astobj2_hash.c

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/*
 * astobj2_hash - Hash table 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 Hash table functions implementing astobj2 containers.
 *
 * \author Richard Mudgett <[email protected]>
 */

#include "asterisk.h"

#include "asterisk/_private.h"
#include "asterisk/astobj2.h"
#include "astobj2_private.h"
#include "astobj2_container_private.h"
#include "asterisk/dlinkedlists.h"
#include "asterisk/utils.h"

/*!
 * A structure to create a linked list of entries,
 * used within a bucket.
 */
struct hash_bucket_node {
 /*!
 * \brief Items common to all container nodes.
 * \note Must be first in the specific node struct.
 */
 struct ao2_container_node common;
 /*! Next node links in the list. */
 AST_DLLIST_ENTRY(hash_bucket_node) links;
 /*! Hash bucket holding the node. */
 int my_bucket;
};

struct hash_bucket {
 /*! List of objects held in the bucket. */
 AST_DLLIST_HEAD_NOLOCK(, hash_bucket_node) list;
#if defined(AO2_DEBUG)
 /*! Number of elements currently in the bucket. */
 int elements;
 /*! Maximum number of elements in the bucket. */
 int max_elements;
#endif /* defined(AO2_DEBUG) */
};

/*!
 * A hash container in addition to values common to all
 * container types, stores the hash callback function, the
 * number of hash buckets, and the hash bucket heads.
 */
struct ao2_container_hash {
 /*!
 * \brief Items common to all containers.
 * \note Must be first in the specific container struct.
 */
 struct ao2_container common;
 ao2_hash_fn *hash_fn;
 /*! Number of hash buckets in this container. */
 int n_buckets;
 /*! Hash bucket array of n_buckets. Variable size. */
 struct hash_bucket buckets[0];
};

/*! Traversal state to restart a hash container traversal. */
struct hash_traversal_state {
 /*! Active sort function in the traversal if not NULL. */
 ao2_sort_fn *sort_fn;
 /*! Saved comparison callback arg pointer. */
 void *arg;
 /*! Starting hash bucket */
 int bucket_start;
 /*! Stopping hash bucket */
 int bucket_last;
 /*! Saved search flags to control traversing the container. */
 enum search_flags flags;
 /*! TRUE if it is a descending search */
 unsigned int descending:1;
};

struct hash_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 hash_traversal_state))];
};

/*!
 * \internal
 * \brief Create an empty copy of this container.
 * \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
 *
 * \retval empty-clone-container on success.
 * \retval NULL on error.
 */
static struct ao2_container *hash_ao2_alloc_empty_clone(struct ao2_container_hash *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_hash(ao2_options_get(self), self->common.options,
 self->n_buckets, self->hash_fn, self->common.sort_fn, self->common.cmp_fn,
 tag, file, line, func);
}

/*!
 * \internal
 * \brief Destroy a hash container list 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.
 *
 * \return Nothing
 */
static void hash_ao2_node_destructor(void *v_doomed)
{
 struct hash_bucket_node *doomed = v_doomed;

 if (doomed->common.is_linked) {
 struct ao2_container_hash *my_container;
 struct hash_bucket *bucket;

 /*
 * 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_hash *) 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) */
 bucket = &my_container->buckets[doomed->my_bucket];
 AST_DLLIST_REMOVE(&bucket->list, doomed, links);
 AO2_DEVMODE_STAT(--my_container->common.nodes);
 }

 /*
 * 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
 *
 * \retval initialized-node on success.
 * \retval NULL on error.
 */
static struct hash_bucket_node *hash_ao2_new_node(struct ao2_container_hash *self, void *obj_new, const char *tag, const char *file, int line, const char *func)
{
 struct hash_bucket_node *node;
 int i;

 node = ao2_alloc_options(sizeof(*node), hash_ao2_node_destructor,
 AO2_ALLOC_OPT_LOCK_NOLOCK | AO2_ALLOC_OPT_NO_REF_DEBUG);
 if (!node) {
 return NULL;
 }

 i = abs(self->hash_fn(obj_new, OBJ_SEARCH_OBJECT) % self->n_buckets);

