contrib/gmp/mpf/ceilfloor.c

   1 /* mpf_ceil, mpf_floor -- round an mpf to an integer.
   2
   3 Copyright 2001, 2004 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 /* dir==1 for ceil, dir==-1 for floor
  25
  26    Notice the use of prec+1 ensures mpf_ceil and mpf_floor are equivalent to
  27    mpf_set if u is already an integer.  */
  28
  29 static void __gmpf_ceil_or_floor __GMP_PROTO ((REGPARM_2_1 (mpf_ptr, mpf_srcptr, int))) REGPARM_ATTR (1);
  30 #define mpf_ceil_or_floor(r,u,dir)  __gmpf_ceil_or_floor (REGPARM_2_1 (r, u, dir))
  31
  32 REGPARM_ATTR (1) static void
  33 mpf_ceil_or_floor (mpf_ptr r, mpf_srcptr u, int dir)
  34 {
  35   mp_ptr     rp, up, p;
  36   mp_size_t  size, asize, prec;
  37   mp_exp_t   exp;
  38
  39   size = SIZ(u);
  40   if (size == 0)
  41     {
  42     zero:
  43       SIZ(r) = 0;
  44       EXP(r) = 0;
  45       return;
  46     }
  47
  48   rp = PTR(r);
  49   exp = EXP(u);
  50   if (exp <= 0)
  51     {
  52       /* u is only a fraction */
  53       if ((size ^ dir) < 0)
  54         goto zero;
  55       rp[0] = 1;
  56       EXP(r) = 1;
  57       SIZ(r) = dir;
  58       return;
  59     }
  60   EXP(r) = exp;
  61
  62   up = PTR(u);
  63   asize = ABS (size);
  64   up += asize;
  65
  66   /* skip fraction part of u */
  67   asize = MIN (asize, exp);
  68
  69   /* don't lose precision in the copy */
  70   prec = PREC (r) + 1;
  71
  72   /* skip excess over target precision */
  73   asize = MIN (asize, prec);
  74
  75   up -= asize;
  76
  77   if ((size ^ dir) >= 0)
  78     {
  79       /* rounding direction matches sign, must increment if ignored part is
  80          non-zero */
  81       for (p = PTR(u); p != up; p++)
  82         {
  83           if (*p != 0)
  84             {
  85               if (mpn_add_1 (rp, up, asize, CNST_LIMB(1)))
  86                 {
  87                   /* was all 0xFF..FFs, which have become zeros, giving just
  88                      a carry */
  89                   rp[0] = 1;
  90                   asize = 1;
  91                   EXP(r)++;
  92                 }
  93               SIZ(r) = (size >= 0 ? asize : -asize);
  94               return;
  95             }
  96         }
  97     }
  98
  99   SIZ(r) = (size >= 0 ? asize : -asize);
 100   if (rp != up)
 101     MPN_COPY_INCR (rp, up, asize);
 102 }
 103
 104
 105 void
 106 mpf_ceil (mpf_ptr r, mpf_srcptr u)
 107 {
 108   mpf_ceil_or_floor (r, u, 1);
 109 }
 110
 111 void
 112 mpf_floor (mpf_ptr r, mpf_srcptr u)
 113 {
 114   mpf_ceil_or_floor (r, u, -1);
 115 }