livetrax/libs/ardour/smf_source.cc

/*
 * Copyright (C) 2006-2016 David Robillard <d@drobilla.net>
 * Copyright (C) 2007-2018 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2008-2009 Hans Baier <hansfbaier@googlemail.com>
 * Copyright (C) 2009-2011 Carl Hetherington <carl@carlh.net>
 * Copyright (C) 2012-2016 Tim Mayberry <mojofunk@gmail.com>
 * Copyright (C) 2014-2015 Robin Gareus <robin@gareus.org>
 * Copyright (C) 2014-2016 John Emmas <john@creativepost.co.uk>
 * Copyright (C) 2016 Nick Mainsbridge <mainsbridge@gmail.com>
 *
 * 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.
 */

#include <vector>

#include <sys/time.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <regex.h>

#include "pbd/file_utils.h"
#include "pbd/stl_delete.h"
#include "pbd/strsplit.h"
#include "pbd/timing.h"

#include "pbd/gstdio_compat.h"
#include <glibmm/miscutils.h>
#include <glibmm/fileutils.h>

#include "evoral/Control.h"
#include "evoral/SMF.h"

#include "temporal/tempo.h"

#include "ardour/debug.h"
#include "ardour/midi_channel_filter.h"
#include "ardour/midi_model.h"
#include "ardour/midi_ring_buffer.h"
#include "ardour/midi_state_tracker.h"
#include "ardour/parameter_types.h"
#include "ardour/session.h"
#include "ardour/smf_source.h"

#include "pbd/i18n.h"

using namespace ARDOUR;
using namespace Glib;
using namespace PBD;
using namespace Evoral;
using namespace std;

/** Constructor used for new internal-to-session files.  File cannot exist. */
SMFSource::SMFSource (Session& s, const string& path, Source::Flag flags)
	: Source(s, DataType::MIDI, path, flags)
	, MidiSource(s, path, flags)
	, FileSource(s, DataType::MIDI, path, string(), flags)
	, Evoral::SMF()
	, _open (false)
	, _last_ev_time_samples(0)
{
	/* note that origin remains empty */

	if (init (_path, false)) {
		throw failed_constructor ();
	}

        assert (!Glib::file_test (_path, Glib::FILE_TEST_EXISTS));
	existence_check ();

	_flags = Source::Flag (_flags | Empty);

	if (_flags & Writable) {
		if (open_for_write ()) {
			throw failed_constructor ();
		}
		/* no fd left open here */
	} else {
		if (open (_path, 1, false)) {
			throw failed_constructor ();
		}
		_open = true;
	}

	/* there's no data to load into the model but create it anyway */

	_model = std::shared_ptr<MidiModel> (new MidiModel (*this));
}

/** Constructor used for external-to-session files.  File must exist. */
SMFSource::SMFSource (Session& s, const string& path)
	: Source(s, DataType::MIDI, path, Source::Flag (0))
	, MidiSource(s, path, Source::Flag (0))
	, FileSource(s, DataType::MIDI, path, string(), Source::Flag (0))
	, Evoral::SMF()
	, _open (false)
	, _last_ev_time_samples(0)
{
	/* note that origin remains empty */

	if (init (_path, true)) {
		throw failed_constructor ();
	}

        assert (Glib::file_test (_path, Glib::FILE_TEST_EXISTS));
	existence_check ();

	if (open (_path, 1, false)) {
		throw failed_constructor ();
	}

	_open = true;

	/* no lock required since we do not actually exist yet */
	load_model_unlocked (true);
}

/** Constructor used for existing internal-to-session files. */
SMFSource::SMFSource (Session& s, const XMLNode& node, bool must_exist)
	: Source(s, node)
	, MidiSource(s, node)
	, FileSource(s, node, must_exist)
	, _open (false)
	, _last_ev_time_samples(0)
{
	if (set_state(node, Stateful::loading_state_version)) {
		throw failed_constructor ();
	}

