snes9xgx/source/snes9x/sdd1emu.cpp

/**********************************************************************************
  Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.

  (c) Copyright 1996 - 2002  Gary Henderson (gary.henderson@ntlworld.com) and
                             Jerremy Koot (jkoot@snes9x.com)

  (c) Copyright 2002 - 2004  Matthew Kendora

  (c) Copyright 2002 - 2005  Peter Bortas (peter@bortas.org)

  (c) Copyright 2004 - 2005  Joel Yliluoma (http://iki.fi/bisqwit/)

  (c) Copyright 2001 - 2006  John Weidman (jweidman@slip.net)

  (c) Copyright 2002 - 2006  Brad Jorsch (anomie@users.sourceforge.net),
                             funkyass (funkyass@spam.shaw.ca),
                             Kris Bleakley (codeviolation@hotmail.com),
                             Nach (n-a-c-h@users.sourceforge.net), and
                             zones (kasumitokoduck@yahoo.com)

  BS-X C emulator code
  (c) Copyright 2005 - 2006  Dreamer Nom,
                             zones

  C4 x86 assembler and some C emulation code
  (c) Copyright 2000 - 2003  _Demo_ (_demo_@zsnes.com),
                             Nach,
                             zsKnight (zsknight@zsnes.com)

  C4 C++ code
  (c) Copyright 2003 - 2006  Brad Jorsch,
                             Nach

  DSP-1 emulator code
  (c) Copyright 1998 - 2006  _Demo_,
                             Andreas Naive (andreasnaive@gmail.com)
                             Gary Henderson,
                             Ivar (ivar@snes9x.com),
                             John Weidman,
                             Kris Bleakley,
                             Matthew Kendora,
                             Nach,
                             neviksti (neviksti@hotmail.com)

  DSP-2 emulator code
  (c) Copyright 2003         John Weidman,
                             Kris Bleakley,
                             Lord Nightmare (lord_nightmare@users.sourceforge.net),
                             Matthew Kendora,
                             neviksti


  DSP-3 emulator code
  (c) Copyright 2003 - 2006  John Weidman,
                             Kris Bleakley,
                             Lancer,
                             z80 gaiden

  DSP-4 emulator code
  (c) Copyright 2004 - 2006  Dreamer Nom,
                             John Weidman,
                             Kris Bleakley,
                             Nach,
                             z80 gaiden

  OBC1 emulator code
  (c) Copyright 2001 - 2004  zsKnight,
                             pagefault (pagefault@zsnes.com),
                             Kris Bleakley,
                             Ported from x86 assembler to C by sanmaiwashi

  SPC7110 and RTC C++ emulator code
  (c) Copyright 2002         Matthew Kendora with research by
                             zsKnight,
                             John Weidman,
                             Dark Force

  S-DD1 C emulator code
  (c) Copyright 2003         Brad Jorsch with research by
                             Andreas Naive,
                             John Weidman

  S-RTC C emulator code
  (c) Copyright 2001-2006    byuu,
                             John Weidman

  ST010 C++ emulator code
  (c) Copyright 2003         Feather,
                             John Weidman,
                             Kris Bleakley,
                             Matthew Kendora

  Super FX x86 assembler emulator code
  (c) Copyright 1998 - 2003  _Demo_,
                             pagefault,
                             zsKnight,

  Super FX C emulator code
  (c) Copyright 1997 - 1999  Ivar,
                             Gary Henderson,
                             John Weidman

  Sound DSP emulator code is derived from SNEeSe and OpenSPC:
  (c) Copyright 1998 - 2003  Brad Martin
  (c) Copyright 1998 - 2006  Charles Bilyue'

  SH assembler code partly based on x86 assembler code
  (c) Copyright 2002 - 2004  Marcus Comstedt (marcus@mc.pp.se)

  2xSaI filter
  (c) Copyright 1999 - 2001  Derek Liauw Kie Fa

  HQ2x filter
  (c) Copyright 2003         Maxim Stepin (maxim@hiend3d.com)

  Specific ports contains the works of other authors. See headers in
  individual files.

