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https://gitea.nishi.boats/pyrite-dev/milsko
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7f523a3d76
git-svn-id: http://svn2.nishi.boats/svn/milsko/trunk@557 b9cfdab3-6d41-4d17-bbe4-086880011989
77 lines
1.8 KiB
C
77 lines
1.8 KiB
C
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/* @(#)s_rint.c 1.3 95/01/18 */
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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 SunSoft, 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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* rint(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 rint(x).
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*/
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#include "math.h"
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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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double rint(double x) {
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int i0, j0, sx;
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unsigned i, i1;
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double w, t;
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i0 = __HI(x);
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sx = (i0 >> 31) & 1;
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i1 = __LO(x);
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j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
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if(j0 < 20) {
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if(j0 < 0) {
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if(((i0 & 0x7fffffff) | i1) == 0) return x;
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i1 |= (i0 & 0x0fffff);
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i0 &= 0xfffe0000;
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i0 |= ((i1 | -i1) >> 12) & 0x80000;
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__HI(x) = i0;
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w = TWO52[sx] + x;
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t = w - TWO52[sx];
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i0 = __HI(t);
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__HI(t) = (i0 & 0x7fffffff) | (sx << 31);
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return t;
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} else {
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i = (0x000fffff) >> j0;
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if(((i0 & i) | i1) == 0) return x; /* x is integral */
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i >>= 1;
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if(((i0 & i) | i1) != 0) {
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if(j0 == 19) i1 = 0x40000000;
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else
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i0 = (i0 & (~i)) | ((0x20000) >> j0);
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}
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}
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} else if(j0 > 51) {
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if(j0 == 0x400) return x + x; /* inf or NaN */
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else
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return x; /* x is integral */
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} else {
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i = ((unsigned)(0xffffffff)) >> (j0 - 20);
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if((i1 & i) == 0) return x; /* x is integral */
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i >>= 1;
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if((i1 & i) != 0) i1 = (i1 & (~i)) | ((0x40000000) >> (j0 - 20));
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}
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__HI(x) = i0;
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__LO(x) = i1;
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w = TWO52[sx] + x;
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return w - TWO52[sx];
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}
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