b7c451c5a4
Gregory Nutt has submitted the SGA and we can migrate the licenses to Apache. Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
87 lines
3.1 KiB
C
87 lines
3.1 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_umul64.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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: umul64
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*
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* Description:
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* Multiply two 64-bit values, factor1 and factor2, and return the
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* 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 umul64(FAR const struct uint64_s *factor1,
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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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/* factor1 = factor1->ms << 32 + factor1->ls
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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->ms * factor2->ms << 64) +
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* factor1->ls * (factor2->ms << 32) +
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* factor2->ls * (factor1->ms << 32) +
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* factor1->ls * factor2->ls
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*
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* Truncated, 64-bit product:
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* factor1 * factor2 = (factor1->ls * factor2->ms +
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* factor2->ls * factor1->ms) << 32) +
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* factor1->ls * factor2->ls
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*
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* part1 = (factor1->ls * factor2->ms +
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* factor2->ls * factor1->ms) << 32)
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* part2 = factor1->ls * factor2->ls
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* factor1 * factor2 = part1 + part2
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*/
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/* Get part1 = factor1->ls * factor2->ms + factor2->ls * factor1->ms,
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* shifting left by 32-bits (truncating to 64-bits)
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*/
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part1.ms = factor1->ls * factor2->ms +
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factor2->ls * factor2->ms;
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part1.ls = 0;
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/* Get the full 64-bit part2 = factor1->ls * factor2->ls */
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umul32(factor1->ls, 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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