contrib/gmp/mpf/trunc.c

   1 /* mpf_trunc -- truncate an mpf to an integer.
   2
   3 Copyright 2001 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 Lesser General Public License as published by
   9 the Free Software Foundation; either version 3 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 Lesser General Public
  15 License for more details.
  16
  17 You should have received a copy of the GNU Lesser General Public License
  18 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
  19
  20 #include "gmp.h"
  21 #include "gmp-impl.h"
  22
  23
  24 /* Notice the use of prec+1 ensures mpf_trunc is equivalent to mpf_set if u
  25    is already an integer.  */
  26
  27 void
  28 mpf_trunc (mpf_ptr r, mpf_srcptr u)
  29 {
  30   mp_ptr     rp;
  31   mp_srcptr  up;
  32   mp_size_t  size, asize, prec;
  33   mp_exp_t   exp;
  34
  35   exp = EXP(u);
  36   size = SIZ(u);
  37   if (size == 0 || exp <= 0)
  38     {
  39       /* u is only a fraction */
  40       SIZ(r) = 0;
  41       EXP(r) = 0;
  42       return;
  43     }
  44
  45   up = PTR(u);
  46   EXP(r) = exp;
  47   asize = ABS (size);
  48   up += asize;
  49
  50   /* skip fraction part of u */
  51   asize = MIN (asize, exp);
  52
  53   /* don't lose precision in the copy */
  54   prec = PREC(r) + 1;
  55
  56   /* skip excess over target precision */
  57   asize = MIN (asize, prec);
  58
  59   up -= asize;
  60   rp = PTR(r);
  61   SIZ(r) = (size >= 0 ? asize : -asize);
  62   if (rp != up)
  63     MPN_COPY_INCR (rp, up, asize);
  64 }