astobj2_rbtree.c

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/*
 * astobj2_hash - RBTree implementation for astobj2.
 *
 * Copyright (C) 2006 Marta Carbone, Luigi Rizzo - Univ. di Pisa, Italy
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */
 
/*! \file
 *
 * \brief RBTree functions implementing astobj2 containers.
 *
 * \author Richard Mudgett <rmudgett@digium.com>
 */
 
#include "asterisk.h"
 
#include "asterisk/_private.h"
#include "asterisk/astobj2.h"
#include "asterisk/utils.h"
#include "astobj2_private.h"
#include "astobj2_container_private.h"
 
/*!
 * A structure to hold the object held by the container and
 * where it is located in it.
 *
 * A red-black tree has the following properties:
 *
 * 1) Every node is either black or red.
 *
 * 2) The root is black.
 *
 * 3) If a node has a NULL child, that "child" is considered
 * black.
 *
 * 4) If a node is red, then both of its children are black.
 *
 * 5) Every path from a node to a descendant NULL child has the
 * same number of black nodes.  (Including the black NULL
 * child.)
 */
struct rbtree_node {
    /*!
     * \brief Items common to all container nodes.
     * \note Must be first in the specific node struct.
     */
    struct ao2_container_node common;
    /*! Parent node of this node. NULL if this is the root node. */
    struct rbtree_node *parent;
    /*! Left child node of this node.  NULL if does not have this child. */
    struct rbtree_node *left;
    /*! Right child node of this node.  NULL if does not have this child. */
    struct rbtree_node *right;
    /*! TRUE if the node is red. */
    unsigned int is_red:1;
};
 
/*!
 * A rbtree container in addition to values common to all
 * container types, stores the pointer to the root node of the
 * tree.
 */
struct ao2_container_rbtree {
    /*!
     * \brief Items common to all containers.
     * \note Must be first in the specific container struct.
     */
    struct ao2_container common;
    /*! Root node of the tree.  NULL if the tree is empty. */
    struct rbtree_node *root;
#if defined(AO2_DEBUG)
    struct {
        /*! Fixup insert left cases 1-3 */
        int fixup_insert_left[3];
        /*! Fixup insert right cases 1-3 */
        int fixup_insert_right[3];
        /*! Fixup delete left cases 1-4 */
        int fixup_delete_left[4];
        /*! Fixup delete right cases 1-4 */
        int fixup_delete_right[4];
        /*! Deletion of node with number of children (0-2). */
        int delete_children[3];
    } stats;
#endif  /* defined(AO2_DEBUG) */
};
 
enum equal_node_bias {
    /*! Bias search toward first matching node in the container. */
    BIAS_FIRST,
    /*! Bias search toward any matching node. */
    BIAS_EQUAL,
    /*! Bias search toward last matching node in the container. */
    BIAS_LAST,
};
 
enum empty_node_direction {
    GO_LEFT,
    GO_RIGHT,
};
 
/*! Traversal state to restart a rbtree container traversal. */
struct rbtree_traversal_state {
    /*! Active sort function in the traversal if not NULL. */
    ao2_sort_fn *sort_fn;
    /*! Saved comparison callback arg pointer. */
    void *arg;
    /*! Saved search flags to control traversing the container. */
    enum search_flags flags;
};
 
struct rbtree_traversal_state_check {
    /*
     * If we have a division by zero compile error here then there
     * is not enough room for the state.  Increase AO2_TRAVERSAL_STATE_SIZE.
     */
    char check[1 / (AO2_TRAVERSAL_STATE_SIZE / sizeof(struct rbtree_traversal_state))];
};
 
/*!
 * \internal
 * \brief Get the most left node in the tree.
 * \since 12.0.0
 *
 * \param node Starting node to find the most left node.
 *
 * \return Left most node.  Never NULL.
 */
static struct rbtree_node *rb_node_most_left(struct rbtree_node *node)
{
    while (node->left) {
        node = node->left;
    }
 
    return node;
}
 
/*!
 * \internal
 * \brief Get the most right node in the tree.
 * \since 12.0.0
 *
 * \param node Starting node to find the most right node.
 *
 * \return Right most node.  Never NULL.
 */
static struct rbtree_node *rb_node_most_right(struct rbtree_node *node)
{
    while (node->right) {
        node = node->right;
    }
 
    return node;
}
 
/*!
 * \internal
 * \brief Get the next node in ascending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \return node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_next(struct rbtree_node *node)
{
    if (node->right) {
        return rb_node_most_left(node->right);
    }
 
    /* Find the parent that the node is a left child of. */
    while (node->parent) {
        if (node->parent->left == node) {
            /* We are the left child.  The parent is the next node. */
            return node->parent;
        }
        node = node->parent;
    }
    return NULL;
}
 
/*!
 * \internal
 * \brief Get the next node in descending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the previous node.
 *
 * \return node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_prev(struct rbtree_node *node)
{
    if (node->left) {
        return rb_node_most_right(node->left);
    }
 
    /* Find the parent that the node is a right child of. */
    while (node->parent) {
        if (node->parent->right == node) {
            /* We are the right child.  The parent is the previous node. */
            return node->parent;
        }
        node = node->parent;
    }
    return NULL;
}
 
/*!
 * \internal
 * \brief Get the next node in pre-order sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \return node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_pre(struct rbtree_node *node)
{
    /* Visit the children if the node has any. */
    if (node->left) {
        return node->left;
    }
    if (node->right) {
        return node->right;
    }
 
    /* Time to go back up. */
    for (;;) {
        if (!node->parent) {
            return NULL;
        }
        if (node->parent->left == node && node->parent->right) {
            /*
             * We came up the left child and there's a right child.  Visit
             * it.
             */
            return node->parent->right;
        }
        node = node->parent;
    }
}
 
/*!
 * \internal
 * \brief Get the next node in post-order sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \return node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_post(struct rbtree_node *node)
{
    /* This node's children have already been visited. */
    for (;;) {
        if (!node->parent) {
            return NULL;
        }
        if (node->parent->left == node) {
            /* We came up the left child. */
            node = node->parent;
 
            /*
             * Find the right child's left most childless node.
             */
            while (node->right) {
                node = rb_node_most_left(node->right);
            }
 
            /*
             * This node's left child has already been visited or it doesn't
             * have any children.
             */
            return node;
        }
 
        /*
         * We came up the right child.
         *
         * This node's children have already been visited.  Time to
         * visit the parent.
         */
        return node->parent;
    }
}
 
/*!
 * \internal
 * \brief Get the next non-empty node in ascending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \return node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_next_full(struct rbtree_node *node)
{
    for (;;) {
        node = rb_node_next(node);
        if (!node || node->common.obj) {
            return node;
        }
    }
}
 
/*!
 * \internal
 * \brief Get the next non-empty node in descending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the previous node.
 *
 * \return node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_prev_full(struct rbtree_node *node)
{
    for (;;) {
        node = rb_node_prev(node);
        if (!node || node->common.obj) {
            return node;
        }
    }
}
 
