87 lines
3.3 KiB
C
87 lines
3.3 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_umul32x64.c
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*
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* Copyright (C) 2016 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 <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: umul32x64
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*
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* Description:
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* Multiply one 32-bit and one 64-bit values, factor1 and factor2,
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* respectively, and return the truncated 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 umul32x64(uint32_t factor1, FAR const struct uint64_s *factor2,
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FAR struct uint64_s *product)
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{
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struct uint64_s part1;
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struct uint64_s part2;
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/* factor2 = factor2->ms << 32 + factor2->ls
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*
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* Full 128-bit product:
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* factor1 * factor2 = factor1 * (factor2->ms << 32) +
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* factor1 * factor2->ls
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*/
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/* Get part1 = factor1 * factor2->ms, shifting left by 32-bits
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* (truncating to 64-bits)
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*/
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part1.ms = factor1 * factor2->ms;
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part1.ls = 0;
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/* Get the full 64-bit part2 = factor1 * factor2->ls */
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umul32(factor1, factor2->ls, &part2);
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/* The product is then the sum */
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uadd64(&part1, &part2, product);
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}
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