	/* we expect the file to exist, but if no MIDI data was ever added
	   it will have been removed at last session close. so, we don't
	   require it to exist if it was marked Empty.
	*/

	try {

		if (init (_path, true)) {
			throw failed_constructor ();
		}

	} catch (MissingSource& err) {
		if (0 == (_flags & Source::Empty)) {
			/* Don't throw, create the source.
			 * Since MIDI is writable, we cannot use a SilentFileSource.
			 */
			_flags = Source::Flag (_flags | Source::Empty | Source::Missing);
		}

		/* we don't care that the file was not found, because
			 it was empty. But FileSource::init() will have
			 failed to set our _path correctly, so we have to do
			 this ourselves. Use the first entry in the search
			 path for MIDI files, which is assumed to be the
			 correct "main" location.
		*/
		std::vector<string> sdirs = s.source_search_path (DataType::MIDI);
		_path = Glib::build_filename (sdirs.front(), _path);
		/* This might be important, too */
		_file_is_new = true;
	}

	if (!(_flags & Source::Empty)) {
		assert (Glib::file_test (_path, Glib::FILE_TEST_EXISTS));
		existence_check ();
		if (open (_path, 1, false)) {
			throw failed_constructor ();
		}
		_open = true;
	} else {
		assert (_flags & Source::Writable);
		if (open_for_write ()) {
			throw failed_constructor ();
		}
		/* no fd left open here */
	}

	/* no lock required since we do not actually exist yet */
	load_model_unlocked (true);
}

SMFSource::~SMFSource ()
{
	if (removable()) {
		::g_unlink (_path.c_str());
	}
}

int
SMFSource::open_for_write ()
{
	if (create (_path)) {
		return -1;
	}
	_open = true;
	return 0;
}

void
SMFSource::close ()
{
	/* nothing to do: file descriptor is never kept open.
	 * Note, keep `_open = true` regardless.
	 */
}

extern PBD::Timing minsert;

timecnt_t
SMFSource::read_unlocked (const ReaderLock&               lock,
                          Evoral::EventSink<samplepos_t>& destination,
                          timepos_t const &               source_start,
                          timepos_t const &               start,
                          timecnt_t const &               duration,
                          Temporal::Range*                loop_range,
                          MidiNoteTracker*                tracker,
                          MidiChannelFilter*              filter) const
{
	int      ret  = 0;
	timepos_t time; // in SMF ticks, 1 tick per _ppqn

	if (writable() && !_open) {
		/* nothing to read since nothing has ben written */
		return timecnt_t();
	}

	DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("SMF read_unlocked: start %1 duration %2\n", start, duration));

	// Output parameters for read_event (which will allocate scratch in buffer as needed)
	uint32_t ev_delta_t = 0;
	uint32_t ev_size    = 0;
	uint8_t* ev_buffer  = 0;

	size_t scratch_size = 0; // keep track of scratch to minimize reallocs

	/* start of read in SMF ticks (which may differ from our own musical ticks */
	const uint64_t start_ticks = llrint (start.beats().to_ticks() * (Temporal::Beats::PPQN / ppqn()));

	DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("SMF read_unlocked: start in ticks %1\n", start_ticks));

	if (_smf_last_read_end.is_zero() || start != _smf_last_read_end) {
		DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("SMF read_unlocked: seek to %1\n", start));
		Evoral::SMF::seek_to_start();
		while (time < start_ticks) {
			Evoral::event_id_t ignored;

			ret = read_event(&ev_delta_t, &ev_size, &ev_buffer, &ignored);
			if (ret == -1) { // EOF
				_smf_last_read_end = start + duration;
				return timecnt_t();
			}
			time += timepos_t::from_ticks (ev_delta_t); // accumulate delta time
		}
	} else {
		DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("SMF read_unlocked: set time to %1\n", _smf_last_read_time));
		time = _smf_last_read_time;
	}

	_smf_last_read_end = start + duration;

	while (true) {
		Evoral::event_id_t ignored; /* XXX don't ignore note id's ??*/

		ret = read_event(&ev_delta_t, &ev_size, &ev_buffer, &ignored);
		if (ret == -1) { // EOF
			break;
		}

		time += timepos_t::from_ticks (ev_delta_t); // accumulate delta time
		_smf_last_read_time = time;

		if (ret == 0) { // meta-event (skipped, just accumulate time)
			continue;
		}

		DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("SMF read_unlocked delta %1, time %2, buf[0] %3\n",
								  ev_delta_t, time, ev_buffer[0]));

		assert(time >= start_ticks);

