1 /* mpfr_set_f -- set a MPFR number from a GNU MPF number 2 3 Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. 4 Contributed by the AriC 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 #define MPFR_NEED_LONGLONG_H 24 #include "mpfr-impl.h" 25 26 int 27 mpfr_set_f (mpfr_ptr y, mpf_srcptr x, mpfr_rnd_t rnd_mode) 28 { 29 mp_limb_t *my, *mx, *tmp; 30 unsigned long cnt, sx, sy; 31 int inexact, carry = 0; 32 MPFR_TMP_DECL(marker); 33 34 sx = ABS(SIZ(x)); /* number of limbs of the mantissa of x */ 35 36 if (sx == 0) /* x is zero */ 37 { 38 MPFR_SET_ZERO(y); 39 MPFR_SET_POS(y); 40 return 0; /* 0 is exact */ 41 } 42 43 if (SIZ(x) * MPFR_FROM_SIGN_TO_INT(MPFR_SIGN(y)) < 0) 44 MPFR_CHANGE_SIGN (y); 45 46 sy = MPFR_LIMB_SIZE (y); 47 my = MPFR_MANT(y); 48 mx = PTR(x); 49 50 count_leading_zeros(cnt, mx[sx - 1]); 51 52 if (sy <= sx) /* we may have to round even when sy = sx */ 53 { 54 unsigned long xprec = sx * GMP_NUMB_BITS; 55 56 MPFR_TMP_MARK(marker); 57 tmp = MPFR_TMP_LIMBS_ALLOC (sx); 58 if (cnt) 59 mpn_lshift (tmp, mx, sx, cnt); 60 else 61 /* FIXME: we may avoid the copy here, and directly call mpfr_round_raw 62 on mx instead of tmp */ 63 MPN_COPY (tmp, mx, sx); 64 carry = mpfr_round_raw (my, tmp, xprec, (SIZ(x) < 0), MPFR_PREC(y), 65 rnd_mode, &inexact); 66 if (MPFR_UNLIKELY(carry)) /* result is a power of two */ 67 my[sy - 1] = MPFR_LIMB_HIGHBIT; 68 MPFR_TMP_FREE(marker); 69 } 70 else 71 { 72 if (cnt) 73 mpn_lshift (my + sy - sx, mx, sx, cnt); 74 else 75 MPN_COPY (my + sy - sx, mx, sx); 76 MPN_ZERO(my, sy - sx); 77 /* no rounding necessary, since y has a larger mantissa */ 78 inexact = 0; 79 } 80 81 /* warning: EXP(x) * GMP_NUMB_BITS may exceed the maximal exponent */ 82 if (EXP(x) > 1 + (__gmpfr_emax - 1) / GMP_NUMB_BITS) 83 { 84 /* EXP(x) >= 2 + floor((__gmpfr_emax-1)/GMP_NUMB_BITS) 85 EXP(x) >= 2 + (__gmpfr_emax - GMP_NUMB_BITS) / GMP_NUMB_BITS 86 >= 1 + __gmpfr_emax / GMP_NUMB_BITS 87 EXP(x) * GMP_NUMB_BITS >= __gmpfr_emax + GMP_NUMB_BITS 88 Since 0 <= cnt <= GMP_NUMB_BITS-1, and 0 <= carry <= 1, 89 we have then EXP(x) * GMP_NUMB_BITS - cnt + carry > __gmpfr_emax */ 90 return mpfr_overflow (y, rnd_mode, MPFR_SIGN (y)); 91 } 92 else 93 { 94 /* Do not use MPFR_SET_EXP as the exponent may be out of range. */ 95 MPFR_EXP (y) = EXP (x) * GMP_NUMB_BITS - (mpfr_exp_t) cnt + carry; 96 } 97 98 return mpfr_check_range (y, inexact, rnd_mode); 99 } 100