mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-11-25 10:30:45 +00:00
354 lines
11 KiB
NASM
354 lines
11 KiB
NASM
; ***************************************************************************
|
|
; ***************************************************************************
|
|
;
|
|
; lzsa1_6502.s
|
|
;
|
|
; NMOS 6502 decompressor for data stored in Emmanuel Marty's LZSA1 format.
|
|
;
|
|
; This code is written for the ACME assembler.
|
|
;
|
|
; Optional code is presented for one minor 6502 optimization that breaks
|
|
; compatibility with the current LZSA1 format standard.
|
|
;
|
|
; The code is 168 bytes for the small version, and 205 bytes for the normal.
|
|
;
|
|
; Copyright John Brandwood 2019.
|
|
;
|
|
; Distributed under the Boost Software License, Version 1.0.
|
|
; (See accompanying file LICENSE_1_0.txt or copy at
|
|
; http://www.boost.org/LICENSE_1_0.txt)
|
|
;
|
|
; ***************************************************************************
|
|
; ***************************************************************************
|
|
|
|
|
|
|
|
; ***************************************************************************
|
|
; ***************************************************************************
|
|
;
|
|
; Decompression Options & Macros
|
|
;
|
|
|
|
;
|
|
; Choose size over space (within sane limits)?
|
|
;
|
|
|
|
LZSA_SMALL_SIZE = 0
|
|
|
|
;
|
|
; Remove code inlining to save space?
|
|
;
|
|
; This saves 15 bytes of code at the cost of 7% speed.
|
|
;
|
|
|
|
!if LZSA_SMALL_SIZE {
|
|
LZSA_NO_INLINE = 1
|
|
} else {
|
|
LZSA_NO_INLINE = 0
|
|
}
|
|
|
|
;
|
|
; Use smaller code for copying literals?
|
|
;
|
|
; This saves 11 bytes of code at the cost of 15% speed.
|
|
;
|
|
|
|
!if LZSA_SMALL_SIZE {
|
|
LZSA_SHORT_CP = 1
|
|
} else {
|
|
LZSA_SHORT_CP = 0
|
|
}
|
|
|
|
;
|
|
; Use smaller code for copying literals?
|
|
;
|
|
; This saves 11 bytes of code at the cost of 30% speed.
|
|
;
|
|
|
|
!if LZSA_SMALL_SIZE {
|
|
LZSA_SHORT_LZ = 1
|
|
} else {
|
|
LZSA_SHORT_LZ = 0
|
|
}
|
|
|
|
;
|
|
; Macro to increment the source pointer to the next page.
|
|
;
|
|
; This should call a subroutine to determine if a bank
|
|
; has been crossed, and a new bank should be paged in.
|
|
;
|
|
|
|
!macro LZSA_INC_PAGE {
|
|
inc <lzsa_srcptr + 1
|
|
}
|
|
|
|
;
|
|
; Macro to read a byte from the compressed source data.
|
|
;
|
|
|
|
!if LZSA_NO_INLINE {
|
|
|
|
!macro LZSA_GET_SRC {
|
|
jsr lzsa1_get_byte
|
|
}
|
|
|
|
} else {
|
|
|
|
!macro LZSA_GET_SRC {
|
|
lda (lzsa_srcptr),y
|
|
inc <lzsa_srcptr + 0
|
|
bne .skip
|
|
+LZSA_INC_PAGE
|
|
.skip:
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
; ***************************************************************************
|
|
; ***************************************************************************
|
|
;
|
|
; Data usage is last 8 bytes of zero-page.
|
|
;
|
|
|
|
!if (LZSA_SHORT_CP | LZSA_SHORT_LZ) {
|
|
lzsa_length = $F8 ; 1 byte.
|
|
}
|
|
|
|
lzsa_cmdbuf = $F9 ; 1 byte.
|
|
lzsa_winptr = $FA ; 1 word.
|
|
lzsa_srcptr = $FC ; 1 word.
|
|
lzsa_dstptr = $FE ; 1 word.
|
|
|
|
LZSA_SRC_LO = $FC
|
|
LZSA_SRC_HI = $FD
|
|
LZSA_DST_LO = $FE
|
|
LZSA_DST_HI = $FF
|
|
|
|
|
|
; ***************************************************************************
|
|
; ***************************************************************************
|
|
;
|
|
; lzsa1_unpack - Decompress data stored in Emmanuel Marty's LZSA1 format.
