143 lines
3.6 KiB
C
143 lines
3.6 KiB
C
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/* _LDscale function -- IEEE 754 version */
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#include "wctype.h"
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#include "xmath.h"
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_STD_BEGIN
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#if !_DLONG
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_CRTIMP2 short _LDscale(long double *px, long lexp)
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{ /* scale *px by 2^lexp with checking */
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return (_Dscale((double *)px, lexp));
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}
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#elif _LONG_DOUBLE_HAS_HIDDEN_BIT
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_CRTIMP2 short _LDscale(long double *px, long lexp)
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{ /* scale *px by 2^lexp with checking -- SPARC */
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unsigned short *ps = (unsigned short *)px;
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unsigned short frac;
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short xchar = ps[_L0] & _LMASK;
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if (xchar == _LMAX)
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return (ps[_L1] != 0 || ps[_L2] != 0 || ps[_L3] != 0
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|| ps[_L4] != 0 || ps[_L5] != 0 || ps[_L6] != 0
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|| ps[_L7] != 0 ? NAN : INF);
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else if (xchar == 0 && 0 < (xchar = _LDnorm(ps)))
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return (0);
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lexp += xchar;
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if (_LMAX <= lexp)
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{ /* overflow, return +/-INF */
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*px = ps[_L0] & _LSIGN ? -_LInf._L : _LInf._L;
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return (INF);
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}
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else if (0 <= lexp)
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{ /* finite result, repack */
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ps[_L0] = ps[_L0] & _LSIGN | (short)lexp;
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return (FINITE);
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}
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else
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{ /* denormalized, scale */
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unsigned short sign = ps[_L0] & _LSIGN;
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ps[_L0] = 1;
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if (--lexp <= -112)
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{ /* underflow, return +/-0 */
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ps[_L1] = 0, ps[_L2] = 0, ps[_L3] = 0, ps[_L4] = 0;
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ps[_L5] = 0, ps[_L6] = 0, ps[_L7] = 0;
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return (0);
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}
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else
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{ /* nonzero, align fraction */
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short xexp;
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for (xexp = lexp; xexp <= -16; xexp += 16)
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{ /* scale by words */
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ps[_L7] = ps[_L6], ps[_L6] = ps[_L5];
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ps[_L5] = ps[_L4], ps[_L4] = ps[_L3];
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ps[_L3] = ps[_L2], ps[_L2] = ps[_L1];
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ps[_L1] = ps[_L0], ps[_L0] = 0;
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}
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if ((xexp = -xexp) != 0)
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{ /* scale by bits */
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ps[_L7] = ps[_L7] >> xexp
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| ps[_L6] << 16 - xexp;
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ps[_L6] = ps[_L6] >> xexp
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| ps[_L5] << 16 - xexp;
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ps[_L5] = ps[_L5] >> xexp
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| ps[_L4] << 16 - xexp;
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ps[_L4] = ps[_L4] >> xexp
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| ps[_L3] << 16 - xexp;
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ps[_L3] = ps[_L3] >> xexp
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| ps[_L2] << 16 - xexp;
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ps[_L2] = ps[_L2] >> xexp
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| ps[_L1] << 16 - xexp;
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ps[_L1] = ps[_L1] >> xexp
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| ps[_L0] << 16 - xexp;
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}
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ps[_L0] = sign;
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return (FINITE);
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}
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}
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}
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#else /* _DLONG && !_LONG_DOUBLE_HAS_HIDDEN_BIT */
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_CRTIMP2 short _LDscale(long double *px, long lexp)
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{ /* scale *px by 2^lexp with checking */
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unsigned short *ps = (unsigned short *)px;
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short xchar = ps[_L0] & _LMASK;
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if (xchar == _LMAX)
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return ((ps[_L1] & 0x7fff) != 0 || ps[_L2] != 0
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|| ps[_L3] != 0 || ps[_L4] != 0 ? NAN : INF);
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else if (xchar == 0 && ps[_L1] == 0 && ps[_L2] == 0
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&& ps[_L3] == 0 && ps[_L4] == 0)
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return (0);
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lexp += xchar + _LDnorm(ps);
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if (_LMAX <= lexp)
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{ /* overflow, return +/-INF */
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*px = ps[_L0] & _LSIGN ? -_LInf._L : _LInf._L;
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return (INF);
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}
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else if (0 <= lexp)
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{ /* finite result, repack */
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ps[_L0] = ps[_L0] & _LSIGN | (short)lexp;
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return (FINITE);
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}
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else
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{ /* denormalized, scale */
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ps[_L0] &= _LSIGN;
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if (lexp <= -64)
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{ /* underflow, return +/-0 */
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ps[_L1] = 0, ps[_L2] = 0;
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ps[_L3] = 0, ps[_L4] = 0;
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return (0);
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}
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else
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{ /* nonzero, align fraction */
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short xexp;
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for (xexp = lexp; xexp <= -16; xexp += 16)
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{ /* scale by words */
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ps[_L4] = ps[_L3], ps[_L3] = ps[_L2];
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ps[_L2] = ps[_L1], ps[_L1] = 0;
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}
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if ((xexp = -xexp) != 0)
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{ /* scale by bits */
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ps[_L4] = ps[_L4] >> xexp
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| ps[_L3] << 16 - xexp;
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ps[_L3] = ps[_L3] >> xexp
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| ps[_L2] << 16 - xexp;
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ps[_L2] = ps[_L2] >> xexp
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| ps[_L1] << 16 - xexp;
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ps[_L1] >>= xexp;
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}
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return (FINITE);
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}
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}
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}
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#endif
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_STD_END
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/*
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* Copyright (c) 1994 by P.J. Plauger. ALL RIGHTS RESERVED.
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* Consult your license regarding permissions and restrictions.
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*/
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/*
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941029 pjp: added _STD machinery
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*/
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