/*!
 * \internal
 * \brief Determine which way to go from an empty node.
 * \since 12.0.0
 *
 * \param empty Empty node to determine which side obj_right goes on.
 * \param sort_fn Sort comparison function for non-empty nodes.
 * \param obj_right pointer to the (user-defined part) of an object.
 * \param flags flags from ao2_callback()
 *   OBJ_SEARCH_OBJECT - if set, 'obj_right', is an object.
 *   OBJ_SEARCH_KEY - if set, 'obj_right', is a search key item that is not an object.
 *   OBJ_SEARCH_PARTIAL_KEY - if set, 'obj_right', is a partial search key item that is not an object.
 * \param bias How to bias search direction for duplicates
 *
 * \return \ref empty_node_direction to proceed.
 */
static enum empty_node_direction rb_find_empty_direction(struct rbtree_node *empty, ao2_sort_fn *sort_fn, void *obj_right, enum search_flags flags, enum equal_node_bias bias)
{
    int cmp;
    struct rbtree_node *cur;
    struct rbtree_node *right_most;
 
    /* Try for a quick definite go left. */
    if (!empty->left) {
        /* The empty node has no left child. */
        return GO_RIGHT;
    }
    right_most = rb_node_most_right(empty->left);
    if (right_most->common.obj) {
        cmp = sort_fn(right_most->common.obj, obj_right, flags);
        if (cmp < 0) {
            return GO_RIGHT;
        }
        if (cmp == 0 && bias == BIAS_LAST) {
            return GO_RIGHT;
        }
        return GO_LEFT;
    }
 
    /* Try for a quick definite go right. */
    if (!empty->right) {
        /* The empty node has no right child. */
        return GO_LEFT;
    }
    cur = rb_node_most_left(empty->right);
    if (cur->common.obj) {
        cmp = sort_fn(cur->common.obj, obj_right, flags);
        if (cmp > 0) {
            return GO_LEFT;
        }
        if (cmp == 0 && bias == BIAS_FIRST) {
            return GO_LEFT;
        }
        return GO_RIGHT;
    }
 
    /*
     * Have to scan the previous nodes from the right_most node of
     * the left subtree for the first non-empty node to determine
     * direction.
     */
    cur = right_most;
    for (;;) {
        /* Find previous node. */
        if (cur->left) {
            cur = rb_node_most_right(cur->left);
        } else {
            /* Find the parent that the node is a right child of. */
            for (;;) {
                if (cur->parent == empty) {
                    /* The left side of the empty node is all empty nodes. */
                    return GO_RIGHT;
                }
                if (cur->parent->right == cur) {
                    /* We are the right child.  The parent is the previous node. */
                    cur = cur->parent;
                    break;
                }
                cur = cur->parent;
            }
        }
 
        if (cur->common.obj) {
            cmp = sort_fn(cur->common.obj, obj_right, flags);
            if (cmp < 0) {
                return GO_RIGHT;
            }
            if (cmp == 0 && bias == BIAS_LAST) {
                return GO_RIGHT;
            }
            return GO_LEFT;
        }
    }
}
 
/*!
 * \internal
 * \brief Tree node rotation left.
 * \since 12.0.0
 *
 * \param self Container holding node.
 * \param node Node to perform a left rotation with.
 *
 *        p                         p
 *        |     Left rotation       |
 *        N        --->             Ch
 *       / \                       / \
 *      a  Ch                     N   c
 *        / \                    / \
 *       b   c                  a   b
 *
 * N = node
 * Ch = child
 * p = parent
 * a,b,c = other nodes that are unaffected by the rotation.
 *
 * \note It is assumed that the node's right child exists.
 */
static void rb_rotate_left(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
    struct rbtree_node *child;  /*!< Node's right child. */
 
    child = node->right;
 
    /* Link the node's parent to the child. */
    if (!node->parent) {
        /* Node is the root so we get a new root node. */
        self->root = child;
    } else if (node->parent->left == node) {
        /* Node is a left child. */
        node->parent->left = child;
    } else {
        /* Node is a right child. */
        node->parent->right = child;
    }
    child->parent = node->parent;
 
    /* Link node's right subtree to the child's left subtree. */
    node->right = child->left;
    if (node->right) {
        node->right->parent = node;
    }
 
    /* Link the node to the child's left. */
    node->parent = child;
    child->left = node;
}
 
/*!
 * \internal
 * \brief Tree node rotation right.
 * \since 12.0.0
 *
 * \param self Container holding node.
 * \param node Node to perform a right rotation with.
 *
 *        p                         p
 *        |     Right rotation      |
 *        Ch                        N
 *       / \       <---            / \
 *      a  N                      Ch  c
 *        / \                    / \
 *       b   c                  a   b
 *
 * N = node
 * Ch = child
 * p = parent
 * a,b,c = other nodes that are unaffected by the rotation.
 *
 * \note It is assumed that the node's left child exists.
 */
static void rb_rotate_right(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
    struct rbtree_node *child;  /*!< Node's left child. */
 
    child = node->left;
 
    /* Link the node's parent to the child. */
    if (!node->parent) {
        /* Node is the root so we get a new root node. */
        self->root = child;
    } else if (node->parent->right == node) {
        /* Node is a right child. */
        node->parent->right = child;
    } else {
        /* Node is a left child. */
        node->parent->left = child;
    }
    child->parent = node->parent;
 
    /* Link node's left subtree to the child's right subtree. */
    node->left = child->right;
    if (node->left) {
        node->left->parent = node;
    }
 
    /* Link the node to the child's right. */
    node->parent = child;
    child->right = node;
}
 
/*!
 * \internal
 * \brief Create an empty copy of this container. (Debug version)
 * \since 14.0.0
 *
 * \param self Container to operate upon.
 * \param tag used for debugging.
 * \param file Debug file name invoked from
 * \param line Debug line invoked from
 * \param func Debug function name invoked from
 *
 * \return empty-clone-container on success.
 * \retval NULL on error.
 */
static struct ao2_container *rb_ao2_alloc_empty_clone(struct ao2_container_rbtree *self,
    const char *tag, const char *file, int line, const char *func)
{
    if (!__is_ao2_object(self, file, line, func)) {
        return NULL;
    }
 
    return __ao2_container_alloc_rbtree(ao2_options_get(self), self->common.options,
        self->common.sort_fn, self->common.cmp_fn, tag, file, line, func);
}
 
