contrib/mpfr/set_uj.c

   1 /* mpfr_set_uj -- set a MPFR number from a huge machine unsigned integer
   2
   3 Copyright 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
   4 Contributed by the Arenaire and Cacao 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 2.1 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.LIB.  If not, write to
  20 the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
  21 MA 02110-1301, USA. */
  22
  23 #ifdef HAVE_CONFIG_H
  24 # include "config.h"       /* for a build within gmp */
  25 #endif
  26
  27 /* The ISO C99 standard specifies that in C++ implementations the
  28    INTMAX_MAX, ... macros should only be defined if explicitly requested.  */
  29 #if defined(__cplusplus)
  30 # define __STDC_LIMIT_MACROS
  31 # define __STDC_CONSTANT_MACROS
  32 #endif
  33
  34 #if HAVE_INTTYPES_H
  35 # include <inttypes.h> /* for intmax_t */
  36 #else
  37 # if HAVE_STDINT_H
  38 #  include <stdint.h>
  39 # endif
  40 #endif
  41
  42 #define MPFR_NEED_LONGLONG_H
  43 #include "mpfr-impl.h"
  44
  45 #ifdef _MPFR_H_HAVE_INTMAX_T
  46
  47 int
  48 mpfr_set_uj (mpfr_t x, uintmax_t j, mp_rnd_t rnd)
  49 {
  50   return mpfr_set_uj_2exp (x, j, 0, rnd);
  51 }
  52
  53 int
  54 mpfr_set_uj_2exp (mpfr_t x, uintmax_t j, intmax_t e, mp_rnd_t rnd)
  55 {
  56   unsigned int cnt, i;
  57   mp_size_t k, len;
  58   mp_limb_t limb;
  59   mp_limb_t yp[sizeof(uintmax_t) / sizeof(mp_limb_t)];
  60   mpfr_t y;
  61   unsigned long uintmax_bit_size = sizeof(uintmax_t) * CHAR_BIT;
  62   unsigned long bpml = BITS_PER_MP_LIMB % uintmax_bit_size;
  63
  64   /* Special case */
  65   if (j == 0)
  66     {
  67       MPFR_SET_POS(x);
  68       MPFR_SET_ZERO(x);
  69       MPFR_RET(0);
  70     }
  71
  72   MPFR_ASSERTN (sizeof(uintmax_t) % sizeof(mp_limb_t) == 0);
  73
  74   /* Create an auxillary var */
  75   MPFR_TMP_INIT1 (yp, y, uintmax_bit_size);
  76   k = numberof (yp);
  77   if (k == 1)
  78     limb = yp[0] = j;
  79   else
  80     {
  81       /* Note: either BITS_PER_MP_LIMB = uintmax_bit_size, then k = 1 the
  82          shift j >>= bpml is never done, or BITS_PER_MP_LIMB < uintmax_bit_size
  83          and bpml = BITS_PER_MP_LIMB. */
  84       for (i = 0; i < k; i++, j >>= bpml)
  85         yp[i] = j; /* Only the low bits are copied */
  86
  87       /* Find the first limb not equal to zero. */
  88       do
  89         {
  90           MPFR_ASSERTD (k > 0);
  91           limb = yp[--k];
  92         }
  93       while (limb == 0);
  94       k++;
  95     }
  96   count_leading_zeros(cnt, limb);
  97   len = numberof (yp) - k;
  98
  99   /* Normalize it: len = number of last 0 limb, k number of non-zero limbs */
 100   if (MPFR_LIKELY(cnt))
 101     mpn_lshift (yp+len, yp, k, cnt);  /* Normalize the High Limb*/
 102   else if (len != 0)
 103     MPN_COPY_DECR (yp+len, yp, k);    /* Must use DECR */
 104   if (len != 0)
 105     /* Note: when numberof(yp)==1, len is constant and null, so the compiler
 106        can optimize out this code. */
 107     {
 108       if (len == 1)
 109         yp[0] = (mp_limb_t) 0;
 110       else
 111         MPN_ZERO (yp, len);   /* Zeroing the last limbs */
 112     }
 113   e += k * BITS_PER_MP_LIMB - cnt;    /* Update Expo */
 114   MPFR_ASSERTD (MPFR_LIMB_MSB(yp[numberof (yp) - 1]) != 0);
 115
 116   /* Check expo underflow / overflow (can't use mpfr_check_range) */
 117   if (MPFR_UNLIKELY(e < __gmpfr_emin))
 118     {
 119       /* The following test is necessary because in the rounding to the
 120        * nearest mode, mpfr_underflow always rounds away from 0. In
 121        * this rounding mode, we need to round to 0 if:
 122        *   _ |x| < 2^(emin-2), or
 123        *   _ |x| = 2^(emin-2) and the absolute value of the exact
 124        *     result is <= 2^(emin-2). */
 125       if (rnd == GMP_RNDN && (e+1 < __gmpfr_emin || mpfr_powerof2_raw(y)))
 126         rnd = GMP_RNDZ;
 127       return mpfr_underflow (x, rnd, MPFR_SIGN_POS);
 128     }
 129   if (MPFR_UNLIKELY(e > __gmpfr_emax))
 130     return mpfr_overflow (x, rnd, MPFR_SIGN_POS);
 131   MPFR_SET_EXP (y, e);
 132
 133   /* Final: set x to y (rounding if necessary) */
 134   return mpfr_set (x, y, rnd);
 135 }
 136
 137 #endif