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51c11efbbc
A new internal table has been added so that no if checks need to be performed for the at() lookup. The old table can still be accessed using getTable or atLegacy(). at() and atLegacy() return the same values, but at() is faster.
83 lines
2.5 KiB
C++
83 lines
2.5 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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// Based on eos' sine tables
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#include "common/scummsys.h"
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#include "common/sinetables.h"
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namespace Common {
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SineTable::SineTable(int nPoints) {
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assert((nPoints >= 16) && (nPoints <= 65536)); // log2 space is in [4,16]
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assert(nPoints % 4 == 0);
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_nPoints = nPoints;
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_radResolution = 2.0 * M_PI / _nPoints;
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_refSize = _nPoints / 4;
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_tableEOS = new float[_nPoints / 2];
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_table = new float[_nPoints];
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for (int i = 0; i < _nPoints; i++)
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_table[i] = sin(i * _radResolution);
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// Table contains sin(2*pi*i/_nPoints) for 0<=i<_nPoints/4,
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// followed by _nPoints/2<=i<3_nPoints/4
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for (int i = 0; i < _nPoints / 4; i++)
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_tableEOS[i] = sin(i * _radResolution);
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for (int i = 0; i < _nPoints / 4; i++)
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_tableEOS[_nPoints / 4 + i] = -_tableEOS[i];
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}
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float SineTable::at(int index) const {
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assert((index >= 0) && (index < _nPoints));
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return _table[index];
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}
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float SineTable::atLegacy(int index) const {
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assert((index >= 0) && (index < _nPoints));
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if (index < _refSize)
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// [0,pi/2)
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return _tableEOS[index];
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if (index == _refSize)
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// pi/2
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return 1.0f; // sin(pi/2) = 1.0
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if ((index > _refSize) && (index < 2 * _refSize))
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// (pi/2,pi)
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return _tableEOS[2 * _refSize - index];
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if ((index >= 2 * _refSize) && (index < 3 * _refSize))
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// [pi,3/2pi)
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return -_tableEOS[index - 2 * _refSize];
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if ((index > 3 * _refSize) && (index < _nPoints))
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// (3/2pi,2pi)
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return -_tableEOS[_nPoints - index];
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return -1.0f; // sin(3pi/2) = -1.0
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}
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SineTable::~SineTable() {
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delete[] _tableEOS;
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delete[] _table;
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}
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} // End of namespace Common
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