/*!
 * \internal
 * \brief Fixup the rbtree after deleting a node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param child Child of the node just deleted from the container.
 *
 * \note The child must be a dummy black node if there really
 * was no child of the deleted node.  Otherwise, the caller must
 * pass in the parent node and which child was deleted.  In
 * addition, the fixup routine would be more complicated.
 */
static void rb_delete_fixup(struct ao2_container_rbtree *self, struct rbtree_node *child)
{
    struct rbtree_node *sibling;
 
    while (self->root != child && !child->is_red) {
        if (child->parent->left == child) {
            /* Child is a left child. */
            sibling = child->parent->right;
            ast_assert(sibling != NULL);
            if (sibling->is_red) {
                /* Case 1: The child's sibling is red. */
                AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[0]);
                sibling->is_red = 0;
                child->parent->is_red = 1;
                rb_rotate_left(self, child->parent);
                sibling = child->parent->right;
                ast_assert(sibling != NULL);
            }
            /*
             * The sibling is black.  A black node must have two children,
             * or one red child, or no children.
             */
            if ((!sibling->left || !sibling->left->is_red)
                && (!sibling->right || !sibling->right->is_red)) {
                /*
                 * Case 2: The sibling is black and both of its children are black.
                 *
                 * This case handles the two black children or no children
                 * possibilities of a black node.
                 */
                AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[1]);
                sibling->is_red = 1;
                child = child->parent;
            } else {
                /* At this point the sibling has at least one red child. */
                if (!sibling->right || !sibling->right->is_red) {
                    /*
                     * Case 3: The sibling is black, its left child is red, and its
                     * right child is black.
                     */
                    AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[2]);
                    ast_assert(sibling->left != NULL);
                    ast_assert(sibling->left->is_red);
                    sibling->left->is_red = 0;
                    sibling->is_red = 1;
                    rb_rotate_right(self, sibling);
                    sibling = child->parent->right;
                    ast_assert(sibling != NULL);
                }
                /* Case 4: The sibling is black and its right child is red. */
                AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[3]);
                sibling->is_red = child->parent->is_red;
                child->parent->is_red = 0;
                if (sibling->right) {
                    sibling->right->is_red = 0;
                }
                rb_rotate_left(self, child->parent);
                child = self->root;
            }
        } else {
            /* Child is a right child. */
            sibling = child->parent->left;
            ast_assert(sibling != NULL);
            if (sibling->is_red) {
                /* Case 1: The child's sibling is red. */
                AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[0]);
                sibling->is_red = 0;
                child->parent->is_red = 1;
                rb_rotate_right(self, child->parent);
                sibling = child->parent->left;
                ast_assert(sibling != NULL);
            }
            /*
             * The sibling is black.  A black node must have two children,
             * or one red child, or no children.
             */
            if ((!sibling->right || !sibling->right->is_red)
                && (!sibling->left || !sibling->left->is_red)) {
                /*
                 * Case 2: The sibling is black and both of its children are black.
                 *
                 * This case handles the two black children or no children
                 * possibilities of a black node.
                 */
                AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[1]);
                sibling->is_red = 1;
                child = child->parent;
            } else {
                /* At this point the sibling has at least one red child. */
                if (!sibling->left || !sibling->left->is_red) {
                    /*
                     * Case 3: The sibling is black, its right child is red, and its
                     * left child is black.
                     */
                    AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[2]);
                    ast_assert(sibling->right != NULL);
                    ast_assert(sibling->right->is_red);
                    sibling->right->is_red = 0;
                    sibling->is_red = 1;
                    rb_rotate_left(self, sibling);
                    sibling = child->parent->left;
                    ast_assert(sibling != NULL);
                }
                /* Case 4: The sibling is black and its left child is red. */
                AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[3]);
                sibling->is_red = child->parent->is_red;
                child->parent->is_red = 0;
                if (sibling->left) {
                    sibling->left->is_red = 0;
                }
                rb_rotate_right(self, child->parent);
                child = self->root;
            }
        }
    }
 
    /*
     * Case 2 could leave the child node red and it needs to leave
     * with it black.
     *
     * Case 4 sets the child node to the root which of course must
     * be black.
     */
    child->is_red = 0;
}
 
/*!
 * \internal
 * \brief Delete the doomed node from this container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param doomed Container node to delete from the container.
 */
static void rb_delete_node(struct ao2_container_rbtree *self, struct rbtree_node *doomed)
{
    struct rbtree_node *child;
    int need_fixup;
 
    if (doomed->left && doomed->right) {
        struct rbtree_node *next;
        int is_red;
 
        /*
         * The doomed node has two children.
         *
         * Find the next child node and swap it with the doomed node in
         * the tree.
         */
        AO2_DEVMODE_STAT(++self->stats.delete_children[2]);
        next = rb_node_most_left(doomed->right);
        SWAP(doomed->parent, next->parent);
        SWAP(doomed->left, next->left);
        SWAP(doomed->right, next->right);
        is_red = doomed->is_red;
        doomed->is_red = next->is_red;
        next->is_red = is_red;
 
        /* Link back in the next node. */
        if (!next->parent) {
            /* Doomed was the root so we get a new root node. */
            self->root = next;
        } else if (next->parent->left == doomed) {
            /* Doomed was the left child. */
            next->parent->left = next;
        } else {
            /* Doomed was the right child. */
            next->parent->right = next;
        }
        next->left->parent = next;
        if (next->right == next) {
            /* The next node was the right child of doomed. */
            next->right = doomed;
            doomed->parent = next;
        } else {
            next->right->parent = next;
            doomed->parent->left = doomed;
        }
 
        /* The doomed node has no left child now. */
        ast_assert(doomed->left == NULL);
 
        /*
         * We don't have to link the right child back in with doomed
         * since we are going to link it with doomed's parent anyway.
         */
        child = doomed->right;
    } else {
        /* Doomed has at most one child. */
        child = doomed->left;
        if (!child) {
            child = doomed->right;
        }
    }
    if (child) {
        AO2_DEVMODE_STAT(++self->stats.delete_children[1]);
    } else {
        AO2_DEVMODE_STAT(++self->stats.delete_children[0]);
    }
 
    need_fixup = (!doomed->is_red && !self->common.destroying);
    if (need_fixup && !child) {
        /*
         * Use the doomed node as a place holder node for the
         * nonexistent child so we also don't have to pass to the fixup
         * routine the parent and which child the deleted node came
         * from.
         */
        rb_delete_fixup(self, doomed);
        ast_assert(doomed->left == NULL);
        ast_assert(doomed->right == NULL);
        ast_assert(!doomed->is_red);
    }
 
    /* Link the child in place of doomed. */
    if (!doomed->parent) {
        /* Doomed was the root so we get a new root node. */
        self->root = child;
    } else if (doomed->parent->left == doomed) {
        /* Doomed was the left child. */
        doomed->parent->left = child;
    } else {
        /* Doomed was the right child. */
        doomed->parent->right = child;
    }
    if (child) {
        child->parent = doomed->parent;
        if (need_fixup) {
            rb_delete_fixup(self, child);
        }
    }
 
    AO2_DEVMODE_STAT(--self->common.nodes);
}
 
/*!
 * \internal
 * \brief Destroy a rbtree container node.
 * \since 12.0.0
 *
 * \param v_doomed Container node to destroy.
 *
 * \details
 * The container node unlinks itself from the container as part
 * of its destruction.  The node must be destroyed while the
 * container is already locked.
 *
 * \note The container must be locked when the node is
 * unreferenced.
 */
static void rb_ao2_node_destructor(void *v_doomed)
{
    struct rbtree_node *doomed = v_doomed;
 
    if (doomed->common.is_linked) {
        struct ao2_container_rbtree *my_container;
 
        /*
         * Promote to write lock if not already there.  Since
         * adjust_lock() can potentially release and block waiting for a
         * write lock, care must be taken to ensure that node references
         * are released before releasing the container references.
         *
         * Node references held by an iterator can only be held while
         * the iterator also holds a reference to the container.  These
         * node references must be unreferenced before the container can
         * be unreferenced to ensure that the node will not get a
         * negative reference and the destructor called twice for the
         * same node.
         */
        my_container = (struct ao2_container_rbtree *) doomed->common.my_container;
#ifdef AST_DEVMODE
        is_ao2_object(my_container);
#endif
 
