src/init2.c - master - niceSOFT/mpfr

src/init2.c
71 строка3 KB
Vincent Lefevre
01 янв 2026, 04:57
01 янв 2026, 04:57bb962f6
/* mpfr_init2 -- initialize a floating-point number with given precision

Copyright 2001-2026 Free Software Foundation, Inc.
Contributed by the Pascaline and Caramba 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 3 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.LESSER.
If not, see <https://www.gnu.org/licenses/>. */

#include "mpfr-impl.h"

/* Note: the purpose of MPFR_SET_POS(x) in this function is just to
 * ensure that the sign field has a valid sign value. You must not
 * assume that the sign bit is necessarily positive. This may change
 * in the future, e.g. via optimizations if the language and build
 * process become powerful enough (e.g. with a transparent pool of
 * MPFR objects to avoid free/malloc calls).
 */

MPFR_HOT_FUNCTION_ATTR void
mpfr_init2 (mpfr_ptr x, mpfr_prec_t p)
{
  mp_size_t xsize;
  mpfr_size_limb_t *tmp;

  /* Check if we can represent the number of limbs
   * associated to the maximum of mpfr_prec_t*/
  MPFR_STAT_STATIC_ASSERT (MP_SIZE_T_MAX >=
                           MPFR_PREC_MAX / MPFR_BYTES_PER_MP_LIMB);

  /* Check for correct GMP_NUMB_BITS and MPFR_BYTES_PER_MP_LIMB */
  MPFR_STAT_STATIC_ASSERT(GMP_NUMB_BITS == MPFR_BYTES_PER_MP_LIMB * CHAR_BIT);
  MPFR_STAT_STATIC_ASSERT(sizeof(mp_limb_t) == MPFR_BYTES_PER_MP_LIMB);
  /* Check for mp_bits_per_limb (a global variable inside GMP library) */
  MPFR_ASSERTN (mp_bits_per_limb == GMP_NUMB_BITS);

  /* Check for consistent EXP MAX, NAN, ZERO & INF in
     both mpfr.h and mpfr-impl.h */
  MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_MAX  == MPFR_EXP_MAX  );
  MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_NAN  == MPFR_EXP_NAN  );
  MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_ZERO == MPFR_EXP_ZERO );
  MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_INF  == MPFR_EXP_INF  );

  MPFR_STAT_STATIC_ASSERT( MPFR_EMAX_MAX <= (MPFR_EXP_MAX >> 1)  );
  MPFR_STAT_STATIC_ASSERT( MPFR_EMIN_MIN >= -(MPFR_EXP_MAX >> 1) );

  MPFR_ASSERTN (MPFR_PREC_COND (p));

  xsize = MPFR_PREC2LIMBS (p);
  tmp   = (mpfr_size_limb_t *) mpfr_allocate_func(MPFR_MALLOC_SIZE(xsize));

  MPFR_PREC(x) = p;                /* Set prec */
  MPFR_EXP (x) = MPFR_EXP_INVALID; /* Make sure that the exp field has a
                                      valid value in the C point of view */
  MPFR_SET_POS(x);                 /* Set an arbitrary sign */
  MPFR_SET_MANT_PTR(x, tmp);       /* Set mantissa ptr */
  MPFR_SET_ALLOC_SIZE(x, xsize);   /* Fix alloc size of mantissa */
  MPFR_SET_NAN(x);                 /* Initialize to NaN */
}