1 /* mpfr_mul_2ui -- multiply a floating-point number by a power of two 2 3 Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc. 4 Contributed by the Arenaire and Caramel 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 http://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_2ui (mpfr_ptr y, mpfr_srcptr x, unsigned long int n, mpfr_rnd_t rnd_mode) 27 { 28 int inexact; 29 30 MPFR_LOG_FUNC 31 (("x[%Pu]=%.*Rg n=%lu rnd=%d", 32 mpfr_get_prec (x), mpfr_log_prec, x, n, rnd_mode), 33 ("y[%Pu]=%.*Rg inexact=%d", 34 mpfr_get_prec (y), mpfr_log_prec, y, inexact)); 35 36 inexact = MPFR_UNLIKELY(y != x) ? mpfr_set (y, x, rnd_mode) : 0; 37 38 if (MPFR_LIKELY( MPFR_IS_PURE_FP(y)) ) 39 { 40 /* n will have to be casted to long to make sure that the addition 41 and subtraction below (for overflow detection) are signed */ 42 while (MPFR_UNLIKELY(n > LONG_MAX)) 43 { 44 int inex2; 45 46 n -= LONG_MAX; 47 inex2 = mpfr_mul_2ui(y, y, LONG_MAX, rnd_mode); 48 if (inex2) 49 return inex2; /* overflow */ 50 } 51 52 /* MPFR_EMIN_MIN + (long) n is signed and doesn't lead to an overflow; 53 the first test useful so that the real test can't lead to an 54 overflow. */ 55 { 56 mpfr_exp_t exp = MPFR_GET_EXP (y); 57 if (MPFR_UNLIKELY( __gmpfr_emax < MPFR_EMIN_MIN + (long) n || 58 exp > __gmpfr_emax - (long) n)) 59 return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y)); 60 61 MPFR_SET_EXP (y, exp + (long) n); 62 } 63 } 64 65 return inexact; 66 } 67