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-rwxr-xr-xsrc/avl.c398
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+/*
+ * ANSI C Library for maintainance of AVL Balanced Trees
+ *
+ * ref.:
+ * G. M. Adelson-Velskij & E. M. Landis
+ * Doklady Akad. Nauk SSSR 146 (1962), 263-266
+ *
+ * see also:
+ * D. E. Knuth: The Art of Computer Programming Vol.3 (Sorting and Searching)
+ *
+ * (C) 2000 Daniel Nagy, Budapest University of Technology and Economics
+ * Released under GNU General Public License (GPL) version 2
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include "avl.h"
+
+/* Private methods */
+int _avl_removeroot(avl_tree* t);
+
+/* Swing to the left
+ * Warning: no balance maintainance
+ */
+void avl_swl(avl** root) {
+ avl* a = *root;
+ avl* b = a->right;
+ *root = b;
+ a->right = b->left;
+ b->left = a;
+}
+
+/* Swing to the right
+ * Warning: no balance maintainance
+ */
+void avl_swr(avl** root) {
+ avl* a = *root;
+ avl* b = a->left;
+ *root = b;
+ a->left = b->right;
+ b->right = a;
+}
+
+/* Balance maintainance after especially nasty swings
+ */
+void avl_nasty(avl* root) {
+ switch (root->balance) {
+ case -1:
+ root->left->balance = 0;
+ root->right->balance = 1;
+ break;
+ case 1:
+ root->left->balance = -1;
+ root->right->balance = 0;
+ break;
+ case 0:
+ root->left->balance = 0;
+ root->right->balance = 0;
+ }
+ root->balance = 0;
+}
+
+/* Public methods */
+
+/* Insert element a into the AVL tree t
+ * returns 1 if the depth of the tree has grown
+ * Warning: do not insert elements already present
+ */
+int _avl_insert(avl_tree* t, avl* a) {
+ /* initialize */
+ a->left = 0;
+ a->right = 0;
+ a->balance = 0;
+ /* insert into an empty tree */
+ if (!t->root) {
+ t->root = a;
+ return 1;
+ }
+
+ if (t->compar(t->root, a) > 0) {
+ /* insert into the left subtree */
+ if (t->root->left) {
+ avl_tree left_subtree;
+ left_subtree.root = t->root->left;
+ left_subtree.compar = t->compar;
+ if (_avl_insert(&left_subtree, a)) {
+ switch (t->root->balance--) {
+ case 1:
+ return 0;
+ case 0:
+ return 1;
+ }
+ if (t->root->left->balance < 0) {
+ avl_swr(&(t->root));
+ t->root->balance = 0;
+ t->root->right->balance = 0;
+ } else {
+ avl_swl(&(t->root->left));
+ avl_swr(&(t->root));
+ avl_nasty(t->root);
+ }
+ } else
+ t->root->left = left_subtree.root;
+ return 0;
+ } else {
+ t->root->left = a;
+ if (t->root->balance--)
+ return 0;
+ return 1;
+ }
+ } else {
+ /* insert into the right subtree */
+ if (t->root->right) {
+ avl_tree right_subtree;
+ right_subtree.root = t->root->right;
+ right_subtree.compar = t->compar;
+ if (_avl_insert(&right_subtree, a)) {
+ switch (t->root->balance++) {
+ case -1:
+ return 0;
+ case 0:
+ return 1;
+ }
+ if (t->root->right->balance > 0) {
+ avl_swl(&(t->root));
+ t->root->balance = 0;
+ t->root->left->balance = 0;
+ } else {
+ avl_swr(&(t->root->right));
+ avl_swl(&(t->root));
+ avl_nasty(t->root);
+ }
+ } else
+ t->root->right = right_subtree.root;
+ return 0;
+ } else {
+ t->root->right = a;
+ if (t->root->balance++)
+ return 0;
+ return 1;
+ }
+ }
+}
+int avl_insert(avl_tree* t, avl* a) {
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_lock(&t->mutex);
+#else
+ pthread_rwlock_wrlock(&t->rwlock);
+#endif
+
+ int ret = _avl_insert(t, a);
+
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_unlock(&t->mutex);
+#else
+ pthread_rwlock_unlock(&t->rwlock);
+#endif
+ return ret;
+}
+
+/* Remove an element a from the AVL tree t
+ * returns -1 if the depth of the tree has shrunk
+ * Warning: if the element is not present in the tree,
+ * returns 0 as if it had been removed succesfully.
