87 lines
2.9 KiB
C
87 lines
2.9 KiB
C
/****************************************************************************
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* libs/libc/fixedmath/lib_b16atan2.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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#include <sys/param.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define B16_C1 0x00000373 /* 0.013480470 */
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#define B16_C2 0x00000eb7 /* 0.057477314 */
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#define B16_C3 0x00001f0a /* 0.121239071 */
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#define B16_C4 0x00003215 /* 0.195635925 */
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#define B16_C5 0x0000553f /* 0.332994597 */
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#define B16_C6 0x00010000 /* 0.999995630 */
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#define B16_HALFPI 0x00019220 /* 1.570796327 */
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#define B16_PI 0x00032440 /* 3.141592654 */
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#ifndef ABS
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# define ABS(a) ((a) < 0 ? -(a) : (a))
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: b16atan2
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*
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* Description:
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* atan2 calculates the arctangent of y/x. (Based on a algorithm I saw
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* posted on the internet... now I have lost the link -- sorry).
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*
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****************************************************************************/
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b16_t b16atan2(b16_t y, b16_t x)
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{
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b16_t t0;
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b16_t t1;
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b16_t t2;
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b16_t t3;
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t2 = ABS(x);
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t1 = ABS(y);
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t0 = MAX(t2, t1);
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t1 = MIN(t2, t1);
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t2 = ub16inv(t0);
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t2 = b16mulb16(t1, t2);
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t3 = b16mulb16(t2, t2);
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t0 = - B16_C1;
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t0 = b16mulb16(t0, t3) + B16_C2;
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t0 = b16mulb16(t0, t3) - B16_C3;
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t0 = b16mulb16(t0, t3) + B16_C4;
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t0 = b16mulb16(t0, t3) - B16_C5;
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t0 = b16mulb16(t0, t3) + B16_C6;
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t2 = b16mulb16(t0, t2);
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t2 = (ABS(y) > ABS(x)) ? B16_HALFPI - t2 : t2;
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t2 = (x < 0) ? B16_PI - t2 : t2;
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t2 = (y < 0) ? -t2 : t2;
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return t2;
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}
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