lib/libm/src/s_lround.c

   1 /*      $OpenBSD: s_lround.c,v 1.6 2013/03/28 18:09:38 martynas Exp $   */
   2 /* $NetBSD: lround.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 <sys/types.h>
  31 #include <sys/limits.h>
  32 #include <float.h>
  33 #include <math.h>
  34 #include <ieeefp.h>
  35 #include <machine/ieee.h>
  36 #include "math_private.h"
  37
  38 #ifndef LROUNDNAME
  39 #define LROUNDNAME lround
  40 #define RESTYPE long int
  41 #define RESTYPE_MIN LONG_MIN
  42 #define RESTYPE_MAX LONG_MAX
  43 #endif
  44
  45 #define RESTYPE_BITS (sizeof(RESTYPE) * 8)
  46
  47 RESTYPE
  48 LROUNDNAME(double x)
  49 {
  50         u_int32_t i0, i1;
  51         int e, s, shift;
  52         RESTYPE res;
  53
  54         GET_HIGH_WORD(i0, x);
  55         e = i0 >> DBL_FRACHBITS;
  56         s = e >> DBL_EXPBITS;
  57         e = (e & 0x7ff) - DBL_EXP_BIAS;
  58
  59         /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
  60         if (e < -1)
  61                 return (0);
  62         /* 1.0 x 2^31 (or 2^63) is already too large */
  63         if (e >= (int)RESTYPE_BITS - 1)
  64                 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
  65
  66         /* >= 2^52 is already an exact integer */
  67         if (e < DBL_FRACBITS) {
  68                 /* add 0.5, extraction below will truncate */
  69                 x += (s ? -0.5 : 0.5);
  70         }
  71
  72         EXTRACT_WORDS(i0, i1, x);
  73         e = ((i0 >> DBL_FRACHBITS) & 0x7ff) - DBL_EXP_BIAS;
  74         i0 &= 0xfffff;
  75         i0 |= (1 << DBL_FRACHBITS);
  76
  77         shift = e - DBL_FRACBITS;
  78         if (shift >=0)
  79                 res = (shift < RESTYPE_BITS ? (RESTYPE)i1 << shift : 0);
  80         else
  81                 res = (shift > -RESTYPE_BITS ? (RESTYPE)i1 >> -shift : 0);
  82         shift += 32;
  83         if (shift >=0)
  84                 res |= (shift < RESTYPE_BITS ? (RESTYPE)i0 << shift : 0);
  85         else
  86                 res |= (shift > -RESTYPE_BITS ? (RESTYPE)i0 >> -shift : 0);
  87
  88         return (s ? -res : res);
  89 }
  90
  91 #if     LDBL_MANT_DIG == 53
  92 __strong_alias(lroundl, lround);
  93 #endif  /* LDBL_MANT_DIG == 53 */