source/libs/mpfr/mpfr-3.1.3/src/init2.c

   1 /* mpfr_init2 -- initialize a floating-point number with given precision
   2
   3 Copyright 2001-2015 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 #include "mpfr-impl.h"
  24
  25 void
  26 mpfr_init2 (mpfr_ptr x, mpfr_prec_t p)
  27 {
  28   mp_size_t xsize;
  29   mpfr_limb_ptr tmp;
  30
  31   /* Check if we can represent the number of limbs
  32    * associated to the maximum of mpfr_prec_t*/
  33   MPFR_ASSERTN( MP_SIZE_T_MAX >= (MPFR_PREC_MAX/MPFR_BYTES_PER_MP_LIMB) );
  34
  35   /* Check for correct GMP_NUMB_BITS and MPFR_BYTES_PER_MP_LIMB */
  36   MPFR_ASSERTN( GMP_NUMB_BITS == MPFR_BYTES_PER_MP_LIMB * CHAR_BIT
  37                 && sizeof(mp_limb_t) == MPFR_BYTES_PER_MP_LIMB );
  38
  39   MPFR_ASSERTN (mp_bits_per_limb == GMP_NUMB_BITS);
  40
  41   /* Check for correct EXP NAN, ZERO & INF in both mpfr.h and mpfr-impl.h */
  42   MPFR_ASSERTN( __MPFR_EXP_NAN  == MPFR_EXP_NAN  );
  43   MPFR_ASSERTN( __MPFR_EXP_ZERO == MPFR_EXP_ZERO );
  44   MPFR_ASSERTN( __MPFR_EXP_INF  == MPFR_EXP_INF  );
  45
  46   MPFR_ASSERTN( MPFR_EMAX_MAX <= (MPFR_EXP_MAX >> 1)  );
  47   MPFR_ASSERTN( MPFR_EMIN_MIN >= -(MPFR_EXP_MAX >> 1) );
  48
  49   /* p=1 is not allowed since the rounding to nearest even rule requires at
  50      least two bits of mantissa: the neighbours of 3/2 are 1*2^0 and 1*2^1,
  51      which both have an odd mantissa */
  52   MPFR_ASSERTN(p >= MPFR_PREC_MIN && p <= MPFR_PREC_MAX);
  53
  54   xsize = MPFR_PREC2LIMBS (p);
  55   tmp   = (mpfr_limb_ptr) (*__gmp_allocate_func)(MPFR_MALLOC_SIZE(xsize));
  56
  57   MPFR_PREC(x) = p;                /* Set prec */
  58   MPFR_EXP (x) = MPFR_EXP_INVALID; /* make sure that the exp field has a
  59                                       valid value in the C point of view */
  60   MPFR_SET_POS(x);                 /* Set a sign */
  61   MPFR_SET_MANT_PTR(x, tmp);       /* Set Mantissa ptr */
  62   MPFR_SET_ALLOC_SIZE(x, xsize);   /* Fix alloc size of Mantissa */
  63   MPFR_SET_NAN(x);                 /* initializes to NaN */
  64 }
  65
  66 #ifdef MPFR_USE_OWN_MPFR_TMP_ALLOC
  67 static unsigned char mpfr_stack_tab[8000000];
  68 unsigned char *mpfr_stack = mpfr_stack_tab;
  69 #endif