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Diffstat (limited to 'Build/source/libs/mpfr/mpfr-3.1.2/src/scale2.c')
-rw-r--r-- | Build/source/libs/mpfr/mpfr-3.1.2/src/scale2.c | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/Build/source/libs/mpfr/mpfr-3.1.2/src/scale2.c b/Build/source/libs/mpfr/mpfr-3.1.2/src/scale2.c new file mode 100644 index 00000000000..5de38c32cc6 --- /dev/null +++ b/Build/source/libs/mpfr/mpfr-3.1.2/src/scale2.c @@ -0,0 +1,91 @@ +/* mpfr_scale2 -- multiply a double float by 2^exp + +Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. +Contributed by the AriC and Caramel projects, INRIA. + +This file is part of the GNU MPFR Library. + +The GNU MPFR Library is free software; you can redistribute it and/or modify +it under the terms of the GNU Lesser General Public License as published by +the Free Software Foundation; either version 3 of the License, or (at your +option) any later version. + +The GNU MPFR Library is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public +License for more details. + +You should have received a copy of the GNU Lesser General Public License +along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see +http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., +51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ + +#include <float.h> /* for DBL_EPSILON */ +#include "mpfr-impl.h" + +/* Note: we could use the ldexp function, but since we want not to depend on + math.h, we write our own implementation. */ + +/* multiplies 1/2 <= d <= 1 by 2^exp */ +double +mpfr_scale2 (double d, int exp) +{ +#if _GMP_IEEE_FLOATS + { + union ieee_double_extract x; + + if (MPFR_UNLIKELY (d == 1.0)) + { + d = 0.5; + exp ++; + } + + /* now 1/2 <= d < 1 */ + + /* infinities and zeroes have already been checked */ + MPFR_ASSERTD (-1073 <= exp && exp <= 1025); + + x.d = d; + if (MPFR_UNLIKELY (exp < -1021)) /* subnormal case */ + { + x.s.exp += exp + 52; + x.d *= DBL_EPSILON; + } + else /* normalized case */ + { + x.s.exp += exp; + } + return x.d; + } +#else /* _GMP_IEEE_FLOATS */ + { + double factor; + + /* An overflow may occurs (example: 0.5*2^1024) */ + if (d < 1.0) + { + d += d; + exp--; + } + /* Now 1.0 <= d < 2.0 */ + + if (exp < 0) + { + factor = 0.5; + exp = -exp; + } + else + { + factor = 2.0; + } + while (exp != 0) + { + if ((exp & 1) != 0) + d *= factor; + exp >>= 1; + factor *= factor; + } + return d; + } +#endif +} |