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u6m.cpp

/*
 * Adplug - Replayer for many OPL2/OPL3 audio file formats.
 * Copyright (C) 1999 - 2003 Simon Peter, <dn.tlp@gmx.net>, et al.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * u6m.cpp - Ultima 6 Music Player by Marc Winterrowd.
 * This code extends the Adlib Winamp plug-in by Simon Peter <dn.tlp@gmx.net>
 */

#include "u6m.h"

CPlayer *Cu6mPlayer::factory(Copl *newopl)
{
  return new Cu6mPlayer(newopl);
}

bool Cu6mPlayer::load(const std::string &filename, const CFileProvider &fp)
{
    // file validation section
    // this section only checks a few *necessary* conditions
    unsigned long filesize, decompressed_filesize;
    binistream *f;

    f = fp.open(filename); if(!f) return false;
    filesize = fp.filesize(f);

    if (filesize >= 6)
    {
        // check if the file has a valid pseudo-header
        unsigned char pseudo_header[6];
        f->readString((char *)pseudo_header, 6);
        decompressed_filesize = pseudo_header[0] + (pseudo_header[1] << 8);

        if (!( (pseudo_header[2]==0) && (pseudo_header[3]==0) &&
               (pseudo_header[4] + ((pseudo_header[5] & 0x1)<<8) == 0x100) &&
               (decompressed_filesize > (filesize-4)) ))
        {
          fp.close(f);
            return(false);
        }
    }
    else
    {
        fp.close(f);
        return(false);
    }

    // load section
    song_data = new unsigned char[decompressed_filesize];
    unsigned char* compressed_song_data = new unsigned char[filesize-4];

    f->seek(4);
    f->readString((char *)compressed_song_data, filesize - 4);
    fp.close(f);

    // attempt to decompress the song data
    // if unsuccessful, deallocate song_data[] on the spot, and return(false)
    data_block source, destination;
    source.size = filesize-4;
    source.data = compressed_song_data;
    destination.size = decompressed_filesize;
    destination.data = song_data;
      
    if (!lzw_decompress(source,destination))
    {
        delete[] compressed_song_data;
        delete[] song_data;
        return(false);
    }

    // deallocation section
    delete[] compressed_song_data;

    rewind(0);
    return (true);
}


bool Cu6mPlayer::update()
{
    if (!driver_active)
    {
        driver_active = true;
        dec_clip(read_delay);
        if (read_delay == 0)
        {
            command_loop();
        }

        // on all Adlib channels: freq slide/vibrato, mute factor slide
        for (int i = 0; i < 9; i++)
        {
            if (channel_freq_signed_delta[i]!=0)
            // frequency slide + mute factor slide
            {
                // freq slide
                freq_slide(i);

                // mute factor slide
                if (carrier_mf_signed_delta[i]!=0)
                {
                    mf_slide(i);
                }
            }
            else
            // vibrato + mute factor slide
            {
                // vibrato
                if ((vb_multiplier[i]!=0) && ((channel_freq[i].hi & 0x20)==0x20))
                {
                    vibrato(i);
                }

                // mute factor slide
                if (carrier_mf_signed_delta[i]!=0)
                {
                    mf_slide(i);
                }
            }
        }

        driver_active = false;
    }

    return !songend;
}


void Cu6mPlayer::rewind(int subsong)
{
      played_ticks = 0;
      songend = false;

    // set the driver's internal variables
    byte_pair freq_word = {0,0};

    driver_active = false;
    song_pos = 0;
    loop_position = 0;   // position of the loop point
    read_delay = 0;      // delay (in timer ticks) before further song data is read
 
    for (int i = 0; i < 9; i++)
    {
        // frequency
        channel_freq_signed_delta[i] = 0;
        channel_freq[i] = freq_word;  // Adlib freq settings for each channel

        // vibrato ("vb")
        vb_current_value[i] = 0;
        vb_double_amplitude[i] = 0;
        vb_multiplier[i] = 0;
        vb_direction_flag[i] = 0;

        // mute factor ("mf") == ~(volume)
        carrier_mf[i] = 0;
        carrier_mf_signed_delta[i] = 0;
        carrier_mf_mod_delay_backup[i] = 0;
        carrier_mf_mod_delay[i] = 0;
    }

      while (!subsong_stack.empty())            // empty subsong stack
            subsong_stack.pop();

    opl->init();
      out_adlib(1,32);  // go to OPL2 mode
}


float Cu6mPlayer::getrefresh()
{
    return ((float)60);   // the Ultima 6 music driver expects to be called at 60 Hz
}


