fixpt.h

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/*                         F I X P T . H
 * BRL-CAD
 *
 * Copyright (c) 2004-2006 United States Government as represented by
 * the U.S. Army Research Laboratory.
 *
 * 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this file; see the file named COPYING for more
 * information.
 */

/** \addtogroup librt */
/*@{*/
/** @file fixpt.h
 *  Data structures and macros for dealing with integer-based
 *  fixed point math.
 *
 *  These macros use integer instructions for
 *  a special "fixed point" format.
 *  The fractional part is stored in 28-bit integer form,
 *  to prevent roundoff errors.
 *
 *  Author -
 *      Michael John Muuss
 *
 *  Source -
 *      SECAD/VLD Computing Consortium, Bldg 394
 *      The U. S. Army Ballistic Research Laboratory
 *      Aberdeen Proving Ground, Maryland  21005
 *
 *
 *  $Header: /cvsroot/brlcad/brlcad/src/librt/fixpt.h,v 14.9 2006/01/18 06:46:17 brlcad Exp $
 */
/*@}*/

#ifndef FIXPT_H
#define FIXPT_H seen

#define FIXPT_SCALE     ((1<<28)-1)
struct fixpt  {
        int     i;
        int     f;              /* Ranges 0 to FIXPT_SCALE-1 */
};

#define FIXPT_FLOAT( fp, fl )   { \
        register double d = fl; \
        fp.f = (d - (fp.i = (int)d)) * FIXPT_SCALE; \
        FIXPT_NORMALIZE(fp); }

#define FLOAT_FIXPT( fp )  ( fp.i + ((double)fp.f)/FIXPT_SCALE )

#define FIXPT_NORMALIZE(fp)     { \
        if( fp.f < 0 )  { \
                do {  \
                        fp.i--; \
                        fp.f += FIXPT_SCALE; \
                } while( fp.f < 0 ); \
        } else if( fp.f >= FIXPT_SCALE )  { \
                do { \
                        fp.i++; \
                        fp.f -= FIXPT_SCALE; \
                } while( fp.f >= FIXPT_SCALE ); \
        } }

#define FIXPT_ROUND(fp)         { \
        if( fp.f > FIXPT_SCALE/2 )  { \
                if( fp.i >= 0 ) fp.i++; \
                else fp.i--; \
        }  fp.f = 0; }

#define FIXPT_ADD2( o, a, b )   {\
        o.i = a.i + b.i; \
        o.f = a.f + b.f; \
        FIXPT_NORMALIZE(o); }

#define PR_FIX( str, fp )       bu_log("%s = %2d+x%8.8x\n", str, fp.i, fp.f )

#define PR_FIX2( str, fp )      bu_log("%s = (%2d+x%8.8x,%2d+x%8.8x)\n", \
                                str, fp[0].i, fp[0].f, fp[1].i, fp[1].f )

#endif /* FIXPT_H */

/*
 * Local Variables:
 * mode: C
 * tab-width: 8
 * c-basic-offset: 4
 * indent-tabs-mode: t
 * End:
 * ex: shiftwidth=4 tabstop=8
 */

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