nuttx/libs/libc/misc/lib_umul32x64.c
Alin Jerpelea b7c451c5a4 libs: Gregory Nutt: update licenses to Apache
Gregory Nutt has submitted the SGA and we can migrate the licenses
 to Apache.

Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
2021-04-02 11:12:25 -05:00

72 lines
2.5 KiB
C

/****************************************************************************
* libs/libc/misc/lib_umul32x64.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* 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);
}