// ============================================================================================
//
//
//    Functions called by load()
//
//
// ============================================================================================


// decompress from memory to memory
bool Cu6mPlayer::lzw_decompress(Cu6mPlayer::data_block source, Cu6mPlayer::data_block dest)
{
    bool end_marker_reached = false;
    int codeword_size = 9;
    long bits_read = 0;
    int next_free_codeword = 0x102;
    int dictionary_size = 0x200;
    MyDict dictionary = MyDict();
      std::stack<unsigned char> root_stack;

    long bytes_written = 0;

    int cW;
    int pW;
    unsigned char C;

    while (!end_marker_reached)
    {
        cW = get_next_codeword(bits_read, source.data, codeword_size);
        switch (cW)
        {
            // re-init the dictionary
            case 0x100:
                codeword_size = 9;
                next_free_codeword = 0x102;
                dictionary_size = 0x200;
                dictionary.reset();
                cW = get_next_codeword(bits_read, source.data, codeword_size);
                output_root((unsigned char)cW, dest.data, bytes_written);
                break;
            // end of compressed file has been reached
            case 0x101:
                end_marker_reached = true;
                break;
            // (cW <> 0x100) && (cW <> 0x101)
            default:
                if (cW < next_free_codeword)  // codeword is already in the dictionary
                {
                    // create the string associated with cW (on the stack)
                    get_string(cW,dictionary,root_stack);
                    C = root_stack.top();
                    // output the string represented by cW
                    while (!root_stack.empty())
                    {
                        output_root(root_stack.top(), dest.data, bytes_written);
                        root_stack.pop();
                    }
                    // add pW+C to the dictionary
                    dictionary.add(C,pW);

                    next_free_codeword++;
                    if (next_free_codeword >= dictionary_size)
                    {
                        if (codeword_size < max_codeword_length)
                        {
                            codeword_size += 1;
                            dictionary_size *= 2;
                        }
                    }
                }
                else  // codeword is not yet defined
                {
                    // create the string associated with pW (on the stack)
                    get_string(pW,dictionary,root_stack);
                    C = root_stack.top();
                    // output the string represented by pW
                    while (!root_stack.empty())
                    {
                        output_root(root_stack.top(), dest.data, bytes_written);
                        root_stack.pop();
                    }
                    // output the char C
                    output_root(C, dest.data, bytes_written);

                    // the new dictionary entry must correspond to cW
                    // if it doesn't, something is wrong with the lzw-compressed data.
                    if (cW != next_free_codeword)
                    {
/*                        printf("cW != next_free_codeword!\n");
                        exit(-1); */
                                    return false;
                    }
                    // add pW+C to the dictionary
                    dictionary.add(C,pW);
 
                    next_free_codeword++;
                    if (next_free_codeword >= dictionary_size)
                    {
                        if (codeword_size < max_codeword_length)
                        {
                            codeword_size += 1;
                            dictionary_size *= 2;
                        }
                    }
                };
                break;
        }
        // shift roles - the current cW becomes the new pW
        pW = cW;
    }

      return(true);   // indicate successful decompression
}


// --------------------
// Additional functions
// --------------------


// Read the next code word from the source buffer
int Cu6mPlayer::get_next_codeword (long& bits_read, unsigned char *source, int codeword_size)
{
    unsigned char b0,b1,b2;
    int codeword;
 
    b0 = source[bits_read/8];
    b1 = source[bits_read/8+1];
    b2 = source[bits_read/8+2];

    codeword = ((b2 << 16) + (b1 << 8) + b0);
    codeword = codeword >> (bits_read % 8);
    switch (codeword_size)
    {
        case 0x9:
           codeword = codeword & 0x1ff;
            break;
        case 0xa:
            codeword = codeword & 0x3ff;
            break;
        case 0xb:
            codeword = codeword & 0x7ff;
            break;
        case 0xc:
            codeword = codeword & 0xfff;
            break;
        default:
            codeword = -1;   // indicates that an error has occurred
            break;
    }

    bits_read += codeword_size;
    return (codeword);
}


// output a root to memory
void Cu6mPlayer::output_root(unsigned char root, unsigned char *destination, long& position)
{
    destination[position] = root;
    position++;
}


