partition.c revision 60484 
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
36partition
37partition_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
58void
59partition_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
70int
71partition_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
122static int
123elem_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
140void
141partition_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
186