This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
93 lines
2.8 KiB
C
93 lines
2.8 KiB
C
/* $NetBSD: lrint.c,v 1.4 2008/04/26 23:49:50 christos Exp $ */
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/*-
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* Copyright (c) 2004
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* Matthias Drochner. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <math.h>
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#include <sys/ieee754.h>
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#include <machine/limits.h>
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#include "math_private.h"
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#ifndef LRINTNAME
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#define LRINTNAME lrint
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#define RESTYPE long int
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#define RESTYPE_MIN LONG_MIN
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#define RESTYPE_MAX LONG_MAX
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#endif
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#define RESTYPE_BITS (sizeof(RESTYPE) * 8)
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static const double
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TWO52[2]={
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4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
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-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
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};
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RESTYPE
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LRINTNAME(double x)
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{
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uint32_t i0, i1;
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int e, s, shift;
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RESTYPE res;
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GET_HIGH_WORD(i0, x);
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e = i0 >> 20;
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s = (uint32_t)e >> DBL_EXPBITS;
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e = (e & 0x7ff) - DBL_EXP_BIAS;
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/* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
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if (e < -1)
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return (0);
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/* 1.0 x 2^31 (or 2^63) is already too large */
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if (e >= (int)RESTYPE_BITS - 1)
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return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
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/* >= 2^52 is already an exact integer */
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if (e < DBL_FRACBITS) {
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/* round, using current direction */
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x += TWO52[s];
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x -= TWO52[s];
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}
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EXTRACT_WORDS(i0, i1, x);
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e = ((i0 >> 20) & 0x7ff) - DBL_EXP_BIAS;
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i0 &= 0xfffff;
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i0 |= (1 << 20);
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shift = e - DBL_FRACBITS;
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if (shift >=0)
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res = (shift < 32 ? (RESTYPE)i1 << shift : 0);
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else
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res = (shift > -32 ? i1 >> -shift : 0);
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shift += 32;
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if (shift >=0)
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res |= (shift < 32 ? (RESTYPE)i0 << shift : 0);
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else
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res |= (shift > -32 ? i0 >> -shift : 0);
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return (s ? -res : res);
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}
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