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This commit is contained in:
Peter Ferrie 2019-07-10 16:04:42 -07:00
parent 36e7316f30
commit 7861ef1552
1 changed files with 28 additions and 32 deletions
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60
asm/6502/decompress_v2.asm
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@ -29,15 +29,10 @@
; 3. This notice may not be removed or altered from any source distribution. ; 3. This notice may not be removed or altered from any source distribution.
; ----------------------------------------------------------------------------- ; -----------------------------------------------------------------------------
OFFSLO = $43 ; zero-page location for temp offset NIBCOUNT = $FC ; zero-page location for temp offset
OFFSHI = $44
FIXUP = $4B
NIBBLES = $FB
NIBCOUNT = $FC
DECOMPRESS_LZSA2 DECOMPRESS_LZSA2
LDY #$00 LDY #$00
STY NIBBLES
STY NIBCOUNT STY NIBCOUNT
DECODE_TOKEN DECODE_TOKEN
@ -51,7 +46,7 @@ DECODE_TOKEN
JSR GETNIBBLE ; get extra literals length nibble JSR GETNIBBLE ; get extra literals length nibble
; add nibble to len from token ; add nibble to len from token
ADC #$03 ; (LITERALS_RUN_LEN_V2) ADC #$02 ; (LITERALS_RUN_LEN_V2) minus carry
CMP #$12 ; LITERALS_RUN_LEN_V2 + 15 ? CMP #$12 ; LITERALS_RUN_LEN_V2 + 15 ?
BNE PREPARE_COPY_LITERALS ; if less, literals count is complete BNE PREPARE_COPY_LITERALS ; if less, literals count is complete
@ -87,22 +82,22 @@ COPY_LITERALS
NO_LITERALS NO_LITERALS
PLA ; retrieve token from stack PLA ; retrieve token from stack
PHA ; preserve token again PHA ; preserve token again
BMI REPMATCH_OR_LARGE_OFFSET ; 1YZ: rep-match or 13/16 bit offset ASL
BCS REPMATCH_OR_LARGE_OFFSET ; 1YZ: rep-match or 13/16 bit offset
ASL ; 0YZ: 5 or 9 bit offset ASL ; 0YZ: 5 or 9 bit offset
BMI OFFSET_9_BIT BCS OFFSET_9_BIT
; 00Z: 5 bit offset ; 00Z: 5 bit offset
LDX #$0FF ; set offset bits 15-8 to 1 LDX #$0FF ; set offset bits 15-8 to 1
STX OFFSHI
JSR GETCOMBINEDBITS ; rotate Z bit into bit 0, read nibble for bits 4-1 JSR GETCOMBINEDBITS ; rotate Z bit into bit 0, read nibble for bits 4-1
ORA #$E0 ; set bits 7-5 to 1 ORA #$E0 ; set bits 7-5 to 1
BNE GOT_OFFSET_LO ; go store low byte of match offset and prepare match BNE GOT_OFFSET_LO ; go store low byte of match offset and prepare match
OFFSET_9_BIT ; 01Z: 9 bit offset OFFSET_9_BIT ; 01Z: 9 bit offset
ASL ; shift Z (offset bit 8) in place ;;ASL ; shift Z (offset bit 8) in place
ROL ROL
ROL ROL
AND #$01 AND #$01
@ -112,7 +107,7 @@ OFFSET_9_BIT ; 01Z: 9 bit offset
REPMATCH_OR_LARGE_OFFSET REPMATCH_OR_LARGE_OFFSET
ASL ; 13 bit offset? ASL ; 13 bit offset?
BMI REPMATCH_OR_16_BIT ; handle rep-match or 16-bit offset if not BCS REPMATCH_OR_16_BIT ; handle rep-match or 16-bit offset if not
; 10Z: 13 bit offset ; 10Z: 13 bit offset
@ -122,36 +117,38 @@ REPMATCH_OR_LARGE_OFFSET
; (*same as JMP GOT_OFFSET_HI but shorter) ; (*same as JMP GOT_OFFSET_HI but shorter)
REPMATCH_OR_16_BIT ; rep-match or 16 bit offset REPMATCH_OR_16_BIT ; rep-match or 16 bit offset
ASL ; XYZ=111? ;;ASL ; XYZ=111?
