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-3 bytes for 6809 LZSA2 depacker, slightly faster

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Emmanuel Marty 2020-06-19 20:08:09 +02:00 committed by GitHub
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commit f920485899
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1 changed files with 7 additions and 7 deletions
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14
asm/6809/unlzsa2.s
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@ -1,4 +1,4 @@
; unlzsa2.s - 6809 decompression routine for raw LZSA2 - 190 bytes
; unlzsa2.s - 6809 decompression routine for raw LZSA2 - 187 bytes
; compress with lzsa -f2 -r <original_file> <compressed_file>
;
; in: x = start of compressed data
@ -29,7 +29,7 @@ decompress_lzsa2
lz2token ldb ,x+ ; load next token into B: XYZ|LL|MMM
pshs b ; save it
lda #$00 ; clear A (high part of literals count)
clra ; clear A (high part of literals count)
andb #$18 ; isolate LLL (embedded literals count) in B
beq lz2nolt ; skip if no literals
cmpb #$18 ; LITERALS_RUN_LEN_V2?
@ -78,7 +78,7 @@ lz2nolt ldb ,s ; get token again, don't pop it from the stack
lda #$ff ; set bits 8-15 of offset
bra lz2gotof
lz2offs9 lda #$00 ; clear A (to prepare for high 8 bits of offset)
lz2offs9 clra ; clear A (to prepare for high 8 bits of offset)
lslb ; push token's Z flag bit into carry
rola ; shift Z flag from carry into bit 0 of A
coma ; set bits 9-15 of offset, reverse bit 8
@ -89,12 +89,12 @@ lz2offs9 lda #$00 ; clear A (to prepare for high 8 bits of offset)
lz2nibct fcb $00 ; nibble ready flag
lz2nibl ldb #$aa
lsr lz2nibct,pcr ; nibble ready?
lsr <lz2nibct,pcr ; nibble ready?
bcs lz2gotnb
inc lz2nibct,pcr ; flag nibble as ready for next time
inc <lz2nibct,pcr ; flag nibble as ready for next time
ldb ,x+ ; load two nibbles
stb lz2nibl+1,pcr ; store nibble for next time (low 4 bits)
stb <lz2nibl+1,pcr ; store nibble for next time (low 4 bits)
lsrb ; shift 4 high bits of nibble down
lsrb
@ -131,7 +131,7 @@ lz2repof ldd #$aaaa ; load match offset
puls b ; restore token
lda #$00 ; clear A (high part of match length)
clra ; clear A (high part of match length)
andb #$07 ; isolate MMM (embedded match length)
addb #$02 ; add MIN_MATCH_SIZE_V2
cmpb #$09 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2?