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-rw-r--r--libnetdata/avl/avl.c404
1 files changed, 404 insertions, 0 deletions
diff --git a/libnetdata/avl/avl.c b/libnetdata/avl/avl.c
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+++ b/libnetdata/avl/avl.c
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+// SPDX-License-Identifier: LGPL-3.0-or-later
+
+#include "../libnetdata.h"
+
+/* ------------------------------------------------------------------------- */
+/*
+ * avl_insert(), avl_remove() and avl_search()
+ * are adaptations (by Costa Tsaousis) of the AVL algorithm found in libavl
+ * v2.0.3, so that they do not use any memory allocations and their memory
+ * footprint is optimized (by eliminating non-necessary data members).
+ *
+ * libavl - library for manipulation of binary trees.
+ * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004 Free Software
+ * Foundation, Inc.
+*/
+
+
+/* Search |tree| for an item matching |item|, and return it if found.
+ Otherwise return |NULL|. */
+avl *avl_search(avl_tree *tree, avl *item) {
+ avl *p;
+
+ // assert (tree != NULL && item != NULL);
+
+ for (p = tree->root; p != NULL; ) {
+ int cmp = tree->compar(item, p);
+
+ if (cmp < 0)
+ p = p->avl_link[0];
+ else if (cmp > 0)
+ p = p->avl_link[1];
+ else /* |cmp == 0| */
+ return p;
+ }
+
+ return NULL;
+}
+
+/* Inserts |item| into |tree| and returns a pointer to |item|'s address.
+ If a duplicate item is found in the tree,
+ returns a pointer to the duplicate without inserting |item|.
+ */
+avl *avl_insert(avl_tree *tree, avl *item) {
+ avl *y, *z; /* Top node to update balance factor, and parent. */
+ avl *p, *q; /* Iterator, and parent. */
+ avl *n; /* Newly inserted node. */
+ avl *w; /* New root of rebalanced subtree. */
+ unsigned char dir; /* Direction to descend. */
+
+ unsigned char da[AVL_MAX_HEIGHT]; /* Cached comparison results. */
+ int k = 0; /* Number of cached results. */
+
+ // assert(tree != NULL && item != NULL);
+
+ z = (avl *) &tree->root;
+ y = tree->root;
+ dir = 0;
+ for (q = z, p = y; p != NULL; q = p, p = p->avl_link[dir]) {
+ int cmp = tree->compar(item, p);
+ if (cmp == 0)
+ return p;
+
+ if (p->avl_balance != 0)
+ z = q, y = p, k = 0;
+ da[k++] = dir = (unsigned char)(cmp > 0);
+ }
+
+ n = q->avl_link[dir] = item;
+
+ // tree->avl_count++;
+ n->avl_link[0] = n->avl_link[1] = NULL;
+ n->avl_balance = 0;
+ if (y == NULL) return n;
+
+ for (p = y, k = 0; p != n; p = p->avl_link[da[k]], k++)
+ if (da[k] == 0)
+ p->avl_balance--;
+ else
+ p->avl_balance++;
+
+ if (y->avl_balance == -2) {
+ avl *x = y->avl_link[0];
+ if (x->avl_balance == -1) {
+ w = x;
+ y->avl_link[0] = x->avl_link[1];
+ x->avl_link[1] = y;
+ x->avl_balance = y->avl_balance = 0;
+ }
+ else {
+ // assert (x->avl_balance == +1);
+ w = x->avl_link[1];
+ x->avl_link[1] = w->avl_link[0];
+ w->avl_link[0] = x;
+ y->avl_link[0] = w->avl_link[1];
+ w->avl_link[1] = y;
+ if (w->avl_balance == -1)
+ x->avl_balance = 0, y->avl_balance = +1;
+ else if (w->avl_balance == 0)
+ x->avl_balance = y->avl_balance = 0;
+ else /* |w->avl_balance == +1| */
+ x->avl_balance = -1, y->avl_balance = 0;
+ w->avl_balance = 0;
+ }
+ }
+ else if (y->avl_balance == +2) {
+ avl *x = y->avl_link[1];
+ if (x->avl_balance == +1) {
+ w = x;
+ y->avl_link[1] = x->avl_link[0];
+ x->avl_link[0] = y;
+ x->avl_balance = y->avl_balance = 0;
+ }
+ else {
+ // assert (x->avl_balance == -1);
+ w = x->avl_link[0];
+ x->avl_link[0] = w->avl_link[1];
+ w->avl_link[1] = x;
+ y->avl_link[1] = w->avl_link[0];
+ w->avl_link[0] = y;
+ if (w->avl_balance == +1)
+ x->avl_balance = 0, y->avl_balance = -1;
+ else if (w->avl_balance == 0)
+ x->avl_balance = y->avl_balance = 0;
+ else /* |w->avl_balance == -1| */
+ x->avl_balance = +1, y->avl_balance = 0;
+ w->avl_balance = 0;
+ }
+ }
+ else return n;
+
+ z->avl_link[y != z->avl_link[0]] = w;
+
+ // tree->avl_generation++;
+ return n;
+}
+
+/* Deletes from |tree| and returns an item matching |item|.
