Home | History | Annotate | Line # | Download | only in string
popcount64.c revision 1.4 
      1 /*	$NetBSD: popcount64.c,v 1.4 2009/07/21 19:56:55 drochner Exp $	*/
      2 /*-
      3  * Copyright (c) 2009 The NetBSD Foundation, Inc.
      4  * All rights reserved.
      5  *
      6  * This code is derived from software contributed to The NetBSD Foundation
      7  * by Joerg Sonnenberger.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  *
     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
     17  *    the documentation and/or other materials provided with the
     18  *    distribution.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
     24  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
     26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     27  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     30  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #include <sys/cdefs.h>
     35 __RCSID("$NetBSD: popcount64.c,v 1.4 2009/07/21 19:56:55 drochner Exp $");
     36 
     37 #if !defined(_KERNEL) && !defined(_STANDALONE)
     38 #include <limits.h>
     39 #include <strings.h>
     40 #else
     41 #include <lib/libkern/libkern.h>
     42 #include <machine/limits.h>
     43 #endif
     44 
     45 /*
     46  * If uint64_t is larger than size_t, the follow assumes that
     47  * splitting into 32bit halfes is faster.
     48  *
     49  * The native pocount64 version is based on the same ideas as popcount64(3),
     50  * see popcount64.c for comments.
     51  */
     52 
     53 #if SIZE_MAX < 0xffffffffffffffffULL
     54 unsigned int
     55 popcount64(uint64_t v)
     56 {
     57 	return popcount32((uint32_t)(v >> 32)) +
     58 	    popcount32((uint32_t)(v & 0xffffffffULL));
     59 }
     60 #else
     61 unsigned int
     62 popcount64(uint64_t v)
     63 {
     64 	unsigned int c;
     65 
     66 	v = v - ((v >> 1) & 0x5555555555555555ULL);
     67 	v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL);
     68 	v = ((v + (v >> 4)) & 0x0f0f0f0f0f0f0f0fULL) * 0x0101010101010101ULL;
     69 	c = v >> 56;
     70 
     71 	return c;
     72 }
     73 #endif
     74 
     75 #if ULONG_MAX == 0xffffffffffffffffULL
     76 __strong_alias(popcountl, popcount64)
     77 #endif
     78 
     79 #if ULLONG_MAX == 0xffffffffffffffffULL
     80 __strong_alias(popcountll, popcount64)
     81 #endif
     82 
     83