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Simplify short offset handling in 6502 depacker

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emmanuel-marty 2019-04-10 17:37:36 +02:00
parent c220694531
commit 8c3fc6d652
1 changed files with 3 additions and 4 deletions
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7
asm/6502/decompress.asm
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@ -85,18 +85,17 @@ NO_LITERALS
AND #$80 ; isolate match offset mode (O)
BNE GET_LONG_OFFSET ; $80: 16 bit offset
JSR GETSRC ; get 8 bit offset from stream
TAX ; store as low 8 bits of offset
JSR GETSRC ; get 8 bit offset from stream in A
; Y (high 8 bits) is already set to 0 here
JMP FIX_OFFSET ; go increase offset
GET_LONG_OFFSET ; $00: 2-byte offset
JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A
TAY ; put high 8 bits in Y
TXA ; put low 8 bits in A
FIX_OFFSET
TXA ; add 1 to offset
CLC
CLC ; add 1 to offset
ADC #$01
BCC OFFSET_FIXED