+ Returns a null pointer if no matching item found. */
+avl *avl_remove(avl_tree *tree, avl *item) {
+ /* Stack of nodes. */
+ avl *pa[AVL_MAX_HEIGHT]; /* Nodes. */
+ unsigned char da[AVL_MAX_HEIGHT]; /* |avl_link[]| indexes. */
+ int k; /* Stack pointer. */
+
+ avl *p; /* Traverses tree to find node to delete. */
+ int cmp; /* Result of comparison between |item| and |p|. */
+
+ // assert (tree != NULL && item != NULL);
+
+ k = 0;
+ p = (avl *) &tree->root;
+ for(cmp = -1; cmp != 0; cmp = tree->compar(item, p)) {
+ unsigned char dir = (unsigned char)(cmp > 0);
+
+ pa[k] = p;
+ da[k++] = dir;
+
+ p = p->avl_link[dir];
+ if(p == NULL) return NULL;
+ }
+
+ item = p;
+
+ if (p->avl_link[1] == NULL)
+ pa[k - 1]->avl_link[da[k - 1]] = p->avl_link[0];
+ else {
+ avl *r = p->avl_link[1];
+ if (r->avl_link[0] == NULL) {
+ r->avl_link[0] = p->avl_link[0];
+ r->avl_balance = p->avl_balance;
+ pa[k - 1]->avl_link[da[k - 1]] = r;
+ da[k] = 1;
+ pa[k++] = r;
+ }
+ else {
+ avl *s;
+ int j = k++;
+
+ for (;;) {
+ da[k] = 0;
+ pa[k++] = r;
+ s = r->avl_link[0];
+ if (s->avl_link[0] == NULL) break;
+
+ r = s;
+ }
+
+ s->avl_link[0] = p->avl_link[0];
+ r->avl_link[0] = s->avl_link[1];
+ s->avl_link[1] = p->avl_link[1];
+ s->avl_balance = p->avl_balance;
+
+ pa[j - 1]->avl_link[da[j - 1]] = s;
+ da[j] = 1;
+ pa[j] = s;
+ }
+ }
+
+ // assert (k > 0);
+ while (--k > 0) {
+ avl *y = pa[k];
+
+ if (da[k] == 0) {
+ y->avl_balance++;
+ if (y->avl_balance == +1) break;
+ else if (y->avl_balance == +2) {
+ avl *x = y->avl_link[1];
+ if (x->avl_balance == -1) {
+ avl *w;
+ // assert (x->avl_balance == -1);
+ w = x->avl_link[0];
+ x->avl_link[0] = w->avl_link[1];
+ w->avl_link[1] = x;
+ y->avl_link[1] = w->avl_link[0];
+ w->avl_link[0] = y;
+ if (w->avl_balance == +1)
+ x->avl_balance = 0, y->avl_balance = -1;
+ else if (w->avl_balance == 0)
+ x->avl_balance = y->avl_balance = 0;
+ else /* |w->avl_balance == -1| */
+ x->avl_balance = +1, y->avl_balance = 0;
+ w->avl_balance = 0;
+ pa[k - 1]->avl_link[da[k - 1]] = w;
+ }
+ else {
+ y->avl_link[1] = x->avl_link[0];
+ x->avl_link[0] = y;
+ pa[k - 1]->avl_link[da[k - 1]] = x;
+ if (x->avl_balance == 0) {
+ x->avl_balance = -1;
+ y->avl_balance = +1;
+ break;
+ }
+ else x->avl_balance = y->avl_balance = 0;
+ }
+ }
+ }
+ else
+ {
+ y->avl_balance--;
+ if (y->avl_balance == -1) break;
+ else if (y->avl_balance == -2) {
+ avl *x = y->avl_link[0];
+ if (x->avl_balance == +1) {
+ avl *w;
+ // assert (x->avl_balance == +1);
+ w = x->avl_link[1];
+ x->avl_link[1] = w->avl_link[0];
+ w->avl_link[0] = x;
+ y->avl_link[0] = w->avl_link[1];
+ w->avl_link[1] = y;
+ if (w->avl_balance == -1)
+ x->avl_balance = 0, y->avl_balance = +1;
+ else if (w->avl_balance == 0)
+ x->avl_balance = y->avl_balance = 0;
+ else /* |w->avl_balance == +1| */
+ x->avl_balance = -1, y->avl_balance = 0;
+ w->avl_balance = 0;
+ pa[k - 1]->avl_link[da[k - 1]] = w;
+ }
+ else {
+ y->avl_link[0] = x->avl_link[1];
+ x->avl_link[1] = y;
+ pa[k - 1]->avl_link[da[k - 1]] = x;
+ if (x->avl_balance == 0) {
+ x->avl_balance = +1;
+ y->avl_balance = -1;
+ break;
+ }
