102 lines
3.9 KiB
C
102 lines
3.9 KiB
C
/****************************************************************************
|
|
* libc/fixedmath/lib_umul64.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/math32.h>
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: umul64
|
|
*
|
|
* Description:
|
|
* Multiply two 64-bit values, factor1 and factor2, 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 umul64(FAR const struct uint64_s *factor1,
|
|
FAR const struct uint64_s *factor2,
|
|
FAR struct uint64_s *product)
|
|
{
|
|
struct uint64_s part1;
|
|
struct uint64_s part2;
|
|
|
|
/* factor1 = factor1->ms << 32 + factor1->ls
|
|
* factor2 = factor2->ms << 32 + factor2->ls
|
|
*
|
|
* Full 128-bit product:
|
|
* factor1 * factor2 = (factor1->ms * factor2->ms << 64) +
|
|
* factor1->ls * (factor2->ms << 32) +
|
|
* factor2->ls * (factor1->ms << 32) +
|
|
* factor1->ls * factor2->ls
|
|
*
|
|
* Truncated, 64-bit product:
|
|
* factor1 * factor2 = (factor1->ls * factor2->ms +
|
|
* factor2->ls * factor1->ms) << 32) +
|
|
* factor1->ls * factor2->ls
|
|
*
|
|
* part1 = (factor1->ls * factor2->ms +
|
|
* factor2->ls * factor1->ms) << 32)
|
|
* part2 = factor1->ls * factor2->ls
|
|
* factor1 * factor2 = part1 + part2
|
|
*/
|
|
|
|
/* Get part1 = factor1->ls * factor2->ms + factor2->ls * factor1->ms,
|
|
* shifting left by 32-bits (truncating to 64-bits)
|
|
*/
|
|
|
|
part1.ms = factor1->ls * factor2->ms +
|
|
factor2->ls * factor2->ms;
|
|
part1.ls = 0;
|
|
|
|
/* Get the full 64-bit part2 = factor1->ls * factor2->ls */
|
|
|
|
umul32(factor1->ls, factor2->ls, &part2);
|
|
|
|
/* The product is then the sum */
|
|
|
|
uadd64(&part1, &part2, product);
|
|
}
|