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- /****************************************************************************
- * libs/libc/misc/lib_umul32.c
- *
- * Copyright (C) 2016 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- * used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/lib/math32.h>
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: umul32
- *
- * Description:
- * Multiply two 32-bit values, factor1 and factor2, and return the
- * full 64-bit product.
- *
- * Input Parameters:
- * factor1 and factor2 - The values to be multiplied
- * product - The location to return the product of the two values.
- *
- ****************************************************************************/
- void umul32(uint32_t factor1, uint32_t factor2, FAR struct uint64_s *product)
- {
- struct uint64_s part2;
- uint32_t ms1;
- uint32_t ls1;
- uint32_t ms2;
- uint32_t ls2;
- uint32_t tmp;
- /* factor1 = ms1 << 16 + ls1
- * factor2 = ms2 << 16 + ls2
- */
- ms1 = factor1 >> 16;
- ls1 = factor1 & 0x0000ffff;
- ms2 = factor2 >> 16;
- ls2 = factor2 & 0x0000ffff;
- /* factor1 * factor2 = (ms1 * ms2 << 32) +
- * ls1 * (ms2 << 16) + ls2 * (ms1 << 16) +
- * ls1 * ls2
- * part1 = (ms1 * ms2 << 32) + ls1 * ls2
- * part2 = ls1 * (ms2 << 16) + ls2 * (ms1 << 16)
- * factor1 * factor2 = part1 + part2
- */
- product->ms = ms1 * ms2;
- product->ls = ls1 * ls2;
- tmp = ls1 * ms2 + ls2 * ms1;
- part2.ms = tmp >> 16;
- part2.ls = tmp << 16;
- uadd64(product, &part2, product);
- }
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