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 #ifdef HAVE_STRING_H
  31 #include <string.h>
  32 #endif
  33
  34 #include "libiberty.h"
  35 #include "partition.h"
  36
  37 static int elem_compare PARAMS ((const void *, const void *));
  38
  39 /* Creates a partition of NUM_ELEMENTS elements.  Initially each
  40    element is in a class by itself.  */
  41
  42 partition
  43 partition_new (num_elements)
  44      int num_elements;
  45 {
  46   int e;
  47
  48   partition part = (partition)
  49     xmalloc (sizeof (struct partition_def) +
  50              (num_elements - 1) * sizeof (struct partition_elem));
  51   part->num_elements = num_elements;
  52   for (e = 0; e < num_elements; ++e)
  53     {
  54       part->elements[e].class_element = e;
  55       part->elements[e].next = &(part->elements[e]);
  56       part->elements[e].class_count = 1;
  57     }
  58
  59   return part;
  60 }
  61
  62 /* Freeds a partition.  */
  63
  64 void
  65 partition_delete (part)
  66       partition part;
  67 {
  68   free (part);
  69 }
  70
  71 /* Unites the classes containing ELEM1 and ELEM2 into a single class
  72    of partition PART.  If ELEM1 and ELEM2 are already in the same
  73    class, does nothing.  Returns the canonical element of the
  74    resulting union class.  */
  75
  76 int
  77 partition_union (part, elem1, elem2)
  78      partition part;
  79      int elem1;
  80      int elem2;
  81 {
  82   struct partition_elem *elements = part->elements;
  83   struct partition_elem *e1;
  84   struct partition_elem *e2;
  85   struct partition_elem *p;
  86   struct partition_elem *old_next;
  87   /* The canonical element of the resulting union class.  */
  88   int class_element = elements[elem1].class_element;
  89
  90   /* If they're already in the same class, do nothing.  */
  91   if (class_element == elements[elem2].class_element)
  92     return class_element;
  93
  94   /* Make sure ELEM1 is in the larger class of the two.  If not, swap
  95      them.  This way we always scan the shorter list.  */
  96   if (elements[elem1].class_count < elements[elem2].class_count)
  97     {
  98       int temp = elem1;
  99       elem1 = elem2;
 100       elem2 = temp;
 101       class_element = elements[elem1].class_element;
 102     }
 103
 104   e1 = &(elements[elem1]);
 105   e2 = &(elements[elem2]);
 106
 107   /* Keep a count of the number of elements in the list.  */
 108   elements[class_element].class_count
 109     += elements[e2->class_element].class_count;
 110
 111   /* Update the class fields in elem2's class list.  */
 112   e2->class_element = class_element;
 113   for (p = e2->next; p != e2; p = p->next)
 114     p->class_element = class_element;
 115
 116   /* Splice ELEM2's class list into ELEM1's.  These are circular
 117      lists.  */
 118   old_next = e1->next;
 119   e1->next = e2->next;
 120   e2->next = old_next;
 121
 122   return class_element;
 123 }
 124
 125 /* Compare elements ELEM1 and ELEM2 from array of integers, given a
 126    pointer to each.  Used to qsort such an array.  */
 127
 128 static int
 129 elem_compare (elem1, elem2)
 130      const void *elem1;
 131      const void *elem2;
 132 {
 133   int e1 = * (const int *) elem1;
 134   int e2 = * (const int *) elem2;
 135   if (e1 < e2)
 136     return -1;
 137   else if (e1 > e2)
 138     return 1;
 139   else
 140     return 0;
 141 }
 142
 143 /* Prints PART to the file pointer FP.  The elements of each
 144    class are sorted.  */
 145
 146 void
 147 partition_print (part, fp)
 148      partition part;
 149      FILE *fp;
 150 {
 151   char *done;
 152   int num_elements = part->num_elements;
 153   struct partition_elem *elements = part->elements;
 154   int *class_elements;
 155   int e;
 156
 157   /* Flag the elements we've already printed.  */
 158   done = (char *) xmalloc (num_elements);
 159   memset (done, 0, num_elements);
 160
 161   /* A buffer used to sort elements in a class.  */
 162   class_elements = (int *) xmalloc (num_elements * sizeof (int));
 163
 164   fputc ('[', fp);
 165   for (e = 0; e < num_elements; ++e)
 166     /* If we haven't printed this element, print its entire class.  */
 167     if (! done[e])
 168       {
 169         int c = e;
 170         int count = elements[elements[e].class_element].class_count;
 171         int i;
 172
 173       /* Collect the elements in this class.  */
 174         for (i = 0; i < count; ++i) {
 175           class_elements[i] = c;
 176           done[c] = 1;
 177           c = elements[c].next - elements;
 178         }
 179         /* Sort them.  */
 180         qsort ((void *) class_elements, count, sizeof (int), elem_compare);
 181         /* Print them.  */
 182         fputc ('(', fp);
 183         for (i = 0; i < count; ++i)
 184           fprintf (fp, i == 0 ? "%d" : " %d", class_elements[i]);
 185         fputc (')', fp);
 186       }
 187   fputc (']', fp);
 188
 189   free (done);
 190 }
 191