1/* mpfr_set_q -- set a floating-point number from a multiple-precision rational 2 3Copyright 2000-2002, 2004-2023 Free Software Foundation, Inc. 4Contributed by the AriC and Caramba projects, INRIA. 5 6This file is part of the GNU MPFR Library. 7 8The GNU MPFR Library is free software; you can redistribute it and/or modify 9it under the terms of the GNU Lesser General Public License as published by 10the Free Software Foundation; either version 3 of the License, or (at your 11option) any later version. 12 13The GNU MPFR Library is distributed in the hope that it will be useful, but 14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16License for more details. 17 18You should have received a copy of the GNU Lesser General Public License 19along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see 20https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 2151 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 22 23#define MPFR_NEED_LONGLONG_H 24#include "mpfr-impl.h" 25 26#ifndef MPFR_USE_MINI_GMP 27/* 28 * Set f to z, choosing the smallest precision for f 29 * so that z = f*(2^BPML)*zs*2^(RetVal) 30 */ 31static int 32set_z (mpfr_ptr f, mpz_srcptr z, mp_size_t *zs) 33{ 34 mp_limb_t *p; 35 mp_size_t s; 36 int c; 37 mpfr_prec_t pf; 38 39 MPFR_ASSERTD (mpz_sgn (z) != 0); 40 41 /* Remove useless ending 0 */ 42 for (p = PTR (z), s = *zs = ABSIZ (z) ; *p == 0; p++, s--) 43 MPFR_ASSERTD (s >= 0); 44 45 /* Get working precision */ 46 count_leading_zeros (c, p[s-1]); 47 pf = s * GMP_NUMB_BITS - c; 48 MPFR_ASSERTD (pf >= 1); 49 mpfr_init2 (f, pf >= MPFR_PREC_MIN ? pf : MPFR_PREC_MIN); 50 51 /* Copy Mantissa */ 52 if (MPFR_LIKELY (c)) 53 mpn_lshift (MPFR_MANT (f), p, s, c); 54 else 55 MPN_COPY (MPFR_MANT (f), p, s); 56 57 MPFR_SET_SIGN (f, mpz_sgn (z)); 58 MPFR_SET_EXP (f, 0); 59 60 return -c; 61} 62 63/* set f to the rational q */ 64int 65mpfr_set_q (mpfr_ptr f, mpq_srcptr q, mpfr_rnd_t rnd) 66{ 67 mpz_srcptr num, den; 68 mpfr_t n, d; 69 int inexact; 70 int cn, cd; 71 long shift; 72 mp_size_t sn, sd; 73 MPFR_SAVE_EXPO_DECL (expo); 74 75 num = mpq_numref (q); 76 den = mpq_denref (q); 77 /* NAN and INF for mpq are not really documented, but could be found */ 78 if (MPFR_UNLIKELY (mpz_sgn (num) == 0)) 79 { 80 if (MPFR_UNLIKELY (mpz_sgn (den) == 0)) 81 { 82 MPFR_SET_NAN (f); 83 MPFR_RET_NAN; 84 } 85 else 86 { 87 MPFR_SET_ZERO (f); 88 MPFR_SET_POS (f); 89 MPFR_RET (0); 90 } 91 } 92 if (MPFR_UNLIKELY (mpz_sgn (den) == 0)) 93 { 94 MPFR_SET_INF (f); 95 MPFR_SET_SIGN (f, mpz_sgn (num)); 96 MPFR_RET (0); 97 } 98 99 MPFR_SAVE_EXPO_MARK (expo); 100 101 cn = set_z (n, num, &sn); 102 cd = set_z (d, den, &sd); 103 104 /* sn is the number of limbs of the numerator, sd that of the denominator */ 105 106 sn -= sd; 107#if GMP_NUMB_BITS <= 32 /* overflow/underflow cannot happen on 64-bit 108 processors, where MPFR_EMAX_MAX is 2^62 - 1, due to 109 memory limits */ 110 /* If sn >= 0, the quotient has at most sn limbs, thus is larger or equal to 111 2^((sn-1)*GMP_NUMB_BITS), thus its exponent >= (sn-1)*GMP_NUMB_BITS)+1. 112 (sn-1)*GMP_NUMB_BITS)+1 > emax yields (sn-1)*GMP_NUMB_BITS) >= emax, 113 i.e., sn-1 >= floor(emax/GMP_NUMB_BITS). */ 114 if (MPFR_UNLIKELY (sn > MPFR_EMAX_MAX / GMP_NUMB_BITS)) 115 { 116 MPFR_SAVE_EXPO_FREE (expo); 117 inexact = mpfr_overflow (f, rnd, MPFR_SIGN (f)); 118 goto end; 119 } 120 /* If sn < 0, the inverse quotient is >= 2^((-sn-1)*GMP_NUMB_BITS), 121 thus the quotient is <= 2^((sn+1)*GMP_NUMB_BITS), and thus its 122 exponent is <= (sn+1)*GMP_NUMB_BITS+1. 123 (sn+1)*GMP_NUMB_BITS+1 < emin yields (sn+1)*GMP_NUMB_BITS+2 <= emin, 124 i.e., sn+1 <= floor((emin-2)/GMP_NUMB_BITS). */ 125 if (MPFR_UNLIKELY (sn <= (MPFR_EMIN_MIN - 2) / GMP_NUMB_BITS - 1)) 126 { 127 MPFR_SAVE_EXPO_FREE (expo); 128 if (rnd == MPFR_RNDN) 129 rnd = MPFR_RNDZ; 130 inexact = mpfr_underflow (f, rnd, MPFR_SIGN (f)); 131 goto end; 132 } 133#endif 134 135 inexact = mpfr_div (f, n, d, rnd); 136 shift = GMP_NUMB_BITS*sn+cn-cd; 137 MPFR_ASSERTD (shift == GMP_NUMB_BITS*sn+cn-cd); 138 cd = mpfr_mul_2si (f, f, shift, rnd); 139 MPFR_SAVE_EXPO_FREE (expo); 140 /* we can have cd <> 0 only in case of underflow or overflow, but since we 141 are still in extended exponent range, this cannot happen on 64-bit (see 142 above) */ 143#if GMP_NUMB_BITS <= 32 144 if (MPFR_UNLIKELY (cd != 0)) 145 inexact = cd; 146 else 147 inexact = mpfr_check_range (f, inexact, rnd); 148 end: 149#else 150 MPFR_ASSERTD(cd == 0); 151 inexact = mpfr_check_range (f, inexact, rnd); 152#endif 153 mpfr_clear (d); 154 mpfr_clear (n); 155 MPFR_RET (inexact); 156} 157#endif 158