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48 lines
1.6 KiB
C
48 lines
1.6 KiB
C
/* Copyright (C) 1995-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include <ieee754.h>
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#include <float.h>
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/* Convert a multi-precision integer of the needed number of bits (53 for
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double) and an integral power of two to a `double' in IEEE754 double-
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precision format. */
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double
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__mpn_construct_double (mp_srcptr frac_ptr, int expt, int negative)
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{
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union ieee754_double u;
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u.ieee.negative = negative;
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u.ieee.exponent = expt + IEEE754_DOUBLE_BIAS;
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#if BITS_PER_MP_LIMB == 32
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u.ieee.mantissa1 = frac_ptr[0];
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u.ieee.mantissa0 = frac_ptr[1] & (((mp_limb_t) 1
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<< (DBL_MANT_DIG - 32)) - 1);
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#elif BITS_PER_MP_LIMB == 64
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u.ieee.mantissa1 = frac_ptr[0] & (((mp_limb_t) 1 << 32) - 1);
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u.ieee.mantissa0 = (frac_ptr[0] >> 32) & (((mp_limb_t) 1
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<< (DBL_MANT_DIG - 32)) - 1);
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#else
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# error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
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#endif
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return u.d;
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}
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