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midiparser.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program 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 General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL: https://scummvm.svn.sourceforge.net/svnroot/scummvm/scummvm/tags/release-0-11-1/sound/midiparser.h $
 * $Id: midiparser.h 30944 2008-02-23 22:50:18Z sev $
 *
 */

//! \brief Declarations related to the MidiParser class

#ifndef SOUND_MIDIPARSER_H
#define SOUND_MIDIPARSER_H

#include "common/scummsys.h"
#include "common/endian.h"

class MidiParser;
class MidiDriver;



//////////////////////////////////////////////////
//
// Support entities
//
//////////////////////////////////////////////////

//! Maintains time and position state within a MIDI stream.
/*! A single Tracker struct is used by MidiParser to keep track
 *  of its current position in the MIDI stream. The Tracker
 *  struct, however, allows alternative locations to be cached.
 *  See MidiParser::jumpToTick() for an example of tracking
 *  multiple locations within a MIDI stream. NOTE: It is
 *  important to also maintain pre-parsed EventInfo data for
 *  each Tracker location.
 */

00055 struct Tracker {
00056       byte * _play_pos;        //!< A pointer to the next event to be parsed
00057       uint32 _play_time;       //!< Current time in microseconds; may be in between event times
00058       uint32 _play_tick;       //!< Current MIDI tick; may be in between event ticks
00059       uint32 _last_event_time; //!< The time, in microseconds, of the last event that was parsed
00060       uint32 _last_event_tick; //!< The tick at which the last parsed event occurs
00061       byte   _running_status;  //!< Cached MIDI command, for MIDI streams that rely on implied event codes

      Tracker() { clear(); }

      //! Copy constructor for each duplication of Tracker information.
00066       Tracker(const Tracker &copy) :
      _play_pos(copy._play_pos),
      _play_time(copy._play_time),
      _play_tick(copy._play_tick),
      _last_event_time(copy._last_event_time),
      _last_event_tick(copy._last_event_tick),
      _running_status(copy._running_status)
      { }

      //! Clears all data; used by the constructor for initialization.
00076       void clear() {
            _play_pos = 0;
            _play_time = 0;
            _play_tick = 0;
            _last_event_time = 0;
            _last_event_tick = 0;
            _running_status = 0;
      }
};

//! Provides comprehensive information on the next event in the MIDI stream.
/*! An EventInfo struct is instantiated by format-specific implementations
 *  of MidiParser::parseNextEvent() each time another event is needed.
 */

00091 struct EventInfo {
00092       byte * start; //!< Position in the MIDI stream where the event starts.
                    //!< For delta-based MIDI streams (e.g. SMF and XMIDI), this points to the delta.
00094       uint32 delta; //!< The number of ticks after the previous event that this event should occur.
00095       byte   event; //!< Upper 4 bits are the command code, lower 4 bits are the MIDI channel.
                    //!< For META, event == 0xFF. For SysEx, event == 0xF0.
      union {
            struct {
00099                   byte param1; //!< The first parameter in a simple MIDI message.
00100                   byte param2; //!< The second parameter in a simple MIDI message.
            } basic;
            struct {
00103                   byte   type; //!< For META events, this indicates the META type.
00104                   byte * data; //!< For META and SysEx events, this points to the start of the data.
            } ext;
      };
00107       uint32 length; //!< For META and SysEx blocks, this indicates the length of the data.
                     //!< For Note On events, a non-zero value indicates that no Note Off event
                     //!< will occur, and the MidiParser will have to generate one itself.
                     //!< For all other events, this value should always be zero.

00112       byte channel() { return event & 0x0F; } //!< Separates the MIDI channel from the event.
00113       byte command() { return event >> 4; }   //!< Separates the command code from the event.
};

//! Provides expiration tracking for hanging notes.
/*! Hanging notes are used when a MIDI format does not include explicit Note Off
 *  events, or when "Smart Jump" is enabled so that active notes are intelligently
 *  expired when a jump occurs. The NoteTimer struct keeps track of how much
 *  longer a note should remain active before being turned off.
 */

00123 struct NoteTimer {
00124       byte channel;     //!< The MIDI channel on which the note was played
00125       byte note;        //!< The note number for the active note
00126       uint32 time_left; //!< The time, in microseconds, remaining before the note should be turned off
      NoteTimer() : channel(0), note(0), time_left(0) {}
};




//////////////////////////////////////////////////
//
// MidiParser declaration
//
//////////////////////////////////////////////////

