95 lines
2.3 KiB
C
95 lines
2.3 KiB
C
/* $NetBSD: s_nextafterl.c,v 1.2 2010/09/17 20:39:39 christos Exp $ */
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/* @(#)s_nextafter.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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#include <sys/cdefs.h>
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__RCSID("$NetBSD: s_nextafterl.c,v 1.2 2010/09/17 20:39:39 christos Exp $");
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#include <float.h>
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#include <math.h>
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#include <machine/ieee.h>
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#ifdef EXT_EXP_INFNAN
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#if LDBL_MAX_EXP != 0x4000
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#error "Unsupported long double format"
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#endif
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/*
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* IEEE functions
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* nextafterl(x,y)
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* return the next machine floating-point number of x in the
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* direction toward y.
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* Special cases:
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* If x == y, y shall be returned
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* If x or y is NaN, a NaN shall be returned
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*/
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long double
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nextafterl(long double x, long double y)
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{
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volatile long double t;
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union ieee_ext_u ux, uy;
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ux.extu_ld = x;
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uy.extu_ld = y;
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if ((ux.extu_exp == EXT_EXP_NAN &&
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((ux.extu_frach &~ LDBL_NBIT)|ux.extu_fracl) != 0) ||
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(uy.extu_exp == EXT_EXP_NAN &&
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((uy.extu_frach &~ LDBL_NBIT)|uy.extu_fracl) != 0))
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return x+y; /* x or y is nan */
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if (x == y) return y; /* x=y, return y */
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if (x == 0.0) {
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ux.extu_frach = 0; /* return +-minsubnormal */
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ux.extu_fracl = 1;
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ux.extu_sign = uy.extu_sign;
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t = ux.extu_ld * ux.extu_ld;
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if (t == ux.extu_ld)
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return t;
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else
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return ux.extu_ld; /* raise underflow flag */
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}
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if ((x>0.0) ^ (x<y)) { /* x -= ulp */
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if (ux.extu_fracl == 0) {
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if ((ux.extu_frach & ~LDBL_NBIT) == 0)
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ux.extu_exp -= 1;
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ux.extu_frach = (ux.extu_frach - 1) |
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(ux.extu_frach & LDBL_NBIT);
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}
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ux.extu_fracl -= 1;
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} else { /* x += ulp */
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ux.extu_fracl += 1;
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if (ux.extu_fracl == 0) {
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ux.extu_frach = (ux.extu_frach + 1) |
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(ux.extu_frach & LDBL_NBIT);
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if ((ux.extu_frach & ~LDBL_NBIT) == 0)
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ux.extu_exp += 1;
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}
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}
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if (ux.extu_exp == EXT_EXP_INF)
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return x+x; /* overflow */
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if (ux.extu_exp == 0) { /* underflow */
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mask_nbit_l(ux);
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t = ux.extu_ld * ux.extu_ld;
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if (t != ux.extu_ld) /* raise underflow flag */
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return ux.extu_ld;
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}
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return ux.extu_ld;
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}
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#endif
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