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math/sinetables.cpp

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+/* 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+// Based on eos' sine tables
+
+#include "math/sinetables.h"
+
+namespace Math {
+
+SineTable::SineTable(int nPoints) {
+	assert((nPoints >= 16) && (nPoints <= 65536)); // log2 space is in [4,16]
+	assert(nPoints % 4 == 0);
+
+	_nPoints = nPoints;
+	_radResolution = 2.0 * M_PI / _nPoints;
+	_refSize = _nPoints / 4;
+	_tableEOS = new float[_nPoints / 2];
+	_table = new float[_nPoints];
+
+	for (int i = 0; i < _nPoints; i++)
+		_table[i] = sin(i * _radResolution);
+
+	// Table contains sin(2*pi*i/_nPoints) for 0<=i<_nPoints/4,
+	// followed by _nPoints/2<=i<3_nPoints/4
+	for (int i = 0; i < _nPoints / 4; i++)
+		_tableEOS[i] = sin(i * _radResolution);
+
+	for (int i = 0; i < _nPoints / 4; i++)
+		_tableEOS[_nPoints / 4 + i] = -_tableEOS[i];
+}
+
+float SineTable::at(int index) const {
+	assert((index >= 0) && (index < _nPoints));
+	return _table[index];
+}
+
+float SineTable::atLegacy(int index) const {
+	assert((index >= 0) && (index < _nPoints));
+	if (index < _refSize)
+		// [0,pi/2)
+		return _tableEOS[index];
+	if (index == _refSize)
+		// pi/2
+		return 1.0f; // sin(pi/2) = 1.0
+	if ((index > _refSize) && (index < 2 * _refSize))
+		// (pi/2,pi)
+		return _tableEOS[2 * _refSize - index];
+	if ((index >= 2 * _refSize) && (index < 3 * _refSize))
+		// [pi,3/2pi)
+		return -_tableEOS[index - 2 * _refSize];
+	if ((index > 3 * _refSize) && (index < _nPoints))
+		// (3/2pi,2pi)
+		return -_tableEOS[_nPoints - index];
+	return -1.0f; // sin(3pi/2) = -1.0
+}
+
+SineTable::~SineTable() {
+	delete[] _tableEOS;
+	delete[] _table;
+}
+
+} // End of namespace Math