aboutsummaryrefslogtreecommitdiff
path: root/libiberty/partition.c
blob: 31e178cff2f6840a01cf6f757494fbe25bfe6009 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
/* List implementation of a partition of consecutive integers.
   Copyright (C) 2000-2022 Free Software Foundation, Inc.
   Contributed by CodeSourcery, LLC.

   This file is part of GNU CC.

   GNU CC is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   GNU CC is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GNU CC; see the file COPYING.  If not, write to
   the Free Software Foundation, 51 Franklin Street - Fifth Floor,
   Boston, MA 02110-1301, USA.  */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif

#ifdef HAVE_STRING_H
#include <string.h>
#endif

#include "libiberty.h"
#include "partition.h"

static int elem_compare (const void *, const void *);

/* Creates a partition of NUM_ELEMENTS elements.  Initially each
   element is in a class by itself.  */

partition
partition_new (int num_elements)
{
  int e;
  
  partition part = (partition) 
    xmalloc (sizeof (struct partition_def) + 
	     (num_elements - 1) * sizeof (struct partition_elem));
  part->num_elements = num_elements;
  for (e = 0; e < num_elements; ++e) 
    {
      part->elements[e].class_element = e;
      part->elements[e].next = &(part->elements[e]);
      part->elements[e].class_count = 1;
    }

  return part;
}

/* Freeds a partition.  */

void
partition_delete (partition part)
{
  free (part);
}

/* Unites the classes containing ELEM1 and ELEM2 into a single class
   of partition PART.  If ELEM1 and ELEM2 are already in the same
   class, does nothing.  Returns the canonical element of the
   resulting union class.  */

int
partition_union (partition part, int elem1, int elem2)
{
  struct partition_elem *elements = part->elements;
  struct partition_elem *e1;
  struct partition_elem *e2;
  struct partition_elem *p;
  struct partition_elem *old_next;
  /* The canonical element of the resulting union class.  */
  int class_element = elements[elem1].class_element;

  /* If they're already in the same class, do nothing.  */
  if (class_element == elements[elem2].class_element)
    return class_element;

  /* Make sure ELEM1 is in the larger class of the two.  If not, swap
     them.  This way we always scan the shorter list.  */
  if (elements[elem1].class_count < elements[elem2].class_count) 
    {
      int temp = elem1;
      elem1 = elem2;
      elem2 = temp;
      class_element = elements[elem1].class_element;
    }

  e1 = &(elements[elem1]);
  e2 = &(elements[elem2]);

  /* Keep a count of the number of elements in the list.  */
  elements[class_element].class_count 
    += elements[e2->class_element].class_count;

  /* Update the class fields in elem2's class list.  */
  e2->class_element = class_element;
  for (p = e2->next; p != e2; p = p->next)
    p->class_element = class_element;
  
  /* Splice ELEM2's class list into ELEM1's.  These are circular
     lists.  */
  old_next = e1->next;
  e1->next = e2->next;
  e2->next = old_next;

  return class_element;
}

/* Compare elements ELEM1 and ELEM2 from array of integers, given a
   pointer to each.  Used to qsort such an array.  */

static int 
elem_compare (const void *elem1, const void *elem2)
{
  int e1 = * (const int *) elem1;
  int e2 = * (const int *) elem2;
  if (e1 < e2)
    return -1;
  else if (e1 > e2)
    return 1;
  else
    return 0;
}

/* Prints PART to the file pointer FP.  The elements of each
   class are sorted.  */

void
partition_print (partition part, FILE *fp)
{
  char *done;
  int num_elements = part->num_elements;
  struct partition_elem *elements = part->elements;
  int *class_elements;
  int e;

  /* Flag the elements we've already printed.  */
  done = (char *) xmalloc (num_elements);
  memset (done, 0, num_elements);

  /* A buffer used to sort elements in a class.  */
  class_elements = (int *) xmalloc (num_elements * sizeof (int));

  fputc ('[', fp);
  for (e = 0; e < num_elements; ++e)
    /* If we haven't printed this element, print its entire class.  */
    if (! done[e]) 
      {
	int c = e;
	int count = elements[elements[e].class_element].class_count;
	int i;

      /* Collect the elements in this class.  */
	for (i = 0; i < count; ++i) {
	  class_elements[i] = c;
	  done[c] = 1;
	  c = elements[c].next - elements;
	}
	/* Sort them.  */
	qsort ((void *) class_elements, count, sizeof (int), elem_compare);
	/* Print them.  */
	fputc ('(', fp);
	for (i = 0; i < count; ++i) 
	  fprintf (fp, i == 0 ? "%d" : " %d", class_elements[i]);
	fputc (')', fp);
      }
  fputc (']', fp);

  free (class_elements);
  free (done);
}