chromium / native_client / nacl-gcc / f80d6b9ee7f94755c697ffb7194fb01dd0c537dd / . / mpfr-2.4.1 / get_z_exp.c

/* mpfr_get_z_exp -- get a multiple-precision integer and an exponent | |

from a floating-point number | |

Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. | |

Contributed by the Arenaire and Cacao 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 2.1 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.LIB. If not, write to | |

the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, | |

MA 02110-1301, USA. */ | |

#include "mpfr-impl.h" | |

/* puts the mantissa of f into z, and returns 'exp' such that f = z * 2^exp | |

* | |

* 0 doesn't have an exponent, therefore the returned exponent in this case | |

* isn't really important. We choose to return __gmpfr_emin because | |

* 1) it is in the exponent range [__gmpfr_emin,__gmpfr_emax], | |

* 2) the smaller a number is (in absolute value), the smaller its | |

* exponent is. In other words, the f -> exp function is monotonous | |

* on nonnegative numbers. | |

* Note that this is different from the C function frexp(). | |

*/ | |

mp_exp_t | |

mpfr_get_z_exp (mpz_ptr z, mpfr_srcptr f) | |

{ | |

mp_size_t fn; | |

int sh; | |

MPFR_ASSERTD (MPFR_IS_FP (f)); | |

if (MPFR_UNLIKELY (MPFR_IS_ZERO (f))) | |

{ | |

mpz_set_ui (z, 0); | |

return __gmpfr_emin; | |

} | |

fn = MPFR_LIMB_SIZE(f); | |

/* check whether allocated space for z is enough */ | |

if (MPFR_UNLIKELY (ALLOC (z) < fn)) | |

MPZ_REALLOC (z, fn); | |

MPFR_UNSIGNED_MINUS_MODULO (sh, MPFR_PREC (f)); | |

if (MPFR_LIKELY (sh)) | |

mpn_rshift (PTR (z), MPFR_MANT (f), fn, sh); | |

else | |

MPN_COPY (PTR (z), MPFR_MANT (f), fn); | |

SIZ(z) = MPFR_IS_NEG (f) ? -fn : fn; | |

/* Test if the result is representable. Later, we could choose | |

to return MPFR_EXP_MIN if it isn't, or perhaps MPFR_EXP_MAX | |

to signal an error. The mantissa would still be meaningful. */ | |

MPFR_ASSERTD ((mp_exp_unsigned_t) MPFR_GET_EXP (f) - MPFR_EXP_MIN | |

>= (mp_exp_unsigned_t) MPFR_PREC(f)); | |

return MPFR_GET_EXP (f) - MPFR_PREC (f); | |

} |