6502/lzsa
1
0
Fork 0
mirror of https://github.com/emmanuel-marty/lzsa.git synced 2024-06-01 06:41:43 +00:00
Code Issues Projects Releases Wiki Activity

Slight speed and space improvement to nibble processing in 6809 LZSA2 depackers

Browse Source
This commit is contained in:
Doug Masten 2020-06-30 14:05:59 -05:00
parent 214e03555f
commit 31d5dc2419
2 changed files with 10 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
asm/6809/unlzsa2.s
View File

@ -1,4 +1,4 @@
; unlzsa2.s - 6809 decompression routine for raw LZSA2 - 172 bytes
; unlzsa2.s - 6809 decompression routine for raw LZSA2 - 169 bytes
; compress with lzsa -f2 -r <original_file> <compressed_file>
;
; in: x = start of compressed data
@ -24,7 +24,7 @@
; 3. This notice may not be removed or altered from any source distribution.
decompress_lzsa2
lsr <lz2nibct,pcr ; reset nibble available flag
clr <lz2nibct,pcr ; reset nibble available flag
lz2token ldb ,x+ ; load next token into B: XYZ|LL|MMM
pshs b ; save it
@ -83,10 +83,9 @@ lz2offs9 deca ; set bits 9-15 of offset, reverse bit 8
lz2nibct fcb $00 ; nibble ready flag
lz2nibl ldb #$aa
lsr <lz2nibct,pcr ; nibble ready?
bcs lz2gotnb
com <lz2nibct,pcr ; toggle nibble ready flag and check
bpl lz2gotnb
inc <lz2nibct,pcr ; flag nibble as ready for next time
ldb ,x+ ; load two nibbles
stb <lz2nibl+1,pcr ; store nibble for next time (low 4 bits)

13
asm/6809/unlzsa2b.s
View File

@ -1,4 +1,4 @@
; unlzsa2b.s - 6809 backward decompression routine for raw LZSA2 - 174 bytes
; unlzsa2b.s - 6809 backward decompression routine for raw LZSA2 - 171 bytes
; compress with lzsa -f2 -r -b <original_file> <compressed_file>
;
; in: x = last byte of compressed data
@ -24,7 +24,7 @@
; 3. This notice may not be removed or altered from any source distribution.
decompress_lzsa2
lsr <lz2nibct,pcr ; reset nibble available flag
clr <lz2nibct,pcr ; reset nibble available flag
leax 1,x
leay 1,y
@ -41,7 +41,7 @@ lz2token ldb ,-x ; load next token into B: XYZ|LL|MMM
cmpb #$12 ; LITERALS_RUN_LEN_V2 + 15 ?
bne lz2gotla ; if not, we have the full literals count, go copy
addb ,-x ; add extra literals count byte + LITERALS_RUN_LEN + 15
addb ,-x ; add extra literals count byte + LITERALS_RUN_LEN + 15
bcc lz2gotla ; if no overflow, we got the complete count, copy
ldd ,--x ; load 16 bit count in D (low part in B, high in A)
@ -77,16 +77,15 @@ lz2nolt ldb ,s ; get token again, don't pop it from the stack
sex ; set bits 8-15 of offset to $FF
bra lz2gotof
lz2offs9 deca ; set bits 9-15 of offset, reverse bit 8
lz2offs9 deca ; set bits 9-15 of offset, reverse bit 8
bra lz2lowof
lz2nibct fcb $00 ; nibble ready flag
lz2nibl ldb #$aa
lsr <lz2nibct,pcr ; nibble ready?
bcs lz2gotnb
com <lz2nibct,pcr ; toggle nibble ready flag and check
bpl lz2gotnb
inc <lz2nibct,pcr ; flag nibble as ready for next time
ldb ,-x ; load two nibbles
stb <lz2nibl+1,pcr ; store nibble for next time (low 4 bits)