        __adjust_lock(my_container, AO2_LOCK_REQ_WRLOCK, 1);
 
#if defined(AO2_DEBUG)
        if (!my_container->common.destroying
            && ao2_container_check(doomed->common.my_container, OBJ_NOLOCK)) {
            ast_log(LOG_ERROR, "Container integrity failed before node deletion.\n");
        }
#endif  /* defined(AO2_DEBUG) */
        rb_delete_node(my_container, doomed);
#if defined(AO2_DEBUG)
        if (!my_container->common.destroying
            && ao2_container_check(doomed->common.my_container, OBJ_NOLOCK)) {
            ast_log(LOG_ERROR, "Container integrity failed after node deletion.\n");
        }
#endif  /* defined(AO2_DEBUG) */
    }
 
    /*
     * We could have an object in the node if the container is being
     * destroyed or the node had not been linked in yet.
     */
    if (doomed->common.obj) {
        __container_unlink_node(&doomed->common, AO2_UNLINK_NODE_UNLINK_OBJECT);
    }
}
 
/*!
 * \internal
 * \brief Create a new container node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param obj_new Object to put into the node.
 * \param tag used for debugging.
 * \param file Debug file name invoked from
 * \param line Debug line invoked from
 * \param func Debug function name invoked from
 *
 * \return initialized-node on success.
 * \retval NULL on error.
 */
static struct rbtree_node *rb_ao2_new_node(struct ao2_container_rbtree *self, void *obj_new, const char *tag, const char *file, int line, const char *func)
{
    struct rbtree_node *node;
 
    node = ao2_alloc_options(sizeof(*node), rb_ao2_node_destructor,
        AO2_ALLOC_OPT_LOCK_NOLOCK | AO2_ALLOC_OPT_NO_REF_DEBUG);
    if (!node) {
        return NULL;
    }
 
    __ao2_ref(obj_new, +1, tag ?: "Container node creation", file, line, func);
    node->common.obj = obj_new;
    node->common.my_container = (struct ao2_container *) self;
 
    return node;
}
 
/*!
 * \internal
 * \brief Fixup the rbtree after inserting a node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param node Container node just inserted into the container.
 *
 * \note The just inserted node is red.
 */
static void rb_insert_fixup(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
    struct rbtree_node *g_parent;   /* Grand parent node. */
 
    while (node->parent && node->parent->is_red) {
        g_parent = node->parent->parent;
 
        /* The grand parent must exist if the parent is red. */
        ast_assert(g_parent != NULL);
 
        if (node->parent == g_parent->left) {
            /* The parent is a left child. */
            if (g_parent->right && g_parent->right->is_red) {
                /* Case 1: Push the black down from the grand parent node. */
                AO2_DEVMODE_STAT(++self->stats.fixup_insert_left[0]);
                g_parent->right->is_red = 0;
                g_parent->left->is_red = 0;
                g_parent->is_red = 1;
 
                node = g_parent;
            } else {
                /* The uncle node is black. */
                if (node->parent->right == node) {
                    /*
                     * Case 2: The node is a right child.
                     *
                     * Which node is the grand parent does not change.
                     */
                    AO2_DEVMODE_STAT(++self->stats.fixup_insert_left[1]);
                    node = node->parent;
                    rb_rotate_left(self, node);
                }
                /* Case 3: The node is a left child. */
                AO2_DEVMODE_STAT(++self->stats.fixup_insert_left[2]);
                node->parent->is_red = 0;
                g_parent->is_red = 1;
                rb_rotate_right(self, g_parent);
            }
        } else {
            /* The parent is a right child. */
            if (g_parent->left && g_parent->left->is_red) {
                /* Case 1: Push the black down from the grand parent node. */
                AO2_DEVMODE_STAT(++self->stats.fixup_insert_right[0]);
                g_parent->left->is_red = 0;
                g_parent->right->is_red = 0;
                g_parent->is_red = 1;
 
                node = g_parent;
            } else {
                /* The uncle node is black. */
                if (node->parent->left == node) {
                    /*
                     * Case 2: The node is a left child.
                     *
                     * Which node is the grand parent does not change.
                     */
                    AO2_DEVMODE_STAT(++self->stats.fixup_insert_right[1]);
                    node = node->parent;
                    rb_rotate_right(self, node);
                }
                /* Case 3: The node is a right child. */
                AO2_DEVMODE_STAT(++self->stats.fixup_insert_right[2]);
                node->parent->is_red = 0;
                g_parent->is_red = 1;
                rb_rotate_left(self, g_parent);
            }
        }
    }
 
    /*
     * The root could be red here because:
     * 1) We just inserted the root node in an empty tree.
     *
     * 2) Case 1 could leave the root red if the grand parent were
     * the root.
     */
    self->root->is_red = 0;
}
 
/*!
 * \internal
 * \brief Insert a node into this container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param node Container node to insert into the container.
 *
 * \return \ref ao2_container_insert value.
 */
static enum ao2_container_insert rb_ao2_insert_node(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
    int cmp;
    struct rbtree_node *cur;
    struct rbtree_node *next;
    ao2_sort_fn *sort_fn;
    uint32_t options;
    enum equal_node_bias bias;
 
    if (!self->root) {
        /* The tree is empty. */
        self->root = node;
        return AO2_CONTAINER_INSERT_NODE_INSERTED;
    }
 
    sort_fn = self->common.sort_fn;
    options = self->common.options;
    switch (options & AO2_CONTAINER_ALLOC_OPT_DUPS_MASK) {
    default:
    case AO2_CONTAINER_ALLOC_OPT_DUPS_ALLOW:
        if (options & AO2_CONTAINER_ALLOC_OPT_INSERT_BEGIN) {
            bias = BIAS_FIRST;
        } else {
            bias = BIAS_LAST;
        }
        break;
    case AO2_CONTAINER_ALLOC_OPT_DUPS_REJECT:
    case AO2_CONTAINER_ALLOC_OPT_DUPS_OBJ_REJECT:
    case AO2_CONTAINER_ALLOC_OPT_DUPS_REPLACE:
        bias = BIAS_EQUAL;
        break;
    }
 
    /*
     * New nodes are always colored red when initially inserted into
     * the tree.  (Except for the root which is always black.)
     */
    node->is_red = 1;
 
    /* Find node where normal insert would put a new node. */
    cur = self->root;
    for (;;) {
        if (!cur->common.obj) {
            /* Which direction do we go to insert this node? */
            if (rb_find_empty_direction(cur, sort_fn, node->common.obj, OBJ_SEARCH_OBJECT, bias)
                == GO_LEFT) {
                if (cur->left) {
                    cur = cur->left;
                    continue;
                }
 
                /* Node becomes a left child */
                cur->left = node;
                node->parent = cur;
                rb_insert_fixup(self, node);
                return AO2_CONTAINER_INSERT_NODE_INSERTED;
            }
            if (cur->right) {
                cur = cur->right;
                continue;
            }
 
