96 lines
2.7 KiB
C
96 lines
2.7 KiB
C
/****************************************************************************
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* libs/libc/fixedmath/lib_b16sin.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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:
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* 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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