1/* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer 2 3Copyright 2004, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc. 4Contributed by the Arenaire and Cacao projects, INRIA. 5 6This file is part of the GNU MPFR Library. 7 8The GNU MPFR Library is free software; you can redistribute it and/or modify 9it under the terms of the GNU Lesser General Public License as published by 10the Free Software Foundation; either version 3 of the License, or (at your 11option) any later version. 12 13The GNU MPFR Library is distributed in the hope that it will be useful, but 14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16License for more details. 17 18You should have received a copy of the GNU Lesser General Public License 19along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see 20http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 2151 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 22 23#ifdef HAVE_CONFIG_H 24# include "config.h" /* for a build within gmp */ 25#endif 26 27/* The ISO C99 standard specifies that in C++ implementations the 28 INTMAX_MAX, ... macros should only be defined if explicitly requested. */ 29#if defined __cplusplus 30# define __STDC_LIMIT_MACROS 31# define __STDC_CONSTANT_MACROS 32#endif 33 34#if HAVE_INTTYPES_H 35# include <inttypes.h> /* for intmax_t */ 36#else 37# if HAVE_STDINT_H 38# include <stdint.h> 39# endif 40#endif 41 42#include "mpfr-impl.h" 43 44#ifdef _MPFR_H_HAVE_INTMAX_T 45 46intmax_t 47mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd) 48{ 49 intmax_t r; 50 mpfr_prec_t prec; 51 mpfr_t x; 52 53 if (MPFR_UNLIKELY (!mpfr_fits_intmax_p (f, rnd))) 54 { 55 MPFR_SET_ERANGE (); 56 return MPFR_IS_NAN (f) ? 0 : 57 MPFR_IS_NEG (f) ? MPFR_INTMAX_MIN : MPFR_INTMAX_MAX; 58 } 59 60 if (MPFR_IS_ZERO (f)) 61 return (intmax_t) 0; 62 63 /* determine the precision of intmax_t */ 64 for (r = MPFR_INTMAX_MIN, prec = 0; r != 0; r /= 2, prec++) 65 { } 66 /* Note: though INTMAX_MAX would have been sufficient for the conversion, 67 we chose INTMAX_MIN so that INTMAX_MIN - 1 is always representable in 68 precision prec; this is useful to detect overflows in MPFR_RNDZ (will 69 be needed later). */ 70 71 /* Now, r = 0. */ 72 73 mpfr_init2 (x, prec); 74 mpfr_rint (x, f, rnd); 75 MPFR_ASSERTN (MPFR_IS_FP (x)); 76 77 if (MPFR_NOTZERO (x)) 78 { 79 mp_limb_t *xp; 80 int sh, n; /* An int should be sufficient in this context. */ 81 82 xp = MPFR_MANT (x); 83 sh = MPFR_GET_EXP (x); 84 MPFR_ASSERTN ((mpfr_prec_t) sh <= prec); 85 if (MPFR_INTMAX_MIN + MPFR_INTMAX_MAX != 0 86 && MPFR_UNLIKELY ((mpfr_prec_t) sh == prec)) 87 { 88 /* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t 89 has the same size as intmax_t, we cannot use the code in 90 the for loop since the operations would be performed in 91 unsigned arithmetic. */ 92 MPFR_ASSERTN (MPFR_IS_NEG (x) && (mpfr_powerof2_raw (x))); 93 r = MPFR_INTMAX_MIN; 94 } 95 else if (MPFR_IS_POS (x)) 96 { 97 /* Note: testing the condition sh >= 0 is necessary to avoid 98 an undefined behavior on xp[n] >> S when S >= GMP_NUMB_BITS 99 (even though xp[n] == 0 in such a case). This can happen if 100 sizeof(mp_limb_t) < sizeof(intmax_t) and |x| is small enough 101 because of the trailing bits due to its normalization. */ 102 for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--) 103 { 104 sh -= GMP_NUMB_BITS; 105 /* Note the concerning the casts below: 106 When sh >= 0, the cast must be performed before the shift 107 for the case sizeof(intmax_t) > sizeof(mp_limb_t). 108 When sh < 0, the cast must be performed after the shift 109 for the case sizeof(intmax_t) == sizeof(mp_limb_t), as 110 mp_limb_t is unsigned, therefore not representable as an 111 intmax_t when the MSB is 1 (this is the case here). */ 112 MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS); 113 r += (sh >= 0 114 ? (intmax_t) xp[n] << sh 115 : (intmax_t) (xp[n] >> (-sh))); 116 } 117 } 118 else 119 { 120 /* See the comments for the case x positive. */ 121 for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--) 122 { 123 sh -= GMP_NUMB_BITS; 124 MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS); 125 r -= (sh >= 0 126 ? (intmax_t) xp[n] << sh 127 : (intmax_t) (xp[n] >> (-sh))); 128 } 129 } 130 } 131 132 mpfr_clear (x); 133 134 return r; 135} 136 137#endif 138