source/libs/gmp/gmp-src/mpf/ceilfloor.c

   1 /* mpf_ceil, mpf_floor -- round an mpf to an integer.
   2
   3 Copyright 2001, 2004, 2012 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 either:
   9
  10   * the GNU Lesser General Public License as published by the Free
  11     Software Foundation; either version 3 of the License, or (at your
  12     option) any later version.
  13
  14 or
  15
  16   * the GNU General Public License as published by the Free Software
  17     Foundation; either version 2 of the License, or (at your option) any
  18     later version.
  19
  20 or both in parallel, as here.
  21
  22 The GNU MP Library is distributed in the hope that it will be useful, but
  23 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  24 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  25 for more details.
  26
  27 You should have received copies of the GNU General Public License and the
  28 GNU Lesser General Public License along with the GNU MP Library.  If not,
  29 see https://www.gnu.org/licenses/.  */
  30
  31 #include "gmp.h"
  32 #include "gmp-impl.h"
  33
  34
  35 /* dir==1 for ceil, dir==-1 for floor
  36
  37    Notice the use of prec+1 ensures mpf_ceil and mpf_floor are equivalent to
  38    mpf_set if u is already an integer.  */
  39
  40 static void __gmpf_ceil_or_floor (REGPARM_2_1 (mpf_ptr, mpf_srcptr, int)) REGPARM_ATTR (1);
  41 #define mpf_ceil_or_floor(r,u,dir)  __gmpf_ceil_or_floor (REGPARM_2_1 (r, u, dir))
  42
  43 REGPARM_ATTR (1) static void
  44 mpf_ceil_or_floor (mpf_ptr r, mpf_srcptr u, int dir)
  45 {
  46   mp_ptr     rp, up, p;
  47   mp_size_t  size, asize, prec;
  48   mp_exp_t   exp;
  49
  50   size = SIZ(u);
  51   if (size == 0)
  52     {
  53     zero:
  54       SIZ(r) = 0;
  55       EXP(r) = 0;
  56       return;
  57     }
  58
  59   rp = PTR(r);
  60   exp = EXP(u);
  61   if (exp <= 0)
  62     {
  63       /* u is only a fraction */
  64       if ((size ^ dir) < 0)
  65         goto zero;
  66       rp[0] = 1;
  67       EXP(r) = 1;
  68       SIZ(r) = dir;
  69       return;
  70     }
  71   EXP(r) = exp;
  72
  73   up = PTR(u);
  74   asize = ABS (size);
  75   up += asize;
  76
  77   /* skip fraction part of u */
  78   asize = MIN (asize, exp);
  79
  80   /* don't lose precision in the copy */
  81   prec = PREC (r) + 1;
  82
  83   /* skip excess over target precision */
  84   asize = MIN (asize, prec);
  85
  86   up -= asize;
  87
  88   if ((size ^ dir) >= 0)
  89     {
  90       /* rounding direction matches sign, must increment if ignored part is
  91          non-zero */
  92       for (p = PTR(u); p != up; p++)
  93         {
  94           if (*p != 0)
  95             {
  96               if (mpn_add_1 (rp, up, asize, CNST_LIMB(1)))
  97                 {
  98                   /* was all 0xFF..FFs, which have become zeros, giving just
  99                      a carry */
 100                   rp[0] = 1;
 101                   asize = 1;
 102                   EXP(r)++;
 103                 }
 104               SIZ(r) = (size >= 0 ? asize : -asize);
 105               return;
 106             }
 107         }
 108     }
 109
 110   SIZ(r) = (size >= 0 ? asize : -asize);
 111   if (rp != up)
 112     MPN_COPY_INCR (rp, up, asize);
 113 }
 114
 115
 116 void
 117 mpf_ceil (mpf_ptr r, mpf_srcptr u)
 118 {
 119   mpf_ceil_or_floor (r, u, 1);
 120 }
 121
 122 void
 123 mpf_floor (mpf_ptr r, mpf_srcptr u)
 124 {
 125   mpf_ceil_or_floor (r, u, -1);
 126 }