		/* Note that we add on the source start time (in session samples) here so that ev_sample_time
		   is in session samples.
		*/
		const samplepos_t ev_sample_time = (time + timepos_t (source_start.beats())).samples();
		timepos_t est (ev_sample_time);

		if (loop_range) {
			est = loop_range->squish (est);
		}

		if (est < start + duration) {
			if (!filter || !filter->filter(ev_buffer, ev_size)) {
				destination.write (est.samples(), Evoral::MIDI_EVENT, ev_size, ev_buffer);
				if (tracker) {
					tracker->track(ev_buffer);
				}
			}
		} else {
			break;
		}

		if (ev_size > scratch_size) {
			scratch_size = ev_size;
		}
		ev_size = scratch_size; // ensure read_event only allocates if necessary
	}

	return duration;
}

timecnt_t
SMFSource::write_unlocked (const WriterLock&            lock,
                           MidiRingBuffer<samplepos_t>& source,
                           timepos_t const &            position,
                           timecnt_t const &            cnt)
{

	if (!_writing) {
		mark_streaming_write_started (lock);
	}

	samplepos_t        time;
	const samplepos_t        pos_samples = position.samples();
	const samplecnt_t        cnt_samples = cnt.samples();
	Evoral::EventType type;
	uint32_t          size;

	size_t   buf_capacity = 4;
	uint8_t* buf          = (uint8_t*)malloc(buf_capacity);

	if (_model && !_model->writing()) {
		_model->start_write();
	}

	Evoral::Event<samplepos_t> ev;
	while (true) {
		/* Get the event time, in samples since session start but ignoring looping. */
		bool ret;
		if (!(ret = source.peek ((uint8_t*)&time, sizeof (time)))) {
			/* Ring is empty, no more events. */
			break;
		}

		if ((cnt != timecnt_t::max (cnt.time_domain())) &&
		    (time > pos_samples + _capture_length + cnt_samples)) {
			/* The diskstream doesn't want us to write everything, and this
			   event is past the end of this block, so we're done for now. */
			break;
		}

		/* Read the time, type, and size of the event. */
		if (!(ret = source.read_prefix (&time, &type, &size))) {
			error << _("Unable to read event prefix, corrupt MIDI ring") << endmsg;
			break;
		}

		/* Enlarge body buffer if necessary now that we know the size. */
		if (size > buf_capacity) {
			buf_capacity = size;
			buf = (uint8_t*)realloc(buf, size);
		}

		/* Read the event body into buffer. */
		ret = source.read_contents(size, buf);
		if (!ret) {
			error << _("Event has time and size but no body, corrupt MIDI ring") << endmsg;
			break;
		}

		/* Convert event time from absolute to source relative. */
		if (time < pos_samples) {
			error << _("Event time is before MIDI source position") << endmsg;
			break;
		}
		time -= pos_samples;

		ev.set(buf, size, time);
		ev.set_event_type(Evoral::MIDI_EVENT);
		ev.set_id(Evoral::next_event_id());

		if (!(ev.is_channel_event() || ev.is_smf_meta_event() || ev.is_sysex())) {
			continue;
		}

		append_event_samples(lock, ev, pos_samples);
	}

	Evoral::SMF::flush ();
	free (buf);

	return cnt;
}

void
SMFSource::update_length (timepos_t const & dur)
{
	assert (!_length || (_length.time_domain() == dur.time_domain()));
	_length = dur;
}

/** Append an event with a timestamp in beats */
void
SMFSource::append_event_beats (const WriterLock&   lock,
                               const Evoral::Event<Temporal::Beats>& ev)
{
	if (!_writing || ev.size() == 0)  {
		return;
	}

#if 0
	printf("SMFSource: %s - append_event_beats ID = %d time = %lf, size = %u, data = ",
               name().c_str(), ev.id(), ev.time(), ev.size());
	       for (size_t i = 0; i < ev.size(); ++i) printf("%X ", ev.buffer()[i]); printf("\n");
#endif

