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git-svn-id: file:///srv/svn/repos/haiku/buildtools/trunk@29042 a95241bf-73f2-0310-859d-f6bbb57e9c96
73 lines
2.5 KiB
C
73 lines
2.5 KiB
C
/* mpfr_get_z_exp -- get a multiple-precision integer and an exponent
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from a floating-point number
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Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao projects, INRIA.
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This file is part of the MPFR Library.
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The MPFR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The MPFR Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the MPFR Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "mpfr-impl.h"
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/* puts the mantissa of f into z, and returns 'exp' such that f = z * 2^exp
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*
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* 0 doesn't have an exponent, therefore the returned exponent in this case
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* isn't really important. We choose to return __gmpfr_emin because
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* 1) it is in the exponent range [__gmpfr_emin,__gmpfr_emax],
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* 2) the smaller a number is (in absolute value), the smaller its
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* exponent is. In other words, the f -> exp function is monotonous
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* on nonnegative numbers.
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* Note that this is different from the C function frexp().
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*/
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mp_exp_t
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mpfr_get_z_exp (mpz_ptr z, mpfr_srcptr f)
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{
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mp_size_t fn;
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int sh;
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MPFR_ASSERTD (MPFR_IS_FP (f));
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if (MPFR_UNLIKELY (MPFR_IS_ZERO (f)))
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{
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mpz_set_ui (z, 0);
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return __gmpfr_emin;
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}
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fn = MPFR_LIMB_SIZE(f);
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/* check whether allocated space for z is enough */
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if (MPFR_UNLIKELY (ALLOC (z) < fn))
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MPZ_REALLOC (z, fn);
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MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC (f));
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if (MPFR_LIKELY (sh))
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mpn_rshift (PTR (z), MPFR_MANT (f), fn, sh);
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else
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MPN_COPY (PTR (z), MPFR_MANT (f), fn);
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SIZ(z) = MPFR_IS_NEG (f) ? -fn : fn;
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/* Test if the result is representable. Later, we could choose
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to return MPFR_EXP_MIN if it isn't, or perhaps MPFR_EXP_MAX
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to signal an error. The mantissa would still be meaningful. */
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MPFR_ASSERTD ((mp_exp_unsigned_t) MPFR_GET_EXP (f) - MPFR_EXP_MIN
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>= (mp_exp_unsigned_t) MPFR_PREC(f));
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return MPFR_GET_EXP (f) - MPFR_PREC (f);
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}
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