// output the string represented by a codeword
void Cu6mPlayer::get_string(int codeword, Cu6mPlayer::MyDict& dictionary, std::stack<unsigned char>& root_stack)
{
   unsigned char root;
   int current_codeword;

   current_codeword = codeword;

   while (current_codeword > 0xff)
   {
      root = dictionary.get_root(current_codeword);
      current_codeword = dictionary.get_codeword(current_codeword);
      root_stack.push(root);
   }

   // push the root at the leaf
   root_stack.push((unsigned char)current_codeword);
}


// ============================================================================================
//
//
//    Functions called by update()
//
//
// ============================================================================================


// This function reads the song data and executes the embedded commands.
void Cu6mPlayer::command_loop()
{
    unsigned char command_byte;   // current command byte
    int command_nibble_hi;        // command byte, bits 4-7
    int command_nibble_lo;        // command byte, bite 0-3
    bool repeat_loop = true;      //

    do
    {
        // extract low and high command nibbles
        command_byte = read_song_byte();   // implicitly increments song_pos
        command_nibble_hi = command_byte >> 4;
        command_nibble_lo = command_byte & 0xf;
 
        switch (command_nibble_hi)
        {
            case 0x0: command_0(command_nibble_lo); break;
            case 0x1: command_1(command_nibble_lo); break;
            case 0x2: command_2(command_nibble_lo); break;
            case 0x3: command_3(command_nibble_lo); break;
            case 0x4: command_4(command_nibble_lo); break;
            case 0x5: command_5(command_nibble_lo); break;
            case 0x6: command_6(command_nibble_lo); break;
            case 0x7: command_7(command_nibble_lo); break;
            case 0x8:
                switch (command_nibble_lo)
                {
                    case 1: command_81(); break;
                    case 2: command_82(); repeat_loop = false; break;
                    case 3: command_83(); break;
                    case 5: command_85(); break;
                    case 6: command_86(); break;
                    default: break; // maybe generate an error?
                }
                break;
            case 0xE: command_E(); break;
            case 0xF: command_F(); break;
            default: break; // maybe generate an error?
        }

    } while (repeat_loop);
}


// --------------------------------------------------------
//    The commands supported by the U6 music file format
// --------------------------------------------------------

// ----------------------------------------
// Set octave and frequency, note off
// Format: 0c nn
// c = channel, nn = packed Adlib frequency
// ----------------------------------------
void Cu6mPlayer::command_0(int channel)
{
    unsigned char freq_byte;
    byte_pair freq_word;

    freq_byte = read_song_byte();
    freq_word = expand_freq_byte(freq_byte);
    set_adlib_freq(channel,freq_word);
}


// ---------------------------------------------------
// Set octave and frequency, old note off, new note on
// Format: 1c nn
// c = channel, nn = packed Adlib frequency
// ---------------------------------------------------
void Cu6mPlayer::command_1(int channel)
{
    unsigned char freq_byte;
    byte_pair freq_word;

    vb_direction_flag[channel] = 0;
    vb_current_value[channel] = 0;
 
    freq_byte = read_song_byte();
    freq_word = expand_freq_byte(freq_byte);
    set_adlib_freq(channel,freq_word);

    freq_word.hi = freq_word.hi | 0x20; // note on
    set_adlib_freq(channel,freq_word);
}


// ----------------------------------------
// Set octave and frequency, note on
// Format: 2c nn
// c = channel, nn = packed Adlib frequency
// ----------------------------------------
void Cu6mPlayer::command_2(int channel)
{
    unsigned char freq_byte;
    byte_pair freq_word;
 
    freq_byte = read_song_byte();
    freq_word = expand_freq_byte(freq_byte);
    freq_word.hi = freq_word.hi | 0x20; // note on
    set_adlib_freq(channel,freq_word);
}


// --------------------------------------
// Set "carrier mute factor"==not(volume)
// Format: 3c nn
// c = channel, nn = mute factor
// --------------------------------------
void Cu6mPlayer::command_3(int channel)
{
    unsigned char mf_byte;

    carrier_mf_signed_delta[channel] = 0;
    mf_byte = read_song_byte();
    set_carrier_mf(channel,mf_byte);
}


