68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_usub64.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: usub64
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*
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* Description:
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* Subtract two 64-bit values and return the 64-bit difference.
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*
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* Input Parameters:
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* minuend - The number from which another number (the Subtrahend) is
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* to be subtracted.
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* subtrahend - The number that is to be subtracted.
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* difference - The location to return the difference of the two values.
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* difference may the same as one of minuend or subtrahend.
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*
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****************************************************************************/
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void usub64(FAR const struct uint64_s *minuend,
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FAR const struct uint64_s *subtrahend,
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FAR struct uint64_s *difference)
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{
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/* Get the MS part of the difference */
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difference->ms = minuend->ms - subtrahend->ms;
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/* Check for a borrow, i.e., that is when:
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*
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* subtrahend->ls > minuend->ls
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*/
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if (subtrahend->ls > minuend->ls)
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{
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difference->ms--;
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}
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/* Get the LS part of the difference */
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difference->ls = minuend->ls - subtrahend->ls;
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}
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