 __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;
 node->my_bucket = i;

 return node;
}

/*!
 * \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 enum ao2_container_insert value.
 */
static enum ao2_container_insert hash_ao2_insert_node(struct ao2_container_hash *self,
 struct hash_bucket_node *node)
{
 int cmp;
 struct hash_bucket *bucket;
 struct hash_bucket_node *cur;
 ao2_sort_fn *sort_fn;
 uint32_t options;

 bucket = &self->buckets[node->my_bucket];
 sort_fn = self->common.sort_fn;
 options = self->common.options;

 if (options & AO2_CONTAINER_ALLOC_OPT_INSERT_BEGIN) {
 if (sort_fn) {
 AST_DLLIST_TRAVERSE_BACKWARDS_SAFE_BEGIN(&bucket->list, cur, links) {
 cmp = sort_fn(cur->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
 if (cmp > 0) {
 continue;
 }
 if (cmp < 0) {
 AST_DLLIST_INSERT_AFTER_CURRENT(node, links);
 return AO2_CONTAINER_INSERT_NODE_INSERTED;
 }
 switch (options & AO2_CONTAINER_ALLOC_OPT_DUPS_MASK) {
 default:
 case AO2_CONTAINER_ALLOC_OPT_DUPS_ALLOW:
 break;
 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;
 }
 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;
 }
 }
 AST_DLLIST_TRAVERSE_BACKWARDS_SAFE_END;
 }
 AST_DLLIST_INSERT_HEAD(&bucket->list, node, links);
 } else {
 if (sort_fn) {
 AST_DLLIST_TRAVERSE_SAFE_BEGIN(&bucket->list, cur, links) {
 cmp = sort_fn(cur->common.obj, node->common.obj, OBJ_SEARCH_OBJECT);
 if (cmp < 0) {
 continue;
 }
 if (cmp > 0) {
 AST_DLLIST_INSERT_BEFORE_CURRENT(node, links);
 return AO2_CONTAINER_INSERT_NODE_INSERTED;
 }
 switch (options & AO2_CONTAINER_ALLOC_OPT_DUPS_MASK) {
 default:
 case AO2_CONTAINER_ALLOC_OPT_DUPS_ALLOW:
 break;
 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;
 }
 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;
 }
 }
 AST_DLLIST_TRAVERSE_SAFE_END;
 }
 AST_DLLIST_INSERT_TAIL(&bucket->list, node, links);
 }
 return AO2_CONTAINER_INSERT_NODE_INSERTED;
}

/*!
 * \internal
 * \brief Find the first hash 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 hash container traversal.
 *
 * \retval node-ptr of found node (Reffed).
 * \retval NULL when no node found.
 */
static struct hash_bucket_node *hash_ao2_find_first(struct ao2_container_hash *self, enum search_flags flags, void *arg, struct hash_traversal_state *state)
{
 struct hash_bucket_node *node;
 int bucket_cur;
 int cmp;

 memset(state, 0, sizeof(*state));
 state->arg = arg;
 state->flags = flags;

 /* Determine traversal order. */
 switch (flags & OBJ_ORDER_MASK) {
 case OBJ_ORDER_POST:
 case OBJ_ORDER_DESCENDING:
 state->descending = 1;
 break;
 case OBJ_ORDER_PRE:
 case OBJ_ORDER_ASCENDING:
 default:
 break;
 }