|
|
;
|
|
; Args: lzsa_srcptr = ptr to compessed data
|
|
; Args: lzsa_dstptr = ptr to output buffer
|
|
; Uses: lots!
|
|
;
|
|
|
|
DECOMPRESS_LZSA1_FAST:
|
|
lzsa1_unpack: ldy #0 ; Initialize source index.
|
|
ldx #0 ; Initialize hi-byte of length.
|
|
|
|
;
|
|
; Copy bytes from compressed source data.
|
|
;
|
|
; N.B. X=0 is expected and guaranteed when we get here.
|
|
;
|
|
|
|
.cp_length: +LZSA_GET_SRC
|
|
sta <lzsa_cmdbuf ; Preserve this for later.
|
|
and #$70 ; Extract literal length.
|
|
beq .lz_offset ; Skip directly to match?
|
|
|
|
lsr ; Get 3-bit literal length.
|
|
lsr
|
|
lsr
|
|
lsr
|
|
cmp #$07 ; Extended length?
|
|
bne .got_cp_len
|
|
|
|
jsr .get_length ; CS from CMP, X=0.
|
|
|
|
!if LZSA_SHORT_CP {
|
|
|
|
.got_cp_len: cmp #0 ; Check the lo-byte of length.
|
|
beq .put_cp_len
|
|
|
|
inx ; Increment # of pages to copy.
|
|
|
|
.put_cp_len: stx <lzsa_length
|
|
tax
|
|
|
|
.cp_page: lda (lzsa_srcptr),y
|
|
sta (lzsa_dstptr),y
|
|
inc <lzsa_srcptr + 0
|
|
bne .skip1
|
|
inc <lzsa_srcptr + 1
|
|
.skip1: inc <lzsa_dstptr + 0
|
|
bne .skip2
|
|
inc <lzsa_dstptr + 1
|
|
.skip2: dex
|
|
bne .cp_page
|
|
dec <lzsa_length ; Any full pages left to copy?
|
|
bne .cp_page
|
|
|
|
} else {
|
|
|
|
.got_cp_len: tay ; Check the lo-byte of length.
|
|
beq .cp_page
|
|
|
|
inx ; Increment # of pages to copy.
|
|
|
|
.get_cp_src: clc ; Calc address of partial page.
|
|
adc <lzsa_srcptr + 0
|
|
sta <lzsa_srcptr + 0
|
|
bcs .get_cp_dst
|
|
dec <lzsa_srcptr + 1
|
|
|
|
.get_cp_dst: tya
|
|
clc ; Calc address of partial page.
|
|
adc <lzsa_dstptr + 0
|
|
sta <lzsa_dstptr + 0
|
|
bcs .get_cp_idx
|
|
dec <lzsa_dstptr + 1
|
|
|
|
.get_cp_idx: tya ; Negate the lo-byte of length.
|
|
eor #$FF
|
|
tay
|
|
iny
|
|
|
|
.cp_page: lda (lzsa_srcptr),y
|
|
sta (lzsa_dstptr),y
|
|
iny
|
|
bne .cp_page
|
|
inc <lzsa_srcptr + 1
|
|
inc <lzsa_dstptr + 1
|
|
dex ; Any full pages left to copy?
|
|
bne .cp_page
|
|
|
|
}
|
|
|
|
;
|
|
; Copy bytes from decompressed window.
|
|
;
|
|
; N.B. X=0 is expected and guaranteed when we get here.
|
|
;
|
|
|
|
.lz_offset: +LZSA_GET_SRC
|
|
clc
|
|
adc <lzsa_dstptr + 0
|
|
sta <lzsa_winptr + 0
|
|
|
|
lda #$FF
|
|
bit <lzsa_cmdbuf
|
|
bpl .hi_offset
|
|
+LZSA_GET_SRC
|
|
|
|
.hi_offset: adc <lzsa_dstptr + 1
|
|
sta <lzsa_winptr + 1
|
|
|
|
.lz_length: lda <lzsa_cmdbuf ; X=0 from previous loop.