            /* Node becomes a right child */
            cur->right = node;
            node->parent = cur;
            rb_insert_fixup(self, node);
            return AO2_CONTAINER_INSERT_NODE_INSERTED;
        }
        cmp = sort_fn(cur->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
        if (cmp > 0) {
            if (cur->left) {
                cur = cur->left;
                continue;
            }
 
            /* Node becomes a left child */
            cur->left = node;
            node->parent = cur;
            rb_insert_fixup(self, node);
            return AO2_CONTAINER_INSERT_NODE_INSERTED;
        } else if (cmp < 0) {
            if (cur->right) {
                cur = cur->right;
                continue;
            }
 
            /* Node becomes a right child */
            cur->right = node;
            node->parent = cur;
            rb_insert_fixup(self, node);
            return AO2_CONTAINER_INSERT_NODE_INSERTED;
        }
        switch (bias) {
        case BIAS_FIRST:
            /* Duplicate nodes unconditionally accepted. */
            if (cur->left) {
                cur = cur->left;
                continue;
            }
 
            /* Node becomes a left child */
            cur->left = node;
            node->parent = cur;
            rb_insert_fixup(self, node);
            return AO2_CONTAINER_INSERT_NODE_INSERTED;
        case BIAS_EQUAL:
            break;
        case BIAS_LAST:
            /* Duplicate nodes unconditionally accepted. */
            if (cur->right) {
                cur = cur->right;
                continue;
            }
 
            /* Node becomes a right child */
            cur->right = node;
            node->parent = cur;
            rb_insert_fixup(self, node);
            return AO2_CONTAINER_INSERT_NODE_INSERTED;
        }
 
        break;
    }
 
    /* Node is a duplicate */
    switch (options & AO2_CONTAINER_ALLOC_OPT_DUPS_MASK) {
    default:
    case AO2_CONTAINER_ALLOC_OPT_DUPS_ALLOW:
        ast_assert(0);/* Case already handled by BIAS_FIRST/BIAS_LAST. */
        return AO2_CONTAINER_INSERT_NODE_REJECTED;
    case AO2_CONTAINER_ALLOC_OPT_DUPS_REJECT:
        /* Reject all objects with the same key. */
        return AO2_CONTAINER_INSERT_NODE_REJECTED;
    case AO2_CONTAINER_ALLOC_OPT_DUPS_OBJ_REJECT:
        if (cur->common.obj == node->common.obj) {
            /* Reject inserting the same object */
            return AO2_CONTAINER_INSERT_NODE_REJECTED;
        }
        next = cur;
        if (options & AO2_CONTAINER_ALLOC_OPT_INSERT_BEGIN) {
            /* Search to end of duplicates for the same object. */
            for (;;) {
                next = rb_node_next_full(next);
                if (!next) {
                    break;
                }
                if (next->common.obj == node->common.obj) {
                    /* Reject inserting the same object */
                    return AO2_CONTAINER_INSERT_NODE_REJECTED;
                }
                cmp = sort_fn(next->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
                if (cmp) {
                    break;
                }
            }
 
            /* Find first duplicate node. */
            for (;;) {
                next = rb_node_prev_full(cur);
                if (!next) {
                    break;
                }
                if (next->common.obj == node->common.obj) {
                    /* Reject inserting the same object */
                    return AO2_CONTAINER_INSERT_NODE_REJECTED;
                }
                cmp = sort_fn(next->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
                if (cmp) {
                    break;
                }
                cur = next;
            }
            if (!cur->left) {
                /* Node becomes a left child */
                cur->left = node;
            } else {
                /* Node becomes a right child */
                cur = rb_node_most_right(cur->left);
                cur->right = node;
            }
        } else {
            /* Search to beginning of duplicates for the same object. */
            for (;;) {
                next = rb_node_prev_full(next);
                if (!next) {
                    break;
                }
                if (next->common.obj == node->common.obj) {
                    /* Reject inserting the same object */
                    return AO2_CONTAINER_INSERT_NODE_REJECTED;
                }
                cmp = sort_fn(next->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
                if (cmp) {
                    break;
                }
            }
 
            /* Find last duplicate node. */
            for (;;) {
                next = rb_node_next_full(cur);
                if (!next) {
                    break;
                }
                if (next->common.obj == node->common.obj) {
                    /* Reject inserting the same object */
                    return AO2_CONTAINER_INSERT_NODE_REJECTED;
                }
                cmp = sort_fn(next->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
                if (cmp) {
                    break;
                }
                cur = next;
            }
            if (!cur->right) {
                /* Node becomes a right child */
                cur->right = node;
            } else {
                /* Node becomes a left child */
                cur = rb_node_most_left(cur->right);
                cur->left = node;
            }
        }
        break;
    case AO2_CONTAINER_ALLOC_OPT_DUPS_REPLACE:
        SWAP(cur->common.obj, node->common.obj);
        ao2_ref(node, -1);
        return AO2_CONTAINER_INSERT_NODE_OBJ_REPLACED;
    }
 
    /* Complete inserting duplicate node. */
    node->parent = cur;
    rb_insert_fixup(self, node);
    return AO2_CONTAINER_INSERT_NODE_INSERTED;
}
 
/*!
 * \internal
 * \brief Find the next rbtree container node in a traversal.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param state Traversal state to restart rbtree container traversal.
 * \param prev Previous node returned by the traversal search functions.
 *    The ref ownership is passed back to this function.
 *
 * \return node-ptr of found node (Reffed).
 * \retval NULL when no node found.
 */
static struct rbtree_node *rb_ao2_find_next(struct ao2_container_rbtree *self, struct rbtree_traversal_state *state, struct rbtree_node *prev)
{
    struct rbtree_node *node;
    void *arg;
    enum search_flags flags;
    int cmp;
 
    arg = state->arg;
    flags = state->flags;
 
    node = prev;
    for (;;) {
        /* Find next node in traversal order. */
        switch (flags & OBJ_ORDER_MASK) {
        default:
        case OBJ_ORDER_ASCENDING:
            node = rb_node_next(node);
            break;
        case OBJ_ORDER_DESCENDING:
            node = rb_node_prev(node);
            break;
        case OBJ_ORDER_PRE:
            node = rb_node_pre(node);
            break;
        case OBJ_ORDER_POST:
            node = rb_node_post(node);
            break;
        }
        if (!node) {
            /* No more nodes left to traverse. */
            break;
        }
        if (!node->common.obj) {
            /* Node is empty */
            continue;
        }
 
        if (state->sort_fn) {
            /* Filter node through the sort_fn */
            cmp = state->sort_fn(node->common.obj, arg, flags & OBJ_SEARCH_MASK);
            if (cmp) {
                /* No more nodes in this container are possible to match. */
                break;
            }
        }
 
        /* We have the next traversal node */
        ao2_ref(node, +1);
 
        /*
         * Dereferencing the prev node may result in our next node
         * object being removed by another thread.  This could happen if
         * the container uses RW locks and the container was read
         * locked.
         */
        ao2_ref(prev, -1);
        if (node->common.obj) {
            return node;
        }
        prev = node;
    }
 
    /* No more nodes in the container left to traverse. */
    ao2_ref(prev, -1);
    return NULL;
}
 