	Temporal::Beats time = ev.time();
	if (time < _last_ev_time_beats) {
		const Temporal::Beats difference = _last_ev_time_beats - time;
		if (difference < Temporal::Beats::ticks (ppqn())) {
			/* Close enough.  This problem occurs because Sequence is not
			   actually ordered due to fuzzy time comparison.  I'm pretty sure
			   this is inherently a bad idea which causes problems all over the
			   place, but tolerate it here for now anyway. */
			time = _last_ev_time_beats;
		} else {
			/* Out of order by more than a tick. */
			warning << string_compose(_("Skipping event with unordered beat time %1 < %2 (off by %3 beats, %4 ticks)"),
			                          ev.time(), _last_ev_time_beats, difference, difference)
			        << endmsg;
			return;
		}
	}

	Evoral::event_id_t event_id;

	if (ev.id() < 0) {
		event_id  = Evoral::next_event_id();
	} else {
		event_id = ev.id();
	}

	if (_model) {
		_model->append (ev, event_id);
	}

	assert (!_length || (_length.time_domain() == Temporal::BeatTime));
	_length  = timepos_t (max (_length.beats(), time));

	const Temporal::Beats delta_time_beats = time - _last_ev_time_beats;
	const uint32_t      delta_time_ticks = delta_time_beats.to_ticks(ppqn());

	Evoral::SMF::append_event_delta(delta_time_ticks, ev.size(), ev.buffer(), event_id);
	_last_ev_time_beats = time;
	_flags = Source::Flag (_flags & ~Empty);
	_flags = Source::Flag (_flags & ~Missing);
}

/** Append an event with a timestamp in samples (samplepos_t) */
void
SMFSource::append_event_samples (const WriterLock& lock,
                                const Evoral::Event<samplepos_t>&  ev,
                                samplepos_t                        position)
{
	if (!_writing || ev.size() == 0)  {
		return;
	}

	// printf("SMFSource: %s - append_event_samples ID = %d time = %u, size = %u, data = ",
	// name().c_str(), ev.id(), ev.time(), ev.size());
	// for (size_t i=0; i < ev.size(); ++i) printf("%X ", ev.buffer()[i]); printf("\n");

	if (ev.time() < _last_ev_time_samples) {
		warning << string_compose(_("Skipping event with unordered sample time %1 < %2"),
		                          ev.time(), _last_ev_time_samples)
		        << endmsg;
		return;
	}

	/* a distance measure that starts at @p position (audio time) and
	   extends for ev.time() (audio time)
	*/
	const timecnt_t distance (timepos_t (ev.time()), timepos_t (position));
	const Temporal::Beats  ev_time_beats = distance.beats ();
	Evoral::event_id_t   event_id;

	if (ev.id() < 0) {
		event_id  = Evoral::next_event_id();
	} else {
		event_id = ev.id();
	}

	if (_model) {
		const Evoral::Event<Temporal::Beats> beat_ev (ev.event_type(),
		                                              ev_time_beats,
		                                              ev.size(),
		                                              const_cast<uint8_t*>(ev.buffer()));
		_model->append (beat_ev, event_id);
	}

	assert (!_length || (_length.time_domain() == Temporal::BeatTime));
	_length = timepos_t (max (_length.beats(), ev_time_beats));

	/* a distance measure that starts at @p _last_ev_time_samples (audio time) and
	   extends for ev.time() (audio time)
	*/
	const timecnt_t       delta_distance (timepos_t (ev.time()), timepos_t (_last_ev_time_samples));
	const Temporal::Beats delta_time_beats = delta_distance.beats ();
	const uint32_t        delta_time_ticks = delta_time_beats.to_ticks(ppqn());

	Evoral::SMF::append_event_delta (delta_time_ticks, ev.size(), ev.buffer(), event_id);
	_last_ev_time_samples = ev.time();
	_flags = Source::Flag (_flags & ~Empty);
	_flags = Source::Flag (_flags & ~Missing);
}

