102 lines
2.4 KiB
C
102 lines
2.4 KiB
C
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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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* From: @(#)s_ceil.c 5.1 93/09/24
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* ceill(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 ceill(x).
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*/
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#include <float.h>
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#include <math.h>
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#include <stdint.h>
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#include "fpmath.h"
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#ifdef LDBL_IMPLICIT_NBIT
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#define MANH_SIZE (LDBL_MANH_SIZE + 1)
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#define INC_MANH(u, c) do { \
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uint64_t o = u.bits.manh; \
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u.bits.manh += (c); \
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if (u.bits.manh < o) \
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u.bits.exp++; \
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} while (0)
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#else
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#define MANH_SIZE LDBL_MANH_SIZE
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#define INC_MANH(u, c) do { \
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uint64_t o = u.bits.manh; \
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u.bits.manh += (c); \
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if (u.bits.manh < o) { \
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u.bits.exp++; \
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u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \
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} \
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} while (0)
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#endif
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static const long double huge = 1.0e300;
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long double
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ceill(long double x)
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{
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union IEEEl2bits u = { .e = x };
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int e = u.bits.exp - LDBL_MAX_EXP + 1;
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if (e < MANH_SIZE - 1) {
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if (e < 0) { /* raise inexact if x != 0 */
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if (huge + x > 0.0)
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if (u.bits.exp > 0 ||
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(u.bits.manh | u.bits.manl) != 0)
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u.e = u.bits.sign ? -0.0 : 1.0;
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} else {
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uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
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if (((u.bits.manh & m) | u.bits.manl) == 0)
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return (x); /* x is integral */
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if (!u.bits.sign) {
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#ifdef LDBL_IMPLICIT_NBIT
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if (e == 0)
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u.bits.exp++;
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else
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#endif
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INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
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}
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if (huge + x > 0.0) { /* raise inexact flag */
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u.bits.manh &= ~m;
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u.bits.manl = 0;
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}
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}
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} else if (e < LDBL_MANT_DIG - 1) {
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uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
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if ((u.bits.manl & m) == 0)
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return (x); /* x is integral */
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if (!u.bits.sign) {
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if (e == MANH_SIZE - 1)
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INC_MANH(u, 1);
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else {
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uint64_t o = u.bits.manl;
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u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
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if (u.bits.manl < o) /* got a carry */
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INC_MANH(u, 1);
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}
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}
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if (huge + x > 0.0) /* raise inexact flag */
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u.bits.manl &= ~m;
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}
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return (u.e);
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}
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