1  /* mpfr_check -- Check if a floating-point number has not been corrupted.
       2  
       3  Copyright 2003-2004, 2006-2023 Free Software Foundation, Inc.
       4  Contributed by the AriC and Caramba 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  https://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  #include "mpfr-impl.h"
      24  
      25  /*
      26   * Check if x is a valid mpfr_t initialized by mpfr_init
      27   * Returns 0 if isn't valid
      28   *
      29   * Note: Due to the MPFR_GET_ALLOC_SIZE test, this function must not
      30   * be called on statically allocated numbers (only used inside MPFR).
      31   * Anyway, this test should not be useful on such numbers.
      32   */
      33  int
      34  mpfr_check (mpfr_srcptr x)
      35  {
      36    mp_size_t s, i;
      37    mp_limb_t tmp;
      38    volatile mp_limb_t *xm;
      39    mpfr_prec_t prec;
      40    int rw;
      41  
      42    /* Check sign */
      43    if (MPFR_SIGN(x) != MPFR_SIGN_POS &&
      44        MPFR_SIGN(x) != MPFR_SIGN_NEG)
      45      return 0;
      46    /* Check precision */
      47    prec = MPFR_PREC(x);
      48    if (! MPFR_PREC_COND (prec))
      49      return 0;
      50    /* Check mantissa */
      51    xm = MPFR_MANT(x);
      52    if (xm == NULL)
      53      return 0;
      54    /* Check size of mantissa */
      55    s = MPFR_GET_ALLOC_SIZE(x);
      56    if (s <= 0 || s > MP_SIZE_T_MAX ||
      57        prec > (mpfr_prec_t) s * GMP_NUMB_BITS)
      58      return 0;
      59    /* Access all the mp_limb of the mantissa: may do a seg fault */
      60    for (i = 0 ; i < s ; i++)
      61      tmp = xm[i];
      62    /* Check singular numbers (do not use MPFR_IS_PURE_FP() in order to avoid
      63       any assertion checking, as this function mpfr_check() does something
      64       similar by returning a Boolean instead of doing an abort if the format
      65       is incorrect). */
      66    if (MPFR_IS_SINGULAR (x))
      67      return MPFR_IS_ZERO(x) || MPFR_IS_NAN(x) || MPFR_IS_INF(x);
      68    /* Check the most significant limb (its MSB must be 1) */
      69    if (! MPFR_IS_NORMALIZED (x))
      70      return 0;
      71    /* Check the least significant limb (the trailing bits must be 0) */
      72    rw = prec % GMP_NUMB_BITS;
      73    if (rw != 0)
      74      {
      75        tmp = MPFR_LIMB_MASK (GMP_NUMB_BITS - rw);
      76        if ((xm[0] & tmp) != 0)
      77          return 0;
      78      }
      79    /* Check exponent range */
      80    return MPFR_EXP_IN_RANGE (MPFR_EXP (x));
      81  }