/*!
 * \internal
 * \brief Find an initial matching node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param obj_right pointer to the (user-defined part) of an object.
 * \param flags flags from ao2_callback()
 *   OBJ_SEARCH_OBJECT - if set, 'obj_right', is an object.
 *   OBJ_SEARCH_KEY - if set, 'obj_right', is a search key item that is not an object.
 *   OBJ_SEARCH_PARTIAL_KEY - if set, 'obj_right', is a partial search key item that is not an object.
 * \param bias How to bias search direction for duplicates
 *
 * \return node on success.
 * \retval NULL if not found.
 */
static struct rbtree_node *rb_find_initial(struct ao2_container_rbtree *self, void *obj_right, enum search_flags flags, enum equal_node_bias bias)
{
    int cmp;
    enum search_flags sort_flags;
    struct rbtree_node *node;
    struct rbtree_node *next = NULL;
    ao2_sort_fn *sort_fn;
 
    sort_flags = flags & OBJ_SEARCH_MASK;
    sort_fn = self->common.sort_fn;
 
    /* Find node where normal search would find it. */
    node = self->root;
    if (!node) {
        return NULL;
    }
    for (;;) {
        if (!node->common.obj) {
            /* Which direction do we go to find the node? */
            if (rb_find_empty_direction(node, sort_fn, obj_right, sort_flags, bias)
                == GO_LEFT) {
                next = node->left;
            } else {
                next = node->right;
            }
            if (!next) {
                switch (bias) {
                case BIAS_FIRST:
                    /* Check successor node for match. */
                    next = rb_node_next_full(node);
                    break;
                case BIAS_EQUAL:
                    break;
                case BIAS_LAST:
                    /* Check previous node for match. */
                    next = rb_node_prev_full(node);
                    break;
                }
                if (next) {
                    cmp = sort_fn(next->common.obj, obj_right, sort_flags);
                    if (cmp == 0) {
                        /* Found the first/last matching node. */
                        return next;
                    }
                    next = NULL;
                }
 
                /* No match found. */
                return next;
            }
        } else {
            cmp = sort_fn(node->common.obj, obj_right, sort_flags);
            if (cmp > 0) {
                next = node->left;
            } else if (cmp < 0) {
                next = node->right;
            } else {
                switch (bias) {
                case BIAS_FIRST:
                    next = node->left;
                    break;
                case BIAS_EQUAL:
                    return node;
                case BIAS_LAST:
                    next = node->right;
                    break;
                }
                if (!next) {
                    /* Found the first/last matching node. */
                    return node;
                }
            }
            if (!next) {
                switch (bias) {
                case BIAS_FIRST:
                    if (cmp < 0) {
                        /* Check successor node for match. */
                        next = rb_node_next_full(node);
                    }
                    break;
                case BIAS_EQUAL:
                    break;
                case BIAS_LAST:
                    if (cmp > 0) {
                        /* Check previous node for match. */
                        next = rb_node_prev_full(node);
                    }
                    break;
                }
                if (next) {
                    cmp = sort_fn(next->common.obj, obj_right, sort_flags);
                    if (cmp == 0) {
                        /* Found the first/last matching node. */
                        return next;
                    }
                }
 
                /* No match found. */
                return NULL;
            }
        }
        node = next;
    }
}
 
/*!
 * \internal
 * \brief Find the first rbtree container node in a traversal.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param flags search_flags to control traversing the container
 * \param arg Comparison callback arg parameter.
 * \param state Traversal state to restart rbtree container traversal.
 *
 * \return node-ptr of found node (Reffed).
 * \retval NULL when no node found.
 */
static struct rbtree_node *rb_ao2_find_first(struct ao2_container_rbtree *self, enum search_flags flags, void *arg, struct rbtree_traversal_state *state)
{
    struct rbtree_node *node;
    enum equal_node_bias bias;
 
    if (self->common.destroying) {
        /* Force traversal to be post order for tree destruction. */
        flags = OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE | OBJ_ORDER_POST;
    }
 
    memset(state, 0, sizeof(*state));
    state->arg = arg;
    state->flags = flags;
 
    switch (flags & OBJ_SEARCH_MASK) {
    case OBJ_SEARCH_OBJECT:
    case OBJ_SEARCH_KEY:
    case OBJ_SEARCH_PARTIAL_KEY:
        /* We are asked to do a directed search. */
        state->sort_fn = self->common.sort_fn;
        break;
    default:
        /* Don't know, let's visit all nodes */
        state->sort_fn = NULL;
        break;
    }
 
    if (!self->root) {
        /* Tree is empty. */
        return NULL;
    }
 
    /* Find first traversal node. */
    switch (flags & OBJ_ORDER_MASK) {
    default:
    case OBJ_ORDER_ASCENDING:
        if (!state->sort_fn) {
            /* Find left most child. */
            node = rb_node_most_left(self->root);
            if (!node->common.obj) {
                node = rb_node_next_full(node);
                if (!node) {
                    return NULL;
                }
            }
            break;
        }
 
        /* Search for initial node. */
        switch (self->common.options & AO2_CONTAINER_ALLOC_OPT_DUPS_MASK) {
        case AO2_CONTAINER_ALLOC_OPT_DUPS_REJECT:
        case AO2_CONTAINER_ALLOC_OPT_DUPS_REPLACE:
            if ((flags & OBJ_SEARCH_MASK) != OBJ_SEARCH_PARTIAL_KEY) {
                /* There are no duplicates allowed. */
                bias = BIAS_EQUAL;
                break;
            }
            /* Fall through */
        default:
        case AO2_CONTAINER_ALLOC_OPT_DUPS_ALLOW:
        case AO2_CONTAINER_ALLOC_OPT_DUPS_OBJ_REJECT:
            /* Find first duplicate node. */
            bias = BIAS_FIRST;
            break;
        }
        node = rb_find_initial(self, arg, flags, bias);
        if (!node) {
            return NULL;
        }
        break;
    case OBJ_ORDER_DESCENDING:
        if (!state->sort_fn) {
            /* Find right most child. */
            node = rb_node_most_right(self->root);
            if (!node->common.obj) {
                node = rb_node_prev_full(node);
                if (!node) {
                    return NULL;
                }
            }
            break;
        }
 
        /* Search for initial node. */
        switch (self->common.options & AO2_CONTAINER_ALLOC_OPT_DUPS_MASK) {
        case AO2_CONTAINER_ALLOC_OPT_DUPS_REJECT:
        case AO2_CONTAINER_ALLOC_OPT_DUPS_REPLACE:
            if ((flags & OBJ_SEARCH_MASK) != OBJ_SEARCH_PARTIAL_KEY) {
                /* There are no duplicates allowed. */
                bias = BIAS_EQUAL;
                break;
            }
            /* Fall through */
        default:
        case AO2_CONTAINER_ALLOC_OPT_DUPS_ALLOW:
        case AO2_CONTAINER_ALLOC_OPT_DUPS_OBJ_REJECT:
            /* Find last duplicate node. */
            bias = BIAS_LAST;
            break;
        }
        node = rb_find_initial(self, arg, flags, bias);
        if (!node) {
            return NULL;
        }
        break;
    case OBJ_ORDER_PRE:
        /* This is a tree structure traversal so we must visit all nodes. */
        state->sort_fn = NULL;
 
        node = self->root;
 