+ */
+int _avl_remove(avl_tree* t, avl* a) {
+ int b;
+ if (t->root == a)
+ return _avl_removeroot(t);
+ b = t->compar(t->root, a);
+ if (b >= 0) {
+ /* remove from the left subtree */
+ int ch;
+ avl_tree left_subtree;
+ if ((left_subtree.root = t->root->left)) {
+ left_subtree.compar = t->compar;
+ ch = _avl_remove(&left_subtree, a);
+ t->root->left = left_subtree.root;
+ if (ch) {
+ switch (t->root->balance++) {
+ case -1:
+ return -1;
+ case 0:
+ return 0;
+ }
+ switch (t->root->right->balance) {
+ case 0:
+ avl_swl(&(t->root));
+ t->root->balance = -1;
+ t->root->left->balance = 1;
+ return 0;
+ case 1:
+ avl_swl(&(t->root));
+ t->root->balance = 0;
+ t->root->left->balance = 0;
+ return -1;
+ }
+ avl_swr(&(t->root->right));
+ avl_swl(&(t->root));
+ avl_nasty(t->root);
+ return -1;
+ }
+ }
+ }
+ if (b <= 0) {
+ /* remove from the right subtree */
+ int ch;
+ avl_tree right_subtree;
+ if ((right_subtree.root = t->root->right)) {
+ right_subtree.compar = t->compar;
+ ch = _avl_remove(&right_subtree, a);
+ t->root->right = right_subtree.root;
+ if (ch) {
+ switch (t->root->balance--) {
+ case 1:
+ return -1;
+ case 0:
+ return 0;
+ }
+ switch (t->root->left->balance) {
+ case 0:
+ avl_swr(&(t->root));
+ t->root->balance = 1;
+ t->root->right->balance = -1;
+ return 0;
+ case -1:
+ avl_swr(&(t->root));
+ t->root->balance = 0;
+ t->root->right->balance = 0;
+ return -1;
+ }
+ avl_swl(&(t->root->left));
+ avl_swr(&(t->root));
+ avl_nasty(t->root);
+ return -1;
+ }
+ }
+ }
+ return 0;
+}
+
+int avl_remove(avl_tree* t, avl* a) {
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_lock(&t->mutex);
+#else
+ pthread_rwlock_wrlock(&t->rwlock);
+#endif
+
+ int ret = _avl_remove(t, a);
+
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_unlock(&t->mutex);
+#else
+ pthread_rwlock_unlock(&t->rwlock);
+#endif
+ return ret;
+}
+
+/* Remove the root of the AVL tree t
+ * Warning: dumps core if t is empty
+ */
+int _avl_removeroot(avl_tree* t) {
+ int ch;
+ avl* a;
+ if (!t->root->left) {
+ if (!t->root->right) {
+ t->root = 0;
+ return -1;
+ }
+ t->root = t->root->right;
+ return -1;
+ }
+ if (!t->root->right) {
+ t->root = t->root->left;
+ return -1;
+ }
+ if (t->root->balance < 0) {
+ /* remove from the left subtree */
+ a = t->root->left;
+ while (a->right)
+ a = a->right;
+ } else {
+ /* remove from the right subtree */
+ a = t->root->right;
+ while (a->left)
+ a = a->left;
+ }
+ ch = _avl_remove(t, a);
+ a->left = t->root->left;
+ a->right = t->root->right;
+ a->balance = t->root->balance;
+ t->root = a;
+ if (a->balance == 0)
+ return ch;
+ return 0;
+}
+
+int avl_removeroot(avl_tree* t) {
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_lock(&t->mutex);
+#else
+ pthread_rwlock_wrlock(&t->rwlock);
+#endif
+
+ int ret = _avl_removeroot(t);
+
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_unlock(&t->mutex);
+#else
+ pthread_rwlock_unlock(&t->rwlock);
+#endif
+ return ret;
+}
+
+/* Iterate through elements in t from a range between a and b (inclusive)
+ * for each element calls iter(a) until it returns 0
+ * returns the last value returned by iterator or 0 if there were no calls
+ * Warning: a<=b must hold
+ */
+int _avl_range(avl_tree* t, avl* a, avl* b, int (*iter)(avl*), avl** ret) {
+ int x, c = 0;
+ if (!t->root)
+ return 0;
+ x = t->compar(t->root, a);
+ if (a != b) {
+ if (x < 0) {
+ x = t->compar(t->root, b);
+ if (x > 0)
+ x = 0;
+ }
+ }
+ if (x >= 0) {
+ /* search in the left subtree */
+ avl_tree left_subtree;
+ if ((left_subtree.root = t->root->left)) {
+ left_subtree.compar = t->compar;
+ if (!(c = _avl_range(&left_subtree, a, b, iter, ret)))
+ if (x > 0)
+ return 0;
+ }
+ }
+ if (x == 0) {
+ if (!(c = iter(t->root))) {
+ if (ret)
+ *ret = t->root;
+ return 0;
+ }
+ }
+ if (x <= 0) {
+ /* search in the right subtree */
+ avl_tree right_subtree;
+ if ((right_subtree.root = t->root->right)) {
+ right_subtree.compar = t->compar;
+ if (!(c = _avl_range(&right_subtree, a, b, iter, ret)))
+ if (x < 0)
+ return 0;
+ }
+ }
+ return c;
+}
+
+int avl_range(avl_tree* t, avl* a, avl* b, int (*iter)(avl*), avl** ret) {
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_lock(&t->mutex);
+#else
+ pthread_rwlock_wrlock(&t->rwlock);
+#endif
+
+ int ret2 = _avl_range(t, a, b, iter, ret);
+
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_unlock(&t->mutex);
+#else
+ pthread_rwlock_unlock(&t->rwlock);
+#endif
+
+ return ret2;
+}
+
+/* Iterate through elements in t equal to a
+ * for each element calls iter(a) until it returns 0
+ * returns the last value returned by iterator or 0 if there were no calls
+ */
+int avl_search(avl_tree* t, avl* a, int (*iter)(avl* a), avl** ret) {
+ return avl_range(t, a, a, iter, ret);
+}
+
+void avl_init(avl_tree* t, int (*compar)(void* a, void* b)) {
+ t->root = NULL;
+ t->compar = compar;
+#ifdef AVL_LOCK_WITH_MUTEX
+ pthread_mutex_init(&t->mutex, NULL);
+#else
+ pthread_rwlock_init(&t->rwlock, NULL);
+#endif
+}
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