efee5258bc
The MPFR library is a C library for multiple-precision floating-point computations with exact rounding (also called correct rounding). It is based on the GMP multiple-precision library and should replace the MPF class in further releases of GMP. GCC >= 4.2 requires MPFR.
138 lines
4.6 KiB
C
138 lines
4.6 KiB
C
/* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer
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Copyright 2004, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao projects, INRIA.
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This file is part of the GNU MPFR Library.
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The GNU MPFR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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The GNU MPFR Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
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http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
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51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
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#ifdef HAVE_CONFIG_H
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# include "config.h" /* for a build within gmp */
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#endif
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/* The ISO C99 standard specifies that in C++ implementations the
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INTMAX_MAX, ... macros should only be defined if explicitly requested. */
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#if defined __cplusplus
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# define __STDC_LIMIT_MACROS
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# define __STDC_CONSTANT_MACROS
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#endif
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#if HAVE_INTTYPES_H
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# include <inttypes.h> /* for intmax_t */
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#else
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# if HAVE_STDINT_H
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# include <stdint.h>
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# endif
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#endif
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#include "mpfr-impl.h"
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#ifdef _MPFR_H_HAVE_INTMAX_T
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intmax_t
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mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd)
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{
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intmax_t r;
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mpfr_prec_t prec;
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mpfr_t x;
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if (MPFR_UNLIKELY (!mpfr_fits_intmax_p (f, rnd)))
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{
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MPFR_SET_ERANGE ();
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return MPFR_IS_NAN (f) ? 0 :
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MPFR_IS_NEG (f) ? MPFR_INTMAX_MIN : MPFR_INTMAX_MAX;
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}
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if (MPFR_IS_ZERO (f))
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return (intmax_t) 0;
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/* determine the precision of intmax_t */
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for (r = MPFR_INTMAX_MIN, prec = 0; r != 0; r /= 2, prec++)
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{ }
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/* Note: though INTMAX_MAX would have been sufficient for the conversion,
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we chose INTMAX_MIN so that INTMAX_MIN - 1 is always representable in
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precision prec; this is useful to detect overflows in MPFR_RNDZ (will
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be needed later). */
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/* Now, r = 0. */
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mpfr_init2 (x, prec);
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mpfr_rint (x, f, rnd);
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MPFR_ASSERTN (MPFR_IS_FP (x));
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if (MPFR_NOTZERO (x))
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{
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mp_limb_t *xp;
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int sh, n; /* An int should be sufficient in this context. */
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xp = MPFR_MANT (x);
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sh = MPFR_GET_EXP (x);
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MPFR_ASSERTN ((mpfr_prec_t) sh <= prec);
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if (MPFR_INTMAX_MIN + MPFR_INTMAX_MAX != 0
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&& MPFR_UNLIKELY ((mpfr_prec_t) sh == prec))
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{
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/* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t
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has the same size as intmax_t, we cannot use the code in
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the for loop since the operations would be performed in
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unsigned arithmetic. */
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MPFR_ASSERTN (MPFR_IS_NEG (x) && (mpfr_powerof2_raw (x)));
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r = MPFR_INTMAX_MIN;
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}
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else if (MPFR_IS_POS (x))
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{
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/* Note: testing the condition sh >= 0 is necessary to avoid
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an undefined behavior on xp[n] >> S when S >= GMP_NUMB_BITS
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(even though xp[n] == 0 in such a case). This can happen if
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sizeof(mp_limb_t) < sizeof(intmax_t) and |x| is small enough
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because of the trailing bits due to its normalization. */
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for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--)
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{
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sh -= GMP_NUMB_BITS;
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/* Note the concerning the casts below:
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When sh >= 0, the cast must be performed before the shift
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for the case sizeof(intmax_t) > sizeof(mp_limb_t).
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When sh < 0, the cast must be performed after the shift
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for the case sizeof(intmax_t) == sizeof(mp_limb_t), as
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mp_limb_t is unsigned, therefore not representable as an
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intmax_t when the MSB is 1 (this is the case here). */
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MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS);
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r += (sh >= 0
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? (intmax_t) xp[n] << sh
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: (intmax_t) (xp[n] >> (-sh)));
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}
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}
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else
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{
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/* See the comments for the case x positive. */
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for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--)
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{
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sh -= GMP_NUMB_BITS;
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MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS);
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r -= (sh >= 0
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? (intmax_t) xp[n] << sh
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: (intmax_t) (xp[n] >> (-sh)));
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}
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}
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}
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mpfr_clear (x);
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return r;
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}
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#endif
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