bignum-copy.c

早期freebsd实现

/* bignum_copy.c - copy a bignum
   Copyright (C) 1987 Free Software Foundation, Inc.

This file is part of GAS, the GNU Assembler.

GAS is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 1, or (at your option)
any later version.

GAS 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with GAS; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "bignum.h"

#ifdef USG
#define bzero(s,n) memset(s,0,n)
#define bcopy(from,to,n) memcpy(to,from,n)
#endif

/*
 *			bignum_copy ()
 *
 * Copy a bignum from in to out.
 * If the output is shorter than the input, copy lower-order littlenums.
 * Return 0 or the number of significant littlenums dropped.
 * Assumes littlenum arrays are densely packed: no unused chars between
 * the littlenums. Uses bcopy() to move littlenums, and wants to
 * know length (in chars) of the input bignum.
 */

/* void */
int
bignum_copy (in, in_length, out, out_length)
     register LITTLENUM_TYPE *	in;
     register int		in_length; /* in sizeof(littlenum)s */
     register LITTLENUM_TYPE *	out;
     register int		out_length; /* in sizeof(littlenum)s */
{
  register int	significant_littlenums_dropped;

  if (out_length < in_length)
    {
      register LITTLENUM_TYPE *	p; /* -> most significant (non-zero) input littlenum. */

      bcopy ((char *)in, (char *)out, out_length << LITTLENUM_SHIFT);
      for (p = in + in_length - 1;   p >= in;   -- p)
	{
	  if (* p) break;
	}
      significant_littlenums_dropped = p - in - in_length + 1;
      if (significant_littlenums_dropped < 0)
	{
	  significant_littlenums_dropped = 0;
	}
    }
  else
    {
      bcopy ((char *)in, (char *)out, in_length << LITTLENUM_SHIFT);
      if (out_length > in_length)
	{
	  bzero ((char *)(out + out_length), (out_length - in_length) << LITTLENUM_SHIFT);
	}
      significant_littlenums_dropped = 0;
    }
  return (significant_littlenums_dropped);
}

/* end: bignum_copy.c */