Home | History | Annotate | Line # | Download | only in src 
      1 /* mpfr_mul_2si -- multiply a floating-point number by a power of two
      2 
      3 Copyright 1999, 2001-2023 Free Software Foundation, Inc.
      4 Contributed by the AriC and Caramba projects, INRIA.
      5 
      6 This file is part of the GNU MPFR Library.
      7 
      8 The GNU MPFR Library is free software; you can redistribute it and/or modify
      9 it under the terms of the GNU Lesser General Public License as published by
     10 the Free Software Foundation; either version 3 of the License, or (at your
     11 option) any later version.
     12 
     13 The GNU MPFR Library is distributed in the hope that it will be useful, but
     14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     15 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
     16 License for more details.
     17 
     18 You should have received a copy of the GNU Lesser General Public License
     19 along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
     20 https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
     21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
     22 
     23 #include "mpfr-impl.h"
     24 
     25 int
     26 mpfr_mul_2si (mpfr_ptr y, mpfr_srcptr x, long int n, mpfr_rnd_t rnd_mode)
     27 {
     28   int inexact;
     29 
     30   MPFR_LOG_FUNC
     31     (("x[%Pd]=%.*Rg n=%ld rnd=%d",
     32       mpfr_get_prec (x), mpfr_log_prec, x, n, rnd_mode),
     33      ("y[%Pd]=%.*Rg inexact=%d",
     34       mpfr_get_prec (y), mpfr_log_prec, y, inexact));
     35 
     36   if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
     37     return mpfr_set (y, x, rnd_mode);
     38   else
     39     {
     40       mpfr_exp_t exp = MPFR_GET_EXP (x);
     41       MPFR_SETRAW (inexact, y, x, exp, rnd_mode);
     42       if (MPFR_UNLIKELY(n >= 0 && (__gmpfr_emax < MPFR_EMIN_MIN + n ||
     43                                    exp > __gmpfr_emax - n)))
     44         return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y));
     45       else if (MPFR_UNLIKELY(n < 0 && (__gmpfr_emin > MPFR_EMAX_MAX + n ||
     46                                        exp < __gmpfr_emin - n)))
     47         {
     48           if (rnd_mode == MPFR_RNDN &&
     49               (__gmpfr_emin > MPFR_EMAX_MAX + (n + 1) ||
     50                exp < __gmpfr_emin - (n + 1) ||
     51                ((MPFR_IS_NEG (y) ? inexact <= 0 : inexact >= 0) &&
     52                 mpfr_powerof2_raw (y))))
     53             rnd_mode = MPFR_RNDZ;
     54           return mpfr_underflow (y, rnd_mode, MPFR_SIGN(y));
     55         }
     56       MPFR_SET_EXP (y, exp + n);
     57     }
     58 
     59   MPFR_RET (inexact);
     60 }
     61