lib/libm/src/s_lroundf.c

   1 /*      $OpenBSD: s_lroundf.c,v 1.2 2011/04/17 13:59:54 martynas Exp $  */
   2 /* $NetBSD: lroundf.c,v 1.2 2004/10/13 15:18:32 drochner Exp $ */
   3
   4 /*-
   5  * Copyright (c) 2004
   6  *      Matthias Drochner. All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include <math.h>
  31 #include <sys/types.h>
  32 #include <sys/limits.h>
  33 #include <ieeefp.h>
  34 #include <machine/ieee.h>
  35 #include "math_private.h"
  36
  37 #ifndef LROUNDNAME
  38 #define LROUNDNAME lroundf
  39 #define RESTYPE long int
  40 #define RESTYPE_MIN LONG_MIN
  41 #define RESTYPE_MAX LONG_MAX
  42 #endif
  43
  44 #define RESTYPE_BITS (sizeof(RESTYPE) * 8)
  45
  46 RESTYPE
  47 LROUNDNAME(float x)
  48 {
  49         u_int32_t i0;
  50         int e, s, shift;
  51         RESTYPE res;
  52
  53         GET_FLOAT_WORD(i0, x);
  54         e = i0 >> SNG_FRACBITS;
  55         s = e >> SNG_EXPBITS;
  56         e = (e & 0xff) - SNG_EXP_BIAS;
  57
  58         /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
  59         if (e < -1)
  60                 return (0);
  61         /* 1.0 x 2^31 (or 2^63) is already too large */
  62         if (e >= (int)RESTYPE_BITS - 1)
  63                 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
  64
  65         /* >= 2^23 is already an exact integer */
  66         if (e < SNG_FRACBITS) {
  67                 /* add 0.5, extraction below will truncate */
  68                 x += (s ? -0.5 : 0.5);
  69         }
  70
  71         GET_FLOAT_WORD(i0, x);
  72         e = ((i0 >> SNG_FRACBITS) & 0xff) - SNG_EXP_BIAS;
  73         i0 &= 0x7fffff;
  74         i0 |= (1 << SNG_FRACBITS);
  75
  76         shift = e - SNG_FRACBITS;
  77         if (shift >=0)
  78                 res = (shift < RESTYPE_BITS ? (RESTYPE)i0 << shift : 0);
  79         else
  80                 res = (shift > -RESTYPE_BITS ? (RESTYPE)i0 >> -shift : 0);
  81
  82         return (s ? -res : res);
  83 }