Added support for GME (Game_Music_Emu).

This makes it possible for LÖVE to play music files for NES, SNES, MegaDrive,
and many more. It's pretty cool.

The feature is disabled until each platform is ready to link with GME. Packages
exist for Debian and Arch, and it compiled without any issues in MSVC++, so
I don't expect this to a problem for anyone.

src/modules/sound/lullaby/GmeDecoder.cpp

@@ -0,0 +1,141 @@
+/**
+ * Copyright (c) 2006-2012 LOVE Development Team
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ **/
+
+#include "common/config.h"
+
+#ifdef LOVE_SUPPORT_GME
+
+#include "common/Exception.h"
+#include "GmeDecoder.h"
+
+namespace love
+{
+namespace sound
+{
+namespace lullaby
+{
+
+GmeDecoder::GmeDecoder(Data *data, const std::string &ext, int bufferSize)
+	: Decoder(data, ext, bufferSize)
+	, emu(0)
+	, num_tracks(0)
+	, cur_track(0)
+{
+	void *d = data->getData();
+	int s = data->getSize();
+
+	if (gme_open_data(d, s, &emu, sampleRate) != 0)
+		throw love::Exception("Could not open game music file");
+
+	num_tracks = gme_track_count(emu);
+
+	if (num_tracks <= 0)
+		throw love::Exception("Game music file has no tracks");
+
+	if (gme_start_track(emu, cur_track) != 0)
+		throw love::Exception("Could not start game music playback");
+}
+
+GmeDecoder::~GmeDecoder()
+{
+	if (emu)
+		gme_delete(emu);
+}
+
+bool GmeDecoder::accepts(const std::string &ext)
+{
+	static const std::string supported[] =
+	{
+		"ay", "gbs", "gym", "hes", "kss", "nsf",
+		"nsfe", "sap", "spc", "vgm", "vgz"
+	};
+
+	for (int i = 0; !(supported[i].empty()); i++)
+	{
+		if (supported[i].compare(ext) == 0)
+			return true;
+	}
+
+	return false;
+}
+
+love::sound::Decoder *GmeDecoder::clone()
+{
+	return new GmeDecoder(data, ext, bufferSize);
+}
+
+int GmeDecoder::decode()
+{
+	short *sbuf = static_cast<short*>(buffer);
+	int size = bufferSize / sizeof(short);
+
+	if (gme_play(emu, size, sbuf) != 0)
+		throw love::Exception("Error while decoding game music");
+
+	if (!eof && gme_track_ended(emu))
+	{
+		// Start the next track if this one ended.
+		if (cur_track < num_tracks - 1)
+			gme_start_track(emu, ++cur_track);
+		else
+			eof = true;
+	}
+
+	return bufferSize;
+}
+
+bool GmeDecoder::seek(float s)
+{
+	return gme_seek(emu, static_cast<long>(s * 1000.f)) != 0;
+}
+
+bool GmeDecoder::rewind()
+{
+	// If we're in the first track, rewind.
+	if (cur_track == 0)
+		return gme_seek(emu, 0) == 0;
+	else
+	{
+		// Otherwise, start from the first track again.
+		cur_track = 0;
+		return gme_start_track(emu, cur_track) == 0;
+	}
+}
+
+bool GmeDecoder::isSeekable()
+{
+	return true;
+}
+
+int GmeDecoder::getChannels() const
+{
+	return 2;
+}
+
+int GmeDecoder::getBits() const
+{
+	return 16;
+}
+
+} // lullaby
+} // sound
+} // love
+
+#endif // LOVE_SUPPORT_GME

src/modules/sound/lullaby/GmeDecoder.h

@@ -0,0 +1,68 @@
+/**
+ * Copyright (c) 2006-2012 LOVE Development Team
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ **/
+
+#ifndef LOVE_SOUND_LULLABY_GME_DECODER_H
+#define LOVE_SOUND_LULLABY_GME_DECODER_H
+
+#ifdef LOVE_SUPPORT_GME
+
+// LOVE
+#include "common/Data.h"
+#include "Decoder.h"
+
+#include <gme.h>
+
+namespace love
+{
+namespace sound
+{
+namespace lullaby
+{
+
+class GmeDecoder : public Decoder
+{
+public:
+
+	GmeDecoder(Data *data, const std::string &ext, int bufferSize);
+	virtual ~GmeDecoder();
+
+	static bool accepts(const std::string &ext);
+
+	love::sound::Decoder *clone();
+	int decode();
+	bool seek(float s);
+	bool rewind();
+	bool isSeekable();
+	int getChannels() const;
+	int getBits() const;
+
+private:
+	Music_Emu *emu;
+	int num_tracks;
+	int cur_track;
+}; // Decoder
+
+} // lullaby
+} // sound
+} // love
+
+#endif // LOVE_SUPPORT_GME
+
+#endif // LOVE_SOUND_LULLABY_GME_DECODER_H

src/modules/sound/lullaby/Sound.cpp

@@ -18,11 +18,14 @@
  * 3. This notice may not be removed or altered from any source distribution.
  **/
 
+#include "common/config.h"
+
 #include "Sound.h"
 
 #include "ModPlugDecoder.h"
 #include "Mpg123Decoder.h"
 #include "VorbisDecoder.h"
+#include "GmeDecoder.h"
 //#include "FLACDecoder.h"
 
 namespace love
@@ -64,6 +67,10 @@ sound::Decoder *Sound::newDecoder(love::filesystem::File *file, int bufferSize)
 #endif // LOVE_NOMPG123
 	else if (VorbisDecoder::accepts(ext))
 		decoder = new VorbisDecoder(data, ext, bufferSize);
+#ifdef LOVE_SUPPORT_GME
+	else if (GmeDecoder::accepts(ext))
+		decoder = new GmeDecoder(data, ext, bufferSize);
+#endif // LOVE_SUPPORT_GME
 	/*else if (FLACDecoder::accepts(ext))
 		decoder = new FLACDecoder(data, ext, bufferSize);*/