111 lines
3.5 KiB
C
111 lines
3.5 KiB
C
/****************************************************************************
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* libc/fixedmath/lib_b16sin.c
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*
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* Copyright (C) 2008, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <fixedmath.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define b16_P225 0x0000399a
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#define b16_P405284735 0x000067c1
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#define b16_1P27323954 0x000145f3
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: b16sin
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* Ref: http://lab.polygonal.de/2007/07/18/fast-and-accurate-sinecosine-approximation/
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****************************************************************************/
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b16_t b16sin(b16_t rad)
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{
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b16_t tmp1;
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b16_t tmp2;
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b16_t tmp3;
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/* Force angle into the good range */
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if (rad < -b16PI)
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{
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rad += b16TWOPI;
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}
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else if (rad > b16PI)
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{
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rad -= b16TWOPI;
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}
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/* tmp1 = 1.27323954 * rad
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* tmp2 = .405284735 * rad * rad
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*/
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tmp1 = b16mulb16(b16_1P27323954, rad);
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tmp2 = b16mulb16(b16_P405284735, b16sqr(rad));
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if (rad < 0)
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{
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/* tmp3 = 1.27323954 * rad + .405284735 * rad * rad */
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tmp3 = tmp1 + tmp2;
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}
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else
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{
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/* tmp3 = 1.27323954 * rad - 0.405284735 * rad * rad */
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tmp3 = tmp1 - tmp2;
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}
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/* tmp1 = tmp3*tmp3 */
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tmp1 = b16sqr(tmp3);
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if (tmp3 < 0)
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{
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/* tmp1 = tmp3 * -tmp3 */
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tmp1 = -tmp1;
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}
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/* Return sin = .225 * (tmp3 * (+/-tmp3) - tmp3) + tmp3 */
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return b16mulb16(b16_P225, (tmp1 - tmp3)) + tmp3;
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}
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