Application: gvSIG desktop » gvSIG raster

/* Copyright (C) 2001-2007 Peter Selinger.

   This file is part of Potrace. It is free software and it is covered

   by the GNU General Public License. See the file COPYING for details. */

/* $Id: bitops.h 147 2007-04-09 00:44:09Z selinger $ */

/* bits.h: this file defines some macros for bit manipulations. We

   provide a generic implementation, as well as machine- and

   compiler-specific fast implementations */

/* lobit: return the position of the rightmost "1" bit of an int, or

   32 if none. hibit: return 1 + the position of the leftmost "1" bit

   of an int, or 0 if none. Note: these functions work on 32-bit

   integers. */

#ifndef BITOPS_H

#define BITOPS_H

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

/* ---------------------------------------------------------------------- */

/* machine specific macros */

#if defined(HAVE_I386)

static inline unsigned int lobit(unsigned int x) {

  unsigned int res;

  asm ("bsf        %1,%0\n\t"

       "jnz        0f\n\t"

       "movl        $32,%0\n"

       "0:"

       : "=r" (res)

       : "r" (x));

  return res;

}

static inline unsigned int hibit(unsigned int x) {

  unsigned int res;                                        

  asm ("bsr        %1,%0\n\t"

       "jnz        0f\n\t"

       "movl        $-1,%0\n"

       "0:"

       : "=r" (res)

       : "r" (x));

  return res+1;

}

/* ---------------------------------------------------------------------- */

#else /* generic macros */

static inline unsigned int lobit(unsigned int x) {

  unsigned int res = 32;

  while (x & 0xffffff) {

    x <<= 8;

    res -= 8;

  }

  while (x) {

    x <<= 1;

    res -= 1;

  }

  return res;

}

static inline unsigned int hibit(unsigned int x) {

  unsigned int res = 0;

  while (x > 0xff) {

    x >>= 8;

    res += 8;

  }

  while (x) {

    x >>= 1;

    res += 1;

  }

  return res;

}

#endif 

#endif /* BITOPS_H */