79 lines
2.6 KiB
C
79 lines
2.6 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_umul32.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/lib/math32.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: umul32
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*
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* Description:
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* Multiply two 32-bit values, factor1 and factor2, and return the
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* full 64-bit product.
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*
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* Input Parameters:
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* factor1 and factor2 - The values to be multiplied
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* product - The location to return the product of the two values.
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*
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****************************************************************************/
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void umul32(uint32_t factor1, uint32_t factor2, FAR struct uint64_s *product)
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{
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struct uint64_s part2;
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uint32_t ms1;
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uint32_t ls1;
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uint32_t ms2;
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uint32_t ls2;
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uint32_t tmp;
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/* factor1 = ms1 << 16 + ls1
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* factor2 = ms2 << 16 + ls2
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*/
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ms1 = factor1 >> 16;
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ls1 = factor1 & 0x0000ffff;
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ms2 = factor2 >> 16;
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ls2 = factor2 & 0x0000ffff;
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/* factor1 * factor2 = (ms1 * ms2 << 32) +
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* ls1 * (ms2 << 16) + ls2 * (ms1 << 16) +
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* ls1 * ls2
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* part1 = (ms1 * ms2 << 32) + ls1 * ls2
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* part2 = ls1 * (ms2 << 16) + ls2 * (ms1 << 16)
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* factor1 * factor2 = part1 + part2
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*/
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product->ms = ms1 * ms2;
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product->ls = ls1 * ls2;
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tmp = ls1 * ms2 + ls2 * ms1;
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part2.ms = tmp >> 16;
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part2.ls = tmp << 16;
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uadd64(product, &part2, product);
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}
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