cycles/byte
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* Advance srcptr by savlen+1, and dstptr by savlen
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lda srcptr
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txa
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sec ;this gets us the +1
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adc savlen
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adc srcptr
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sta srcptr
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bcc :nohi
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inc srcptr+1
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clc
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:nohi
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lda dstptr
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adc savlen
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bcs hi3
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nohi3
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txa
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adc dstptr
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sta dstptr
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bcc :nohi1
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inc dstptr+1
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:nohi1
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ldy #$ff ;next INY rolls back to zero
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bcs hi4
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nohi4
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dey ;next INY rolls back to zero
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* Handle match. Y holds an offset into srcptr such
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* that we need to increment it once to get the next
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@ -155,13 +198,19 @@ _desthi ora #$00 ;OR in hi-res page
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* remember how many bytes it took to encode. Y is
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* indexing the last value used, so we want to go
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* advance srcptr by Y+1.
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DO smaller
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sty savsrc
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ELSE
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tya
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sec
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adc srcptr
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sta srcptr
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bcc :nohi
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inc srcptr+1
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:nohi
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bcs hi5
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nohi5
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FIN
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* Copy the match. The length is in X. Note this
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* must be a forward copy so overlapped data works.
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@ -180,21 +229,41 @@ _desthi ora #$00 ;OR in hi-res page
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* advance dstptr past copied data
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lda dstptr
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clc
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adc savlen
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sta dstptr
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bcc :nohi1
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inc dstptr+1
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:nohi1
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DO smaller
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ldy savsrc
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linkadv
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bcc advsrc
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ELSE
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bcc mainloop
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FIN
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inc dstptr+1
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DO overrun_check
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LDA dstptr+1
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CMP #$60
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BLT :OKAY
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DO smaller
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bcc linkadv
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ELSE
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bcc mainloop
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FIN
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BRK
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BRK
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:OKAY
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jmp mainloop
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ELSE
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DO smaller
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bne advsrc2
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ELSE
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@ -202,24 +271,4 @@ _desthi ora #$00 ;OR in hi-res page
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FIN
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* handle "special" match values (value in A)
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specialmatch
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cmp #tok_empty
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bne :notempty
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tya ;empty match, advance srcptr
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adc srcptr ; past and jump to main loop
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sta srcptr
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bcc :nohi
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inc srcptr+1
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clc
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:nohi
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jmp mainloop
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:notempty
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cmp #tok_eod
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bne fail
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rts ;success!
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fail
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jsr bell
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jmp monitor
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FIN
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