partition.c revision 77298 
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
37static 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
42partition
43partition_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
64void
65partition_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
76int
77partition_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
128static int
129elem_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
146void
147partition_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
192