// ----------------------------------------
// set "modulator mute factor"==not(volume)
// Format: 4c nn
// c = channel, nn = mute factor
// ----------------------------------------
void Cu6mPlayer::command_4(int channel)
{
    unsigned char mf_byte;

    mf_byte = read_song_byte();
    set_modulator_mf(channel,mf_byte);
}


// --------------------------------------------
// Set portamento (pitch slide)
// Format: 5c nn
// c = channel, nn = signed channel pitch delta
// --------------------------------------------
void Cu6mPlayer::command_5(int channel)
{
    channel_freq_signed_delta[channel] = read_signed_song_byte();
}


// --------------------------------------------
// Set vibrato paramters
// Format: 6c mn
// c = channel
// m = vibrato double amplitude
// n = vibrato multiplier
// --------------------------------------------
void Cu6mPlayer::command_6(int channel)
{
    unsigned char vb_parameters;

    vb_parameters = read_song_byte();
    vb_double_amplitude[channel] = vb_parameters >> 4; // high nibble
    vb_multiplier[channel] = vb_parameters & 0xF; // low nibble
}


// ----------------------------------------
// Assign Adlib instrument to Adlib channel
// Format: 7c nn
// c = channel, nn = instrument number
// ----------------------------------------
void Cu6mPlayer::command_7(int channel)
{
    int instrument_offset = instrument_offsets[read_song_byte()];
    out_adlib_opcell(channel, false, 0x20, *(song_data + instrument_offset+0));
    out_adlib_opcell(channel, false, 0x40, *(song_data + instrument_offset+1));
    out_adlib_opcell(channel, false, 0x60, *(song_data + instrument_offset+2));
    out_adlib_opcell(channel, false, 0x80, *(song_data + instrument_offset+3));
    out_adlib_opcell(channel, false, 0xE0, *(song_data + instrument_offset+4));
    out_adlib_opcell(channel, true, 0x20, *(song_data + instrument_offset+5));
    out_adlib_opcell(channel, true, 0x40, *(song_data + instrument_offset+6));
    out_adlib_opcell(channel, true, 0x60, *(song_data + instrument_offset+7));
    out_adlib_opcell(channel, true, 0x80, *(song_data + instrument_offset+8));
    out_adlib_opcell(channel, true, 0xE0, *(song_data + instrument_offset+9));
    out_adlib(0xC0+channel, *(song_data + instrument_offset+10));
}


// -------------------------------------------
// Branch to a new subsong
// Format: 81 nn aa bb
// nn == number of times to repeat the subsong
// aa == subsong offset (low byte)
// bb == subsong offset (high byte)
// -------------------------------------------
void Cu6mPlayer::command_81()
{
    subsong_info new_ss_info;
 
    new_ss_info.subsong_repetitions = read_song_byte();
    new_ss_info.subsong_start = read_song_byte(); new_ss_info.subsong_start += read_song_byte() << 8;
    new_ss_info.continue_pos = song_pos;

    subsong_stack.push(new_ss_info);
    song_pos = new_ss_info.subsong_start;
}


// ------------------------------------------------------------
// Stop interpreting commands for this timer tick
// Format: 82 nn
// nn == delay (in timer ticks) until further data will be read
// ------------------------------------------------------------
void Cu6mPlayer::command_82()
{
    read_delay = read_song_byte();
}


// -----------------------------
// Adlib instrument data follows
// Format: 83 nn <11 bytes>
// nn == instrument number
// -----------------------------
void Cu6mPlayer::command_83()
{
    unsigned char instrument_number = read_song_byte();
    instrument_offsets[instrument_number] = song_pos;
    song_pos += 11;
}


// ----------------------------------------------
// Set -1 mute factor slide (upward volume slide)
// Format: 85 cn
// c == channel
// n == slide delay
// ----------------------------------------------
void Cu6mPlayer::command_85()
{
    unsigned char data_byte = read_song_byte();
    int channel = data_byte >> 4; // high nibble
    unsigned char slide_delay = data_byte & 0xF; // low nibble
    carrier_mf_signed_delta[channel] = +1;
    carrier_mf_mod_delay[channel] = slide_delay + 1;
    carrier_mf_mod_delay_backup[channel] = slide_delay + 1;
}