//! A framework and common functionality for parsing event-based music streams.
/*! The MidiParser provides a framework in which to load,
 *  parse and traverse event-based music data. Note the
 *  avoidance of the phrase "MIDI data." Despite its name,
 *  MidiParser derivatives can be used to manage a wide
 *  variety of event-based music formats. It is, however,
 *  based on the premise that the format in question can
 *  be played in the form of specification MIDI events.
 *
 *  In order to use MidiParser to parse your music format,
 *  follow these steps:
 *
 *  <b>STEP 1: Write a MidiParser derivative.</b>
 *  The MidiParser base class provides functionality
 *  considered common to the task of parsing event-based
 *  music. In order to parse a particular format, create
 *  a derived class that implements, at minimum, the
 *  following format-specific methods:
 *    - loadMusic
 *    - parseNextEvent
 *
 *  In addition to the above functions, the derived class
 *  may also override the default MidiParser behavior for
 *  the following methods:
 *    - resetTracking
 *    - allNotesOff
 *    - unloadMusic
 *    - property
 *    - getTick
 *
 *  Please see the documentation for these individual
 *  functions for more information on their use.
 *
 *  The naming convention for classes derived from
 *  MidiParser is MidiParser_XXX, where "XXX" is some
 *  short designator for the format the class will
 *  support. For instance, the MidiParser derivative
 *  for parsing the Standard MIDI File format is
 *  MidiParser_SMF.
 *
 *  <b>STEP 2: Create an object of your derived class.</b>
 *  Each MidiParser object can parse at most one (1) song
 *  at a time. However, a MidiParser object can be reused
 *  to play another song once it is no longer needed to
 *  play whatever it was playing. In other words, MidiParser
 *  objects do not have to be destroyed and recreated from
 *  one song to the next.
 *
 *  <b>STEP 3: Specify a MidiDriver to send events to.</b>
 *  MidiParser works by sending MIDI and meta events to a
 *  MidiDriver. In the simplest configuration, you can plug
 *  a single MidiParser directly into the output MidiDriver
 *  being used. However, you can only plug in one at a time;
 *  otherwise channel conflicts will occur. Furthermore,
 *  meta events that may be needed to interactively control
 *  music flow cannot be handled because they are being
 *  sent directly to the output device.
 *
 *  If you need more control over the MidiParser while it's
 *  playing, you can create your own "pseudo-MidiDriver" and
 *  place it in between your MidiParser and the output
 *  MidiDriver. The MidiParser will send events to your
 *  pseudo-MidiDriver, which in turn must send them to the
 *  output MidiDriver (or do whatever special handling is
 *  required).
 *
 *  To specify the MidiDriver to send music output to,
 *  use the MidiParser::setMidiDriver method.
 *
 *  <b>STEP 4: Specify the onTimer call rate.</b>
 *  MidiParser bases the timing of its parsing on an external
 *  clock. Every time MidiParser::onTimer is called, a bit
 *  more music is parsed. You must specify how many
 *  microseconds will occur between each call to onTimer,
 *  in order to ensure an accurate music tempo.
 *
 *  To set the onTimer call rate, in microseconds,
 *  use the MidiParser::setTimerRate method. The onTimer
 *  call rate will typically match the timer rate for
 *  the output MidiDriver used. This rate can be obtained
 *  by calling MidiDriver::getBaseTempo.
 *
 *  <b>STEP 5: Load the music.</b>
 *  MidiParser requires that the music data already be loaded
 *  into memory. The client code is responsible for memory
 *  management on this block of memory. That means that the
 *  client code must ensure that the data remain in memory
 *  while the MidiParser is using it, and properly freed
 *  after it is no longer needed. Some MidiParser variants may
 *  require internal buffers as well; memory management for those
 *  buffers is the responsibility of the MidiParser object.
 *
 *  To load the music into the MidiParser, use the
 *  MidiParser::loadMusic method, specifying a memory pointer
 *  to the music data and the size of the data. (NOTE: Some
 *  MidiParser variants don't require a size, and 0 is fine.
 *  However, when writing client code to use MidiParser, it is
 *  best to assume that a valid size will be required.
 *
 *  Convention requires that each implementation of
 *  MidiParser::loadMusic automatically set up default tempo
 *  and current track. This effectively means that the
 *  MidiParser will start playing as soon as timer events
 *  start coming in.
 *
 *  <b>STEP 6: Activate a timer source for the MidiParser.</b>
 *  The easiest timer source to use is the timer of the
 *  output MidiDriver. You can attach the MidiDriver's
 *  timer output directly to a MidiParser by calling
 *  MidiDriver::setTimerCallback. In this case, the timer_proc
 *  will be the static method MidiParser::timerCallback,
 *  and timer_param will be a pointer to your MidiParser object.
 *
 *  This configuration only allows one MidiParser to be driven
 *  by the MidiDriver at a time. To drive more MidiDrivers, you
 *  will need to create a "pseudo-MidiDriver" as described earlier,
 *  In such a configuration, the pseudo-MidiDriver should be set
 *  as the timer recipient in MidiDriver::setTimerCallback, and
 *  could then call MidiParser::onTimer for each MidiParser object.
 *
 *  <b>STEP 7: Music shall begin to play!</b>
 *  Congratulations! At this point everything should be hooked up
 *  and the MidiParser should generate music. Note that there is
 *  no way to "stop" the MidiParser. You can "pause" the MidiParser
 *  simply by not sending timer events to it, or you can call
 *  MidiParser::unloadMusic to permanently stop the music. (This
 *  method resets everything and detaches the MidiParser from the
 *  memory block containing the music data.)
 */

