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Merge pull request #13 from peterferrie/master

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Emmanuel Marty 2019-07-11 08:57:10 +02:00 committed by GitHub
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1 changed files with 7 additions and 10 deletions
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17
asm/6502/decompress_v1.asm
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@ -37,8 +37,12 @@ DECODE_TOKEN
AND #$70 ; isolate literals count AND #$70 ; isolate literals count
BEQ NO_LITERALS ; skip if no literals to copy BEQ NO_LITERALS ; skip if no literals to copy
CMP #$70 ; LITERALS_RUN_LEN? LSR A ; shift literals count into place
BNE EMBEDDED_LITERALS ; if not, count is directly embedded in token LSR A
LSR A
LSR A
CMP #$07 ; LITERALS_RUN_LEN?
BNE PREPARE_COPY_LITERALS ; if not, count is directly embedded in token
JSR GETSRC ; get extra byte of variable literals count JSR GETSRC ; get extra byte of variable literals count
; the carry is always set by the CMP above ; the carry is always set by the CMP above
@ -55,14 +59,7 @@ LARGE_VARLEN_LITERALS ; handle 16 bits literals count
; literals count = directly these 16 bits ; literals count = directly these 16 bits
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
BCS PREPARE_COPY_LITERALS_HIGH ; (*like JMP PREPARE_COPY_LITERALS_HIGH but shorter) BYTE $A9 ; mask TAX (faster than BCS)
EMBEDDED_LITERALS
LSR A ; shift literals count into place
LSR A
LSR A
LSR A
PREPARE_COPY_LITERALS PREPARE_COPY_LITERALS
TAX TAX
PREPARE_COPY_LITERALS_HIGH PREPARE_COPY_LITERALS_HIGH