SCUMM: Add support for CD audio tracks in the Steam versions of Loom

Many Thanks to Ben Castricum for the original patch

engines/scumm/cdda.cpp

@@ -0,0 +1,120 @@
+/* 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.
+ *
+ */
+
+#include "scumm/cdda.h"
+#include "common/stream.h"
+#include "audio/audiostream.h"
+
+namespace Scumm {
+
+
+#pragma mark -
+#pragma mark --- CDDA stream ---
+#pragma mark -
+
+#define START_OF_CDDA_DATA 800
+#define BLOCK_SIZE 1177
+
+class CDDAStream : public Audio::SeekableAudioStream {
+private:
+	Common::SeekableReadStream *_stream;
+	DisposeAfterUse::Flag _disposeAfterUse;
+	byte _shiftLeft;
+	byte _shiftRight;
+	uint32 _pos;
+	Audio::Timestamp _length;
+
+public:
+	CDDAStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse);
+	virtual ~CDDAStream();
+	
+	int readBuffer(int16 *buffer, const int numSamples);
+	bool isStereo() const { return true; }
+	int getRate() const { return 44100; }
+	bool endOfData() const { return _stream->eos(); }
+	bool seek(const Audio::Timestamp &where);
+	Audio::Timestamp getLength() const { return _length; }
+};
+
+CDDAStream::CDDAStream(Common::SeekableReadStream *stream, DisposeAfterUse::Flag disposeAfterUse) :
+	_stream(stream), _disposeAfterUse(disposeAfterUse), _pos(START_OF_CDDA_DATA) {
+	_stream->seek(START_OF_CDDA_DATA, SEEK_SET);
+	// The total size of CDDA.SOU is 289,808,802 bytes or (289808802 - 800) / 1177 = 246226 blocks
+	// We also deduct the shift values to return the correct length
+	uint32 blocks = (_stream->size() - START_OF_CDDA_DATA) / BLOCK_SIZE;
+	_length = Audio::Timestamp(0, (_stream->size() - START_OF_CDDA_DATA - blocks) / (isStereo() ? 2 : 1), getRate());
+}
+
+CDDAStream::~CDDAStream() {
+	if (_disposeAfterUse == DisposeAfterUse::YES)
+		delete _stream;
+}
+
+bool CDDAStream::seek(const Audio::Timestamp &where) {
+	const uint32 seekSample = convertTimeToStreamPos(where, getRate(), isStereo()).totalNumberOfFrames();
+	uint32 blocks = seekSample / 1176;
+
+	// Before seeking, read the shift values from the beginning of that block
+	_stream->seek(START_OF_CDDA_DATA + blocks * BLOCK_SIZE, SEEK_SET);
+	byte shiftVal = _stream->readByte();
+	_shiftLeft = shiftVal >> 4;
+	_shiftRight = shiftVal & 0x0F;
+
+	_pos = START_OF_CDDA_DATA + blocks + seekSample;
+	return _stream->seek(_pos, SEEK_SET);
+}
+
+int CDDAStream::readBuffer(int16 *buffer, const int numSamples) {
+	int samples;
+
+	for (samples = 0 ; samples < numSamples && !_stream->eos() ; ) {
+		if (!((_pos - START_OF_CDDA_DATA) % BLOCK_SIZE)) {
+			byte shiftVal = _stream->readByte();
+			_shiftLeft = shiftVal >> 4;
+			_shiftRight = shiftVal & 0x0F;
+			_pos++;
+		}
+		buffer[samples++] = _stream->readSByte() << _shiftLeft;
+		buffer[samples++] = _stream->readSByte() << _shiftRight;
+		_pos += 2;
+	}
+	return samples;
+}
+
+#pragma mark -
+#pragma mark --- CDDA factory functions ---
+#pragma mark -
+
+Audio::SeekableAudioStream *makeCDDAStream(
+	Common::SeekableReadStream *stream,
+	DisposeAfterUse::Flag disposeAfterUse) {
+	Audio::SeekableAudioStream *s = new CDDAStream(stream, disposeAfterUse);
+	if (s && s->endOfData()) {
+		delete s;
+		return 0;
+	} else {
+		return s;
+	}
+	return 0;
+}
+
+} // End of namespace Scumm