1 /* mpfr_init2 -- initialize a floating-point number with given precision
2
3 Copyright 2001-2023 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 MPFR_HOT_FUNCTION_ATTR void
mpfr_init2(mpfr_ptr x,mpfr_prec_t p)26 mpfr_init2 (mpfr_ptr x, mpfr_prec_t p)
27 {
28 mp_size_t xsize;
29 mpfr_size_limb_t *tmp;
30
31 /* Check if we can represent the number of limbs
32 * associated to the maximum of mpfr_prec_t*/
33 MPFR_STAT_STATIC_ASSERT( 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_STAT_STATIC_ASSERT(GMP_NUMB_BITS == MPFR_BYTES_PER_MP_LIMB * CHAR_BIT);
37 MPFR_STAT_STATIC_ASSERT(sizeof(mp_limb_t) == MPFR_BYTES_PER_MP_LIMB);
38 /* Check for mp_bits_per_limb (a global variable inside GMP library) */
39 MPFR_ASSERTN (mp_bits_per_limb == GMP_NUMB_BITS);
40
41 /* Check for consistent EXP MAX, NAN, ZERO & INF in
42 both mpfr.h and mpfr-impl.h */
43 MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_MAX == MPFR_EXP_MAX );
44 MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_NAN == MPFR_EXP_NAN );
45 MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_ZERO == MPFR_EXP_ZERO );
46 MPFR_STAT_STATIC_ASSERT( __MPFR_EXP_INF == MPFR_EXP_INF );
47
48 MPFR_STAT_STATIC_ASSERT( MPFR_EMAX_MAX <= (MPFR_EXP_MAX >> 1) );
49 MPFR_STAT_STATIC_ASSERT( MPFR_EMIN_MIN >= -(MPFR_EXP_MAX >> 1) );
50
51 /* p=1 is not allowed since the rounding to nearest even rule requires at
52 least two bits of mantissa: the neighbors of 3/2 are 1*2^0 and 1*2^1,
53 which both have an odd mantissa */
54 MPFR_ASSERTN (MPFR_PREC_COND (p));
55
56 xsize = MPFR_PREC2LIMBS (p);
57 tmp = (mpfr_size_limb_t *) mpfr_allocate_func(MPFR_MALLOC_SIZE(xsize));
58
59 MPFR_PREC(x) = p; /* Set prec */
60 MPFR_EXP (x) = MPFR_EXP_INVALID; /* make sure that the exp field has a
61 valid value in the C point of view */
62 MPFR_SET_POS(x); /* Set a sign */
63 MPFR_SET_MANT_PTR(x, tmp); /* Set Mantissa ptr */
64 MPFR_SET_ALLOC_SIZE(x, xsize); /* Fix alloc size of Mantissa */
65 MPFR_SET_NAN(x); /* initializes to NaN */
66 }
67