  Snes9x homepage: http://www.snes9x.com

  Permission to use, copy, modify and/or distribute Snes9x in both binary
  and source form, for non-commercial purposes, is hereby granted without 
  fee, providing that this license information and copyright notice appear 
  with all copies and any derived work.

  This software is provided 'as-is', without any express or implied
  warranty. In no event shall the authors be held liable for any damages
  arising from the use of this software or it's derivatives.

  Snes9x is freeware for PERSONAL USE only. Commercial users should
  seek permission of the copyright holders first. Commercial use includes,
  but is not limited to, charging money for Snes9x or software derived from
  Snes9x, including Snes9x or derivatives in commercial game bundles, and/or
  using Snes9x as a promotion for your commercial product.

  The copyright holders request that bug fixes and improvements to the code
  should be forwarded to them so everyone can benefit from the modifications
  in future versions.

  Super NES and Super Nintendo Entertainment System are trademarks of
  Nintendo Co., Limited and its subsidiary companies.
**********************************************************************************/

/* S-DD1 decompressor
 *
 * Based on code and documentation by Andreas Naive, who deserves a great deal
 * of thanks and credit for figuring this out.
 *
 * Andreas says:
 * The author is greatly indebted with The Dumper, without whose help and 
 * patience providing him with real S-DD1 data the research had never been 
 * possible. He also wish to note that in the very beggining of his research,
 * Neviksti had done some steps in the right direction. By last, the author is
 * indirectly indebted to all the people that worked and contributed in the
 * S-DD1 issue in the past.
 */

#include <string.h>
#include "port.h"
#include "sdd1emu.h"

static int valid_bits;
static uint16 in_stream;
static uint8 *in_buf;
static uint8 bit_ctr[8];
static uint8 context_states[32];
static int context_MPS[32];
static int bitplane_type;
static int high_context_bits;
static int low_context_bits;
static int prev_bits[8];

static struct {
    uint8 code_size;
    uint8 MPS_next;
    uint8 LPS_next;
} evolution_table[] = {
    /*  0 */ { 0,25,25},
    /*  1 */ { 0, 2, 1},
    /*  2 */ { 0, 3, 1},
    /*  3 */ { 0, 4, 2},
    /*  4 */ { 0, 5, 3},
    /*  5 */ { 1, 6, 4},
    /*  6 */ { 1, 7, 5},
    /*  7 */ { 1, 8, 6},
    /*  8 */ { 1, 9, 7},
    /*  9 */ { 2,10, 8},
    /* 10 */ { 2,11, 9},
    /* 11 */ { 2,12,10},
    /* 12 */ { 2,13,11},
    /* 13 */ { 3,14,12},
    /* 14 */ { 3,15,13},
    /* 15 */ { 3,16,14},
    /* 16 */ { 3,17,15},
    /* 17 */ { 4,18,16},
    /* 18 */ { 4,19,17},
    /* 19 */ { 5,20,18},
    /* 20 */ { 5,21,19},
    /* 21 */ { 6,22,20},
    /* 22 */ { 6,23,21},
    /* 23 */ { 7,24,22},
    /* 24 */ { 7,24,23},
    /* 25 */ { 0,26, 1},
    /* 26 */ { 1,27, 2},
    /* 27 */ { 2,28, 4},
    /* 28 */ { 3,29, 8},
    /* 29 */ { 4,30,12},
    /* 30 */ { 5,31,16},
    /* 31 */ { 6,32,18},
    /* 32 */ { 7,24,22}
};

