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108 lines
3.8 KiB
108 lines
3.8 KiB
/**************************************************************************** |
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* lib/math/lib_b16atan2.c |
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* |
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* Copyright (C) 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_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 MAX |
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# define MAX(a,b) (a > b ? a : b) |
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#endif |
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#ifndef MIN |
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# define MIN(a,b) (a < b ? a : b) |
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#endif |
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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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* Global 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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