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82 lines
2.2 KiB
82 lines
2.2 KiB
/*
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* Copyright 2009-2012 Samy Al Bahra.
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* All rights reserved.
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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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* 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 the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _CK_BACKOFF_H
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#define _CK_BACKOFF_H
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#include <ck_cc.h>
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#ifndef CK_BACKOFF_CEILING
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#define CK_BACKOFF_CEILING ((1 << 21) - 1)
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#endif
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#define CK_BACKOFF_INITIALIZER ((1 << 9) - 1)
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typedef volatile unsigned int ck_backoff_t;
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/*
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* This is an exponential back-off implementation.
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*/
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CK_CC_INLINE static void
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ck_backoff_eb(volatile unsigned int *c)
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{
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volatile unsigned int i;
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unsigned int ceiling;
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ceiling = *c;
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for (i = 0; i < ceiling; i++);
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ceiling *= ceiling;
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ceiling &= CK_BACKOFF_CEILING;
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ceiling += CK_BACKOFF_INITIALIZER;
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*c = ceiling;
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return;
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}
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/*
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* This is a geometric back-off implementation.
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*/
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CK_CC_INLINE static void
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ck_backoff_gb(volatile unsigned int *c)
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{
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volatile unsigned int i;
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unsigned int ceiling;
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ceiling = *c;
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for (i = 0; i < ceiling; i++);
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ceiling <<= 1;
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ceiling &= CK_BACKOFF_CEILING;
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*c = ceiling;
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return;
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}
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#endif /* _CK_BACKOFF_H */
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