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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
75 lines
1.7 KiB
C
75 lines
1.7 KiB
C
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/* @(#)s_floor.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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* floor(x)
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* Return x rounded toward -inf to integral value
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* Method:
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* Bit twiddling.
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* Exception:
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* Inexact flag raised if x not equal to floor(x).
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*/
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#include "math.h"
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static const double hugev = 1.0e300;
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double floor(double x) {
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int i0, i1, j0;
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unsigned i, j;
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i0 = __HI(x);
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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) { /* raise inexact if x != 0 */
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if(hugev + x > 0.0) { /* return 0*sign(x) if |x|<1 */
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if(i0 >= 0) {
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i0 = i1 = 0;
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} else if(((i0 & 0x7fffffff) | i1) != 0) {
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i0 = 0xbff00000;
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i1 = 0;
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}
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}
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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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if(hugev + x > 0.0) { /* raise inexact flag */
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if(i0 < 0) i0 += (0x00100000) >> j0;
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i0 &= (~i);
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i1 = 0;
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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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if(hugev + x > 0.0) { /* raise inexact flag */
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if(i0 < 0) {
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if(j0 == 20) i0 += 1;
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else {
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j = i1 + (1 << (52 - j0));
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if(j < i1) i0 += 1; /* got a carry */
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i1 = j;
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}
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}
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i1 &= (~i);
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}
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}
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__HI(x) = i0;
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__LO(x) = i1;
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return x;
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}
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