        /* Find a non-empty node. */
        while (!node->common.obj) {
            node = rb_node_pre(node);
            if (!node) {
                return NULL;
            }
        }
        break;
    case OBJ_ORDER_POST:
        /* This is a tree structure traversal so we must visit all nodes. */
        state->sort_fn = NULL;
 
        /* Find the left most childless node. */
        node = self->root;
        for (;;) {
            node = rb_node_most_left(node);
            if (!node->right) {
                /* This node has no children. */
                break;
            }
            node = node->right;
        }
 
        /* Find a non-empty node. */
        while (!node->common.obj) {
            node = rb_node_post(node);
            if (!node) {
                return NULL;
            }
        }
        break;
    }
 
    /* We have the first traversal node */
    ao2_ref(node, +1);
    return node;
}
 
/*!
 * \internal
 * \brief Find the next non-empty iteration node in the container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param node Previous node returned by the iterator.
 * \param flags search_flags to control iterating the container.
 *   Only AO2_ITERATOR_DESCENDING is useful by the method.
 *
 * \note The container is already locked.
 *
 * \return node on success.
 * \retval NULL on error or no more nodes in the container.
 */
static struct rbtree_node *rb_ao2_iterator_next(struct ao2_container_rbtree *self, struct rbtree_node *node, enum ao2_iterator_flags flags)
{
    if (flags & AO2_ITERATOR_DESCENDING) {
        if (!node) {
            /* Find right most node. */
            if (!self->root) {
                return NULL;
            }
            node = rb_node_most_right(self->root);
            if (node->common.obj) {
                /* Found a non-empty node. */
                return node;
            }
        }
        /* Find next non-empty node. */
        node = rb_node_prev_full(node);
    } else {
        if (!node) {
            /* Find left most node. */
            if (!self->root) {
                return NULL;
            }
            node = rb_node_most_left(self->root);
            if (node->common.obj) {
                /* Found a non-empty node. */
                return node;
            }
        }
        /* Find next non-empty node. */
        node = rb_node_next_full(node);
    }
 
    return node;
}
 
/*!
 * \internal
 *
 * \brief Destroy this container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 */
static void rb_ao2_destroy(struct ao2_container_rbtree *self)
{
    /* Check that the container no longer has any nodes */
    if (self->root) {
        ast_log(LOG_ERROR, "Node ref leak.  Red-Black tree container still has nodes!\n");
        ast_assert(0);
    }
}
 
#if defined(AO2_DEBUG)
/*!
 * \internal
 * \brief Display contents of the specified container.
 * \since 12.0.0
 *
 * \param self Container to dump.
 * \param where User data needed by prnt to determine where to put output.
 * \param prnt Print output callback function to use.
 * \param prnt_obj Callback function to print the given object's key. (NULL if not available)
 */
static void rb_ao2_dump(struct ao2_container_rbtree *self, void *where, ao2_prnt_fn *prnt, ao2_prnt_obj_fn *prnt_obj)
{
#define FORMAT  "%16s, %16s, %16s, %16s, %5s, %16s, %s\n"
#define FORMAT2 "%16p, %16p, %16p, %16p, %5s, %16p, "
 
    struct rbtree_node *node;
 
    prnt(where, FORMAT, "Node", "Parent", "Left", "Right", "Color", "Obj", "Key");
    for (node = self->root; node; node = rb_node_pre(node)) {
        prnt(where, FORMAT2,
            node,
            node->parent,
            node->left,
            node->right,
            node->is_red ? "Red" : "Black",
            node->common.obj);
        if (node->common.obj && prnt_obj) {
            prnt_obj(node->common.obj, where, prnt);
        }
        prnt(where, "\n");
    }
 
#undef FORMAT
#undef FORMAT2
}
#endif  /* defined(AO2_DEBUG) */
 
#if defined(AO2_DEBUG)
/*!
 * \internal
 * \brief Display statistics of the specified container.
 * \since 12.0.0
 *
 * \param self Container to display statistics.
 * \param where User data needed by prnt to determine where to put output.
 * \param prnt Print output callback function to use.
 *
 * \note The container is already locked for reading.
 */
static void rb_ao2_stats(struct ao2_container_rbtree *self, void *where, ao2_prnt_fn *prnt)
{
    int idx;
 
    for (idx = 0; idx < ARRAY_LEN(self->stats.fixup_insert_left); ++idx) {
        prnt(where, "Number of left insert fixups case %d: %d\n", idx + 1,
            self->stats.fixup_insert_left[idx]);
    }
    for (idx = 0; idx < ARRAY_LEN(self->stats.fixup_insert_right); ++idx) {
        prnt(where, "Number of right insert fixups case %d: %d\n", idx + 1,
            self->stats.fixup_insert_right[idx]);
    }
 
    for (idx = 0; idx < ARRAY_LEN(self->stats.delete_children); ++idx) {
        prnt(where, "Number of nodes deleted with %d children: %d\n", idx,
            self->stats.delete_children[idx]);
    }
    for (idx = 0; idx < ARRAY_LEN(self->stats.fixup_delete_left); ++idx) {
        prnt(where, "Number of left delete fixups case %d: %d\n", idx + 1,
            self->stats.fixup_delete_left[idx]);
    }
    for (idx = 0; idx < ARRAY_LEN(self->stats.fixup_delete_right); ++idx) {
        prnt(where, "Number of right delete fixups case %d: %d\n", idx + 1,
            self->stats.fixup_delete_right[idx]);
    }
}
#endif  /* defined(AO2_DEBUG) */
 
#if defined(AO2_DEBUG)
/*!
 * \internal
 * \brief Check the black height of the given node.
 * \since 12.0.0
 *
 * \param node Node to check black height.
 *
 * \return black-height of node on success.
 * \retval -1 on error.  Node black height did not balance.
 */
static int rb_check_black_height(struct rbtree_node *node)
{
    int height_left;
    int height_right;
 
    if (!node) {
        /* A NULL child is a black node. */
        return 0;
    }
 
    height_left = rb_check_black_height(node->left);
    if (height_left < 0) {
        return -1;
    }
    height_right = rb_check_black_height(node->right);
    if (height_right < 0) {
        return -1;
    }
    if (height_left != height_right) {
        ast_log(LOG_ERROR,
            "Tree node black height of children does not match! L:%d != R:%d\n",
            height_left, height_right);
        return -1;
    }
    if (!node->is_red) {
        /* The node itself is black. */
        ++height_left;
    }
    return height_left;
}
 
#endif  /* defined(AO2_DEBUG) */
 
#if defined(AO2_DEBUG)
/*!
 * \internal
 * \brief Perform an integrity check on the specified container.
 * \since 12.0.0
 *
 * \param self Container to check integrity.
 *
 * \note The container is already locked for reading.
 *
 * \retval 0 on success.
 * \retval -1 on error.
 */
static int rb_ao2_integrity(struct ao2_container_rbtree *self)
{
    int res;
    int count_node;
    int count_obj;
    void *obj_last;
    struct rbtree_node *node;
 
    res = 0;
 
    count_node = 0;
    count_obj = 0;
 
