diff --git a/asm/6502/decompress_v1.asm b/asm/6502/decompress_v1.asm index 9289d32..a922752 100755 --- a/asm/6502/decompress_v1.asm +++ b/asm/6502/decompress_v1.asm @@ -44,8 +44,9 @@ DECODE_TOKEN BNE EMBEDDED_LITERALS ; if not, count is directly embedded in token JSR GETSRC ; get extra byte of variable literals count - CLC ; add extra byte to len from token - ADC #$07 ; (LITERALS_RUN_LEN) + ; the carry is always set by the CMP above + ; GETSRC doesn't change it + SBC #$F9 ; (LITERALS_RUN_LEN) BCC PREPARE_COPY_LITERALS BEQ LARGE_VARLEN_LITERALS ; if adding up to zero, go grab 16-bit count @@ -84,14 +85,34 @@ NO_LITERALS JSR GETSRC ; get 8 bit offset from stream in A - STA OFFSLO ; store final match offset - CLC ; add dest + match offset - LDA PUTDST+1 ; low 8 bits - ADC OFFSLO + ADC PUTDST+1 ; low 8 bits STA COPY_MATCH_LOOP+1 ; store back reference address LDA #$0FF ; high 8 bits - JMP GOT_OFFSET ; go prepare match + BNE GOT_OFFSET ; go prepare match + ; (*like JMP GOT_OFFSET but shorter) + +SHORT_VARLEN_MATCHLEN + JSR GETSRC ; get single extended byte of variable match len + INY ; add 256 to match length + +PREPARE_COPY_MATCH + TAX +PREPARE_COPY_MATCH_Y + INY + +COPY_MATCH_LOOP + LDA $AAAA ; get one byte of backreference + INC COPY_MATCH_LOOP+1 + BNE GETMATCH_DONE + INC COPY_MATCH_LOOP+2 +GETMATCH_DONE + JSR PUTDST ; copy to destination + DEX + BNE COPY_MATCH_LOOP + DEY + BNE COPY_MATCH_LOOP + BEQ DECODE_TOKEN ; (*like JMP DECODE_TOKEN but shorter) GET_LONG_OFFSET ; handle 16 bit offset: JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A @@ -117,8 +138,9 @@ GOT_OFFSET BNE PREPARE_COPY_MATCH ; if not, count is directly embedded in token JSR GETSRC ; get extra byte of variable match length - CLC - ADC #$12 ; add MATCH_RUN_LEN and MIN_MATCH_SIZE to match length + ; the carry is always set by the CMP above + ; GETSRC doesn't change it + SBC #$EE ; add MATCH_RUN_LEN and MIN_MATCH_SIZE to match length BCC PREPARE_COPY_MATCH BNE SHORT_VARLEN_MATCHLEN @@ -127,29 +149,7 @@ GOT_OFFSET TAY ; put high 8 bits in Y ; large match length with zero high byte? BEQ DECOMPRESSION_DONE ; if so, this is the EOD code, bail - JMP PREPARE_COPY_MATCH_Y - -SHORT_VARLEN_MATCHLEN - JSR GETSRC ; get single extended byte of variable match len - INY ; add 256 to match length - -PREPARE_COPY_MATCH - TAX -PREPARE_COPY_MATCH_Y - INY - -COPY_MATCH_LOOP - LDA $AAAA ; get one byte of backreference - INC COPY_MATCH_LOOP+1 - BNE GETMATCH_DONE - INC COPY_MATCH_LOOP+2 -GETMATCH_DONE - JSR PUTDST ; copy to destination - DEX - BNE COPY_MATCH_LOOP - DEY - BNE COPY_MATCH_LOOP - JMP DECODE_TOKEN + BNE PREPARE_COPY_MATCH_Y ; (*like JMP PREPARE_COPY_MATCH_Y but shorter) GETPUT JSR GETSRC