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/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
FUNCTION
<<round>>, <<roundf>>---round to integer, to nearest
INDEX
round
INDEX
roundf
SYNOPSIS
#include <math.h>
double round(double <[x]>);
float roundf(float <[x]>);
DESCRIPTION
The <<round>> functions round their argument to the nearest integer
value in floating-point format, rounding halfway cases away from zero,
regardless of the current rounding direction. (While the "inexact"
floating-point exception behavior is unspecified by the C standard, the
<<round>> functions are written so that "inexact" is not raised if the
result does not equal the argument, which behavior is as recommended by
IEEE 754 for its related functions.)
RETURNS
<[x]> rounded to an integral value.
PORTABILITY
ANSI C, POSIX
SEEALSO
<<nearbyint>>, <<rint>>
*/
#include "fdlibm.h"
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
double round(double x)
#else
double round(x)
double x;
#endif
{
/* Most significant word, least significant word. */
__int32_t msw, exponent_less_1023;
__uint32_t lsw;
EXTRACT_WORDS(msw, lsw, x);
/* Extract exponent field. */
exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;
if (exponent_less_1023 < 20)
{
if (exponent_less_1023 < 0)
{
msw &= 0x80000000;
if (exponent_less_1023 == -1)
/* Result is +1.0 or -1.0. */
msw |= ((__int32_t)1023 << 20);
lsw = 0;
}
else
{
__uint32_t exponent_mask = 0x000fffff >> exponent_less_1023;
if ((msw & exponent_mask) == 0 && lsw == 0)
/* x in an integral value. */
return x;
msw += 0x00080000 >> exponent_less_1023;
msw &= ~exponent_mask;
lsw = 0;
}
}
else if (exponent_less_1023 > 51)
{
if (exponent_less_1023 == 1024)
/* x is NaN or infinite. */
return x + x;
else
return x;
}
else
{
__uint32_t exponent_mask = 0xffffffff >> (exponent_less_1023 - 20);
__uint32_t tmp;
if ((lsw & exponent_mask) == 0)
/* x is an integral value. */
return x;
tmp = lsw + (1 << (51 - exponent_less_1023));
if (tmp < lsw)
msw += 1;
lsw = tmp;
lsw &= ~exponent_mask;
}
INSERT_WORDS(x, msw, lsw);
return x;
}
#endif /* _DOUBLE_IS_32BITS */
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