 /*
 * If lookup by pointer or search key, run the hash and optional
 * sort functions. Otherwise, traverse the whole container.
 */
 switch (flags & OBJ_SEARCH_MASK) {
 case OBJ_SEARCH_OBJECT:
 case OBJ_SEARCH_KEY:
 /* we know hash can handle this case */
 bucket_cur = abs(self->hash_fn(arg, flags & OBJ_SEARCH_MASK)
 % self->n_buckets);
 state->sort_fn = self->common.sort_fn;
 break;
 case OBJ_SEARCH_PARTIAL_KEY:
 /* scan all buckets for partial key matches */
 bucket_cur = -1;
 state->sort_fn = self->common.sort_fn;
 break;
 default:
 /* don't know, let's scan all buckets */
 bucket_cur = -1;
 state->sort_fn = NULL;
 break;
 }

 if (state->descending) {
 /*
 * Determine the search boundaries of a descending traversal.
 *
 * bucket_cur downto state->bucket_last
 */
 if (bucket_cur < 0) {
 bucket_cur = self->n_buckets - 1;
 state->bucket_last = 0;
 } else {
 state->bucket_last = bucket_cur;
 }
 state->bucket_start = bucket_cur;

 /* For each bucket */
 for (; state->bucket_last <= bucket_cur; --bucket_cur) {
 /* For each node in the bucket. */
 for (node = AST_DLLIST_LAST(&self->buckets[bucket_cur].list);
 node;
 node = AST_DLLIST_PREV(node, links)) {
 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 > 0) {
 continue;
 }
 if (cmp < 0) {
 /* No more nodes in this bucket are possible to match. */
 break;
 }
 }

 /* We have the first traversal node */
 ao2_ref(node, +1);
 return node;
 }
 }
 } else {
 /*
 * Determine the search boundaries of an ascending traversal.
 *
 * bucket_cur to state->bucket_last-1
 */
 if (bucket_cur < 0) {
 bucket_cur = 0;
 state->bucket_last = self->n_buckets;
 } else {
 state->bucket_last = bucket_cur + 1;
 }
 state->bucket_start = bucket_cur;

 /* For each bucket */
 for (; bucket_cur < state->bucket_last; ++bucket_cur) {
 /* For each node in the bucket. */
 for (node = AST_DLLIST_FIRST(&self->buckets[bucket_cur].list);
 node;
 node = AST_DLLIST_NEXT(node, links)) {
 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 < 0) {
 continue;
 }
 if (cmp > 0) {
 /* No more nodes in this bucket are possible to match. */
 break;
 }
 }

 /* We have the first traversal node */
 ao2_ref(node, +1);
 return node;
 }
 }
 }

 return NULL;
}

/*!
 * \internal
 * \brief Find the next hash container node in a traversal.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param state Traversal state to restart hash container traversal.
 * \param prev Previous node returned by the traversal search functions.
 * The ref ownership is passed back to this function.
 *
 * \retval node-ptr of found node (Reffed).
 * \retval NULL when no node found.
 */
static struct hash_bucket_node *hash_ao2_find_next(struct ao2_container_hash *self, struct hash_traversal_state *state, struct hash_bucket_node *prev)
{
 struct hash_bucket_node *node;
 void *arg;
 enum search_flags flags;
 int bucket_cur;
 int cmp;

 arg = state->arg;
 flags = state->flags;
 bucket_cur = prev->my_bucket;
 node = prev;

 /*
 * This function is structured the same as hash_ao2_find_first()
 * intentionally. We are resuming the search loops from
 * hash_ao2_find_first() in order to find the next node. The
 * search loops must be resumed where hash_ao2_find_first()
 * returned with the first node.
 */
 if (state->descending) {
 goto hash_descending_resume;

 /* For each bucket */
 for (; state->bucket_last <= bucket_cur; --bucket_cur) {
 /* For each node in the bucket. */
 for (node = AST_DLLIST_LAST(&self->buckets[bucket_cur].list);
 node;
 node = AST_DLLIST_PREV(node, links)) {
 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 > 0) {
 continue;
 }
 if (cmp < 0) {
 /* No more nodes in this bucket 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;

hash_descending_resume:;
 }
 }
 } else {
 goto hash_ascending_resume;

