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/* List implentation of a partition of consecutive integers.

   Copyright (C) 2000 Free Software Foundation, Inc.

   Contributed by CodeSourcery, LLC.

   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, 59 Temple Place - Suite 330,

   Boston, MA 02111-1307, USA.  */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#include "libiberty.h"

#include "partition.h"

/* Creates a partition of NUM_ELEMENTS elements.  Initially each

   element is in a class by itself.  */

partition

partition_new (num_elements)

     int num_elements;

{

  int e;

  partition part = (partition)

    xmalloc (sizeof (struct partition_def) +

             (num_elements - 1) * sizeof (struct partition_elem));

  part->num_elements = num_elements;

  for (e = 0; e < num_elements; ++e)

    {

      part->elements[e].class_element = e;

      part->elements[e].next = &(part->elements[e]);

      part->elements[e].class_count = 1;

    }

  return part;

}

/* Freeds a partition.  */

void

partition_delete (part)

      partition part;

{

  free (part);

}

/* Unites the classes containing ELEM1 and ELEM2 into a single class

   of partition PART.  If ELEM1 and ELEM2 are already in the same

   class, does nothing.  Returns the canonical element of the

   resulting union class.  */

int

partition_union (part, elem1, elem2)

     partition part;

     int elem1;

     int elem2;

{

  struct partition_elem *elements = part->elements;

  struct partition_elem *e1;

  struct partition_elem *e2;

  struct partition_elem *p;

  struct partition_elem *old_next;

  /* The canonical element of the resulting union class.  */

  int class_element = elements[elem1].class_element;

  /* If they're already in the same class, do nothing.  */

  if (class_element == elements[elem2].class_element)

    return class_element;

  /* Make sure ELEM1 is in the larger class of the two.  If not, swap

     them.  This way we always scan the shorter list.  */

  if (elements[elem1].class_count < elements[elem2].class_count)

    {

      int temp = elem1;

      elem1 = elem2;

      elem2 = temp;

      class_element = elements[elem1].class_element;

    }

  e1 = &(elements[elem1]);

  e2 = &(elements[elem2]);

  /* Keep a count of the number of elements in the list.  */

  elements[class_element].class_count

    += elements[e2->class_element].class_count;

  /* Update the class fields in elem2's class list.  */

  e2->class_element = class_element;

  for (p = e2->next; p != e2; p = p->next)

    p->class_element = class_element;

  /* Splice ELEM2's class list into ELEM1's.  These are circular

     lists.  */

  old_next = e1->next;

  e1->next = e2->next;

  e2->next = old_next;

  return class_element;

}

/* Compare elements ELEM1 and ELEM2 from array of integers, given a

   pointer to each.  Used to qsort such an array.  */

static int

elem_compare (elem1, elem2)

     const void *elem1;

     const void *elem2;

{

  int e1 = * (int *) elem1;

  int e2 = * (int *) elem2;

  if (e1 < e2)

    return -1;

  else if (e1 > e2)

    return 1;

  else

    return 0;

}

/* Prints PART to the file pointer FP.  The elements of each

   class are sorted.  */

void

partition_print (part, fp)

     partition part;

     FILE *fp;

{

  char *done;

  int num_elements = part->num_elements;

  struct partition_elem *elements = part->elements;

  int *class_elements;

  int e;

  /* Flag the elements we've already printed.  */

  done = (char *) xmalloc (num_elements);

  memset (done, 0, num_elements);

  /* A buffer used to sort elements in a class.  */

  class_elements = (int *) xmalloc (num_elements * sizeof (int));

  fputc ('[', fp);

  for (e = 0; e < num_elements; ++e)

    /* If we haven't printed this element, print its entire class.  */

    if (! done[e])

      {

        int c = e;

        int count = elements[elements[e].class_element].class_count;

        int i;

      /* Collect the elements in this class.  */

        for (i = 0; i < count; ++i) {

          class_elements[i] = c;

          done[c] = 1;

          c = elements[c].next - elements;

        }

        /* Sort them.  */

        qsort ((void *) class_elements, count, sizeof (int), &elem_compare);

        /* Print them.  */

        fputc ('(', fp);

        for (i = 0; i < count; ++i)

          fprintf (fp, i == 0 ? "%d" : " %d", class_elements[i]);

        fputc (')', fp);

      }

  fputc (']', fp);

  free (done);

}