/* Implement POWERSET runtime actions for CHILL.
   Copyright (C) 1992,1993 Free Software Foundation, Inc.
   Author: Wilfried Moser, et al

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#define __CHILL_LIB__

#include <stdio.h>
#include "powerset.h"

/*
 * function __ffsetclrpowerset
 *
 * parameters:
 *	ps		powerset
 *	bitlength	length of powerset
 *
 * returns:
 *	int		-1 .. nothing found
 *			>=0 .. index of first true bit found
 * exceptions:
 *  none
 */

int
__ffsetclrpowerset (ps, bitlength, first_bit)
     SET_WORD      *ps;
     unsigned long  bitlength;
     int first_bit;
{
  register int bitno;

  if (first_bit >= bitlength)
    return -1;

#ifndef USE_CHARS
  if (bitlength <= SET_CHAR_SIZE)
    {
      for (bitno = first_bit; bitno < bitlength; bitno++)
	if (GET_BIT_IN_CHAR (*((SET_CHAR *)ps), bitno))
	  break;
      return bitno == bitlength ? -1 : bitno;
    }
  else if (bitlength <= SET_SHORT_SIZE)
    {
      for (bitno = first_bit; bitno < bitlength; bitno++)
	if (GET_BIT_IN_SHORT (*((SET_SHORT *)ps), bitno))
	  break;
      return bitno == bitlength ? -1 : bitno;
    }
  else
#endif
    {
      unsigned int words_to_skip = (unsigned) first_bit / SET_WORD_SIZE;
      unsigned long cnt = words_to_skip * SET_WORD_SIZE;
      SET_WORD	*p = ps + words_to_skip;
      SET_WORD	*endp = ps + BITS_TO_WORDS(bitlength);
      SET_WORD	c;
      first_bit = (unsigned) first_bit % (unsigned) SET_WORD_SIZE;

      c = *p++;
      if (c)
	{
	  for (bitno = first_bit; bitno < SET_WORD_SIZE; bitno++)
	    if (GET_BIT_IN_WORD(c, bitno))
	      goto found;
	}
      cnt += SET_WORD_SIZE;

      while (p < endp)
	{
	  if ((c = *p++))
	    {
	      /* found a bit set .. calculate which */
	      for (bitno = 0; bitno < SET_WORD_SIZE; bitno++)
		if (GET_BIT_IN_WORD(c, bitno))
		  goto found;
	    }
	  cnt += SET_WORD_SIZE;
	}
      return -1;
    found:
      bitno += cnt;
      return bitno >= bitlength ? -1 : bitno;
    }
}