gonzui

    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: }