mirror of https://github.com/fadden/fhpack.git
Split "small" version out, tweaked the others
I split the "small" source into its own file. I think it could become smaller, but not without changes that make #ifdefs untenable. The "small" version need a couple of fixes (define "savsrc", branch to "advsrc1" not "advsrc"). Merlin apparently detects SEC+XCE and automatically switches back to 8-bit registers, so I added an MX %00 to the 65816 version after the exit section. Added comments. This just updates the git copy of the sources. An updated set of disk images will appear soonish.
This commit is contained in:
Andy McFadden
parent
efa2bf71a9
commit
dcabf12d97
70
LZ4FH6502.S
70
LZ4FH6502.S
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@ -2,7 +2,10 @@
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* *
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* LZ4FH uncompression for 6502 *
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* By Andy McFadden *
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* Version 1.0, August 2015 *
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* Version 1.0.1, August 2015 *
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* *
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* Refactored for size & speed *
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* by Peter Ferrie. *
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* *
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* Developed with Merlin-16 *
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* *
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@ -18,7 +21,6 @@ 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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@ -65,6 +67,10 @@ fail
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jsr bell
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jmp monitor
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* These stubs increment the high byte and then jump
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* back. This saves a cycle because branch-not-taken
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* becomes the common case. We assume that we're not
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* unpacking data at $FFxx, so BNE is branch-always.
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hi2
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inc srcptr+1
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bne nohi2
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@ -83,15 +89,10 @@ notempty
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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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* 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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@ -100,16 +101,11 @@ advsrc2
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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 mainloop
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@ -125,7 +121,7 @@ mainloop
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lsr A
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lsr A
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beq noliteral
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cmp #$0f
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cmp #$0f ;sets carry for >= 15
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bne shortlit
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inc srcptr
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@ -158,13 +154,13 @@ shortlit tax
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adc srcptr
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sta srcptr
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bcs hi3
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nohi3
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nohi3 ;carry cleared by hi3
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txa
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adc dstptr
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sta dstptr
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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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dey ;Y=0; DEY so next INY goes to 0
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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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@ -199,18 +195,12 @@ _desthi ora #$00 ;OR in hi-res page
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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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bcs hi5
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nohi5
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FIN
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nohi5 ;hi5 clears carry
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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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@ -229,46 +219,24 @@ nohi5
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* advance dstptr past copied data
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lda dstptr
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adc savlen
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adc savlen ;carry is clear
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sta dstptr
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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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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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ELSE
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DO smaller
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bne advsrc2
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ELSE
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bne mainloop ;branch always
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bne mainloop ;always (not unpacking at $FFxx)
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FIN
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FIN
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lst on
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sav LZ4FH6502
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lst off
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@ -0,0 +1,240 @@
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********************************
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* *
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* LZ4FH uncompression for 6502 *
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* By Andy McFadden *
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* Version 1.0.1, August 2015 *
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* *
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* Refactored for size & speed *
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* by Peter Ferrie. (This *
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* version favors code size.) *
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* *
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* Developed with Merlin-16 *
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* *
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********************************
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lst off
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org $0300
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*
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* Constants
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*
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lz4fh_magic equ $66 ;ascii 'f'
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tok_empty equ 253
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tok_eod equ 254
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overrun_check equ 0
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*
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* Variable storage
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*
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srcptr equ $3c ;2b a1l
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dstptr equ $3e ;2b a1h
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copyptr equ $00 ;2b
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savmix equ $02 ;1b
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savlen equ $03 ;1b
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savsrc equ $04 ;1b
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*
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* ROM routines
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*
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bell equ $ff3a
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monitor equ $ff69
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*
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* Parameters, stashed at the top of the text input
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* buffer. We use this, rather than just having them
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* poked directly into the code, so that the 6502 and
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* 65816 implementations work the same way without
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* either getting weird.
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*
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in_src equ $2fc ;2b
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in_dst equ $2fe ;2b
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entry
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lda in_src ;copy source address to zero page
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sta srcptr
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lda in_src+1
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sta srcptr+1
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lda in_dst ;copy destination address to zero page
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sta dstptr
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lda in_dst+1
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sta dstptr+1
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sta _desthi+1
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ldy #$00
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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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fail
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jsr bell
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jmp monitor
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* These stubs increment the high byte and then jump
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* back. This saves a cycle because branch-not-taken
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* becomes the common case. We assume that we're not
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* unpacking data at $ffxx, so BNE is branch-always.
