121 lines
3.1 KiB
C
121 lines
3.1 KiB
C
/****************************************************************************
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* libs/libc/fixedmath/lib_ubsqrt.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 <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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while (xk)
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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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/* '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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while (xk)
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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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/* '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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