; ; Copyright (c) 2002, 2003 Magnus Lind. ; ; 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 distribution. ; ; 4. The names of this software and/or it's copyright holders may not be ; used to endorse or promote products derived from this software without ; specific prior written permission. ; ; ------------------------------------------------------------------- ; this file is intended to be assembled and linked with the cc65 toolchain. ; It has not been tested with any other assemblers or linkers. ; ------------------------------------------------------------------- ; ------------------------------------------------------------------- ; the circular buffer needs to be page aligned, so only the high-bytes ; of the buffer start and len is imported to enforce this. ; the data that are to be decrunched must not have been crunched with ; a maximum offset size greater than the buffer size. use the -m option ; with a value of (buffer_len_hi * 256) or less. ; ------------------------------------------------------------------- .import buffer_start_hi: absolute .import buffer_len_hi: absolute .import decrunched_chunk_size: absolute ; ------------------------------------------------------------------- ; The decruncher jsr:s to the get_crunched_byte address when it wants to ; read a crunched byte. This subroutine has to preserve x and y register ; and must not modify the state of the carry flag. ; ------------------------------------------------------------------- .import get_crunched_byte ; ------------------------------------------------------------------- ; this subsoutine is called before decrunching. It initializes the ; decruncher zeropage locations and precalculates the decrunch tables. ; ------------------------------------------------------------------- .export init_decruncher ; ------------------------------------------------------------------- ; this function is the heart of the decruncher. Call this whenever you ; want a chunk of decrunched data. the zero page pointer $fe will point to it. ; Calling this function will also destroy the values in y and x reg and mess up ; the status flags. This function will not change the interrupt status bit and ; it will not modify the memory configuration. ; ------------------------------------------------------------------- .export get_decrunched_chunk ; ------------------------------------------------------------------- ; zero page addresses used ; ------------------------------------------------------------------- zp_src_lo = $a7 zp_src_hi = zp_src_lo + 1 zp_len_lo = $ae zp_len_hi = zp_len_lo + 1 zp_bits_lo = $fb zp_bits_hi = zp_bits_lo + 1 zp_bitbuf = $fd zp_dest_lo = $fe ; dest addr lo zp_dest_hi = zp_dest_lo + 1 ; dest addr hi ; ------------------------------------------------------------------- ; symbolic names for constants ; ------------------------------------------------------------------- buffer_end_hi = buffer_start_hi + buffer_len_hi tabl_bi = decrunch_table tabl_lo = decrunch_table + 52 tabl_hi = decrunch_table + 104 ; ------------------------------------------------------------------- ; no code below this comment has to be modified in order to generate ; a working decruncher of this source file. ; However, you may want to relocate the tables last in the file to a ; more suitable address. ; ------------------------------------------------------------------- ; ------------------------------------------------------------------- ; this 156 byte table area may be relocated. It may also be clobbered ; by other data between decrunches. ; ------------------------------------------------------------------- decrunch_table: .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0,0,0,0,0 ; ------------------------------------------------------------------- ; end of decruncher ; ------------------------------------------------------------------- ; ------------------------------------------------------------------- ; jsr this label to init the decruncher, it will init used zeropage ; zero page locations and the decrunch tables ; no constraints on register content, however the ; decimal flag has to be #0 (it almost always is, otherwise do a cld) ; ------------------------------------------------------------------- init_decruncher: jsr get_crunched_byte sta zp_bitbuf ldx #