static uint8 run_table[128] = {
    128,  64,  96,  32, 112,  48,  80,  16, 120,  56,  88,  24, 104,  40,  72,
      8, 124,  60,  92,  28, 108,  44,  76,  12, 116,  52,  84,  20, 100,  36,
     68,   4, 126,  62,  94,  30, 110,  46,  78,  14, 118,  54,  86,  22, 102,
     38,  70,   6, 122,  58,  90,  26, 106,  42,  74,  10, 114,  50,  82,  18,
     98,  34,  66,   2, 127,  63,  95,  31, 111,  47,  79,  15, 119,  55,  87,
     23, 103,  39,  71,   7, 123,  59,  91,  27, 107,  43,  75,  11, 115,  51,
     83,  19,  99,  35,  67,   3, 125,  61,  93,  29, 109,  45,  77,  13, 117,
     53,  85,  21, 101,  37,  69,   5, 121,  57,  89,  25, 105,  41,  73,   9,
    113,  49,  81,  17,  97,  33,  65,   1
};

static inline uint8 GetCodeword(int bits){
    uint8 tmp;

    if(!valid_bits){
        in_stream|=*(in_buf++);
        valid_bits=8;
    }
    in_stream<<=1;
    valid_bits--;
    in_stream^=0x8000;
    if(in_stream&0x8000) return 0x80+(1<<bits);
    tmp=(in_stream>>8) | (0x7f>>bits);
    in_stream<<=bits;
    valid_bits-=bits;
    if(valid_bits<0){
        in_stream |= (*(in_buf++))<<(-valid_bits);
        valid_bits+=8;
    }
    return run_table[tmp];
}

static inline uint8 GolombGetBit(int code_size){
    if(!bit_ctr[code_size]) bit_ctr[code_size]=GetCodeword(code_size);
    bit_ctr[code_size]--;
    if(bit_ctr[code_size]==0x80){
        bit_ctr[code_size]=0;
        return 2; /* secret code for 'last zero'. ones are always last. */
    }
    return (bit_ctr[code_size]==0)?1:0;
}

static inline uint8 ProbGetBit(uint8 context){
    uint8 state=context_states[context];
    uint8 bit=GolombGetBit(evolution_table[state].code_size);

    if(bit&1){
        context_states[context]=evolution_table[state].LPS_next;
        if(state<2){
            context_MPS[context]^=1;
            return context_MPS[context]; /* just inverted, so just return it */
        } else{
            return context_MPS[context]^1; /* we know bit is 1, so use a constant */
        }
    } else if(bit){
        context_states[context]=evolution_table[state].MPS_next;
        /* zero here, zero there, no difference so drop through. */
    }
    return context_MPS[context]; /* we know bit is 0, so don't bother xoring */
}

static inline uint8 GetBit(uint8 cur_bitplane){
    uint8 bit;
    
    bit=ProbGetBit(((cur_bitplane&1)<<4)
                   | ((prev_bits[cur_bitplane]&high_context_bits)>>5)
                   | (prev_bits[cur_bitplane]&low_context_bits));

    prev_bits[cur_bitplane] <<= 1;
    prev_bits[cur_bitplane] |= bit;
    return bit;
}

void SDD1_decompress(uint8 *out, uint8 *in, int len){
    uint8 bit, i, plane;
    uint8 byte1, byte2;

    if(len==0) len=0x10000;
    
    bitplane_type=in[0]>>6;

    switch(in[0]&0x30){
      case 0x00:
        high_context_bits=0x01c0;
        low_context_bits =0x0001;
        break;
      case 0x10:
        high_context_bits=0x0180;
        low_context_bits =0x0001;
        break;
      case 0x20:
        high_context_bits=0x00c0;
        low_context_bits =0x0001;
        break;
      case 0x30:
        high_context_bits=0x0180;
        low_context_bits =0x0003;
        break;
    }

    in_stream=(in[0]<<11) | (in[1]<<3);
    valid_bits=5;
    in_buf=in+2;
    memset(bit_ctr, 0, sizeof(bit_ctr));
    memset(context_states, 0, sizeof(context_states));
    memset(context_MPS, 0, sizeof(context_MPS));
    memset(prev_bits, 0, sizeof(prev_bits));