00269 class MidiParser {
private:
00271       uint16    _active_notes[128];   //!< Each uint16 is a bit mask for channels that have that note on.
00272       NoteTimer _hanging_notes[32];   //!< Maintains expiration info for up to 32 notes.
                                      //!< Used for "Smart Jump" and MIDI formats that do not include explicit Note Off events.
00274       byte      _hanging_notes_count; //!< Count of hanging notes, used to optimize expiration.

protected:
00277       MidiDriver *_driver;    //!< The device to which all events will be transmitted.
00278       uint32 _timer_rate;     //!< The time in microseconds between onTimer() calls. Obtained from the MidiDriver.
00279       uint32 _ppqn;           //!< Pulses Per Quarter Note. (We refer to "pulses" as "ticks".)
00280       uint32 _tempo;          //!< Microseconds per quarter note.
00281       uint32 _psec_per_tick;  //!< Microseconds per tick (_tempo / _ppqn).
00282       bool   _autoLoop;       //!< For lightweight clients that don't provide their own flow control.
00283       bool   _smartJump;      //!< Support smart expiration of hanging notes when jumping
00284       bool   _centerPitchWheelOnUnload;  //!< Center the pitch wheels when unloading a song

      // FIXME: Was 32 here, Kyra tracks use 120(!!!) which seems wrong. this is a hacky
      // workaround until situation is investigated.
00288       byte * _tracks[120];     //!< Multi-track MIDI formats are supported, up to 120 tracks.
00289       byte   _num_tracks;     //!< Count of total tracks for multi-track MIDI formats. 1 for single-track formats.
00290       byte   _active_track;   //!< Keeps track of the currently active track, in multi-track formats.

00292       Tracker _position;      //!< The current time/position in the active track.
00293       EventInfo _next_event;  //!< The next event to transmit. Events are preparsed
                              //!< so each event is parsed only once; this permits
                              //!< simulated events in certain formats.
00296       bool   _abort_parse;    //!< If a jump or other operation interrupts parsing, flag to abort.

protected:
      static uint32 readVLQ(byte * &data);
      virtual void resetTracking();
      virtual void allNotesOff();
      virtual void parseNextEvent(EventInfo &info) = 0;

      void activeNote(byte channel, byte note, bool active);
      void hangingNote(byte channel, byte note, uint32 ticks_left, bool recycle = true);
      void hangAllActiveNotes();

      //! Platform independent BE uint32 read-and-advance.
      /*! This helper function reads Big Endian 32-bit numbers
       *  from a memory pointer, at the same time advancing
       *  the pointer.
       */
00313       uint32 read4high(byte * &data) {
            uint32 val = READ_BE_UINT32(data);
            data += 4;
            return val;
      }

      //! Platform independent LE uint16 read-and-advance.
      /*! This helper function reads Little Endian 16-bit numbers
       *  from a memory pointer, at the same time advancing
       *  the pointer.
       */
00324       uint16 read2low(byte * &data) {
            uint16 val = READ_LE_UINT16(data);
            data += 2;
            return val;
      }

public:
      //! Configuration options for MidiParser
      /*! The following options can be set to modify MidiParser's
       *  behavior.
       *
       *  \b mpMalformedPitchBends - Events containing a pitch bend
       *  command should be treated as single-byte padding before the
       *  real event. This allows the MidiParser to work with some
       *  malformed SMF files from Simon 1/2.
       *
       *  \b mpAutoLoop - Sets auto-looping, which can be used by
       *  lightweight clients that don't provide their own flow control.
       *
       *  \b mpSmartJump - Sets smart jumping, which intelligently
       *  expires notes that are active when a jump is made, rather
       *  than just cutting them off.
       */
      enum {
            mpMalformedPitchBends = 1,
            mpAutoLoop = 2,
            mpSmartJump = 3,
            mpCenterPitchWheelOnUnload = 4
      };

public:
      MidiParser();
      virtual ~MidiParser() { allNotesOff(); }

      virtual bool loadMusic(byte *data, uint32 size) = 0;
      virtual void unloadMusic();
      virtual void property(int prop, int value);

      void setMidiDriver(MidiDriver *driver) { _driver = driver; }
      void setTimerRate(uint32 rate) { _timer_rate = rate; }
      void setTempo(uint32 tempo);
      void onTimer();

      bool setTrack(int track);
      bool jumpToTick(uint32 tick, bool fireEvents = false);

      uint32 getPPQN() { return _ppqn; }
      virtual uint32 getTick() { return _position._play_tick; }

      static MidiParser *createParser_SMF();
      static MidiParser *createParser_XMIDI();
      static void timerCallback(void *data) { ((MidiParser *) data)->onTimer(); }
};

#endif

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