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Diffstat (limited to 'mpfr/src/get_sj.c')
-rw-r--r-- | mpfr/src/get_sj.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/mpfr/src/get_sj.c b/mpfr/src/get_sj.c new file mode 100644 index 0000000000..9bd68a181c --- /dev/null +++ b/mpfr/src/get_sj.c @@ -0,0 +1,123 @@ +/* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer + +Copyright 2004, 2006-2016 Free Software Foundation, Inc. +Contributed by the AriC 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 +http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., +51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ + +#ifdef HAVE_CONFIG_H +# include "config.h" /* for a build within gmp */ +#endif + +#include "mpfr-intmax.h" +#include "mpfr-impl.h" + +#ifdef _MPFR_H_HAVE_INTMAX_T + +intmax_t +mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd) +{ + intmax_t r; + mpfr_prec_t prec; + mpfr_t x; + + if (MPFR_UNLIKELY (!mpfr_fits_intmax_p (f, rnd))) + { + MPFR_SET_ERANGE (); + return MPFR_IS_NAN (f) ? 0 : + MPFR_IS_NEG (f) ? MPFR_INTMAX_MIN : MPFR_INTMAX_MAX; + } + + if (MPFR_IS_ZERO (f)) + return (intmax_t) 0; + + /* determine the precision of intmax_t */ + for (r = MPFR_INTMAX_MIN, prec = 0; r != 0; r /= 2, prec++) + { } + /* Note: though INTMAX_MAX would have been sufficient for the conversion, + we chose INTMAX_MIN so that INTMAX_MIN - 1 is always representable in + precision prec; this is useful to detect overflows in MPFR_RNDZ (will + be needed later). */ + + /* Now, r = 0. */ + + mpfr_init2 (x, prec); + mpfr_rint (x, f, rnd); + MPFR_ASSERTN (MPFR_IS_FP (x)); + + if (MPFR_NOTZERO (x)) + { + mp_limb_t *xp; + int sh, n; /* An int should be sufficient in this context. */ + + xp = MPFR_MANT (x); + sh = MPFR_GET_EXP (x); + MPFR_ASSERTN ((mpfr_prec_t) sh <= prec); + if (MPFR_INTMAX_MIN + MPFR_INTMAX_MAX != 0 + && MPFR_UNLIKELY ((mpfr_prec_t) sh == prec)) + { + /* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t + has the same size as intmax_t, we cannot use the code in + the for loop since the operations would be performed in + unsigned arithmetic. */ + MPFR_ASSERTN (MPFR_IS_NEG (x) && (mpfr_powerof2_raw (x))); + r = MPFR_INTMAX_MIN; + } + else if (MPFR_IS_POS (x)) + { + /* Note: testing the condition sh >= 0 is necessary to avoid + an undefined behavior on xp[n] >> S when S >= GMP_NUMB_BITS + (even though xp[n] == 0 in such a case). This can happen if + sizeof(mp_limb_t) < sizeof(intmax_t) and |x| is small enough + because of the trailing bits due to its normalization. */ + for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--) + { + sh -= GMP_NUMB_BITS; + /* Note the concerning the casts below: + When sh >= 0, the cast must be performed before the shift + for the case sizeof(intmax_t) > sizeof(mp_limb_t). + When sh < 0, the cast must be performed after the shift + for the case sizeof(intmax_t) == sizeof(mp_limb_t), as + mp_limb_t is unsigned, therefore not representable as an + intmax_t when the MSB is 1 (this is the case here). */ + MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS); + r += (sh >= 0 + ? (intmax_t) xp[n] << sh + : (intmax_t) (xp[n] >> (-sh))); + } + } + else + { + /* See the comments for the case x positive. */ + for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--) + { + sh -= GMP_NUMB_BITS; + MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS); + r -= (sh >= 0 + ? (intmax_t) xp[n] << sh + : (intmax_t) (xp[n] >> (-sh))); + } + } + } + + mpfr_clear (x); + + return r; +} + +#endif |