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; Copyright (c) 2003-2004 Arjan Bakker
;
; Permission is hereby granted, free of charge, to any person obtaining a copy of
; this software and associated documentation files (the "Software"), to deal in
; the Software without restriction, including without limitation the rights to
; use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
; the Software, and to permit persons to whom the Software is furnished to do so,
; subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
; FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
; COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
; IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
; CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
MODULE bitbuster
; File: bitbuster
;
; The bitbuster module gives you depack support for data packed
; using the bitbuster algorithm.
;
; FUNCTION NAMES:
; The functions <depack> and <depack_raw> are MODULE local, which means you
; have to add the prefix "bitbuster." to its name. This is to prevent possible
; name clashes with functions from other libraries you might be using.
; However, if you define <MAKE_BITBUSTER_GLOBAL> then these functions will be
; available without the "bitbuster." prefix as well.
;
; COPYRIGHT & CREDITS:
; This module has been released by Arjan Bakker under the MIT License;
; please see the top of the source file(s) for the full copyright statement.
; DEFINE: MAKE_BITBUSTER_GLOBAL
; Defining this will make all public functions that are normally only
; available with the "bitbuster." prefix to also be available without
; this prefix. See the introduction of <bitbuster> for more information.
; DEFINE: BITBUSTER_OPTIMIZE_SPEED
; Defining this will optimize the bitbuster depacker for speed, at the cost of
; bigger code.
IFDEF BITBUSTER_OPTIMIZE_SPEED
; use macro's for getbit routines when optimizing bitbuster depacker for speed
; (inlined code, no overhead by calls)
; macro to get a bit from the bitstream
; carry if bit is set, nocarry if bit is clear
; must be entered with second registerset switched in!
MACRO GET_BIT_FROM_BITSTREAM
add a,a ; shift out new bit
jp nz,.done ; if remaining value isn't zere, we're done
ld a,(hl) ; get 8 bits from bitstream
inc hl ; increase source data address
rla ; (bit 0 will be set!!!!)
.done:
ENDM
ENDIF ; IFDEF BITBUSTER_OPTIMIZE_SPEED
IFNDEF BITBUSTER_OPTIMIZE_SPEED
; use calls for getbit code when not optimizing for speed
; macro to get a bit from the bitstream
; carry if bit is set, nocarry if bit is clear
; must be entered with second registerset switched in!
MACRO GET_BIT_FROM_BITSTREAM
call get_bit_from_bitstream
ENDM
ENDIF ; IFNDEF BITBUSTER_OPTIMIZE_SPEED
; FUNCTION: depack
; Depack a blob of data that was packed with Bitbuster.
;
; ENTRY:
; HL - Address of packed data
; DE - Address to depack to
;
; EXIT:
; HL - Size of depacked data
; A - Number of blocks left to decompress
; FZ - Last block has been decompressed
; FNZ- Last block hasn't been decompressed
;
; MODIFIES:
; #AF, BC, BC', DE, DE', HL, HL'#
;
depack: ;EXPORT bitbuster.depack
;IFDEF MAKE_BITBUSTER_GLOBAL
@depack: ;EXPORT depack
;ENDIF
ld a,(block_count)
or a
jr nz,depack_continue ; continue depacking a block if more blocks left
ld a,(hl)
ld (block_count),a ; store block count
inc hl ; move to size of first block
ld (block_start),hl ; store starting address of block
depack_continue:
ld hl,(block_start) ; load starting address of block
inc hl
inc hl ; move over block size
push de
call depack_raw
ld (block_start),hl ; store starting address of next chunk
pop hl
ex de,hl
OR A,A
SBC HL,DE
ld a,(block_count)
dec a
ld (block_count),a ; decrease number of blocks to decompress
ret
; FUNCTION: depack_raw
; Depack data that was packed with Bitbuster.
; Decompresses the RAW data, i.e. the data that is storead after the block
; count and block size!
;
; ENTRY:
; HL - Address of packed data
; DE - Address to depack to
;
; EXIT:
; HL - Address of first byte after compressed data
; DE - Address of first byte after decompressed data
;
; MODIFIES:
; #AF, BC, BC', DE, DE', HL, HL'#
;
depack_raw: ;EXPORT bitbuster.depack_raw
;IFDEF MAKE_BITBUSTER_GLOBAL
@depack_raw: ;EXPORT depack_raw
;ENDIF
ld a,128
depack_loop: GET_BIT_FROM_BITSTREAM ; get compression type bit
jp c,output_compressed ; if set, we got lz77 compression
ldi ; copy byte from compressed data to destination (literal byte)
IFDEF BITBUSTER_OPTIMIZE_SPEED
GET_BIT_FROM_BITSTREAM ; get compression type bit
jp c,output_compressed ; if set, we got lz77 compression
ldi ; copy byte from compressed data to destination (literal byte)
GET_BIT_FROM_BITSTREAM ; get compression type bit
jp c,output_compressed ; if set, we got lz77 compression
ldi ; copy byte from compressed data to destination (literal byte)
ENDIF
jp depack_loop
;handle compressed data
output_compressed:
; calculate length value
ld bc,1
get_gamma_value:
GET_BIT_FROM_BITSTREAM ; get more bits
jr nc,get_gamma_value_end
GET_BIT_FROM_BITSTREAM ; get next bit of value from bitstream
rl c
rl b
jp nc,get_gamma_value ; repeat unless overflow occurred (=end of block marker)
ret
get_gamma_value_end:
inc bc ; length was stored as length-2 so correct this
ld (source_length),bc
ld c,(hl) ; get lowest 7 bits of offset, plus offset extension bit
inc hl ; to next byte in compressed data
ld b,0
bit 7,c
jr z,output_match1 ; no need to get extra bits if carry not set
GET_BIT_FROM_BITSTREAM ; get offset bit 10
rl b
GET_BIT_FROM_BITSTREAM ; get offset bit 9
rl b
GET_BIT_FROM_BITSTREAM ; get offset bit 8
rl b
GET_BIT_FROM_BITSTREAM ; get offset bit 7
jp c,output_match2 ; since extension mark already makes bit 7 set
res 7,c ; only clear it if the bit should be cleared
output_match1: scf
output_match2: push hl ; address compressed data on stack
ld h,d
ld l,e ; destination address in HL...
sbc hl,bc ; calculate source address
ld bc,(source_length)
ldir ; transfer data
pop hl ; address compressed data back from stack
IFDEF BITBUSTER_OPTIMIZE_SPEED
GET_BIT_FROM_BITSTREAM ; get compression type bit
jp c,output_compressed ; if set, we got lz77 compression
ldi ; copy byte from compressed data to destination (literal byte)
GET_BIT_FROM_BITSTREAM ; get compression type bit
jp c,output_compressed ; if set, we got lz77 compression
ldi ; copy byte from compressed data to destination (literal byte)
ENDIF
jp depack_loop
IFNDEF BITBUSTER_OPTIMIZE_SPEED
; get a bit from the bitstream
; carry if bit is set, nocarry if bit is clear
; must be entered with regular registerset switched in!
get_bit_from_bitstream:
add a,a ; shift out new bit
ret nz ; if remaining value isn't zere, we're done
ld a,(hl) ; get 8 bits from bitstream
inc hl ; increase source data address
rla ;(bit 0 will be set!!!!)
ret
ENDIF ; IFNDEF BITBUSTER_OPTIMIZE_SPEED
source_length: dw 0 ; length of source string
block_count: db 0 ; number of blocks to decompress
block_start: dw 0 ; starting address of next block
ENDMODULE