    /*
     * See the properties listed at struct rbtree_node definition.
     *
     * The rbtree properties 1 and 3 are not testable.
     *
     * Property 1 is not testable because we are not rebalancing at
     * this time so all nodes are either red or black.
     *
     * Property 3 is not testable because it is the definition of a
     * NULL child.
     */
    if (self->root) {
        /* Check tree links. */
        if (self->root->parent) {
            if (self->root->parent == self->root) {
                ast_log(LOG_ERROR, "Tree root parent pointer points to itself!\n");
            } else {
                ast_log(LOG_ERROR, "Tree root is not a root node!\n");
            }
            return -1;
        }
        if (self->root->is_red) {
            /* Violation rbtree property 2. */
            ast_log(LOG_ERROR, "Tree root is red!\n");
            res = -1;
        }
        node = self->root;
        do {
            if (node->left) {
                if (node->left == node) {
                    ast_log(LOG_ERROR, "Tree node's left pointer points to itself!\n");
                    return -1;
                }
                if (node->left->parent != node) {
                    ast_log(LOG_ERROR, "Tree node's left child does not link back!\n");
                    return -1;
                }
            }
            if (node->right) {
                if (node->right == node) {
                    ast_log(LOG_ERROR, "Tree node's right pointer points to itself!\n");
                    return -1;
                }
                if (node->right->parent != node) {
                    ast_log(LOG_ERROR, "Tree node's right child does not link back!\n");
                    return -1;
                }
            }
 
            /* Check red/black node flags. */
            if (node->is_red) {
                /* A red node must have two black children or no children. */
                if (node->left && node->right) {
                    /* Node has two children. */
                    if (node->left->is_red) {
                        /* Violation rbtree property 4. */
                        ast_log(LOG_ERROR, "Tree node is red and its left child is red!\n");
                        res = -1;
                    }
                    if (node->right->is_red) {
                        /* Violation rbtree property 4. */
                        ast_log(LOG_ERROR, "Tree node is red and its right child is red!\n");
                        res = -1;
                    }
                } else if (node->left || node->right) {
                    /*
                     * Violation rbtree property 4 if the child is red.
                     * Violation rbtree property 5 if the child is black.
                     */
                    ast_log(LOG_ERROR, "Tree node is red and it only has one child!\n");
                    res = -1;
                }
            } else {
                /*
                 * A black node must have two children, or one red child, or no
                 * children.  If the black node has two children and only one of
                 * them is red, that red child must have two children.
                 */
                if (node->left && node->right) {
                    /* Node has two children. */
                    if (node->left->is_red != node->right->is_red) {
                        /* The children are not the same color. */
                        struct rbtree_node *red;
 
                        if (node->left->is_red) {
                            red = node->left;
                        } else {
                            red = node->right;
                        }
                        if (!red->left || !red->right) {
                            /* Violation rbtree property 5. */
                            ast_log(LOG_ERROR,
                                "Tree node is black and the red child does not have two children!\n");
                            res = -1;
                        }
                    }
                } else if ((node->left && !node->left->is_red)
                    || (node->right && !node->right->is_red)) {
                    /* Violation rbtree property 5. */
                    ast_log(LOG_ERROR, "Tree node is black and its only child is black!\n");
                    res = -1;
                }
            }
 
            /* Count nodes and objects. */
            ++count_node;
            if (node->common.obj) {
                ++count_obj;
            }
 
            node = rb_node_pre(node);
        } while (node);
 
        /* Check node key sort order. */
        obj_last = NULL;
        for (node = rb_node_most_left(self->root); node; node = rb_node_next(node)) {
            if (!node->common.obj) {
                /* Node is empty. */
                continue;
            }
 
            if (obj_last) {
                if (self->common.sort_fn(obj_last, node->common.obj, OBJ_SEARCH_OBJECT) > 0) {
                    ast_log(LOG_ERROR, "Tree nodes are out of sorted order!\n");
                    return -1;
                }
            }
            obj_last = node->common.obj;
        }
 
        /* Completely check property 5 */
        if (!res && rb_check_black_height(self->root) < 0) {
            /* Violation rbtree property 5. */
            res = -1;
        }
    }
 
    /* Check total obj count. */
    if (count_obj != ao2_container_count(&self->common)) {
        ast_log(LOG_ERROR, "Total object count does not match ao2_container_count()!\n");
        return -1;
    }
 
    /* Check total node count. */
    if (count_node != self->common.nodes) {
        ast_log(LOG_ERROR, "Total node count of %d does not match stat of %d!\n",
            count_node, self->common.nodes);
        return -1;
    }
 
    return res;
}
#endif  /* defined(AO2_DEBUG) */
 
/*! rbtree container virtual method table. */
static const struct ao2_container_methods v_table_rbtree = {
    .alloc_empty_clone = (ao2_container_alloc_empty_clone_fn) rb_ao2_alloc_empty_clone,
    .new_node = (ao2_container_new_node_fn) rb_ao2_new_node,
    .insert = (ao2_container_insert_fn) rb_ao2_insert_node,
    .traverse_first = (ao2_container_find_first_fn) rb_ao2_find_first,
    .traverse_next = (ao2_container_find_next_fn) rb_ao2_find_next,
    .iterator_next = (ao2_iterator_next_fn) rb_ao2_iterator_next,
    .destroy = (ao2_container_destroy_fn) rb_ao2_destroy,
#if defined(AO2_DEBUG)
    .dump = (ao2_container_display) rb_ao2_dump,
    .stats = (ao2_container_statistics) rb_ao2_stats,
    .integrity = (ao2_container_integrity) rb_ao2_integrity,
#endif  /* defined(AO2_DEBUG) */
};
 
/*!
 * \brief Initialize a rbtree container.
 *
 * \param self Container to initialize.
 * \param options Container behaviour options (See enum ao2_container_opts)
 * \param sort_fn Pointer to a sort function.
 * \param cmp_fn Pointer to a compare function used by ao2_find.
 *
 * \return A pointer to a struct container.
 */
static struct ao2_container *rb_ao2_container_init(struct ao2_container_rbtree *self,
    unsigned int options, ao2_sort_fn *sort_fn, ao2_callback_fn *cmp_fn)
{
    if (!self) {
        return NULL;
    }
 
    self->common.v_table = &v_table_rbtree;
    self->common.sort_fn = sort_fn;
    self->common.cmp_fn = cmp_fn;
    self->common.options = options;
 
#ifdef AO2_DEBUG
    ast_atomic_fetchadd_int(&ao2.total_containers, 1);
#endif  /* defined(AO2_DEBUG) */
 
    return (struct ao2_container *) self;
}
 
struct ao2_container *__ao2_container_alloc_rbtree(unsigned int ao2_options, unsigned int container_options,
    ao2_sort_fn *sort_fn, ao2_callback_fn *cmp_fn,
    const char *tag, const char *file, int line, const char *func)
{
    struct ao2_container_rbtree *self;
 
    if (!sort_fn) {
        /* Sanity checks. */
        ast_log(__LOG_ERROR, file, line, func, "Missing sort_fn()!\n");
        return NULL;
    }
 
    self = __ao2_alloc(sizeof(*self), container_destruct, ao2_options,
        tag ?: __PRETTY_FUNCTION__, file, line, func);
    return rb_ao2_container_init(self, container_options, sort_fn, cmp_fn);
}