1 /* mpfr_frac -- Fractional part of a floating-point number.
3 Copyright 2002, 2003, 2004, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
4 Contributed by the Arenaire and Cacao projects, INRIA.
6 This file is part of the GNU MPFR Library.
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 2.1 of the License, or (at your
11 option) any later version.
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.
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.LIB. If not, write to
20 the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
21 MA 02110-1301, USA. */
24 #define MPFR_NEED_LONGLONG_H
25 #include "mpfr-impl.h"
27 /* Optimization note: it is not a good idea to call mpfr_integer_p,
28 as some cases will take longer (the number may be parsed twice). */
31 mpfr_frac (mpfr_ptr r, mpfr_srcptr u, mp_rnd_t rnd_mode)
36 mp_limb_t *up, *tp, k;
41 MPFR_SAVE_EXPO_DECL (expo);
44 if (MPFR_UNLIKELY(MPFR_IS_NAN(u)))
49 else if (MPFR_UNLIKELY(MPFR_IS_INF(u) || mpfr_integer_p (u)))
52 MPFR_SET_SAME_SIGN(r, u);
54 MPFR_RET(0); /* zero is exact */
57 ue = MPFR_GET_EXP (u);
58 if (ue <= 0) /* |u| < 1 */
59 return mpfr_set (r, u, rnd_mode);
61 /* Now |u| >= 1, meaning that an overflow is not possible. */
64 un = (uq - 1) / BITS_PER_MP_LIMB; /* index of most significant limb */
65 un -= (mp_size_t) (ue / BITS_PER_MP_LIMB);
66 /* now the index of the MSL containing bits of the fractional part */
69 sh = ue % BITS_PER_MP_LIMB;
71 /* the first bit of the fractional part is the MSB of k */
77 count_leading_zeros(cnt, k);
78 /* first bit 1 of the fractional part -> MSB of the number */
81 MPFR_ASSERTN (sh < BITS_PER_MP_LIMB);
86 re = sh - BITS_PER_MP_LIMB;
87 /* searching for the first bit 1 (exists since u isn't an integer) */
89 re -= BITS_PER_MP_LIMB;
90 MPFR_ASSERTN(un >= 0);
92 count_leading_zeros(sh, k);
96 /* The exponent of r will be re */
97 /* un: index of the limb of u that contains the first bit 1 of the FP */
99 t = (mp_size_t) (MPFR_PREC(r) - 1) / BITS_PER_MP_LIMB < un ?
100 (mpfr_init2 (tmp, (un + 1) * BITS_PER_MP_LIMB), tmp) : r;
101 /* t has enough precision to contain the fractional part of u */
102 /* If we use a temporary variable, we take the non-significant bits
103 of u into account, because of the mpn_lshift below. */
105 MPFR_SET_SAME_SIGN(t, u);
107 /* Put the fractional part of u into t */
108 tn = (MPFR_PREC(t) - 1) / BITS_PER_MP_LIMB;
109 MPFR_ASSERTN(tn >= un);
113 MPN_COPY_DECR(tp + t0, up, un + 1);
114 else /* warning: un may be 0 here */
115 tp[tn] = k | ((un) ? mpn_lshift (tp + t0, up, un, sh) : (mp_limb_t) 0);
119 MPFR_SAVE_EXPO_MARK (expo);
123 MPFR_EXP (t) = 0; /* should be re, but not necessarily in the range */
124 inex = mpfr_set (r, t, rnd_mode); /* no underflow */
129 { /* There may be remaining non-significant bits in t (= r). */
133 carry = mpfr_round_raw (tp, tp,
134 (mp_prec_t) (tn + 1) * BITS_PER_MP_LIMB,
135 MPFR_IS_NEG (r), MPFR_PREC (r), rnd_mode,
139 tp[tn] = MPFR_LIMB_HIGHBIT;
144 MPFR_SAVE_EXPO_FREE (expo);
145 return mpfr_check_range (r, inex, rnd_mode);