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