/* 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 "config.h"
#include <stdio.h>
#include "powerset.h"

extern void __cause_ex1 (char *exname, char *file, int lineno);

/*
 * function __flsetpowerset
 *
 * parameters:
 *	ps		powerset
 *	bitlength	length of powerset
 *      minval          set low bound
 *      filename        caller's file name
 *      lineno          caller's line number
 *
 * returns:
 *	int		largest enumeration value
 * exceptions:
 *      "empty"         if set is empty
 *
 * abstract:
 *  Find last bit set in a powerset and return the corresponding value.
 *
 */
long
__flsetpowerset (ps, bitlength, minval, filename, lineno)
     SET_WORD      *ps;
     unsigned long  bitlength;
     long           minval;
     char          *filename;
     int            lineno;
{
  unsigned long bitno;

  if (bitlength <= SET_CHAR_SIZE)
    {
      SET_CHAR cset = *((SET_CHAR *)ps);
      if (cset != 0)
	{
	  /* found a bit set .. calculate which */
	  for (bitno = SET_CHAR_SIZE; bitno >= 1; bitno--)
	    if (GET_BIT_IN_CHAR (cset, bitno - 1))
	      break;
	  /* return its index */
	  return bitno + minval - 1;
	}
    }
  else if (bitlength <= SET_SHORT_SIZE)
    {
      SET_SHORT sset = *((SET_SHORT *)ps);
      if (sset != 0)
	{
	  /* found a bit set .. calculate which */
	  for (bitno = SET_SHORT_SIZE; bitno >= 1; bitno--)
	    if (GET_BIT_IN_SHORT (sset, bitno - 1))
	      break;
	  /* return its index */
	  return bitno + minval - 1;
	}
    }
  else /* set composed of array of one or more WORDs */
    {
      SET_WORD	*endp = ps;
      SET_WORD	*p = ps + BITS_TO_WORDS(bitlength) - 1;
      unsigned long cnt;
      
      /* FIXME: bitorder problems? */
      for (cnt = ((bitlength - 1) / SET_WORD_SIZE) * SET_WORD_SIZE;
	   p >= endp; p--, cnt -= SET_WORD_SIZE)
	{
	  SET_WORD c = *p;
	  if (c)
	    {
	      /* found a bit set .. calculate which */
	      for (bitno = SET_WORD_SIZE; bitno >= 1; bitno--)
		if (GET_BIT_IN_WORD (c, bitno - 1))
		  break;
	      return cnt + bitno + minval - 1;
	    }
	}
    }
  /* no bits found - raise exception */
  __cause_ex1 ("empty", filename, lineno);
}