// ------------------------------------------------
// Set +1 mute factor slide (downward volume slide)
// Format: 86 cn
// c == channel
// n == slide speed
// ------------------------------------------------
void Cu6mPlayer::command_86()
{
    unsigned char data_byte = read_song_byte();
    int channel = data_byte >> 4; // high nibble
    unsigned char slide_delay = data_byte & 0xF; // low nibble
    carrier_mf_signed_delta[channel] = -1;
    carrier_mf_mod_delay[channel] = slide_delay + 1;
    carrier_mf_mod_delay_backup[channel] = slide_delay + 1;
}


// --------------
// Set loop point
// Format: E?
// --------------
void Cu6mPlayer::command_E()
{
    loop_position = song_pos;
}


// ---------------------------
// Return from current subsong
// Format: F?
// ---------------------------
void Cu6mPlayer::command_F()
{
    if (!subsong_stack.empty())
    {
        subsong_info temp = subsong_stack.top();
        subsong_stack.pop();
        temp.subsong_repetitions--;
        if (temp.subsong_repetitions==0)
        {
            song_pos = temp.continue_pos;
        }
        else
        {
            song_pos = temp.subsong_start;
            subsong_stack.push(temp);
        }
    }
    else
    {
        song_pos = loop_position;
            songend = true;
    }
}


// --------------------
// Additional functions
// --------------------

// This function decrements its argument, without allowing it to become negative.
void Cu6mPlayer::dec_clip(int& param)
{
    param--;
    if (param < 0) { param = 0; }
}


// Returns the byte at the current song position.
// Side effect: increments song_pos.
unsigned char Cu6mPlayer::read_song_byte()
{
    unsigned char song_byte;
    song_byte = song_data[song_pos];
    song_pos++;
    return(song_byte);
}


// Same as read_song_byte(), except that it returns a signed byte
signed char Cu6mPlayer::read_signed_song_byte()
{
    unsigned char song_byte;
    int signed_value;
    song_byte = *(song_data + song_pos);
    song_pos++;
    if (song_byte <= 127)
    {
        signed_value = song_byte;
    }
    else
    {
        signed_value = (int)song_byte - 0x100;
    }
    return((signed char)signed_value);
}


Cu6mPlayer::byte_pair Cu6mPlayer::expand_freq_byte(unsigned char freq_byte)
{
    const byte_pair freq_table[24] =
        {
          {0x00,0x00}, {0x58,0x01}, {0x82,0x01}, {0xB0,0x01},
          {0xCC,0x01}, {0x03,0x02}, {0x41,0x02}, {0x86,0x02},
          {0x00,0x00}, {0x6A,0x01}, {0x96,0x01}, {0xC7,0x01},
          {0xE4,0x01}, {0x1E,0x02}, {0x5F,0x02}, {0xA8,0x02},
          {0x00,0x00}, {0x47,0x01}, {0x6E,0x01}, {0x9A,0x01},
          {0xB5,0x01}, {0xE9,0x01}, {0x24,0x02}, {0x66,0x02}
        };

    int packed_freq;
    int octave;
    byte_pair freq_word;

    packed_freq = freq_byte & 0x1F;
    octave = freq_byte >> 5;

    // range check (not present in the original U6 music driver)
    if (packed_freq >= 24) { packed_freq = 0; }

    freq_word.hi = freq_table[packed_freq].hi + (octave << 2);
    freq_word.lo = freq_table[packed_freq].lo;

    return(freq_word);
}


void Cu6mPlayer::set_adlib_freq(int channel,Cu6mPlayer::byte_pair freq_word)
{
    out_adlib(0xA0+channel,freq_word.lo);
    out_adlib(0xB0+channel,freq_word.hi);
    // update the Adlib register backups
    channel_freq[channel] = freq_word;
}


// this function sets the Adlib frequency, but does not update the register backups
void Cu6mPlayer::set_adlib_freq_no_update(int channel,Cu6mPlayer::byte_pair freq_word)
{
    out_adlib(0xA0+channel,freq_word.lo);
    out_adlib(0xB0+channel,freq_word.hi);
}


void Cu6mPlayer::set_carrier_mf(int channel,unsigned char mute_factor)
{
    out_adlib_opcell(channel,true,0x40,mute_factor);
    carrier_mf[channel] = mute_factor;
}


void Cu6mPlayer::set_modulator_mf(int channel,unsigned char mute_factor)
{
    out_adlib_opcell(channel,false,0x40,mute_factor);
}


