83 lines
3.2 KiB
C
83 lines
3.2 KiB
C
/****************************************************************************
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* libc/fixedmath/lib_usub64.c
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*
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* Copyright (C) 2016 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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/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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