    switch(bitplane_type){
      case 0:
        while(1) {
            for(byte1=byte2=0, bit=0x80; bit; bit>>=1){
                if(GetBit(0)) byte1 |= bit;
                if(GetBit(1)) byte2 |= bit;
            }
            *(out++)=byte1;
            if(!--len) return;
            *(out++)=byte2;
            if(!--len) return;
        }
        break;
      case 1:
        i=plane=0;
        while(1) {
            for(byte1=byte2=0, bit=0x80; bit; bit>>=1){
                if(GetBit(plane)) byte1 |= bit;
                if(GetBit(plane+1)) byte2 |= bit;
            }
            *(out++)=byte1;
            if(!--len) return;
            *(out++)=byte2;
            if(!--len) return;
            if(!(i+=32)) plane = (plane+2)&7;
        }
        break;
      case 2:
        i=plane=0;
        while(1) {
            for(byte1=byte2=0, bit=0x80; bit; bit>>=1){
                if(GetBit(plane)) byte1 |= bit;
                if(GetBit(plane+1)) byte2 |= bit;
            }
            *(out++)=byte1;
            if(!--len) return;
            *(out++)=byte2;
            if(!--len) return;
            if(!(i+=32)) plane ^= 2;
        }
        break;
      case 3:
        do {
            for(byte1=plane=0, bit=1; bit; bit<<=1, plane++){
                if(GetBit(plane)) byte1 |= bit;
            }
            *(out++)=byte1;
        } while(--len);
        break;
    }
}

static uint8 cur_plane;
static uint8 num_bits;
static uint8 next_byte;

void SDD1_init(uint8 *in){
    bitplane_type=in[0]>>6;

    switch(in[0]&0x30){
      case 0x00:
        high_context_bits=0x01c0;
        low_context_bits =0x0001;
        break;
      case 0x10:
        high_context_bits=0x0180;
        low_context_bits =0x0001;
        break;
      case 0x20:
        high_context_bits=0x00c0;
        low_context_bits =0x0001;
        break;
      case 0x30:
        high_context_bits=0x0180;
        low_context_bits =0x0003;
        break;
    }

    in_stream=(in[0]<<11) | (in[1]<<3);
    valid_bits=5;
    in_buf=in+2;
    memset(bit_ctr, 0, sizeof(bit_ctr));
    memset(context_states, 0, sizeof(context_states));
    memset(context_MPS, 0, sizeof(context_MPS));
    memset(prev_bits, 0, sizeof(prev_bits));

    cur_plane=0;
    num_bits=0;
}

uint8 SDD1_get_byte(void){
    uint8 bit;
    uint8 byte=0;
    
    switch(bitplane_type){
      case 0:
        num_bits+=16;
        if(num_bits&16){
            next_byte=0;
            for(bit=0x80; bit; bit>>=1){
                if(GetBit(0)) byte |= bit;
                if(GetBit(1)) next_byte |= bit;
            }
            return byte;
        } else {
            return next_byte;
        }

      case 1:
        num_bits+=16;
        if(num_bits&16){
            next_byte=0;
            for(bit=0x80; bit; bit>>=1){
                if(GetBit(cur_plane)) byte |= bit;
                if(GetBit(cur_plane+1)) next_byte |= bit;
            }
            return byte;
        } else {
            if(!num_bits) cur_plane = (cur_plane+2)&7;
            return next_byte;
        }

      case 2:
        num_bits+=16;
        if(num_bits&16){
            next_byte=0;
            for(bit=0x80; bit; bit>>=1){
                if(GetBit(cur_plane)) byte |= bit;
                if(GetBit(cur_plane+1)) next_byte |= bit;
            }
            return byte;
        } else {
            if(!num_bits) cur_plane ^= 2;
            return next_byte;
        }

      case 3:
        for(cur_plane=0, bit=1; bit; bit<<=1, cur_plane++){
            if(GetBit(cur_plane)) byte |= bit;
        }
        return byte;

      default:
        /* should never happen */
        return 0;
    }
}