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