65 lines
2.3 KiB
C
65 lines
2.3 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* fls.c
|
|
* finds the last (most significant) bit that is set
|
|
*
|
|
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
|
|
*
|
|
*
|
|
* IDENTIFICATION
|
|
* src/port/fls.c
|
|
*
|
|
* This file was taken from FreeBSD to provide an implementation of fls()
|
|
* for platforms that lack it. Note that the operating system's version may
|
|
* be substantially more efficient than ours, since some platforms have an
|
|
* assembly instruction that does exactly this.
|
|
*
|
|
* The FreeBSD copyright terms follow.
|
|
*/
|
|
|
|
/*-
|
|
* Copyright (c) 1990, 1993
|
|
* The Regents of the University of California. All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 4. Neither the name of the University nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#include "c.h"
|
|
|
|
/*
|
|
* Find Last Set bit
|
|
*/
|
|
int
|
|
fls(int mask)
|
|
{
|
|
int bit;
|
|
|
|
if (mask == 0)
|
|
return (0);
|
|
for (bit = 1; mask != 1; bit++)
|
|
mask = (unsigned int) mask >> 1;
|
|
return (bit);
|
|
}
|