mpfr-2.4.1/set_uj.c

/* mpfr_set_uj -- set a MPFR number from a huge machine unsigned integer

Copyright 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
Contributed by the Arenaire and Cacao projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.

The GNU MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */

#ifdef HAVE_CONFIG_H
# include "config.h"       /* for a build within gmp */
#endif

/* The ISO C99 standard specifies that in C++ implementations the
   INTMAX_MAX, ... macros should only be defined if explicitly requested.  */
#if defined(__cplusplus)
# define __STDC_LIMIT_MACROS
# define __STDC_CONSTANT_MACROS
#endif

#if HAVE_INTTYPES_H
# include <inttypes.h> /* for intmax_t */
#else
# if HAVE_STDINT_H
#  include <stdint.h>
# endif
#endif

#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"

#ifdef _MPFR_H_HAVE_INTMAX_T

int
mpfr_set_uj (mpfr_t x, uintmax_t j, mp_rnd_t rnd)
{
  return mpfr_set_uj_2exp (x, j, 0, rnd);
}

int
mpfr_set_uj_2exp (mpfr_t x, uintmax_t j, intmax_t e, mp_rnd_t rnd)
{
  unsigned int cnt, i;
  mp_size_t k, len;
  mp_limb_t limb;
  mp_limb_t yp[sizeof(uintmax_t) / sizeof(mp_limb_t)];
  mpfr_t y;
  unsigned long uintmax_bit_size = sizeof(uintmax_t) * CHAR_BIT;
  unsigned long bpml = BITS_PER_MP_LIMB % uintmax_bit_size;

  /* Special case */
  if (j == 0)
    {
      MPFR_SET_POS(x);
      MPFR_SET_ZERO(x);
      MPFR_RET(0);
    }

  MPFR_ASSERTN (sizeof(uintmax_t) % sizeof(mp_limb_t) == 0);

  /* Create an auxillary var */
  MPFR_TMP_INIT1 (yp, y, uintmax_bit_size);
  k = numberof (yp);
  if (k == 1)
    limb = yp[0] = j;
  else
    {
      /* Note: either BITS_PER_MP_LIMB = uintmax_bit_size, then k = 1 the
         shift j >>= bpml is never done, or BITS_PER_MP_LIMB < uintmax_bit_size
         and bpml = BITS_PER_MP_LIMB. */
      for (i = 0; i < k; i++, j >>= bpml)
        yp[i] = j; /* Only the low bits are copied */

      /* Find the first limb not equal to zero. */
      do
        {
          MPFR_ASSERTD (k > 0);
          limb = yp[--k];
        }
      while (limb == 0);
      k++;
    }
  count_leading_zeros(cnt, limb);
  len = numberof (yp) - k;

  /* Normalize it: len = number of last 0 limb, k number of non-zero limbs */
  if (MPFR_LIKELY(cnt))
    mpn_lshift (yp+len, yp, k, cnt);  /* Normalize the High Limb*/
  else if (len != 0)
    MPN_COPY_DECR (yp+len, yp, k);    /* Must use DECR */
  if (len != 0)
    /* Note: when numberof(yp)==1, len is constant and null, so the compiler
       can optimize out this code. */
    {
      if (len == 1)
        yp[0] = (mp_limb_t) 0;
      else
        MPN_ZERO (yp, len);   /* Zeroing the last limbs */
    }
  e += k * BITS_PER_MP_LIMB - cnt;    /* Update Expo */
  MPFR_ASSERTD (MPFR_LIMB_MSB(yp[numberof (yp) - 1]) != 0);

  /* Check expo underflow / overflow (can't use mpfr_check_range) */
  if (MPFR_UNLIKELY(e < __gmpfr_emin))
    {
      /* The following test is necessary because in the rounding to the
       * nearest mode, mpfr_underflow always rounds away from 0. In
       * this rounding mode, we need to round to 0 if:
       *   _ |x| < 2^(emin-2), or
       *   _ |x| = 2^(emin-2) and the absolute value of the exact
       *     result is <= 2^(emin-2). */
      if (rnd == GMP_RNDN && (e+1 < __gmpfr_emin || mpfr_powerof2_raw(y)))
        rnd = GMP_RNDZ;
      return mpfr_underflow (x, rnd, MPFR_SIGN_POS);
    }
  if (MPFR_UNLIKELY(e > __gmpfr_emax))
    return mpfr_overflow (x, rnd, MPFR_SIGN_POS);
  MPFR_SET_EXP (y, e);

  /* Final: set x to y (rounding if necessary) */
  return mpfr_set (x, y, rnd);
}

#endif