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math64.h revision 1.10 
      1 /*	$NetBSD: math64.h,v 1.10 2021/12/19 11:23:09 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2013 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Taylor R. Campbell.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #ifndef _LINUX_MATH64_H_
     33 #define _LINUX_MATH64_H_
     34 
     35 #include <sys/types.h>
     36 
     37 #include <asm/div64.h>
     38 
     39 #include <linux/types.h>
     40 
     41 static inline int64_t
     42 div64_u64(int64_t dividend, uint64_t divisor)
     43 {
     44 	return dividend / divisor;
     45 }
     46 
     47 static inline int64_t
     48 div_u64(int64_t dividend, uint32_t divisor)
     49 {
     50 	return dividend / divisor;
     51 }
     52 
     53 static inline int64_t
     54 div64_s64(int64_t dividend, int64_t divisor)
     55 {
     56 	return dividend / divisor;
     57 }
     58 
     59 static inline int64_t
     60 div_s64(int64_t dividend, int32_t divisor)
     61 {
     62 	return dividend / divisor;
     63 }
     64 
     65 static inline uint32_t
     66 div_u64_rem(uint64_t dividend, uint32_t divisor, uint32_t *rem)
     67 {
     68 	*rem = dividend % divisor;
     69 	return dividend / divisor;
     70 }
     71 
     72 static inline uint64_t
     73 div64_u64_rem(uint64_t dividend, uint64_t divisor, uint64_t *rem)
     74 {
     75 	*rem = dividend % divisor;
     76 	return dividend / divisor;
     77 }
     78 
     79 static inline uint64_t
     80 mul_u32_u32(uint32_t a, uint32_t b)
     81 {
     82 	return (uint64_t)a * (uint64_t)b;
     83 }
     84 
     85 /* return floor((a*b) / 2^c) */
     86 static inline uint64_t
     87 mul_u64_u32_shr(uint64_t a, uint32_t b, unsigned c)
     88 {
     89 	/* 2^32 a_hi + a_lo := a */
     90 	uint64_t a_hi = a >> 32;
     91 	uint64_t a_lo = a & 0xffffffffU;
     92 
     93 	if (c >= 32) {
     94 		/* (a*b) / 2^c = (a_hi b + a_lo b / 2^32) / 2^{c - 32} */
     95 		return ((a_hi * b) + ((a_lo * b) >> 32)) >> (c - 32);
     96 	} else {
     97 		/* (a*b) / 2^c = 2^{32 - c} a_hi b + a_lo b / 2^c */
     98 		return ((a_hi * b) << (32 - c)) + ((a_lo * b) >> c);
     99 	}
    100 }
    101 
    102 #endif  /* _LINUX_MATH64_H_ */
    103