|
|
and #$0F
|
|
adc #$03 - 1 ; CS from previous ADC.
|
|
cmp #$12 ; Extended length?
|
|
bne .got_lz_len
|
|
|
|
jsr .get_length ; CS from CMP, X=0.
|
|
|
|
!if LZSA_SHORT_LZ {
|
|
|
|
.got_lz_len: cmp #0 ; Check the lo-byte of length.
|
|
beq .put_lz_len
|
|
|
|
inx ; Increment # of pages to copy.
|
|
|
|
.put_lz_len: stx <lzsa_length
|
|
tax
|
|
|
|
.lz_page: lda (lzsa_winptr),y
|
|
sta (lzsa_dstptr),y
|
|
inc <lzsa_winptr + 0
|
|
bne .skip3
|
|
inc <lzsa_winptr + 1
|
|
.skip3: inc <lzsa_dstptr + 0
|
|
bne .skip4
|
|
inc <lzsa_dstptr + 1
|
|
.skip4: dex
|
|
bne .lz_page
|
|
dec <lzsa_length ; Any full pages left to copy?
|
|
bne .lz_page
|
|
|
|
jmp .cp_length ; Loop around to the beginning.
|
|
|
|
} else {
|
|
|
|
.got_lz_len: tay ; Check the lo-byte of length.
|
|
beq .lz_page
|
|
|
|
inx ; Increment # of pages to copy.
|
|
|
|
.get_lz_win: clc ; Calc address of partial page.
|
|
adc <lzsa_winptr + 0
|
|
sta <lzsa_winptr + 0
|
|
bcs .get_lz_dst
|
|
dec <lzsa_winptr + 1
|
|
|
|
.get_lz_dst: tya
|
|
clc ; Calc address of partial page.
|
|
adc <lzsa_dstptr + 0
|
|
sta <lzsa_dstptr + 0
|
|
bcs .get_lz_idx
|
|
dec <lzsa_dstptr + 1
|
|
|
|
.get_lz_idx: tya ; Negate the lo-byte of length.
|
|
eor #$FF
|
|
tay
|
|
iny
|
|
|
|
.lz_page: lda (lzsa_winptr),y
|
|
sta (lzsa_dstptr),y
|
|
iny
|
|
bne .lz_page
|
|
inc <lzsa_winptr + 1
|
|
inc <lzsa_dstptr + 1
|
|
dex ; Any full pages left to copy?
|
|
bne .lz_page
|
|
|
|
jmp .cp_length ; Loop around to the beginning.
|
|
|
|
}
|
|
|
|
;
|
|
; Get 16-bit length in X:A register pair.
|
|
;
|
|
; N.B. X=0 is expected and guaranteed when we get here.
|
|
;
|
|
|
|
.get_length: clc ; Add on the next byte to get
|
|
adc (lzsa_srcptr),y ; the length.
|
|
inc <lzsa_srcptr + 0
|
|
bne .skip_inc
|
|
+LZSA_INC_PAGE
|
|
|
|
.skip_inc: bcc .got_length ; No overflow means done.
|
|
cmp #$00 ; Overflow to 256 or 257?
|
|
beq .extra_word
|
|
|
|
.extra_byte: inx
|
|
jmp lzsa1_get_byte ; So rare, this can be slow!
|
|
|
|
.extra_word: jsr lzsa1_get_byte ; So rare, this can be slow!
|
|
pha
|
|
jsr lzsa1_get_byte ; So rare, this can be slow!
|
|
tax
|
|
beq .finished ; Length-hi == 0 at EOF.
|
|
pla ; Length-lo.
|
|
rts
|
|
|
|
lzsa1_get_byte:
|
|
lda (lzsa_srcptr),y ; Subroutine version for when
|
|
inc <lzsa_srcptr + 0 ; inlining isn't advantageous.
|
|
beq lzsa1_next_page
|
|
.got_length: rts
|
|
|
|
lzsa1_next_page:
|
|
inc <lzsa_srcptr + 1 ; Inc & test for bank overflow.
|
|
rts
|
|
|
|
.finished: pla ; Length-lo.
|
|
pla ; Decompression completed, pop
|
|
pla ; return address.
|
|
rts
|