libiberty/partition.c

   1 /* List implentation of a partition of consecutive integers.
   2    Copyright (C) 2000 Free Software Foundation, Inc.
   3    Contributed by CodeSourcery, LLC.
   4
   5    This file is part of GNU CC.
   6
   7    GNU CC is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2, or (at your option)
  10    any later version.
  11
  12    GNU CC is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with GNU CC; see the file COPYING.  If not, write to
  19    the Free Software Foundation, 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #ifdef HAVE_CONFIG_H
  23 #include "config.h"
  24 #endif
  25
  26 #ifdef HAVE_STDLIB_H
  27 #include <stdlib.h>
  28 #endif
  29
  30 #include "libiberty.h"
  31 #include "partition.h"
  32
  33 /* Creates a partition of NUM_ELEMENTS elements.  Initially each
  34    element is in a class by itself.  */
  35
  36 partition
  37 partition_new (num_elements)
  38      int num_elements;
  39 {
  40   int e;
  41
  42   partition part = (partition)
  43     xmalloc (sizeof (struct partition_def) +
  44              (num_elements - 1) * sizeof (struct partition_elem));
  45   part->num_elements = num_elements;
  46   for (e = 0; e < num_elements; ++e)
  47     {
  48       part->elements[e].class_element = e;
  49       part->elements[e].next = &(part->elements[e]);
  50       part->elements[e].class_count = 1;
  51     }
  52
  53   return part;
  54 }
  55
  56 /* Freeds a partition.  */
  57
  58 void
  59 partition_delete (part)
  60       partition part;
  61 {
  62   free (part);
  63 }
  64
  65 /* Unites the classes containing ELEM1 and ELEM2 into a single class
  66    of partition PART.  If ELEM1 and ELEM2 are already in the same
  67    class, does nothing.  Returns the canonical element of the
  68    resulting union class.  */
  69
  70 int
  71 partition_union (part, elem1, elem2)
  72      partition part;
  73      int elem1;
  74      int elem2;
  75 {
  76   struct partition_elem *elements = part->elements;
  77   struct partition_elem *e1;
  78   struct partition_elem *e2;
  79   struct partition_elem *p;
  80   struct partition_elem *old_next;
  81   /* The canonical element of the resulting union class.  */
  82   int class_element = elements[elem1].class_element;
  83
  84   /* If they're already in the same class, do nothing.  */
  85   if (class_element == elements[elem2].class_element)
  86     return class_element;
  87
  88   /* Make sure ELEM1 is in the larger class of the two.  If not, swap
  89      them.  This way we always scan the shorter list.  */
  90   if (elements[elem1].class_count < elements[elem2].class_count)
  91     {
  92       int temp = elem1;
  93       elem1 = elem2;
  94       elem2 = temp;
  95       class_element = elements[elem1].class_element;
  96     }
  97
  98   e1 = &(elements[elem1]);
  99   e2 = &(elements[elem2]);
 100
 101   /* Keep a count of the number of elements in the list.  */
 102   elements[class_element].class_count
 103     += elements[e2->class_element].class_count;
 104
 105   /* Update the class fields in elem2's class list.  */
 106   e2->class_element = class_element;
 107   for (p = e2->next; p != e2; p = p->next)
 108     p->class_element = class_element;
 109
 110   /* Splice ELEM2's class list into ELEM1's.  These are circular
 111      lists.  */
 112   old_next = e1->next;
 113   e1->next = e2->next;
 114   e2->next = old_next;
 115
 116   return class_element;
 117 }
 118
 119 /* Compare elements ELEM1 and ELEM2 from array of integers, given a
 120    pointer to each.  Used to qsort such an array.  */
 121
 122 static int
 123 elem_compare (elem1, elem2)
 124      const void *elem1;
 125      const void *elem2;
 126 {
 127   int e1 = * (int *) elem1;
 128   int e2 = * (int *) elem2;
 129   if (e1 < e2)
 130     return -1;
 131   else if (e1 > e2)
 132     return 1;
 133   else
 134     return 0;
 135 }
 136
 137 /* Prints PART to the file pointer FP.  The elements of each
 138    class are sorted.  */
 139
 140 void
 141 partition_print (part, fp)
 142      partition part;
 143      FILE *fp;
 144 {
 145   char *done;
 146   int num_elements = part->num_elements;
 147   struct partition_elem *elements = part->elements;
 148   int *class_elements;
 149   int e;
 150
 151   /* Flag the elements we've already printed.  */
 152   done = (char *) xmalloc (num_elements);
 153   memset (done, 0, num_elements);
 154
 155   /* A buffer used to sort elements in a class.  */
 156   class_elements = (int *) xmalloc (num_elements * sizeof (int));
 157
 158   fputc ('[', fp);
 159   for (e = 0; e < num_elements; ++e)
 160     /* If we haven't printed this element, print its entire class.  */
 161     if (! done[e])
 162       {
 163         int c = e;
 164         int count = elements[elements[e].class_element].class_count;
 165         int i;
 166
 167       /* Collect the elements in this class.  */
 168         for (i = 0; i < count; ++i) {
 169           class_elements[i] = c;
 170           done[c] = 1;
 171           c = elements[c].next - elements;
 172         }
 173         /* Sort them.  */
 174         qsort ((void *) class_elements, count, sizeof (int), &elem_compare);
 175         /* Print them.  */
 176         fputc ('(', fp);
 177         for (i = 0; i < count; ++i)
 178           fprintf (fp, i == 0 ? "%d" : " %d", class_elements[i]);
 179         fputc (')', fp);
 180       }
 181   fputc (']', fp);
 182
 183   free (done);
 184 }
 185