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

/* mpfr_extract -- bit-extraction function for the binary splitting algorithm | |

Copyright 2000, 2001, 2002, 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" | |

/* given 0 <= |p| < 1, this function extracts limbs of p and puts them in y. | |

It is mainly designed for the "binary splitting" algorithm. | |

More precisely, if B = 2^BITS_PER_MP_LIMB: | |

- for i=0, y = floor(p * B) | |

- for i>0, y = (p * B^(2^i)) mod B^(2^(i-1)) | |

*/ | |

void | |

mpfr_extract (mpz_ptr y, mpfr_srcptr p, unsigned int i) | |

{ | |

unsigned long two_i = 1UL << i; | |

unsigned long two_i_2 = i ? two_i / 2 : 1; | |

mp_size_t size_p = MPFR_LIMB_SIZE (p); | |

/* as 0 <= |p| < 1, we don't have to care with infinities, NaN, ... */ | |

MPFR_ASSERTD (!MPFR_IS_SINGULAR (p)); | |

_mpz_realloc (y, two_i_2); | |

if ((mpfr_uexp_t) size_p < two_i) | |

{ | |

MPN_ZERO (PTR(y), two_i_2); | |

if ((mpfr_uexp_t) size_p >= two_i_2) | |

MPN_COPY (PTR(y) + two_i - size_p, MPFR_MANT(p), size_p - two_i_2); | |

} | |

else | |

MPN_COPY (PTR(y), MPFR_MANT(p) + size_p - two_i, two_i_2); | |

MPN_NORMALIZE (PTR(y), two_i_2); | |

SIZ(y) = (MPFR_IS_NEG (p)) ? -two_i_2 : two_i_2; | |

} |