nuttx/libc/math/lib_floorf.c

/****************************************************************************
 * libc/math/lib_floorf.c
 *
 * This file is a part of NuttX:
 *
 *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
 *   Ported by: Darcy Gong
 *
 * It derives from the Rhombs OS math library by Nick Johnson which has
 * a compatibile, MIT-style license:
 *
 * Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <math.h>

/****************************************************************************
 * Public Functions
 ****************************************************************************/

float floorf(float x)
{
  float modx;

  /* modf() will return the integer part of X.  The return value of floor
   * differs for non-integer, negative values.
   *
   *  x   modff floor
   * ---- ----- -----
   *  2.0  2.0   2.0
   *  2.4  2.0   2.0
   *  2.9  2.0   2.0
   * -2.7 -2.0  -3.0
   * -2.0 -2.0  -2.0
   */

  (void)modff(x, &modx);
  if (x < 0.0F && x < modx)
    {
      modx -= 1.0F;
    }

  return modx;
}