From 9bcf1e97960c0da7322a868efdbc07e2650716fe Mon Sep 17 00:00:00 2001 From: "Juan J. Martinez" Date: Sat, 9 Jan 2021 09:01:05 +0000 Subject: Extra libs: ap.lib aPLib support with apultra. --- tools/apultra/asm/68000/unaplib_68000.S | 117 ++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100644 tools/apultra/asm/68000/unaplib_68000.S (limited to 'tools/apultra/asm/68000') diff --git a/tools/apultra/asm/68000/unaplib_68000.S b/tools/apultra/asm/68000/unaplib_68000.S new file mode 100644 index 0000000..a60ae32 --- /dev/null +++ b/tools/apultra/asm/68000/unaplib_68000.S @@ -0,0 +1,117 @@ +; unaplib_68000.s - aPLib decompressor for 68000 - 154 bytes +; +; in: a0 = start of compressed data +; a1 = start of decompression buffer +; out: d0 = decompressed size +; +; Copyright (C) 2020 Emmanuel Marty +; With parts of the code inspired by Franck "hitchhikr" Charlet +; +; 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. + +apl_decompress: + movem.l a2-a6/d2-d3,-(sp) + + moveq #-128,d1 ; initialize empty bit queue + ; plus bit to roll into carry + lea 32000.w,a2 ; load 32000 offset constant + lea 1280.w,a3 ; load 1280 offset constant + lea 128.w,a4 ; load 128 offset constant + move.l a1,a5 ; save destination pointer + +.literal: move.b (a0)+,(a1)+ ; copy literal byte +.after_lit: moveq #3,d2 ; set LWM flag + +.next_token: bsr.s .get_bit ; read 'literal or match' bit + bcc.s .literal ; if 0: literal + + bsr.s .get_bit ; read '8+n bits or other type' bit + bcs.s .other_match ; if 11x: other type of match + + bsr.s .get_gamma2 ; 10: read gamma2-coded high offset bits + sub.l d2,d0 ; high offset bits == 2 when LWM == 3 ? + bcc.s .no_repmatch ; if not, not a rep-match + + bsr.s .get_gamma2 ; read repmatch length + bra.s .got_len ; go copy large match + +.no_repmatch: lsl.l #8,d0 ; shift high offset bits into place + move.b (a0)+,d0 ; read low offset byte + move.l d0,d3 ; copy offset into d3 + + bsr.s .get_gamma2 ; read match length + cmp.l a2,d3 ; offset >= 32000 ? + bge.s .inc_by_2 ; if so, increase match len by 2 + cmp.l a3,d3 ; offset >= 1280 ? + bge.s .inc_by_1 ; if so, increase match len by 1 + cmp.l a4,d3 ; offset < 128 ? + bge.s .got_len ; if so, increase match len by 2 +.inc_by_2: addq.l #1,d0 ; increase match len by 1 +.inc_by_1: addq.l #1,d0 ; increase match len by 1 + +.got_len: move.l a1,a6 ; calculate backreference address + sub.l d3,a6 ; (dest - match offset) + subq.l #1,d0 ; dbf will loop until d0 is -1, not 0 +.copy_match: move.b (a6)+,(a1)+ ; copy matched byte + dbf d0,.copy_match ; loop for all matched bytes + moveq #2,d2 ; clear LWM flag + bra.s .next_token ; go decode next token + +.other_match: bsr.s .get_bit ; read '7+1 match or short literal' bit + bcs.s .short_match ; if 111: 4 bit offset for 1-byte copy + + moveq #1,d0 ; 110: prepare match length + moveq #0,d3 ; clear high bits of offset + move.b (a0)+,d3 ; read low bits of offset + length bit + lsr.b #1,d3 ; shift offset into place, len into carry + beq.s .done ; check for EOD + addx.b d0,d0 ; len = (1 << 1) + carry bit, ie. 2 or 3 + bra.s .got_len ; go copy match + +.short_match: moveq #0,d0 ; clear short offset before reading 4 bits + bsr.s .get_dibits ; read a data bit into d0, one into carry + addx.b d0,d0 ; shift second bit into d0 + bsr.s .get_dibits ; read a data bit into d0, one into carry + addx.b d0,d0 ; shift second bit into d0 + beq.s .write_zero ; if offset is zero, write a 0 + + move.l a1,a6 ; calculate backreference address + sub.l d0,a6 ; (dest - short offset) + move.b (a6),d0 ; read matched byte +.write_zero: move.b d0,(a1)+ ; write matched byte or 0 + bra.s .after_lit ; set LWM flag and go decode next token + +.done: move.l a1,d0 ; pointer to last decompressed byte + 1 + sub.l a6,d0 ; minus start of decompression buffer = size + movem.l (sp)+,a2-a6/d2-d3 + rts + +.get_gamma2: moveq #1,d0 ; init to 1 so it gets shifted to 2 below +.gamma2_loop: bsr.s .get_dibits ; read data bit, shift into d0 + ; and read continuation bit + bcs.s .gamma2_loop ; loop until a 0 continuation bit is read + rts + +.get_dibits: bsr.s .get_bit ; read bit + addx.l d0,d0 ; shift into d0 + ; fall through +.get_bit: add.b d1,d1 ; shift bit queue, high bit into carry + bne.s .got_bit ; queue not empty, bits remain + move.b (a0)+,d1 ; read 8 new bits + addx.b d1,d1 ; shift bit queue, high bit into carry + ; and shift 1 from carry into bit queue +.got_bit: rts -- cgit v1.2.3