5cb8226727
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5331 42af7a65-404d-4744-a932-0658087f49c3
136 lines
4.3 KiB
C
136 lines
4.3 KiB
C
/************************************************************
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* libc/fixedmath/lib_rint.c
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*
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* Copyright (C) 2007, 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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* Compilation Switches
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************************************************************/
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/************************************************************
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* Included Files
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************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <stdlib.h>
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/************************************************************
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* Definitions
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************************************************************/
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/************************************************************
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* Private Type Declarations
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************************************************************/
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/************************************************************
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* Private Function Prototypes
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************************************************************/
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/**********************************************************
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* Global Constant Data
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**********************************************************/
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/************************************************************
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* Global Variables
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************************************************************/
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/**********************************************************
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* Private Constant Data
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**********************************************************/
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/************************************************************
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* Private Variables
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************************************************************/
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double_t rint(double_t x)
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{
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double_t ret;
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/* If the current rounding mode rounds toward negative
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* infinity, rint() is identical to floor(). If the current
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* rounding mode rounds toward positive infinity, rint() is
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* identical to ceil().
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*/
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#if defined(CONFIG_FP_ROUND_POSITIVE) && CONFIG_FP_ROUNDING_POSITIVE != 0
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ret = ceil(x);
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#elif defined(CONFIG_FP_ROUND_NEGATIVE) && CONFIG_FP_ROUNDING_NEGATIVE != 0
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ret = floor(x);
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#else
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/* In the default rounding mode (round to nearest), rint(x) is the
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* integer nearest x with the additional stipulation that if
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* |rint(x)-x|=1/2, then rint(x) is even.
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*/
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long dwinteger = (long)x;
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double_t fremainder = x - (double_t)dwinteger;
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if (x < 0.0)
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{
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/* fremainder should be in range 0 .. -1 */
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if (fremainder == -0.5)
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{
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dwinteger = ((dwinteger+1)&~1);
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}
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else if (fremainder < -0.5)
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{
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dwinteger--;
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}
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}
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else
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{
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/* fremainder should be in range 0 .. 1 */
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if (fremainder == 0.5)
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{
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dwinteger = ((dwinteger+1)&~1);
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}
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else if (fremainder > 0.5)
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{
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dwinteger++;
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}
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}
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ret = (double_t)dwinteger;
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#endif
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return ret;
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}
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