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      1 /*	$NetBSD: average.h,v 1.2 2021/12/19 10:38:38 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2020 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #ifndef	_LINUX_AVERAGE_H_
     30 #define	_LINUX_AVERAGE_H_
     31 
     32 #define	DECLARE_EWMA(NAME, PREC, RATE)					      \
     33 struct ewma_##NAME {							      \
     34 	unsigned long ewma_state;					      \
     35 };									      \
     36 									      \
     37 static inline void							      \
     38 ewma_##NAME##_init(struct ewma_##NAME *ewma)				      \
     39 {									      \
     40 	ewma->ewma_state = 0;						      \
     41 }									      \
     42 									      \
     43 static inline unsigned long						      \
     44 ewma_##NAME##_read(struct ewma_##NAME *ewma)				      \
     45 {									      \
     46 	return ewma->ewma_state >> (PREC);				      \
     47 }									      \
     48 									      \
     49 static inline void							      \
     50 ewma_##NAME##_add(struct ewma_##NAME *ewma, unsigned long sample)	      \
     51 {									      \
     52 	const unsigned long shift = ilog2(RATE);			      \
     53 	const unsigned long state = ewma->ewma_state;			      \
     54 									      \
     55 	sample <<= (PREC);						      \
     56 	if (state == 0) {						      \
     57 		ewma->ewma_state = sample;				      \
     58 		return;							      \
     59 	}								      \
     60 	ewma->ewma_state = (((state << shift) - state) + sample) >> shift;    \
     61 }
     62 
     63 #endif	/* _LINUX_AVERAGE_H_ */
     64