272 lines
7.7 KiB
C
272 lines
7.7 KiB
C
/*
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Copyright (C) 1997-2007 ZSNES Team ( zsKnight, _Demo_, pagefault, Nach )
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http://www.zsnes.com
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http://sourceforge.net/projects/zsnes
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https://zsnes.bountysource.com
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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version 2 as published by the Free Software Foundation.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*******************************************************************************
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S-DD1 C emulator code
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(c) Copyright 2003 Brad Jorsch with research by
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Andreas Naive and John Weidman
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*******************************************************************************/
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/* S-DD1 decompressor
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*
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* Based on code and documentation by Andreas Naive, who deserves a great deal
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* of thanks and credit for figuring this out.
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*
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* Andreas says:
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* The author is greatly indebted with The Dumper, without whose help and
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* patience providing him with real S-DD1 data the research had never been
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* possible. He also wish to note that in the very beggining of his research,
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* Neviksti had done some steps in the right direction. By last, the author is
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* indirectly indebted to all the people that worked and contributed in the
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* S-DD1 issue in the past.
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*/
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#include <string.h>
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#ifndef __GNUC__
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#define INLINE
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#else
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#define INLINE static inline
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#endif
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static int valid_bits;
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static unsigned short in_stream;
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static unsigned char *in_buf;
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static unsigned char bit_ctr[8];
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static unsigned char context_states[32];
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static int context_MPS[32];
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static int bitplane_type;
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static int high_context_bits;
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static int low_context_bits;
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static int prev_bits[8];
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static struct {
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unsigned char code_size;
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unsigned char MPS_next;
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unsigned char LPS_next;
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} evolution_table[] = {
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/* 0 */ { 0,25,25},
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/* 1 */ { 0, 2, 1},
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/* 2 */ { 0, 3, 1},
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/* 3 */ { 0, 4, 2},
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/* 4 */ { 0, 5, 3},
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/* 5 */ { 1, 6, 4},
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/* 6 */ { 1, 7, 5},
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/* 7 */ { 1, 8, 6},
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/* 8 */ { 1, 9, 7},
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/* 9 */ { 2,10, 8},
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/* 10 */ { 2,11, 9},
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/* 11 */ { 2,12,10},
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/* 12 */ { 2,13,11},
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/* 13 */ { 3,14,12},
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/* 14 */ { 3,15,13},
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/* 15 */ { 3,16,14},
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/* 16 */ { 3,17,15},
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/* 17 */ { 4,18,16},
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/* 18 */ { 4,19,17},
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/* 19 */ { 5,20,18},
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/* 20 */ { 5,21,19},
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/* 21 */ { 6,22,20},
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/* 22 */ { 6,23,21},
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/* 23 */ { 7,24,22},
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/* 24 */ { 7,24,23},
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/* 25 */ { 0,26, 1},
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/* 26 */ { 1,27, 2},
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/* 27 */ { 2,28, 4},
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/* 28 */ { 3,29, 8},
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/* 29 */ { 4,30,12},
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/* 30 */ { 5,31,16},
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/* 31 */ { 6,32,18},
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/* 32 */ { 7,24,22}
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};
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static unsigned char run_table[128] = {
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128, 64, 96, 32, 112, 48, 80, 16, 120, 56, 88, 24, 104, 40, 72,
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8, 124, 60, 92, 28, 108, 44, 76, 12, 116, 52, 84, 20, 100, 36,
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68, 4, 126, 62, 94, 30, 110, 46, 78, 14, 118, 54, 86, 22, 102,
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38, 70, 6, 122, 58, 90, 26, 106, 42, 74, 10, 114, 50, 82, 18,
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98, 34, 66, 2, 127, 63, 95, 31, 111, 47, 79, 15, 119, 55, 87,
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23, 103, 39, 71, 7, 123, 59, 91, 27, 107, 43, 75, 11, 115, 51,
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83, 19, 99, 35, 67, 3, 125, 61, 93, 29, 109, 45, 77, 13, 117,
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53, 85, 21, 101, 37, 69, 5, 121, 57, 89, 25, 105, 41, 73, 9,
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113, 49, 81, 17, 97, 33, 65, 1
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};
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INLINE unsigned char GetCodeword(int bits){
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unsigned char tmp;
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if(!valid_bits){
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in_stream|=*(in_buf++);
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valid_bits=8;
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}
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in_stream<<=1;
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valid_bits--;
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in_stream^=0x8000;
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if(in_stream&0x8000) return 0x80+(1<<bits);
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tmp=(in_stream>>8) | (0x7f>>bits);
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in_stream<<=bits;
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valid_bits-=bits;
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if(valid_bits<0){
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in_stream |= (*(in_buf++))<<(-valid_bits);
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valid_bits+=8;
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}
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return run_table[tmp];
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}
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INLINE unsigned char GolombGetBit(int code_size){