XMLNode&
SMFSource::get_state () const
{
	XMLNode& node = MidiSource::get_state();
	node.set_property (X_("origin"), _origin);
	return node;
}

int
SMFSource::set_state (const XMLNode& node, int version)
{
	if (Source::set_state (node, version)) {
		return -1;
	}

	if (MidiSource::set_state (node, version)) {
		return -1;
	}

	if (FileSource::set_state (node, version)) {
		return -1;
	}

	return 0;
}

void
SMFSource::mark_streaming_midi_write_started (const WriterLock& lock, NoteMode mode)
{
	if (!_open && open_for_write()) {
		error << string_compose (_("cannot open MIDI file %1 for write"), _path) << endmsg;
		/* XXX should probably throw or return something */
		return;
	}

	MidiSource::mark_streaming_midi_write_started (lock, mode);
	Evoral::SMF::begin_write ();
	_last_ev_time_beats  = Temporal::Beats();
	_last_ev_time_samples = 0;
}

void
SMFSource::mark_streaming_write_completed (const WriterLock& lock)
{
	mark_midi_streaming_write_completed (lock, Evoral::Sequence<Temporal::Beats>::DeleteStuckNotes);
}

void
SMFSource::mark_midi_streaming_write_completed (const WriterLock& lm, Evoral::Sequence<Temporal::Beats>::StuckNoteOption stuck_notes_option, Temporal::Beats when)
{
	MidiSource::mark_midi_streaming_write_completed (lm, stuck_notes_option, when);

	if (!writable()) {
		warning << string_compose ("attempt to write to unwritable SMF file %1", _path) << endmsg;
		return;
	}

	if (_model) {
		_model->set_edited(false);
	}

	try {
		Evoral::SMF::end_write (_path);
	} catch (std::exception & e) {
		error << string_compose (_("Exception while writing %1, file may be corrupt/unusable"), _path) << endmsg;
	}

	/* data in the file now, not removable */

	mark_nonremovable ();
}

bool
SMFSource::valid_midi_file (const string& file)
{
	if (safe_midi_file_extension (file) ) {
		return (SMF::test (file) );
	}
	return false;
}

bool
SMFSource::safe_midi_file_extension (const string& file)
{
	static regex_t compiled_pattern;
	static bool compile = true;
	const int nmatches = 2;
	regmatch_t matches[nmatches];

	if (Glib::file_test (file, Glib::FILE_TEST_EXISTS)) {
		if (!Glib::file_test (file, Glib::FILE_TEST_IS_REGULAR)) {
			/* exists but is not a regular file */
			return false;
		}
	}

	if (compile && regcomp (&compiled_pattern, "\\.[mM][iI][dD][iI]?$", REG_EXTENDED)) {
		return false;
	} else {
		compile = false;
	}

	if (regexec (&compiled_pattern, file.c_str(), nmatches, matches, 0)) {
		return false;
	}

	return true;
}

static bool compare_eventlist (
	const std::pair< const Evoral::Event<Temporal::Beats>*, gint >& a,
	const std::pair< const Evoral::Event<Temporal::Beats>*, gint >& b) {
	return ( a.first->time() < b.first->time() );
}

void
SMFSource::load_model (const WriterLock& lock, bool force_reload)
{
	invalidate (lock);
	load_model_unlocked (force_reload);
	invalidate (lock);
}

void
SMFSource::load_model_unlocked (bool force_reload)
{
	assert (!_writing);

	if (!_model) {
		_model = std::shared_ptr<MidiModel> (new MidiModel (*this));
	} else {
		_model->clear();
	}

	_model->start_write();
	Evoral::SMF::seek_to_start();

	uint64_t time = 0; /* in SMF ticks */
	Evoral::Event<Temporal::Beats> ev;

	uint32_t scratch_size = 0; // keep track of scratch and minimize reallocs

	uint32_t delta_t = 0;
	uint32_t size    = 0;
	uint8_t* buf     = NULL;
	int ret;
	Evoral::event_id_t event_id;
	bool have_event_id;

	_num_channels     = 0;
	_n_note_on_events = 0;
	_has_pgm_change   = false;
	_used_channels.reset ();

	// TODO simplify event allocation
	std::list< std::pair< Evoral::Event<Temporal::Beats>*, gint > > eventlist;

	for (unsigned i = 1; i <= num_tracks(); ++i) {
		if (seek_to_track(i)) continue;

		time = 0;
		have_event_id = false;

		while ((ret = read_event (&delta_t, &size, &buf, &event_id)) >= 0) {

			time += delta_t;

			if (ret == 0) {
				/* meta-event : did we get an event ID ?  */
				if (event_id >= 0) {
					have_event_id = true;
				}
				continue;
			}

