mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-11-21 14:31:01 +00:00
134 lines
5.9 KiB
ArmAsm
134 lines
5.9 KiB
ArmAsm
; unlzsa2b-6309.s - H6309 backward decompressor for raw LZSA2 - 155 bytes
|
|
; compress with lzsa -f2 -r -b <original_file> <compressed_file>
|
|
;
|
|
; in: x = last byte of compressed data
|
|
; y = last byte of decompression buffer
|
|
; out: y = first byte of decompressed data
|
|
;
|
|
; Copyright (C) 2020 Emmanuel Marty, Doug Masten
|
|
;
|
|
; This software is provided 'as-is', without any express or implied
|
|
; warranty. In no event will the authors be held liable for any damages
|
|
; arising from the use of this software.
|
|
;
|
|
; Permission is granted to anyone to use this software for any purpose,
|
|
; including commercial applications, and to alter it and redistribute it
|
|
; freely, subject to the following restrictions:
|
|
;
|
|
; 1. The origin of this software must not be misrepresented; you must not
|
|
; claim that you wrote the original software. If you use this software
|
|
; in a product, an acknowledgment in the product documentation would be
|
|
; appreciated but is not required.
|
|
; 2. Altered source versions must be plainly marked as such, and must not be
|
|
; misrepresented as being the original software.
|
|
; 3. This notice may not be removed or altered from any source distribution.
|
|
|
|
decompress_lzsa2
|
|
clr lz2nibct ; reset nibble available flag
|
|
leax 1,x ; adjust compressed data pointer
|
|
bra lz2token
|
|
|
|
lz2nibct fcb 0 ; nibble ready flag
|
|
|
|
lz2replg lslb ; push token's Y flag bit into carry
|
|
bcs lz2rep16 ; if token's Y bit is set, rep or 16 bit offset
|
|
|
|
sex ; push token's Z flag bit into reg A
|
|
bsr lz2nibl ; get offset nibble in B
|
|
lsla ; push token's Z flag bit into carry
|
|
rolb ; shift Z flag from carry into bit 0 of B
|
|
eorb #$e1 ; set bits 13-15 of offset, reverse bit 8
|
|
tfr b,a ; copy bits 8-15 of offset into A
|
|
suba #$02 ; substract 512 from offset
|
|
bra lz2lowof
|
|
|
|
lz2rep16 bmi lz2repof ; if token's Z flag bit is set, rep match
|
|
lda ,-x ; load high 8 bits of (negative, signed) offset
|
|
lz2lowof ldb ,-x ; load low 8 bits of offset
|
|
|
|
lz2gotof negd ; reverse sign of offset in D
|
|
std lz2moff+2 ; store match offset
|
|
|
|
lz2repof ldd #$0007 ; clear MSB match length and set mask for MMM
|
|
andb ,u ; isolate MMM (embedded match length) in token
|
|
lz2moff leau $aaaa,y ; put backreference start address in U (dst+offset)
|
|
addb #$02 ; add MIN_MATCH_SIZE_V2
|
|
cmpb #$09 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2?
|
|
bne lz2gotln ; no, we have the full match length, go copy
|
|
|
|
bsr lz2nibl ; get offset nibble in B
|
|
addb #$09 ; add MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2
|
|
cmpb #$18 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2 + 15?
|
|
bne lz2gotln ; if not, we have the full match length, go copy
|
|
|
|
addb ,-x ; add extra length byte + MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2 + 15
|
|
bcc lz2gotln ; if no overflow, we have the full length
|
|
beq lz2done ; detect EOD code
|
|
|
|
ldd ,--x ; load 16-bit len in D (low part in B, high in A)
|
|
|
|
lz2gotln tfr d,w ; set W with match count for TFM instruction
|
|
tfm u-,y- ; copy match bytes
|
|
|
|
lz2token ldb ,-x ; load next token into B: XYZ|LL|MMM
|
|
tfr x,u ; save token address
|
|
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
|
|
|
|
bsr lz2nibl ; get extra literals length nibble in B
|
|
addb #$03 ; add LITERALS_RUN_LEN_V2
|
|
cmpb #$12 ; LITERALS_RUN_LEN_V2 + 15 ?
|
|
bne lz2gotla ; if not, we have the full literals count, go copy
|
|
|
|
addb ,-x ; add extra literals count byte + LITERALS_RUN_LEN + 15
|
|
bcc lz2gotla ; if no overflow, we got the complete count, copy
|
|
|
|
ldd ,--x ; load 16 bit count in D (low part in B, high in A)
|
|
bra lz2gotlt ; we now have the complete count, go copy
|
|
|
|
lz2nibl com lz2nibct ; nibble ready?
|
|
bpl lz2gotnb
|
|
|
|
ldb ,-x ; load two nibbles
|
|
stb lz2gotnb+1 ; store nibble for next time (low 4 bits)
|
|
lsrb ; shift 4 high bits of nibble down
|
|
lsrb
|
|
lsrb
|
|
lsrb
|
|
rts
|
|
|
|
lz2declt lsrb ; shift literals count into place
|
|
lsrb
|
|
lsrb
|
|
lz2gotla clra ; clear A (high part of literals count)
|
|
|
|
lz2gotlt tfr d,w ; set W with literals count for TFM instruction
|
|
leax -1,x ; tfm is post-decrement
|
|
tfm x-,y- ; copy literal bytes
|
|
leax 1,x
|
|
|
|
lz2nolt ldb ,u ; get token again
|
|
lslb ; push token's X flag bit into carry
|
|
bcs lz2replg ; if token's X bit is set, rep or large offset
|
|
|
|
lslb ; push token's Y flag bit into carry
|
|
sex ; push token's Z flag bit into reg A (carry flag is not effected)
|
|
bcs lz2offs9 ; if token's Y bit is set, 9 bits offset
|
|
|
|
bsr lz2nibl ; get offset nibble in B
|
|
lsla ; retrieve token's Z flag bit and push into carry
|
|
rolb ; shift Z flag from carry into bit 0 of B
|
|
eorb #$e1 ; set bits 5-7 of offset, reverse bit 0
|
|
sex ; set bits 8-15 of offset to $FF
|
|
bra lz2gotof
|
|
|
|
lz2offs9 deca ; set bits 9-15 of offset, reverse bit 8
|
|
bra lz2lowof
|
|
|
|
lz2done leay 1,y ; adjust pointer to first byte of decompressed data and then exit
|
|
lz2gotnb ldb #$aa ; load nibble
|
|
andb #$0f ; only keep low 4 bits
|
|
rts
|