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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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advsrc1
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sec
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advsrc2
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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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goodmagic
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inc srcptr
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bne mainloop
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inc srcptr+1
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mainloop
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* Get the mixed-length byte and handle the literal.
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ldy #$00
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lda (srcptr),y ;get mixed-length byte
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sta savmix
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lsr A ;get the literal length
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lsr A
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lsr A
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lsr A
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beq noliteral
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cmp #$0f ;sets carry for >= 15
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bne shortlit
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inc srcptr
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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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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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* address of the next output location. So we want to
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* read from (srcptr),y+1 and write to (dstptr),y.
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* We can do this by sticking the DEY between the LDA
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* and STA.
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*
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* We could save a couple of cycles by substituting
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* addr,y in place of (dp),y, but the added setup cost
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* would only benefit longer literal strings.
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shortlit tax
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tay
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:litloop
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lda (srcptr),y ;5
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dey ;2 if len is 255, copy 0-254
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sta (dstptr),y ;6
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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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txa
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sec ;this gets us the +1
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adc srcptr
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sta srcptr
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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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bcs hi4
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nohi4
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dey ;Y=0; DEY so next INY goes to 0
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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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* interesting byte.
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noliteral
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lda savmix
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and #$0f
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cmp #$0f
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blt :shortmatch ;BCC
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iny
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lda (srcptr),y ;get length extension
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cmp #237 ;"normal" values are 0-236
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bge specialmatch ;BCS
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adc #15 ;will not exceed 255
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* Put the destination address into copyptr.
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:shortmatch
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adc #4 ;min match; won't exceed 255
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sta savlen ;save match len for later
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tax ;and keep it in X
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iny
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lda (srcptr),y ;match offset, lo
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sta copyptr
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iny
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lda (srcptr),y ;match offset, hi
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_desthi ora #$00 ;OR in hi-res page
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sta copyptr+1
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* Advance srcptr past the encoded match while we still
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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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sty savsrc
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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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*
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* We know the match is at least 4 bytes long, so
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* we could save a few cycles by not doing the
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* ADC #4 earlier, and unrolling the first 4
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* load/store operations here.
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ldy #$00
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:copyloop
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lda (copyptr),y ;5
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sta (dstptr),y ;6
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iny ;2
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dex ;2
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bne :copyloop ;3 -> 18 cycles/byte
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* advance dstptr past copied data
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lda dstptr
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adc savlen ;carry should still be clear
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sta dstptr
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ldy savsrc
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linkadv
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bcc advsrc1
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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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bcc linkadv
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BRK
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BRK
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ELSE
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bne advsrc2
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FIN
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lst on
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sav LZ4FH6502
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lst off
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15
LZ4FH65816.S
15
LZ4FH65816.S
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@ -2,7 +2,10 @@
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* *
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* LZ4FH uncompression for 65816 *
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* By Andy McFadden *
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* Version 1.0, August 2015 *
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* Version 1.0.1, August 2015 *
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* *
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* Refactored for size & speed *
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* by Peter Ferrie. *
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* *
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* Developed with Merlin-16 *
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* *
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@ -62,7 +65,7 @@ fail
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jmp monitor
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notempty
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cmp #tok_eod
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cmp #tok_eod ;end-of-data or error
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* exit
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sec ;return to emulation mode
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@ -70,6 +73,8 @@ notempty
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bne fail
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rts
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mx %00 ;undo the sec/xce
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* handle "special" match length values (in A)
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specialmatch
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cmp #tok_empty
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@ -91,7 +96,7 @@ mainloop
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lda $0000,x ;length >= 15, get next
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inx
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and #$00ff
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adc #14 ;(carry set) add 15 - will not exceed 255
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adc #14 ;(carry set) +15 - won't exceed 255
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* At this point, Y holds the address of the next
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* compressed data byte, X has the address of the
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@ -131,3 +136,7 @@ _dstmod ora #$ff00 ;OR in hi-res page
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mvn $00,$00
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plx ;restore srcptr
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bra mainloop
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lst on
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sav LZ4FH65816
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lst off
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Loading…
Reference in New Issue