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Diffstat (limited to 'mpfr/powerof2.c')
-rw-r--r-- | mpfr/powerof2.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/mpfr/powerof2.c b/mpfr/powerof2.c new file mode 100644 index 000000000..f4bf0d3c6 --- /dev/null +++ b/mpfr/powerof2.c @@ -0,0 +1,44 @@ +/* mpfr_powerof2_raw -- test whether a floating-point number is a power of 2 + +Copyright 2002 Free Software Foundation. + +This file is part of the MPFR Library. + +The 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 2.1 of the License, or (at your +option) any later version. + +The 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 MPFR Library; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" +#include "mpfr.h" +#include "mpfr-impl.h" + +/* This is an internal function and one assumes that x is a real number. */ + +int +mpfr_powerof2_raw (mpfr_srcptr x) +{ + mp_limb_t *xp; + mp_size_t xn; + + MPFR_ASSERTN(MPFR_IS_FP(x)); + xp = MPFR_MANT(x); + xn = (MPFR_PREC(x) - 1) / BITS_PER_MP_LIMB; + if (NOT_POW2(xp[xn])) + return 0; + while (xn > 0) + if (xp[--xn] != 0) + return 0; + return 1; +} |