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/****************************************************************************
* lib/math/lib_b16atan2.c
*
* Copyright (C) 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <fixedmath.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define B16_C1 0x00000373 /* 0.013480470 */
#define B16_C2 0x00000eb7 /* 0.057477314 */
#define B16_C3 0x00001f0a /* 0.121239071 */
#define B16_C4 0x00003215 /* 0.195635925 */
#define B16_C5 0x0000553f /* 0.332994597 */
#define B16_C6 0x00010000 /* 0.999995630 */
#define B16_HALFPI 0x00019220 /* 1.570796327 */
#define B16_PI 0x00032440 /* 3.141592654 */
#ifndef MAX
# define MAX(a,b) (a > b ? a : b)
#endif
#ifndef MIN
# define MIN(a,b) (a < b ? a : b)
#endif
#ifndef ABS
# define ABS(a) (a < 0 ? -a : a)
#endif
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: b16atan2
*
* Description:
* atan2 calculates the arctangent of y/x. (Based on a algorithm I saw
* posted on the internet... now I have lost the link -- sorry).
*
****************************************************************************/
b16_t b16atan2(b16_t y, b16_t x)
{
b16_t t0;
b16_t t1;
b16_t t2;
b16_t t3;
t2 = ABS(x);
t1 = ABS(y);
t0 = MAX(t2, t1);
t1 = MIN(t2, t1);
t2 = ub16inv(t0);
t2 = b16mulb16(t1, t2);
t3 = b16mulb16(t2, t2);
t0 = - B16_C1;
t0 = b16mulb16(t0, t3) + B16_C2;
t0 = b16mulb16(t0, t3) - B16_C3;
t0 = b16mulb16(t0, t3) + B16_C4;
t0 = b16mulb16(t0, t3) - B16_C5;
t0 = b16mulb16(t0, t3) + B16_C6;
t2 = b16mulb16(t0, t2);
t2 = (ABS(y) > ABS(x)) ? B16_HALFPI - t2 : t2;
t2 = (x < 0) ? B16_PI - t2 : t2;
t2 = (y < 0) ? -t2 : t2;
return t2;
}
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