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

   1 /* mpfr_set_uj -- set a MPFR number from a huge machine unsigned integer
   2
   3 Copyright 2004-2015 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 #ifdef HAVE_CONFIG_H
  24 # include "config.h"       /* for a build within gmp */
  25 #endif
  26
  27 #define MPFR_NEED_LONGLONG_H
  28 #include "mpfr-intmax.h"
  29 #include "mpfr-impl.h"
  30
  31 #ifdef _MPFR_H_HAVE_INTMAX_T
  32
  33 int
  34 mpfr_set_uj (mpfr_t x, uintmax_t j, mpfr_rnd_t rnd)
  35 {
  36   return mpfr_set_uj_2exp (x, j, 0, rnd);
  37 }
  38
  39 int
  40 mpfr_set_uj_2exp (mpfr_t x, uintmax_t j, intmax_t e, mpfr_rnd_t rnd)
  41 {
  42   unsigned int cnt, i;
  43   mp_size_t k, len;
  44   mp_limb_t limb;
  45   mp_limb_t yp[sizeof(uintmax_t) / sizeof(mp_limb_t)];
  46   mpfr_t y;
  47   unsigned long uintmax_bit_size = sizeof(uintmax_t) * CHAR_BIT;
  48   unsigned long bpml = GMP_NUMB_BITS % uintmax_bit_size;
  49
  50   /* Special case */
  51   if (j == 0)
  52     {
  53       MPFR_SET_POS(x);
  54       MPFR_SET_ZERO(x);
  55       MPFR_RET(0);
  56     }
  57
  58   MPFR_ASSERTN (sizeof(uintmax_t) % sizeof(mp_limb_t) == 0);
  59
  60   /* Create an auxillary var */
  61   MPFR_TMP_INIT1 (yp, y, uintmax_bit_size);
  62   k = numberof (yp);
  63   if (k == 1)
  64     limb = yp[0] = j;
  65   else
  66     {
  67       /* Note: either GMP_NUMB_BITS = uintmax_bit_size, then k = 1 the
  68          shift j >>= bpml is never done, or GMP_NUMB_BITS < uintmax_bit_size
  69          and bpml = GMP_NUMB_BITS. */
  70       for (i = 0; i < k; i++, j >>= bpml)
  71         yp[i] = j; /* Only the low bits are copied */
  72
  73       /* Find the first limb not equal to zero. */
  74       do
  75         {
  76           MPFR_ASSERTD (k > 0);
  77           limb = yp[--k];
  78         }
  79       while (limb == 0);
  80       k++;
  81     }
  82   count_leading_zeros(cnt, limb);
  83   len = numberof (yp) - k;
  84
  85   /* Normalize it: len = number of last 0 limb, k number of non-zero limbs */
  86   if (MPFR_LIKELY(cnt))
  87     mpn_lshift (yp+len, yp, k, cnt);  /* Normalize the High Limb*/
  88   else if (len != 0)
  89     MPN_COPY_DECR (yp+len, yp, k);    /* Must use DECR */
  90   if (len != 0)
  91     /* Note: when numberof(yp)==1, len is constant and null, so the compiler
  92        can optimize out this code. */
  93     {
  94       if (len == 1)
  95         yp[0] = (mp_limb_t) 0;
  96       else
  97         MPN_ZERO (yp, len);   /* Zeroing the last limbs */
  98     }
  99   e += k * GMP_NUMB_BITS - cnt;    /* Update Expo */
 100   MPFR_ASSERTD (MPFR_LIMB_MSB(yp[numberof (yp) - 1]) != 0);
 101
 102   /* Check expo underflow / overflow (can't use mpfr_check_range) */
 103   if (MPFR_UNLIKELY(e < __gmpfr_emin))
 104     {
 105       /* The following test is necessary because in the rounding to the
 106        * nearest mode, mpfr_underflow always rounds away from 0. In
 107        * this rounding mode, we need to round to 0 if:
 108        *   _ |x| < 2^(emin-2), or
 109        *   _ |x| = 2^(emin-2) and the absolute value of the exact
 110        *     result is <= 2^(emin-2). */
 111       if (rnd == MPFR_RNDN && (e+1 < __gmpfr_emin || mpfr_powerof2_raw(y)))
 112         rnd = MPFR_RNDZ;
 113       return mpfr_underflow (x, rnd, MPFR_SIGN_POS);
 114     }
 115   if (MPFR_UNLIKELY(e > __gmpfr_emax))
 116     return mpfr_overflow (x, rnd, MPFR_SIGN_POS);
 117   MPFR_SET_EXP (y, e);
 118
 119   /* Final: set x to y (rounding if necessary) */
 120   return mpfr_set (x, y, rnd);
 121 }
 122
 123 #endif