137 lines
3.9 KiB
C
137 lines
3.9 KiB
C
/****************************************************************************
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* libs/libc/fixedmath/lib_ubsqrt.c
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*
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* Copyright (C) 2014,2017 Jussi Kivilinna <jussi.kivilinna@haltian.com>
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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 <nuttx/config.h>
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#include <fixedmath.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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#ifdef CONFIG_HAVE_LONG_LONG
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/****************************************************************************
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* Name: ub32sqrtub16
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*
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* Description:
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* ub32sqrtub16 calculates square root for 'a'
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*
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****************************************************************************/
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ub16_t ub32sqrtub16(ub32_t a)
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{
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uint64_t n = a;
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uint64_t xk = n;
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/* Direct conversion of ub32_t to uint64_t is same operation as multiplying
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* 'a' by 2^32, therefore n = a * 2^32.
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*/
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if (xk == UINT64_MAX)
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{
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/* Avoid 'xk + n / xk' overflow on first iteration. */
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xk = (uint64_t)1 << 63;
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}
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do
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{
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uint64_t xk1 = (xk + n / xk) >> 1;
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if (xk1 >= xk)
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{
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break;
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}
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xk = xk1;
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}
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while (1);
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/* 'xk' now holds 'sqrt(n)' => 'sqrt(a * 2^32)' => 'sqrt(a) * 2^16', thus
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* 'xk' holds square root of 'a' in ub16_t format.
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*/
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return (ub16_t)xk;
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}
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#endif
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/****************************************************************************
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* Name: ub16sqrtub8
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*
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* Description:
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* ub16sqrtub8 calculates square root for 'a'
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*
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****************************************************************************/
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ub8_t ub16sqrtub8(ub16_t a)
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{
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uint32_t n = a;
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uint32_t xk = n;
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/* Direct conversion of ub16_t to uint32_t is same operation as multiplying
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* 'a' by 2^16, therefore n = a * 2^16.
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*/
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if (xk == UINT32_MAX)
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{
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/* Avoid 'xk + n / xk' overflow on first iteration. */
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xk = (uint32_t)1 << 31;
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}
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do
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{
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uint32_t xk1 = (xk + n / xk) >> 1;
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if (xk1 >= xk)
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{
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break;
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}
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xk = xk1;
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}
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while (1);
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/* 'xk' now holds 'sqrt(n)' => 'sqrt(a * 2^16)' => 'sqrt(a) * 2^8', thus
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* 'xk' holds square root of 'a' in ub8_t format.
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*/
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return (ub8_t)xk;
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}
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