6502/lzsa
1
0
Fork 0
mirror of https://github.com/emmanuel-marty/lzsa.git synced 2024-11-26 02:49:19 +00:00
Code Issues Projects Releases Wiki Activity

Merge pull request #13 from peterferrie/master

Browse Source 
smaller
This commit is contained in:
Emmanuel Marty 2019-07-11 08:57:10 +02:00 committed by GitHub
commit 455e6ee913
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 7 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
asm/6502/decompress_v1.asm
View File

@ -37,8 +37,12 @@ DECODE_TOKEN
AND #$70 ; isolate literals count
BEQ NO_LITERALS ; skip if no literals to copy
CMP #$70 ; LITERALS_RUN_LEN?
BNE EMBEDDED_LITERALS ; if not, count is directly embedded in token
LSR A ; shift literals count into place
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
; 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
JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A
TAY ; put high 8 bits in Y
BCS PREPARE_COPY_LITERALS_HIGH ; (*like JMP PREPARE_COPY_LITERALS_HIGH but shorter)
EMBEDDED_LITERALS
LSR A ; shift literals count into place
LSR A
LSR A
LSR A
BYTE $A9 ; mask TAX (faster than BCS)
PREPARE_COPY_LITERALS
TAX
PREPARE_COPY_LITERALS_HIGH