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Delay clearing high part of literals count until we really have to in 6809 LZSA2 depacker

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Doug Masten 2020-06-26 15:56:28 -05:00
parent 99db30a732
commit c0f09db364
1 changed files with 5 additions and 5 deletions
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10
asm/6809/unlzsa2.s
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@ -29,8 +29,7 @@ decompress_lzsa2
lz2token ldb ,x+ ; load next token into B: XYZ|LL|MMM
pshs b ; save it
clra ; clear A (high part of literals count)
andb #$18 ; isolate LLL (embedded literals count) in B
andb #$18 ; isolate LL (embedded literals count) in B
beq lz2nolt ; skip if no literals
cmpb #$18 ; LITERALS_RUN_LEN_V2?
bne lz2declt ; if not, we have the complete count, go unshift
@ -38,10 +37,10 @@ lz2token ldb ,x+ ; load next token into B: XYZ|LL|MMM
bsr lz2nibl ; get extra literals length nibble in B
addb #$03 ; add LITERALS_RUN_LEN_V2
cmpb #$12 ; LITERALS_RUN_LEN_V2 + 15 ?
bne lz2gotlt ; if not, we have the full literals count, go copy
bne lz2gotla ; if not, we have the full literals count, go copy
addb ,x+ ; add extra literals count byte + LITERALS_RUN_LEN + 15
bcc lz2gotlt ; if no overflow, we got the complete count, copy
bcc lz2gotla ; if no overflow, we got the complete count, copy
ldb ,x+ ; load low 8 bits of little-endian literals count
lda ,x+ ; load high 8 bits of literal count
@ -50,7 +49,8 @@ lz2token ldb ,x+ ; load next token into B: XYZ|LL|MMM
lz2declt lsrb ; shift literals count into place
lsrb
lsrb
lz2gotla clra ; clear A (high part of literals count)
lz2gotlt tfr x,u
tfr d,x ; transfer 16-bit count into X
lz2cpylt lda ,u+ ; copy literal byte