libiberty/partition.c

   1 /* List implementation of a partition of consecutive integers.
   2    Copyright (C) 2000-2023 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, 51 Franklin Street - Fifth Floor,
  20    Boston, MA 02110-1301, 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 (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 (int num_elements)
  44 {
  45   int e;
  46
  47   partition part = (partition)
  48     xmalloc (sizeof (struct partition_def) +
  49              (num_elements - 1) * sizeof (struct partition_elem));
  50   part->num_elements = num_elements;
  51   for (e = 0; e < num_elements; ++e)
  52     {
  53       part->elements[e].class_element = e;
  54       part->elements[e].next = &(part->elements[e]);
  55       part->elements[e].class_count = 1;
  56     }
  57
  58   return part;
  59 }
  60
  61 /* Freeds a partition.  */
  62
  63 void
  64 partition_delete (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 (partition part, int elem1, int elem2)
  76 {
  77   struct partition_elem *elements = part->elements;
  78   struct partition_elem *e1;
  79   struct partition_elem *e2;
  80   struct partition_elem *p;
  81   struct partition_elem *old_next;
  82   /* The canonical element of the resulting union class.  */
  83   int class_element = elements[elem1].class_element;
  84
  85   /* If they're already in the same class, do nothing.  */
  86   if (class_element == elements[elem2].class_element)
  87     return class_element;
  88
  89   /* Make sure ELEM1 is in the larger class of the two.  If not, swap
  90      them.  This way we always scan the shorter list.  */
  91   if (elements[elem1].class_count < elements[elem2].class_count)
  92     {
  93       int temp = elem1;
  94       elem1 = elem2;
  95       elem2 = temp;
  96       class_element = elements[elem1].class_element;
  97     }
  98
  99   e1 = &(elements[elem1]);
 100   e2 = &(elements[elem2]);
 101
 102   /* Keep a count of the number of elements in the list.  */
 103   elements[class_element].class_count
 104     += elements[e2->class_element].class_count;
 105
 106   /* Update the class fields in elem2's class list.  */
 107   e2->class_element = class_element;
 108   for (p = e2->next; p != e2; p = p->next)
 109     p->class_element = class_element;
 110
 111   /* Splice ELEM2's class list into ELEM1's.  These are circular
 112      lists.  */
 113   old_next = e1->next;
 114   e1->next = e2->next;
 115   e2->next = old_next;
 116
 117   return class_element;
 118 }
 119
 120 /* Compare elements ELEM1 and ELEM2 from array of integers, given a
 121    pointer to each.  Used to qsort such an array.  */
 122
 123 static int
 124 elem_compare (const void *elem1, const void *elem2)
 125 {
 126   int e1 = * (const int *) elem1;
 127   int e2 = * (const int *) elem2;
 128   if (e1 < e2)
 129     return -1;
 130   else if (e1 > e2)
 131     return 1;
 132   else
 133     return 0;
 134 }
 135
 136 /* Prints PART to the file pointer FP.  The elements of each
 137    class are sorted.  */
 138
 139 void
 140 partition_print (partition part, FILE *fp)
 141 {
 142   char *done;
 143   int num_elements = part->num_elements;
 144   struct partition_elem *elements = part->elements;
 145   int *class_elements;
 146   int e;
 147
 148   /* Flag the elements we've already printed.  */
 149   done = (char *) xmalloc (num_elements);
 150   memset (done, 0, num_elements);
 151
 152   /* A buffer used to sort elements in a class.  */
 153   class_elements = (int *) xmalloc (num_elements * sizeof (int));
 154
 155   fputc ('[', fp);
 156   for (e = 0; e < num_elements; ++e)
 157     /* If we haven't printed this element, print its entire class.  */
 158     if (! done[e])
 159       {
 160         int c = e;
 161         int count = elements[elements[e].class_element].class_count;
 162         int i;
 163
 164       /* Collect the elements in this class.  */
 165         for (i = 0; i < count; ++i) {
 166           class_elements[i] = c;
 167           done[c] = 1;
 168           c = elements[c].next - elements;
 169         }
 170         /* Sort them.  */
 171         qsort ((void *) class_elements, count, sizeof (int), elem_compare);
 172         /* Print them.  */
 173         fputc ('(', fp);
 174         for (i = 0; i < count; ++i)
 175           fprintf (fp, i == 0 ? "%d" : " %d", class_elements[i]);
 176         fputc (')', fp);
 177       }
 178   fputc (']', fp);
 179
 180   free (class_elements);
 181   free (done);
 182 }
 183