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Annotation of OpenXM_contrib/gmp/mpf/set_prc.c, Revision 1.1.1.1

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: }