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130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
/*
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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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<<lround>>, <<lroundf>>, <<llround>>, <<llroundf>>---round to integer, to nearest
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INDEX
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lround
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INDEX
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lroundf
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INDEX
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llround
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INDEX
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llroundf
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SYNOPSIS
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#include <math.h>
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long int lround(double <[x]>);
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long int lroundf(float <[x]>);
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long long int llround(double <[x]>);
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long long int llroundf(float <[x]>);
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DESCRIPTION
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The <<lround>> and <<llround>> functions round their argument to the
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nearest integer value, rounding halfway cases away from zero, regardless
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of the current rounding direction. If the rounded value is outside the
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range of the return type, the numeric result is unspecified (depending
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upon the floating-point implementation, not the library). A range
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error may occur if the magnitude of x is too large.
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RETURNS
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<[x]> rounded to an integral value as an integer.
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SEEALSO
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See the <<round>> functions for the return being the same floating-point type
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as the argument. <<lrint>>, <<llrint>>.
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PORTABILITY
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ANSI C, POSIX
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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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long int lround(double x)
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#else
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long int lround(x)
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double x;
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#endif
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{
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__int32_t sign, exponent_less_1023;
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/* Most significant word, least significant word. */
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__uint32_t msw, lsw;
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long int result;
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EXTRACT_WORDS(msw, lsw, x);
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/* Extract sign. */
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sign = ((msw & 0x80000000) ? -1 : 1);
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/* Extract exponent field. */
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exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;
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msw &= 0x000fffff;
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msw |= 0x00100000;
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/* exponent_less_1023 in [-1023,1024] */
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if (exponent_less_1023 < 20)
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{
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/* exponent_less_1023 in [-1023,19] */
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if (exponent_less_1023 < 0)
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{
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if (exponent_less_1023 < -1)
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return 0;
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else
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return sign;
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}
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else
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{
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/* exponent_less_1023 in [0,19] */
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/* shift amt in [0,19] */
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msw += 0x80000 >> exponent_less_1023;
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/* shift amt in [20,1] */
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result = msw >> (20 - exponent_less_1023);
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}
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}
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else if (exponent_less_1023 < (8 * sizeof (long int)) - 1)
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{
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/* 32bit long: exponent_less_1023 in [20,30] */
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/* 64bit long: exponent_less_1023 in [20,62] */
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if (exponent_less_1023 >= 52)
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/* 64bit long: exponent_less_1023 in [52,62] */
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/* 64bit long: shift amt in [32,42] */
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result = ((long int) msw << (exponent_less_1023 - 20))
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/* 64bit long: shift amt in [0,10] */
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| (lsw << (exponent_less_1023 - 52));
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else
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{
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/* 32bit long: exponent_less_1023 in [20,30] */
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/* 64bit long: exponent_less_1023 in [20,51] */
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unsigned int tmp = lsw
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/* 32bit long: shift amt in [0,10] */
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/* 64bit long: shift amt in [0,31] */
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+ (0x80000000 >> (exponent_less_1023 - 20));
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if (tmp < lsw)
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++msw;
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/* 32bit long: shift amt in [0,10] */
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/* 64bit long: shift amt in [0,31] */
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result = ((long int) msw << (exponent_less_1023 - 20))
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/* ***32bit long: shift amt in [32,22] */
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/* ***64bit long: shift amt in [32,1] */
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| SAFE_RIGHT_SHIFT (tmp, (52 - exponent_less_1023));
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}
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}
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else
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/* Result is too large to be represented by a long int. */
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return (long int)x;
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return sign * result;
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}
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#endif /* _DOUBLE_IS_32BITS */
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