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Annotation of OpenXM_contrib/gmp/mpf/set_prc.c, Revision 1.1

1.1     ! maekawa     1: /* mpf_set_prec(x) -- Change the precision of x.
        !             2:
        !             3: Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the GNU MP Library.
        !             6:
        !             7: The GNU MP Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Library General Public License as published by
        !             9: the Free Software Foundation; either version 2 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The GNU MP Library is distributed in the hope that it will be useful, but
        !            13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Library General Public License
        !            18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: MA 02111-1307, USA. */
        !            21:
        !            22: #include "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24:
        !            25: void
        !            26: #if __STDC__
        !            27: mpf_set_prec (mpf_ptr x, unsigned long int prec_in_bits)
        !            28: #else
        !            29: mpf_set_prec (x, prec_in_bits)
        !            30:      mpf_ptr x;
        !            31:      unsigned long int prec_in_bits;
        !            32: #endif
        !            33: {
        !            34:   mp_size_t prec;
        !            35:   mp_size_t size = ABS (x->_mp_size);
        !            36:
        !            37:   prec = (MAX (53, prec_in_bits) + 2 * BITS_PER_MP_LIMB - 1)/BITS_PER_MP_LIMB;
        !            38:
        !            39:   /* We want the most significant limbs, so move the limbs down if we are
        !            40:      about to truncate the value.  */
        !            41:   if (size > prec + 1)
        !            42:     {
        !            43:       mp_size_t offset = size - (prec + 1);
        !            44:       mp_ptr xp = x->_mp_d;
        !            45:
        !            46:       MPN_COPY (xp, xp + offset, prec + 1);
        !            47:     }
        !            48:
        !            49:   x->_mp_d = (mp_ptr) (*_mp_reallocate_func)
        !            50:     (x->_mp_d,
        !            51:      (x->_mp_prec + 1) * BYTES_PER_MP_LIMB, (prec + 1) * BYTES_PER_MP_LIMB);
        !            52:   x->_mp_prec = prec;
        !            53:
        !            54:   /* If the precision decreased, truncate the number.  */
        !            55:   if (size > prec + 1)
        !            56:     x->_mp_size = x->_mp_size >= 0 ? (prec + 1) : -(prec + 1);
        !            57: }