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