void Cu6mPlayer::freq_slide(int channel)
{
    byte_pair freq = channel_freq[channel];

    long freq_word = freq.lo + (freq.hi << 8) + channel_freq_signed_delta[channel];
    if (freq_word < 0) { freq_word += 0x10000; }
    if (freq_word > 0xFFFF) { freq_word -= 0x10000; }

    freq.lo = freq_word & 0xFF;
    freq.hi = (freq_word >> 8) & 0xFF;
    set_adlib_freq(channel,freq);
}


void Cu6mPlayer::vibrato(int channel)
{
    byte_pair freq;

    if (vb_current_value[channel] >= vb_double_amplitude[channel])
    { vb_direction_flag[channel] = 1; }
    else if (vb_current_value[channel] <= 0)
    { vb_direction_flag[channel] = 0; }

    if (vb_direction_flag[channel]==0)
    { vb_current_value[channel]++; }
    else
    { vb_current_value[channel]--; }

    long freq_word = channel_freq[channel].lo + (channel_freq[channel].hi << 8);
    freq_word += (vb_current_value[channel] - (vb_double_amplitude[channel] >> 1))
                 * vb_multiplier[channel];
    if (freq_word < 0) { freq_word += 0x10000; }
    if (freq_word > 0xFFFF) { freq_word -= 0x10000; }

    freq.lo = freq_word & 0xFF;
    freq.hi = (freq_word >> 8) & 0xFF;
    set_adlib_freq_no_update(channel,freq);
}


void Cu6mPlayer::mf_slide(int channel)
{
    carrier_mf_mod_delay[channel]--;
    if (carrier_mf_mod_delay[channel]==0)
    {
        carrier_mf_mod_delay[channel] = carrier_mf_mod_delay_backup[channel];
        int current_mf = carrier_mf[channel] + carrier_mf_signed_delta[channel];
        if (current_mf > 0x3F)
        {
            current_mf = 0x3F;
            carrier_mf_signed_delta[channel] = 0;
        }
        else if (current_mf < 0)
            {
                current_mf = 0;
                carrier_mf_signed_delta[channel] = 0;
            }

        set_carrier_mf(channel,(unsigned char)current_mf);
    }
}


void Cu6mPlayer::out_adlib(unsigned char adlib_register, unsigned char adlib_data)
{
    opl->write(adlib_register,adlib_data);
}


void Cu6mPlayer::out_adlib_opcell(int channel, bool carrier, unsigned char adlib_register, unsigned char out_byte)
{
    const unsigned char adlib_channel_to_carrier_offset[9] =
        {0x03,0x04,0x05,0x0B,0x0C,0x0D,0x13,0x14,0x15};
    const unsigned char adlib_channel_to_modulator_offset[9] =
        {0x00,0x01,0x02,0x08,0x09,0x0A,0x10,0x11,0x12};

    if (carrier)
    {
        out_adlib(adlib_register+adlib_channel_to_carrier_offset[channel],out_byte);
    }
    else
    {
        out_adlib(adlib_register+adlib_channel_to_modulator_offset[channel],out_byte);
    }
}


// ============================================================================================
//
//
//    The Dictionary
//
//
// ============================================================================================


Cu6mPlayer::MyDict::MyDict()
{
    dict_size = default_dict_size;
    dictionary = new dict_entry[dict_size-0x100]; // don't allocate space for the roots
    contains = 0x102;
}


Cu6mPlayer::MyDict::MyDict(int max_size)
{
    dict_size = max_size;
    dictionary = new dict_entry[dict_size-0x100]; // don't allocate space for the roots
    contains = 0x102;
}


// re-initializes the dictionary
void Cu6mPlayer::MyDict::reset()
{
    contains = 0x102;
}


// Note: If the dictionary is already full, this function does nothing.
void Cu6mPlayer::MyDict::add(unsigned char root, int codeword)
{
    if (contains < dict_size)
    {
        dictionary[contains-0x100].root = root;
        dictionary[contains-0x100].codeword = codeword;
        contains++;
    }
}


unsigned char Cu6mPlayer::MyDict::get_root(int codeword)
{
    return (dictionary[codeword-0x100].root);
}


int Cu6mPlayer::MyDict::get_codeword(int codeword)
{
    return (dictionary[codeword-0x100].codeword);
}


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