1 /**
2 * collectd - src/utils_heap.c
3 * Copyright (C) 2009 Florian octo Forster
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 *
23 * Authors:
24 * Florian octo Forster <octo at collectd.org>
25 **/
27 #include <stdlib.h>
28 #include <errno.h>
29 #include <assert.h>
30 #include <pthread.h>
32 #include "utils_heap.h"
34 struct c_heap_s
35 {
36 pthread_mutex_t lock;
37 int (*compare) (const void *, const void *);
39 void **list;
40 size_t list_len; /* # entries used */
41 size_t list_size; /* # entries allocated */
42 };
44 enum reheap_direction
45 {
46 DIR_UP,
47 DIR_DOWN
48 };
50 static void reheap (c_heap_t *h, size_t root, enum reheap_direction dir)
51 {
52 size_t left;
53 size_t right;
54 size_t min;
55 int status;
57 /* Calculate the positions of the children */
58 left = (2 * root) + 1;
59 if (left >= h->list_len)
60 left = 0;
62 right = (2 * root) + 2;
63 if (right >= h->list_len)
64 right = 0;
66 /* Check which one of the children is smaller. */
67 if ((left == 0) && (right == 0))
68 return;
69 else if (left == 0)
70 min = right;
71 else if (right == 0)
72 min = left;
73 else
74 {
75 status = h->compare (h->list[left], h->list[right]);
76 if (status > 0)
77 min = right;
78 else
79 min = left;
80 }
82 status = h->compare (h->list[root], h->list[min]);
83 if (status <= 0)
84 {
85 /* We didn't need to change anything, so the rest of the tree should be
86 * okay now. */
87 return;
88 }
89 else /* if (status > 0) */
90 {
91 void *tmp;
93 tmp = h->list[root];
94 h->list[root] = h->list[min];
95 h->list[min] = tmp;
96 }
98 if ((dir == DIR_UP) && (root == 0))
99 return;
101 if (dir == DIR_UP)
102 reheap (h, (root - 1) / 2, dir);
103 else if (dir == DIR_DOWN)
104 reheap (h, min, dir);
105 } /* void reheap */
107 c_heap_t *c_heap_create (int (*compare) (const void *, const void *))
108 {
109 c_heap_t *h;
111 if (compare == NULL)
112 return (NULL);
114 h = calloc (1, sizeof (*h));
115 if (h == NULL)
116 return (NULL);
118 pthread_mutex_init (&h->lock, /* attr = */ NULL);
119 h->compare = compare;
121 h->list = NULL;
122 h->list_len = 0;
123 h->list_size = 0;
125 return (h);
126 } /* c_heap_t *c_heap_create */
128 void c_heap_destroy (c_heap_t *h)
129 {
130 if (h == NULL)
131 return;
133 h->list_len = 0;
134 h->list_size = 0;
135 free (h->list);
136 h->list = NULL;
138 pthread_mutex_destroy (&h->lock);
140 free (h);
141 } /* void c_heap_destroy */
143 int c_heap_insert (c_heap_t *h, void *ptr)
144 {
145 size_t index;
147 if ((h == NULL) || (ptr == NULL))
148 return (-EINVAL);
150 pthread_mutex_lock (&h->lock);
152 assert (h->list_len <= h->list_size);
153 if (h->list_len == h->list_size)
154 {
155 void **tmp;
157 tmp = realloc (h->list, (h->list_size + 16) * sizeof (*h->list));
158 if (tmp == NULL)
159 {
160 pthread_mutex_unlock (&h->lock);
161 return (-ENOMEM);
162 }
164 h->list = tmp;
165 h->list_size += 16;
166 }
168 /* Insert the new node as a leaf. */
169 index = h->list_len;
170 h->list[index] = ptr;
171 h->list_len++;
173 /* Reorganize the heap from bottom up. */
174 reheap (h, /* parent of this node = */ (index - 1) / 2, DIR_UP);
176 pthread_mutex_unlock (&h->lock);
177 return (0);
178 } /* int c_heap_insert */
180 void *c_heap_get_root (c_heap_t *h)
181 {
182 void *ret = NULL;
184 if (h == NULL)
185 return (NULL);
187 pthread_mutex_lock (&h->lock);
189 if (h->list_len == 0)
190 {
191 pthread_mutex_unlock (&h->lock);
192 return (NULL);
193 }
194 else if (h->list_len == 1)
195 {
196 ret = h->list[0];
197 h->list[0] = NULL;
198 h->list_len = 0;
199 }
200 else /* if (h->list_len > 1) */
201 {
202 ret = h->list[0];
203 h->list[0] = h->list[h->list_len - 1];
204 h->list[h->list_len - 1] = NULL;
205 h->list_len--;
207 reheap (h, /* root = */ 0, DIR_DOWN);
208 }
210 /* free some memory */
211 if ((h->list_len + 32) < h->list_size)
212 {
213 void **tmp;
215 tmp = realloc (h->list, (h->list_len + 16) * sizeof (*h->list));
216 if (tmp != NULL)
217 {
218 h->list = tmp;
219 h->list_size = h->list_len + 16;
220 }
221 }
223 pthread_mutex_unlock (&h->lock);
225 return (ret);
226 } /* void *c_heap_get_root */
228 /* vim: set sw=2 sts=2 et fdm=marker : */