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121 lines
2.6 KiB
C++
121 lines
2.6 KiB
C++
/*
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* \brief Table of sine and cosine values in 16.16 fractional format
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* \author Norman Feske
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* \date 2015-06-19
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*/
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/*
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* Copyright (C) 2015-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__NANO3D__SINCOS_FRAC16_H_
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#define _INCLUDE__NANO3D__SINCOS_FRAC16_H_
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namespace Nano3d { class Sincos_frac16; };
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class Nano3d::Sincos_frac16
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{
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public:
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enum { STEPS = 1024 };
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private:
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int _table[STEPS + STEPS/4];
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public:
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inline Sincos_frac16();
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int sin(int angle) const { return _table[angle & (STEPS - 1)]; }
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int cos(int angle) const { return sin(angle + STEPS/4); }
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};
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Nano3d::Sincos_frac16::Sincos_frac16()
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{
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int const cos_mid = 0x7fff;
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int const cos_low = 0x310b; /* cos(360/1024) = 0x7fff6216 */
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int const sin_mid = 0x00c9;
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int const sin_low = 0x07c4; /* sin(360/1024) = 0x00c90f87 */
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int x_mid = 0x7fff;
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int x_low = 0x7fff; /* x = 1.0 */
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int y_mid = 0;
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int y_low = 0; /* y = 0.0 */
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int nx_high, ny_high;
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int nx_mid, nx_low;
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int ny_mid, ny_low;
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for (unsigned i = 0; i < (STEPS >> 2); i++) {
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/* store current sine value */
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_table[i] = y_mid << 1;
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_table[(STEPS >> 1) - i - 1] = y_mid << 1;
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_table[i + (STEPS >> 1)] = -y_mid << 1;
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_table[STEPS - i - 1] = -y_mid << 1;
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/* rotate sin/cos values */
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/* x' = x*cos - y*sin */
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nx_low = x_low*cos_low
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- y_low*sin_low;
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nx_mid = x_low*cos_mid + x_mid*cos_low
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- y_low*sin_mid - y_mid*sin_low;
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nx_mid += (nx_low >> 14);
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nx_high = x_mid*cos_mid
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- y_mid*sin_mid
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+ (nx_mid >> 15);
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nx_high = nx_high << 1;
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/* y' = y*cos + x*sin */
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ny_low = y_low*cos_low
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+ x_low*sin_low;
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ny_mid = y_low*cos_mid + y_mid*cos_low
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+ x_low*sin_mid + x_mid*sin_low
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+ (ny_low >> 14);
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ny_high = y_mid*cos_mid
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+ x_mid*sin_mid
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+ (ny_mid >> 15);
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ny_high = ny_high << 1;
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/* use new sin/cos values for next iteration, preserve sign */
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x_low = (nx_high & 0x80000000) ? (nx_high | (~0 << 16)) : (nx_high & 0xffff);
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x_low = x_low >> 1;
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x_mid = nx_high >> 16;
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y_low = (ny_high & 0x80000000) ? (ny_high | (~0 << 16)) : (ny_high & 0xffff);
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y_low = y_low >> 1;
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y_mid = ny_high >> 16;
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}
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}
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namespace Nano3d {
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static Sincos_frac16 const &sincos_frac16()
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{
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static Sincos_frac16 inst;
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return inst;
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}
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static inline int sin_frac16(int angle) { return sincos_frac16().sin(angle); }
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static inline int cos_frac16(int angle) { return sincos_frac16().cos(angle); }
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};
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#endif /* _INCLUDE__NANO3D__SINCOS_FRAC16_H_ */
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