BMI REP_MATCH ; reuse previous offset if so (rep-match) BMI REP_MATCH ; reuse previous offset if so (rep-match)
; 110: handle 16 bit offset ; 110: handle 16 bit offset
JSR GETSRC ; grab high 8 bits JSR GETSRC ; grab high 8 bits
GOT_OFFSET_HI GOT_OFFSET_HI
STA OFFSHI ; store high byte of match offset TAX
JSR GETSRC ; grab low 8 bits JSR GETSRC ; grab low 8 bits
GOT_OFFSET_LO GOT_OFFSET_LO
STA OFFSLO ; store low byte of match offset STA OFFSLO ; store low byte of match offset
STX OFFSHI ; store high byte of match offset
REP_MATCH REP_MATCH
CLC ; add dest + match offset CLC ; add dest + match offset
LDA PUTDST+1 ; low 8 bits LDA PUTDST+1 ; low 8 bits
ADC OFFSLO OFFSLO = *+1
ADC #$AA
STA COPY_MATCH_LOOP+1 ; store back reference address STA COPY_MATCH_LOOP+1 ; store back reference address
LDA OFFSHI ; high 8 bits OFFSHI = *+1
LDA #$AA ; high 8 bits
ADC PUTDST+2 ADC PUTDST+2
STA COPY_MATCH_LOOP+2 ; store high 8 bits of address STA COPY_MATCH_LOOP+2 ; store high 8 bits of address
PLA ; retrieve token from stack again PLA ; retrieve token from stack again
AND #$07 ; isolate match len (MMM) AND #$07 ; isolate match len (MMM)
CLC ADC #$01 ; add MIN_MATCH_SIZE_V2 and carry
ADC #$02 ; add MIN_MATCH_SIZE_V2
CMP #$09 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2? CMP #$09 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2?
BNE PREPARE_COPY_MATCH ; if less, length is directly embedded in token BNE PREPARE_COPY_MATCH ; if less, length is directly embedded in token
JSR GETNIBBLE ; get extra match length nibble JSR GETNIBBLE ; get extra match length nibble
; add nibble to len from token ; add nibble to len from token
ADC #$09 ; (MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2) ADC #$08 ; (MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2) minus carry
CMP #$18 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2 + 15? CMP #$18 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2 + 15?
BNE PREPARE_COPY_MATCH ; if less, match length is complete BNE PREPARE_COPY_MATCH ; if less, match length is complete
@ -165,7 +162,7 @@ REP_MATCH
; Handle 16 bits match length ; Handle 16 bits match length
JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A
TAY ; put high 8 bits in Y TAY ; put high 8 bits in Y
TXA .DB $A9 ; mask TAX, faster than TXA/TAX
PREPARE_COPY_MATCH PREPARE_COPY_MATCH
TAX TAX
@ -188,34 +185,33 @@ GETMATCH_INC_HI
BNE GETMATCH_DONE ; (*like JMP GETMATCH_DONE but shorter) BNE GETMATCH_DONE ; (*like JMP GETMATCH_DONE but shorter)
GETCOMBINEDBITS GETCOMBINEDBITS
STA FIXUP EOR #$80
ASL
PHP
JSR GETNIBBLE ; get nibble into bits 0-3 (for offset bits 1-4) JSR GETNIBBLE ; get nibble into bits 0-3 (for offset bits 1-4)
BIT FIXUP ; merge Z bit as the carry bit (for offset bit 0) PLP ; merge Z bit as the carry bit (for offset bit 0)
BVS COMBINEDBITZ
SEC
COMBINEDBITZ COMBINEDBITZ
ROL ; nibble -> bits 1-4; carry(!Z bit) -> bit 0 ; carry cleared ROL ; nibble -> bits 1-4; carry(!Z bit) -> bit 0 ; carry cleared
RTS RTS
GETNIBBLE GETNIBBLE
NIBBLES = *+1
LDA #$AA
LSR NIBCOUNT LSR NIBCOUNT
BCS HAS_NIBBLES BCS HAS_NIBBLES
INC NIBCOUNT INC NIBCOUNT
JSR GETSRC ; get 2 nibbles JSR GETSRC ; get 2 nibbles
STA NIBBLES STA NIBBLES
LSR A LSR
LSR A LSR
LSR A LSR
LSR A LSR
CLC SEC
RTS
HAS_NIBBLES HAS_NIBBLES
LDA NIBBLES
AND #$0F ; isolate low 4 bits of nibble AND #$0F ; isolate low 4 bits of nibble
CLC
RTS RTS
GETPUT GETPUT