			/* aggregate information about channels and pgm-changes */
			uint8_t type = buf[0] & 0xf0;
			uint8_t chan = buf[0] & 0x0f;
			if (type >= 0x80 && type <= 0xE0) {
				_used_channels.set(chan);
				switch (type) {
					case MIDI_CMD_NOTE_ON:
						++_n_note_on_events;
						break;
					case MIDI_CMD_PGM_CHANGE:
						_has_pgm_change = true;
						break;
					default:
						break;
				}
			}

			if (ret > 0) {
				/* not a meta-event */

				if (!have_event_id) {
					event_id = Evoral::next_event_id();
				}
				const Temporal::Beats event_time = Temporal::Beats::ticks_at_rate(time, ppqn());
#ifndef NDEBUG
				std::string ss;

				for (uint32_t xx = 0; xx < size; ++xx) {
					char b[8];
					snprintf (b, sizeof (b), "0x%x ", buf[xx]);
					ss += b;
				}

				DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("SMF %7 load model delta %1, time %2, size %3 buf %4, id %6\n",
							delta_t, time, size, ss, event_id, name()));
#endif

				eventlist.push_back(make_pair (
							new Evoral::Event<Temporal::Beats> (
								Evoral::MIDI_EVENT, event_time,
								size, buf, true)
							, event_id));

				// Set size to max capacity to minimize allocs in read_event
				scratch_size = std::max(size, scratch_size);
				size = scratch_size;

				assert (!_length || (_length.time_domain() == Temporal::BeatTime));
				_length = max (_length, timepos_t (event_time));
			}

			/* event ID's must immediately precede the event they are for */
			have_event_id = false;
		}
	}

	_num_channels = _used_channels.size();

	eventlist.sort(compare_eventlist);

	std::list< std::pair< Evoral::Event<Temporal::Beats>*, gint > >::iterator it;
	for (it=eventlist.begin(); it!=eventlist.end(); ++it) {
		_model->append (*it->first, it->second);
		delete it->first;
	}

        // cerr << "----SMF-SRC-----\n";
        // _playback_buf->dump (cerr);
        // cerr << "----------------\n";

	_model->end_write (Evoral::Sequence<Temporal::Beats>::ResolveStuckNotes, _length.beats());
	_model->set_edited (false);

	free (buf);
}

Evoral::SMF::UsedChannels
SMFSource::used_midi_channels()
{
	return _used_channels;
}

void
SMFSource::destroy_model (const WriterLock& lock)
{
	//cerr << _name << " destroying model " << _model.get() << endl;
	_model.reset();
	invalidate(lock);
}

void
SMFSource::flush_midi (const WriterLock& lock)
{
	if (!writable() || _length.is_zero()) {
		return;
	}

	ensure_disk_file (lock);

	Evoral::SMF::end_write (_path);
	/* data in the file means its no longer removable */
	mark_nonremovable ();

	invalidate(lock);
}

void
SMFSource::set_path (const string& p)
{
	FileSource::set_path (p);
}

/** Ensure that this source has some file on disk, even if it's just a SMF header */
void
SMFSource::ensure_disk_file (const WriterLock& lock)
{
	if (!writable()) {
		return;
	}

	if (_model) {
		/* We have a model, so write it to disk; see MidiSource::session_saved
		   for an explanation of what we are doing here.
		*/
		std::shared_ptr<MidiModel> mm = _model;
		_model.reset ();
		mm->sync_to_source (lock);
		_model = mm;
		invalidate(lock);
	} else {
		/* No model; if it's not already open, it's an empty source, so create
		   and open it for writing.
		*/
		if (!_open) {
			open_for_write ();
		}
	}
}

void
SMFSource::prevent_deletion ()
{
	/* Unlike the audio case, the MIDI file remains mutable (because we can
	   edit MIDI data)
	*/

	_flags = Flag (_flags & ~(Removable|RemovableIfEmpty|RemoveAtDestroy));
}