contrib/gmp/mpf/add_ui.c

   1 /* mpf_add_ui -- Add a float and an unsigned integer.
   2
   3 Copyright 1993, 1994, 1996, 2000, 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 void
  24 mpf_add_ui (mpf_ptr sum, mpf_srcptr u, unsigned long int v)
  25 {
  26   mp_srcptr up = u->_mp_d;
  27   mp_ptr sump = sum->_mp_d;
  28   mp_size_t usize, sumsize;
  29   mp_size_t prec = sum->_mp_prec;
  30   mp_exp_t uexp = u->_mp_exp;
  31
  32   usize = u->_mp_size;
  33   if (usize <= 0)
  34     {
  35       if (usize == 0)
  36         {
  37           mpf_set_ui (sum, v);
  38           return;
  39         }
  40       else
  41         {
  42           __mpf_struct u_negated;
  43           u_negated._mp_size = -usize;
  44           u_negated._mp_exp = u->_mp_exp;
  45           u_negated._mp_d = u->_mp_d;
  46           mpf_sub_ui (sum, &u_negated, v);
  47           sum->_mp_size = -(sum->_mp_size);
  48           return;
  49         }
  50     }
  51
  52   if (v == 0)
  53     {
  54     sum_is_u:
  55       if (u != sum)
  56         {
  57           sumsize = MIN (usize, prec + 1);
  58           MPN_COPY (sum->_mp_d, up + usize - sumsize, sumsize);
  59           sum->_mp_size = sumsize;
  60           sum->_mp_exp = u->_mp_exp;
  61         }
  62       return;
  63     }
  64
  65   if (uexp > 0)
  66     {
  67       /* U >= 1.  */
  68       if (uexp > prec)
  69         {
  70           /* U >> V, V is not part of final result.  */
  71           goto sum_is_u;
  72         }
  73       else
  74         {
  75           /* U's "limb point" is somewhere between the first limb
  76              and the PREC:th limb.
  77              Both U and V are part of the final result.  */
  78           if (uexp > usize)
  79             {
  80               /*   uuuuuu0000. */
  81               /* +          v. */
  82               /* We begin with moving U to the top of SUM, to handle
  83                  samevar(U,SUM).  */
  84               MPN_COPY_DECR (sump + uexp - usize, up, usize);
  85               sump[0] = v;
  86               MPN_ZERO (sump + 1, uexp - usize - 1);
  87 #if 0 /* What is this??? */
  88               if (sum == u)
  89                 MPN_COPY (sum->_mp_d, sump, uexp);
  90 #endif
  91               sum->_mp_size = uexp;
  92               sum->_mp_exp = uexp;
  93             }
  94           else
  95             {
  96               /*   uuuuuu.uuuu */
  97               /* +      v.     */
  98               mp_limb_t cy_limb;
  99               if (usize > prec)
 100                 {
 101                   /* Ignore excess limbs in U.  */
 102                   up += usize - prec;
 103                   usize -= usize - prec; /* Eq. usize = prec */
 104                 }
 105               if (sump != up)
 106                 MPN_COPY_INCR (sump, up, usize - uexp);
 107               cy_limb = mpn_add_1 (sump + usize - uexp, up + usize - uexp,
 108                                    uexp, (mp_limb_t) v);
 109               sump[usize] = cy_limb;
 110               sum->_mp_size = usize + cy_limb;
 111               sum->_mp_exp = uexp + cy_limb;
 112             }
 113         }
 114     }
 115   else
 116     {
 117       /* U < 1, so V > U for sure.  */
 118       /* v.         */
 119       /*  .0000uuuu */
 120       if ((-uexp) >= prec)
 121         {
 122           sump[0] = v;
 123           sum->_mp_size = 1;
 124           sum->_mp_exp = 1;
 125         }
 126       else
 127         {
 128           if (usize + (-uexp) + 1 > prec)
 129             {
 130               /* Ignore excess limbs in U.  */
 131               up += usize + (-uexp) + 1 - prec;
 132               usize -= usize + (-uexp) + 1 - prec;
 133             }
 134           if (sump != up)
 135             MPN_COPY_INCR (sump, up, usize);
 136           MPN_ZERO (sump + usize, -uexp);
 137           sump[usize + (-uexp)] = v;
 138           sum->_mp_size = usize + (-uexp) + 1;
 139           sum->_mp_exp = 1;
 140         }
 141     }
 142 }