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if(!bit_ctr[code_size]) bit_ctr[code_size]=GetCodeword(code_size);
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bit_ctr[code_size]--;
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if(bit_ctr[code_size]==0x80){
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bit_ctr[code_size]=0;
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return 2; /* secret code for 'last zero'. ones are always last. */
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}
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return (bit_ctr[code_size]==0)?1:0;
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}
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INLINE unsigned char ProbGetBit(unsigned char context){
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unsigned char state=context_states[context];
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unsigned char bit=GolombGetBit(evolution_table[state].code_size);
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if(bit&1){
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context_states[context]=evolution_table[state].LPS_next;
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if(state<2){
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context_MPS[context]^=1;
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return context_MPS[context]; /* just inverted, so just return it */
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} else{
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return context_MPS[context]^1; /* we know bit is 1, so use a constant */
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}
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} else if(bit){
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context_states[context]=evolution_table[state].MPS_next;
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/* zero here, zero there, no difference so drop through. */
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}
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return context_MPS[context]; /* we know bit is 0, so don't bother xoring */
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}
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INLINE unsigned char GetBit(unsigned char cur_bitplane){
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unsigned char bit;
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bit=ProbGetBit(((cur_bitplane&1)<<4)
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| ((prev_bits[cur_bitplane]&high_context_bits)>>5)
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| (prev_bits[cur_bitplane]&low_context_bits));
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prev_bits[cur_bitplane] <<= 1;
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prev_bits[cur_bitplane] |= bit;
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return bit;
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}
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static unsigned char cur_plane;
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static unsigned char num_bits;
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static unsigned char next_byte;
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void SDD1_init(unsigned char *in){
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bitplane_type=in[0]>>6;
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switch(in[0]&0x30){
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case 0x00:
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high_context_bits=0x01c0;
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low_context_bits =0x0001;
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break;
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case 0x10:
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high_context_bits=0x0180;
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low_context_bits =0x0001;
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break;
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case 0x20:
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high_context_bits=0x00c0;
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low_context_bits =0x0001;
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break;
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case 0x30:
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high_context_bits=0x0180;
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low_context_bits =0x0003;
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break;
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}
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in_stream=(in[0]<<11) | (in[1]<<3);
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valid_bits=5;
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in_buf=in+2;
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memset(bit_ctr, 0, sizeof(bit_ctr));
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memset(context_states, 0, sizeof(context_states));
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memset(context_MPS, 0, sizeof(context_MPS));
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memset(prev_bits, 0, sizeof(prev_bits));
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cur_plane=0;
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num_bits=0;
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}
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unsigned char SDD1_get_byte(void){
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unsigned char bit;
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unsigned char byte=0;
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switch(bitplane_type){
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case 0:
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num_bits+=16;
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if(num_bits&16){
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next_byte=0;
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for(bit=0x80; bit; bit>>=1){
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if(GetBit(0)) byte |= bit;
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if(GetBit(1)) next_byte |= bit;
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}
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return byte;
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} else {
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return next_byte;
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}
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case 1:
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num_bits+=16;
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if(num_bits&16){
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next_byte=0;
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for(bit=0x80; bit; bit>>=1){
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if(GetBit(cur_plane)) byte |= bit;
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if(GetBit(cur_plane+1)) next_byte |= bit;
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}
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return byte;
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} else {
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if(!num_bits) cur_plane = (cur_plane+2)&7;
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return next_byte;
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}
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case 2:
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num_bits+=16;
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if(num_bits&16){
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next_byte=0;
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for(bit=0x80; bit; bit>>=1){
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if(GetBit(cur_plane)) byte |= bit;
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if(GetBit(cur_plane+1)) next_byte |= bit;
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}
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return byte;
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} else {
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if(!num_bits) cur_plane ^= 2;
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return next_byte;
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}
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case 3:
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for(cur_plane=0, bit=1; bit; bit<<=1, cur_plane++){
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if(GetBit(cur_plane)) byte |= bit;
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}
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return byte;
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default:
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/* should never happen */
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return 0;
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}
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}
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