freebsd-dev/contrib/libgmp/mpf/add_ui.c

/* mpf_add_ui -- Add a float and an unsigned integer.

Copyright (C) 1993, 1994, 1996 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
License for more details.

You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

#include "gmp.h"
#include "gmp-impl.h"

void
#if __STDC__
mpf_add_ui (mpf_ptr sum, mpf_srcptr u, unsigned long int v)
#else
mpf_add_ui (sum, u, v)
     mpf_ptr sum;
     mpf_srcptr u;
     unsigned long int v;
#endif
{
  mp_srcptr up = u->_mp_d;
  mp_ptr sump = sum->_mp_d;
  mp_size_t usize, sumsize;
  mp_size_t prec = sum->_mp_prec;
  mp_exp_t uexp = u->_mp_exp;

  usize = u->_mp_size;
  if (usize <= 0)
    {
      if (usize == 0)
	{
	  mpf_set_ui (sum, v);
	  return;
	}
      else
	{
	  __mpf_struct u_negated;
	  u_negated._mp_size = -usize;
	  u_negated._mp_exp = u->_mp_exp;
	  u_negated._mp_d = u->_mp_d;
	  mpf_sub_ui (sum, &u_negated, v);
	  sum->_mp_size = -(sum->_mp_size);
	  return;
	}
    }

  if (v == 0)
    {
    sum_is_u:
      if (u != sum)
	{
	  sumsize = MIN (usize, prec + 1);
	  MPN_COPY (sum->_mp_d, up + usize - sumsize, sumsize);
	  sum->_mp_size = sumsize;
	  sum->_mp_exp = u->_mp_exp;
	}
      return;
    }

  if (uexp > 0)
    {
      /* U >= 1.  */
      if (uexp > prec)
	{
	  /* U >> V, V is not part of final result.  */
	  goto sum_is_u;
	}
      else
	{
	  /* U's "limb point" is somewhere between the first limb
	     and the PREC:th limb.
	     Both U and V are part of the final result.  */
	  if (uexp > usize)
	    {
	      /*   uuuuuu0000. */
	      /* +          v. */
	      /* We begin with moving U to the top of SUM, to handle
		 samevar(U,SUM).  */
	      MPN_COPY_DECR (sump + uexp - usize, up, usize);
	      sump[0] = v;
	      MPN_ZERO (sump + 1, uexp - usize - 1);
#if 0 /* What is this??? */
	      if (sum == u)
		MPN_COPY (sum->_mp_d, sump, uexp);
#endif
	      sum->_mp_size = uexp;
	      sum->_mp_exp = uexp;
	    }
	  else
	    {
	      /*   uuuuuu.uuuu */
	      /* +      v.     */
	      mp_limb_t cy_limb;
	      if (usize > prec)
		{
		  /* Ignore excess limbs in U.  */
		  up += usize - prec;
		  usize -= usize - prec; /* Eq. usize = prec */
		}
	      if (sump != up)
		MPN_COPY (sump, up, usize - uexp);
	      cy_limb = mpn_add_1 (sump + usize - uexp, up + usize - uexp,
				   uexp, (mp_limb_t) v);
	      sump[usize] = cy_limb;
	      sum->_mp_size = usize + cy_limb;
	      sum->_mp_exp = uexp + cy_limb;
	    }
	}
    }
  else
    {
      /* U < 1, so V > U for sure.  */
      /* v.         */
      /*  .0000uuuu */
      if ((-uexp) >= prec)
	{
	  sump[0] = v;
	  sum->_mp_size = 1;
	  sum->_mp_exp = 1;
	}
      else
	{
	  if (usize + (-uexp) + 1 > prec)
	    {
	      /* Ignore excess limbs in U.  */
	      up += usize + (-uexp) + 1 - prec;
	      usize -= usize + (-uexp) + 1 - prec;
	    }
	  if (sump != up)
	    MPN_COPY (sump, up, usize);
	  MPN_ZERO (sump + usize, -uexp);
	  sump[usize + (-uexp)] = v;
	  sum->_mp_size = usize + (-uexp) + 1;
	  sum->_mp_exp = 1;
	}
    }
}