115 lines
2.8 KiB
C
115 lines
2.8 KiB
C
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/* xxxdtent.h -- common _[FL]Dtento functionality */
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#include "xmath.h"
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_C_STD_BEGIN
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#if !defined(MRTDLL)
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_C_LIB_DECL
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#endif /* defined(MRTDLL) */
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/* macros */
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#define ACSIZE 3 /* size of extended-precision accumulators */
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#define FRAC_BITS_2 (FRAC_BITS * FRAC_BITS)
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#if 113 <= FBITS
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#define FRAC_BITS 72057594037927936.0L /* 2^56 */
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static const FTYPE tenth[] =
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{ /* 113-bit: 0.100000 */
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(FTYPE)(FLIT(7205759403792793.0) / FRAC_BITS),
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(FTYPE)(FLIT(43234556422756761.0) / FRAC_BITS_2),
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(FTYPE)(FLIT(43234556422756761.0) / FRAC_BITS_2 / FRAC_BITS),
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};
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#elif 64 <= FBITS
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#define FRAC_BITS 4294967296.0L /* 2^32 */
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static const FTYPE tenth[] =
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{ /* 64-bit: 0.100000 */
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(FTYPE)(FLIT(429496729.0) / FRAC_BITS),
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(FTYPE)(FLIT(2576980377.0) / FRAC_BITS_2),
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(FTYPE)(FLIT(2576980377.0) / FRAC_BITS_2 / FRAC_BITS),
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};
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#elif 53 <= FBITS
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#define FRAC_BITS 67108864.0L /* 2^26 */
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static const FTYPE tenth[] =
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{ /* 53-bit: 0.100000 */
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(FTYPE)(FLIT(6710886.0) / FRAC_BITS),
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(FTYPE)(FLIT(26843545.0) / FRAC_BITS_2),
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(FTYPE)(FLIT(40265318.0) / FRAC_BITS_2 / FRAC_BITS),
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};
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#elif 24 <= FBITS
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#define FRAC_BITS 4096.0L /* 2^12 */
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static const FTYPE tenth[] =
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{ /* 24-bit: 0.100000 */
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(FTYPE)(FLIT(409.0) / FRAC_BITS),
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(FTYPE)(FLIT(2457.0) / FRAC_BITS_2),
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(FTYPE)(FLIT(2457.0) / FRAC_BITS_2 / FRAC_BITS),
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};
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#elif 11 <= FBITS
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#define FRAC_BITS 32.0 /* 2^5 */
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static const FTYPE tenth[] =
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{ /* 11-bit: 0.100000 */
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FTYPE(3.0 / FRAC_BITS),
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FTYPE(6.0 / FRAC_BITS_2),
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FTYPE(13.0 / FRAC_BITS_2 / FRAC_BITS),
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};
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#else /* FBITS */
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#error _Dtento has too much precision
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#endif /* FBITS */
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_CRTIMP2_PURE FTYPE __CLRCALL_PURE_OR_CDECL FNAME(Dtento)(FTYPE *xpx, long n, int *perr)
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{ /* compute *px * 10**n */
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FTYPE xpf[ACSIZE];
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FTYPE x;
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if (n == 0 || xpx[0] == FLIT(0.0))
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return (FNAME(Xp_getw)(xpx, ACSIZE));
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if (0 < n)
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FNAME(Xp_setw)(xpf, ACSIZE, 10.0); /* factor = 10 */
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else
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{ /* scale down */
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n = -n;
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FNAME(Xp_movx)(xpf, ACSIZE, tenth); /* factor = 1/10 */
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}
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for (; ; )
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{ /* multiply as needed by 10^(2^n) */
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FTYPE xpt[ACSIZE * 2];
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FTYPE xpw[ACSIZE];
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if (n & 1)
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FNAME(Xp_mulx)(xpx, ACSIZE, xpf, ACSIZE, xpt);
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n >>= 1;
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if (n == 0)
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break;
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FNAME(Xp_movx)(xpw, ACSIZE, xpf);
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FNAME(Xp_mulx)(xpf, ACSIZE, xpw, ACSIZE, xpt); /* square 10^n */
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}
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x = FNAME(Xp_getw)(xpx, ACSIZE);
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if (x == FLIT(0.0) || x == FCONST(Inf) || x == -FCONST(Inf))
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{ /* report error and set errno */
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errno = ERANGE;
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if (perr != 0)
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*perr |= 1;
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}
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return (x);
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}
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#if !defined(MRTDLL)
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_END_C_LIB_DECL
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#endif /* !defined(MRTDLL) */
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_C_STD_END
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/*
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* Copyright (c) 1992-2012 by P.J. Plauger. ALL RIGHTS RESERVED.
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* Consult your license regarding permissions and restrictions.
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V6.00:0009 */
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