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s_floor.c
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/* @(#)s_floor.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.
* ====================================================
*/
#if defined(LIBM_SCCS) && !defined(lint)
static const char rcsid[] =
"$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
#endif
/*
* floor(x)
* Return x rounded toward -inf to integral value
* Method:
* Bit twiddling.
* Exception:
* Inexact flag raised if x not equal to floor(x).
*/
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#include "math_libm.h"
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#include "math_private.h"
#ifdef __STDC__
static const double huge_val = 1.0e300;
#else
static double huge_val = 1.0e300;
#endif
libm_hidden_proto(floor)
#ifdef __STDC__
double floor(double x)
#else
double floor(x)
double x;
#endif
{
int32_t i0, i1, j0;
u_int32_t i, j;
EXTRACT_WORDS(i0, i1, x);
j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
if (j0 < 20) {
if (j0 < 0) { /* raise inexact if x != 0 */
if (huge_val + x > 0.0) { /* return 0*sign(x) if |x|<1 */
if (i0 >= 0) {
i0 = i1 = 0;
} else if (((i0 & 0x7fffffff) | i1) != 0) {
i0 = 0xbff00000;
i1 = 0;
}
}
} else {
i = (0x000fffff) >> j0;
if (((i0 & i) | i1) == 0)
return x; /* x is integral */
if (huge_val + x > 0.0) { /* raise inexact flag */
if (i0 < 0)
i0 += (0x00100000) >> j0;
i0 &= (~i);
i1 = 0;
}
}
} else if (j0 > 51) {
if (j0 == 0x400)
return x + x; /* inf or NaN */
else
return x; /* x is integral */
} else {
i = ((u_int32_t) (0xffffffff)) >> (j0 - 20);
if ((i1 & i) == 0)
return x; /* x is integral */
if (huge_val + x > 0.0) { /* raise inexact flag */
if (i0 < 0) {
if (j0 == 20)
i0 += 1;
else {
j = i1 + (1 << (52 - j0));
if (j < (u_int32_t) i1)
i0 += 1; /* got a carry */
i1 = j;
}
}
i1 &= (~i);
}
}
INSERT_WORDS(x, i0, i1);
return x;
}
libm_hidden_def(floor)