libxfs/xfs_rtbit.c

   1 /*
   2  * Copyright (c) 2000 Silicon Graphics, Inc.  All Rights Reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it would be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  11  *
  12  * Further, this software is distributed without any warranty that it is
  13  * free of the rightful claim of any third person regarding infringement
  14  * or the like.  Any license provided herein, whether implied or
  15  * otherwise, applies only to this software file.  Patent licenses, if
  16  * any, provided herein do not apply to combinations of this program with
  17  * other software, or any other product whatsoever.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write the Free Software Foundation, Inc., 59
  21  * Temple Place - Suite 330, Boston MA 02111-1307, USA.
  22  *
  23  * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
  24  * Mountain View, CA  94043, or:
  25  *
  26  * http://www.sgi.com
  27  *
  28  * For further information regarding this notice, see:
  29  *
  30  * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
  31  */
  32
  33 /*
  34  * XFS bit manipulation routines, used only in realtime code.
  35  */
  36
  37 #include <xfs.h>
  38
  39 /*
  40  * xfs_lowbit32: get low bit set out of 32-bit argument, -1 if none set.
  41  */
  42 int
  43 xfs_lowbit32(
  44         __uint32_t      v)
  45 {
  46         int             i;
  47
  48         if (v & 0x0000ffff)
  49                 if (v & 0x000000ff)
  50                         i = 0;
  51                 else
  52                         i = 8;
  53         else if (v & 0xffff0000)
  54                 if (v & 0x00ff0000)
  55                         i = 16;
  56                 else
  57                         i = 24;
  58         else
  59                 return -1;
  60         return i + xfs_lowbit[(v >> i) & 0xff];
  61 }