mutter/cogl/cogl-util.h

/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2007,2008,2009,2010 Intel Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifndef __COGL_UTIL_H
#define __COGL_UTIL_H

#include <glib.h>
#include <math.h>

int
cogl_util_next_p2 (int a);

/* The signbit macro is defined by ISO C99 so it should be available,
   however if it's not we can fallback to an evil hack */
#ifdef signbit
#define cogl_util_float_signbit(x) signbit(x)
#else
/* This trick was stolen from here:
   http://lists.boost.org/Archives/boost/2006/08/108731.php

   It xors the integer reinterpretations of -1.0f and 1.0f. In theory
   they should only differ by the signbit so that gives a mask for the
   sign which we can just test against the value */
static inline gboolean
cogl_util_float_signbit (float x)
{
  static const union { float f; guint32 i; } negative_one = { -1.0f };
  static const union { float f; guint32 i; } positive_one = { +1.0f };
  union { float f; guint32 i; } value = { x };

  return !!((negative_one.i ^ positive_one.i) & value.i);
}
#endif

#endif /* __COGL_UTIL_H */