mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-27 07:31:35 +00:00
167 lines
4.2 KiB
C
167 lines
4.2 KiB
C
|
|
/* @(#)s_lrint.c 5.1 93/09/24 */
|
|
/*
|
|
* ====================================================
|
|
* 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
|
|
<<lrint>>, <<lrintf>>, <<llrint>>, <<llrintf>>--round to integer
|
|
INDEX
|
|
lrint
|
|
INDEX
|
|
lrintf
|
|
INDEX
|
|
llrint
|
|
INDEX
|
|
llrintf
|
|
|
|
ANSI_SYNOPSIS
|
|
#include <math.h>
|
|
long int lrint(double <[x]>);
|
|
long int lrintf(float <[x]>);
|
|
long long int llrint(double <[x]>);
|
|
long long int llrintf(float <[x]>);
|
|
|
|
DESCRIPTION
|
|
The <<lrint>> and <<llrint>> functions round their argument to the nearest
|
|
integer value, using the current rounding direction. If the rounded value is
|
|
outside the range of the return type, the numeric result is unspecified. A
|
|
range error may occur if the magnitude of <[x]> is too large.
|
|
The "inexact" floating-point exception is raised in implementations that
|
|
support it when the result differs in value from the argument (i.e., when
|
|
a fraction actually has been truncated).
|
|
|
|
RETURNS
|
|
<[x]> rounded to an integral value, using the current rounding direction.
|
|
|
|
SEEALSO
|
|
<<lround>>
|
|
|
|
PORTABILITY
|
|
ANSI C, POSIX
|
|
|
|
*/
|
|
|
|
/*
|
|
* lrint(x)
|
|
* Return x rounded to integral value according to the prevailing
|
|
* rounding mode.
|
|
* Method:
|
|
* Using floating addition.
|
|
* Exception:
|
|
* Inexact flag raised if x not equal to lrint(x).
|
|
*/
|
|
|
|
#include "fdlibm.h"
|
|
|
|
#ifndef _DOUBLE_IS_32BITS
|
|
|
|
#ifdef __STDC__
|
|
static const double
|
|
#else
|
|
static double
|
|
#endif
|
|
|
|
/* Adding a double, x, to 2^52 will cause the result to be rounded based on
|
|
the fractional part of x, according to the implementation's current rounding
|
|
mode. 2^52 is the smallest double that can be represented using all 52 significant
|
|
digits. */
|
|
TWO52[2]={
|
|
4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
|
|
-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
|
|
};
|
|
|
|
#ifdef __STDC__
|
|
long int lrint(double x)
|
|
#else
|
|
long int lrint(x)
|
|
double x;
|
|
#endif
|
|
{
|
|
__int32_t i0,j0,sx;
|
|
__uint32_t i1;
|
|
double t;
|
|
volatile double w;
|
|
long int result;
|
|
|
|
EXTRACT_WORDS(i0,i1,x);
|
|
|
|
/* Extract sign bit. */
|
|
sx = (i0>>31)&1;
|
|
|
|
/* Extract exponent field. */
|
|
j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
|
|
/* j0 in [-1023,1024] */
|
|
|
|
if(j0 < 20)
|
|
{
|
|
/* j0 in [-1023,19] */
|
|
if(j0 < -1)
|
|
return 0;
|
|
else
|
|
{
|
|
/* j0 in [0,19] */
|
|
/* shift amt in [0,19] */
|
|
w = TWO52[sx] + x;
|
|
t = w - TWO52[sx];
|
|
GET_HIGH_WORD(i0, t);
|
|
/* Detect the all-zeros representation of plus and
|
|
minus zero, which fails the calculation below. */
|
|
if ((i0 & ~(1L << 31)) == 0)
|
|
return 0;
|
|
/* After round: j0 in [0,20] */
|
|
j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
|
|
i0 &= 0x000fffff;
|
|
i0 |= 0x00100000;
|
|
/* shift amt in [20,0] */
|
|
result = i0 >> (20 - j0);
|
|
}
|
|
}
|
|
else if (j0 < (int)(8 * sizeof (long int)) - 1)
|
|
{
|
|
/* 32bit return: j0 in [20,30] */
|
|
/* 64bit return: j0 in [20,62] */
|
|
if (j0 >= 52)
|
|
/* 64bit return: j0 in [52,62] */
|
|
/* 64bit return: left shift amt in [32,42] */
|
|
result = ((long int) ((i0 & 0x000fffff) | 0x0010000) << (j0 - 20)) |
|
|
/* 64bit return: right shift amt in [0,10] */
|
|
(i1 << (j0 - 52));
|
|
else
|
|
{
|
|
/* 32bit return: j0 in [20,30] */
|
|
/* 64bit return: j0 in [20,51] */
|
|
w = TWO52[sx] + x;
|
|
t = w - TWO52[sx];
|
|
EXTRACT_WORDS (i0, i1, t);
|
|
j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
|
|
i0 &= 0x000fffff;
|
|
i0 |= 0x00100000;
|
|
/* After round:
|
|
* 32bit return: j0 in [20,31];
|
|
* 64bit return: j0 in [20,52] */
|
|
/* 32bit return: left shift amt in [0,11] */
|
|
/* 64bit return: left shift amt in [0,32] */
|
|
/* ***32bit return: right shift amt in [32,21] */
|
|
/* ***64bit return: right shift amt in [32,0] */
|
|
result = ((long int) i0 << (j0 - 20))
|
|
| SAFE_RIGHT_SHIFT (i1, (52 - j0));
|
|
}
|
|
}
|
|
else
|
|
{
|
|
return (long int) x;
|
|
}
|
|
|
|
return sx ? -result : result;
|
|
}
|
|
|
|
#endif /* _DOUBLE_IS_32BITS */
|