158 lines
4.0 KiB
C
158 lines
4.0 KiB
C
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/* @(#)s_lrint.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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FUNCTION
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<<lrint>>, <<lrintf>>, <<llrint>>, <<llrintf>>---round to integer
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INDEX
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lrint
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INDEX
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lrintf
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INDEX
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llrint
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INDEX
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llrintf
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SYNOPSIS
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#include <math.h>
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long int lrint(double <[x]>);
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long int lrintf(float <[x]>);
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long long int llrint(double <[x]>);
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long long int llrintf(float <[x]>);
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DESCRIPTION
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The <<lrint>> and <<llrint>> functions round their argument to the nearest
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integer value, using the current rounding direction. If the rounded value is
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outside the range of the return type, the numeric result is unspecified. A
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range error may occur if the magnitude of <[x]> is too large.
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The "inexact" floating-point exception is raised in implementations that
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support it when the result differs in value from the argument (i.e., when
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a fraction actually has been truncated).
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RETURNS
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<[x]> rounded to an integral value, using the current rounding direction.
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SEEALSO
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<<lround>>
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PORTABILITY
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ANSI C, POSIX
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*/
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/*
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* lrint(x)
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* Return x rounded to integral value according to the prevailing
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* rounding mode.
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* Method:
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* Using floating addition.
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* Exception:
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* Inexact flag raised if x not equal to lrint(x).
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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static const double
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#else
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static double
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#endif
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/* Adding a double, x, to 2^52 will cause the result to be rounded based on
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the fractional part of x, according to the implementation's current rounding
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mode. 2^52 is the smallest double that can be represented using all 52 significant
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digits. */
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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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#ifdef __STDC__
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long int lrint(double x)
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#else
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long int lrint(x)
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double x;
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#endif
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{
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__int32_t i0,j0,sx;
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__uint32_t i1;
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double t;
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volatile double w;
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long int result;
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EXTRACT_WORDS(i0,i1,x);
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/* Extract sign bit. */
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sx = (i0>>31)&1;
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/* Extract exponent field. */
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j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
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/* j0 in [-1023,1024] */
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if(j0 < 20)
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{
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/* j0 in [-1023,19] */
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w = TWO52[sx] + x;
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t = w - TWO52[sx];
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GET_HIGH_WORD(i0, t);
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/* Detect the all-zeros representation of plus and
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minus zero, which fails the calculation below. */
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if ((i0 & ~(1L << 31)) == 0)
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return 0;
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j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
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i0 &= 0x000fffff;
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i0 |= 0x00100000;
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result = (j0 < 0 ? 0 : i0 >> (20 - j0));
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}
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else if (j0 < (int)(8 * sizeof (long int)) - 1)
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{
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/* 32bit return: j0 in [20,30] */
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/* 64bit return: j0 in [20,62] */
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if (j0 >= 52)
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/* 64bit return: j0 in [52,62] */
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/* 64bit return: left shift amt in [32,42] */
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result = ((long int) ((i0 & 0x000fffff) | 0x00100000) << (j0 - 20)) |
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/* 64bit return: right shift amt in [0,10] */
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((long int) i1 << (j0 - 52));
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else
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{
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/* 32bit return: j0 in [20,30] */
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/* 64bit return: j0 in [20,51] */
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w = TWO52[sx] + x;
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t = w - TWO52[sx];
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EXTRACT_WORDS (i0, i1, t);
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j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
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i0 &= 0x000fffff;
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i0 |= 0x00100000;
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/* After round:
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* 32bit return: j0 in [20,31];
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* 64bit return: j0 in [20,52] */
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/* 32bit return: left shift amt in [0,11] */
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/* 64bit return: left shift amt in [0,32] */
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/* ***32bit return: right shift amt in [32,21] */
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/* ***64bit return: right shift amt in [32,0] */
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result = ((long int) i0 << (j0 - 20))
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| SAFE_RIGHT_SHIFT (i1, (52 - j0));
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}
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}
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else
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{
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return (long int) x;
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}
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return sx ? -result : result;
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}
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#endif /* _DOUBLE_IS_32BITS */
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