source/libs/mpfr/mpfr-3.1.3/src/ui_div.c

   1 /* mpfr_ui_div -- divide a machine integer by a floating-point number
   2    mpfr_si_div -- divide a machine number by a floating-point number
   3
   4 Copyright 2000-2015 Free Software Foundation, Inc.
   5 Contributed by the AriC and Caramel projects, INRIA.
   6
   7 This file is part of the GNU MPFR Library.
   8
   9 The GNU MPFR Library is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU Lesser General Public License as published by
  11 the Free Software Foundation; either version 3 of the License, or (at your
  12 option) any later version.
  13
  14 The GNU MPFR Library is distributed in the hope that it will be useful, but
  15 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  16 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  17 License for more details.
  18
  19 You should have received a copy of the GNU Lesser General Public License
  20 along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
  21 http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
  22 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
  23
  24
  25 #define MPFR_NEED_LONGLONG_H
  26 #include "mpfr-impl.h"
  27
  28 int
  29 mpfr_ui_div (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
  30 {
  31   MPFR_LOG_FUNC
  32     (("u=%lu x[%Pu]=%.*Rg rnd=%d",
  33       u, mpfr_get_prec(x), mpfr_log_prec, x, rnd_mode),
  34      ("y[%Pu]=%.*Rg", mpfr_get_prec(y), mpfr_log_prec, y));
  35
  36   if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
  37     {
  38       if (MPFR_IS_NAN(x))
  39         {
  40           MPFR_SET_NAN(y);
  41           MPFR_RET_NAN;
  42         }
  43       else if (MPFR_IS_INF(x)) /* u/Inf = 0 */
  44         {
  45           MPFR_SET_ZERO(y);
  46           MPFR_SET_SAME_SIGN(y,x);
  47           MPFR_RET(0);
  48         }
  49       else /* u / 0 */
  50         {
  51           MPFR_ASSERTD(MPFR_IS_ZERO(x));
  52           if (u)
  53             {
  54               /* u > 0, so y = sign(x) * Inf */
  55               MPFR_SET_SAME_SIGN(y, x);
  56               MPFR_SET_INF(y);
  57               mpfr_set_divby0 ();
  58               MPFR_RET(0);
  59             }
  60           else
  61             {
  62               /* 0 / 0 */
  63               MPFR_SET_NAN(y);
  64               MPFR_RET_NAN;
  65             }
  66         }
  67     }
  68   else if (MPFR_LIKELY(u != 0))
  69     {
  70       mpfr_t uu;
  71       mp_limb_t up[1];
  72       int cnt;
  73       int inex;
  74
  75       MPFR_SAVE_EXPO_DECL (expo);
  76
  77       MPFR_TMP_INIT1(up, uu, GMP_NUMB_BITS);
  78       MPFR_ASSERTN(u == (mp_limb_t) u);
  79       count_leading_zeros(cnt, (mp_limb_t) u);
  80       up[0] = (mp_limb_t) u << cnt;
  81
  82       /* Optimization note: Exponent save/restore operations may be
  83          removed if mpfr_div works even when uu is out-of-range. */
  84       MPFR_SAVE_EXPO_MARK (expo);
  85       MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt);
  86       inex = mpfr_div (y, uu, x, rnd_mode);
  87       MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
  88       MPFR_SAVE_EXPO_FREE (expo);
  89       return mpfr_check_range (y, inex, rnd_mode);
  90     }
  91   else /* u = 0, and x != 0 */
  92     {
  93       MPFR_SET_ZERO(y);         /* if u=0, then set y to 0 */
  94       MPFR_SET_SAME_SIGN(y, x); /* u considered as +0: sign(+0/x) = sign(x) */
  95       MPFR_RET(0);
  96     }
  97 }
  98
  99
 100 int
 101 mpfr_si_div (mpfr_ptr y, long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
 102 {
 103   int res;
 104
 105   if (u >= 0)
 106     res = mpfr_ui_div (y, u, x, rnd_mode);
 107   else
 108     {
 109       res = -mpfr_ui_div (y, -u, x, MPFR_INVERT_RND(rnd_mode));
 110       MPFR_CHANGE_SIGN (y);
 111     }
 112   return res;
 113 }