+ else x->avl_balance = y->avl_balance = 0;
+ }
+ }
+ }
+ }
+
+ // tree->avl_count--;
+ // tree->avl_generation++;
+ return item;
+}
+
+/* ------------------------------------------------------------------------- */
+// below are functions by (C) Costa Tsaousis
+
+// ---------------------------
+// traversing
+
+int avl_walker(avl *node, int (*callback)(void * /*entry*/, void * /*data*/), void *data) {
+ int total = 0, ret = 0;
+
+ if(node->avl_link[0]) {
+ ret = avl_walker(node->avl_link[0], callback, data);
+ if(ret < 0) return ret;
+ total += ret;
+ }
+
+ ret = callback(node, data);
+ if(ret < 0) return ret;
+ total += ret;
+
+ if(node->avl_link[1]) {
+ ret = avl_walker(node->avl_link[1], callback, data);
+ if (ret < 0) return ret;
+ total += ret;
+ }
+
+ return total;
+}
+
+int avl_traverse(avl_tree *tree, int (*callback)(void * /*entry*/, void * /*data*/), void *data) {
+ if(tree->root)
+ return avl_walker(tree->root, callback, data);
+ else
+ return 0;
+}
+
+// ---------------------------
+// locks
+
+void avl_read_lock(avl_tree_lock *t) {
+#ifndef AVL_WITHOUT_PTHREADS
+#ifdef AVL_LOCK_WITH_MUTEX
+ netdata_mutex_lock(&t->mutex);
+#else
+ netdata_rwlock_rdlock(&t->rwlock);
+#endif
+#endif /* AVL_WITHOUT_PTHREADS */
+}
+
+void avl_write_lock(avl_tree_lock *t) {
+#ifndef AVL_WITHOUT_PTHREADS
+#ifdef AVL_LOCK_WITH_MUTEX
+ netdata_mutex_lock(&t->mutex);
+#else
+ netdata_rwlock_wrlock(&t->rwlock);
+#endif
+#endif /* AVL_WITHOUT_PTHREADS */
+}
+
+void avl_unlock(avl_tree_lock *t) {
+#ifndef AVL_WITHOUT_PTHREADS
+#ifdef AVL_LOCK_WITH_MUTEX
+ netdata_mutex_unlock(&t->mutex);
+#else
+ netdata_rwlock_unlock(&t->rwlock);
+#endif
+#endif /* AVL_WITHOUT_PTHREADS */
+}
+
+// ---------------------------
+// operations with locking
+
+void avl_init_lock(avl_tree_lock *tree, int (*compar)(void * /*a*/, void * /*b*/)) {
+ avl_init(&tree->avl_tree, compar);
+
+#ifndef AVL_WITHOUT_PTHREADS
+ int lock;
+
+#ifdef AVL_LOCK_WITH_MUTEX
+ lock = netdata_mutex_init(&tree->mutex, NULL);
+#else
+ lock = netdata_rwlock_init(&tree->rwlock);
+#endif
+
+ if(lock != 0)
+ fatal("Failed to initialize AVL mutex/rwlock, error: %d", lock);
+
+#endif /* AVL_WITHOUT_PTHREADS */
+}
+
+avl *avl_search_lock(avl_tree_lock *tree, avl *item) {
+ avl_read_lock(tree);
+ avl *ret = avl_search(&tree->avl_tree, item);
+ avl_unlock(tree);
+ return ret;
+}
+
+avl * avl_remove_lock(avl_tree_lock *tree, avl *item) {
+ avl_write_lock(tree);
+ avl *ret = avl_remove(&tree->avl_tree, item);
+ avl_unlock(tree);
+ return ret;
+}
+
+avl *avl_insert_lock(avl_tree_lock *tree, avl *item) {
+ avl_write_lock(tree);
+ avl * ret = avl_insert(&tree->avl_tree, item);
+ avl_unlock(tree);
+ return ret;
+}
+
+int avl_traverse_lock(avl_tree_lock *tree, int (*callback)(void * /*entry*/, void * /*data*/), void *data) {
+ int ret;
+ avl_read_lock(tree);
+ ret = avl_traverse(&tree->avl_tree, callback, data);
+ avl_unlock(tree);
+ return ret;
+}
+
+void avl_init(avl_tree *tree, int (*compar)(void * /*a*/, void * /*b*/)) {
+ tree->root = NULL;
+ tree->compar = compar;
+}
+
+// ------------------
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