 /* For each bucket */
 for (; bucket_cur < state->bucket_last; ++bucket_cur) {
 /* For each node in the bucket. */
 for (node = AST_DLLIST_FIRST(&self->buckets[bucket_cur].list);
 node;
 node = AST_DLLIST_NEXT(node, links)) {
 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 < 0) {
 continue;
 }
 if (cmp > 0) {
 /* No more nodes in this bucket 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;

hash_ascending_resume:;
 }
 }
 }

 /* No more nodes in the container left to traverse. */
 ao2_ref(prev, -1);
 return NULL;
}

/*!
 * \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.
 *
 * \retval node on success.
 * \retval NULL on error or no more nodes in the container.
 */
static struct hash_bucket_node *hash_ao2_iterator_next(struct ao2_container_hash *self, struct hash_bucket_node *node, enum ao2_iterator_flags flags)
{
 int cur_bucket;

 if (flags & AO2_ITERATOR_DESCENDING) {
 if (node) {
 cur_bucket = node->my_bucket;

 /* Find next non-empty node. */
 for (;;) {
 node = AST_DLLIST_PREV(node, links);
 if (!node) {
 break;
 }
 if (node->common.obj) {
 /* Found a non-empty node. */
 return node;
 }
 }
 } else {
 /* Find first non-empty node. */
 cur_bucket = self->n_buckets;
 }

 /* Find a non-empty node in the remaining buckets */
 while (0 <= --cur_bucket) {
 node = AST_DLLIST_LAST(&self->buckets[cur_bucket].list);
 while (node) {
 if (node->common.obj) {
 /* Found a non-empty node. */
 return node;
 }
 node = AST_DLLIST_PREV(node, links);
 }
 }
 } else {
 if (node) {
 cur_bucket = node->my_bucket;

 /* Find next non-empty node. */
 for (;;) {
 node = AST_DLLIST_NEXT(node, links);
 if (!node) {
 break;
 }
 if (node->common.obj) {
 /* Found a non-empty node. */
 return node;
 }
 }
 } else {
 /* Find first non-empty node. */
 cur_bucket = -1;
 }

 /* Find a non-empty node in the remaining buckets */
 while (++cur_bucket < self->n_buckets) {
 node = AST_DLLIST_FIRST(&self->buckets[cur_bucket].list);
 while (node) {
 if (node->common.obj) {
 /* Found a non-empty node. */
 return node;
 }
 node = AST_DLLIST_NEXT(node, links);
 }
 }
 }

 /* No more nodes to visit in the container. */
 return NULL;
}

#if defined(AO2_DEBUG)
/*!
 * \internal
 * \brief Increment the hash container linked object statistic.
 * \since 12.0.0
 *
 * \param hash Container to operate upon.
 * \param hash_node Container node linking object to.
 *
 * \return Nothing
 */
static void hash_ao2_link_node_stat(struct ao2_container *hash, struct ao2_container_node *hash_node)
{
 struct ao2_container_hash *self = (struct ao2_container_hash *) hash;
 struct hash_bucket_node *node = (struct hash_bucket_node *) hash_node;
 int i = node->my_bucket;

 ++self->buckets[i].elements;
 if (self->buckets[i].max_elements < self->buckets[i].elements) {
 self->buckets[i].max_elements = self->buckets[i].elements;
 }
}
#endif /* defined(AO2_DEBUG) */

#if defined(AO2_DEBUG)
/*!
 * \internal
 * \brief Decrement the hash container linked object statistic.
 * \since 12.0.0
 *
 * \param hash Container to operate upon.
 * \param hash_node Container node unlinking object from.
 *
 * \return Nothing
 */
static void hash_ao2_unlink_node_stat(struct ao2_container *hash, struct ao2_container_node *hash_node)
{
 struct ao2_container_hash *self = (struct ao2_container_hash *) hash;
 struct hash_bucket_node *node = (struct hash_bucket_node *) hash_node;

 --self->buckets[node->my_bucket].elements;
}
#endif /* defined(AO2_DEBUG) */

/*!
 * \internal
 *
 * \brief Destroy this container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 *
 * \return Nothing
 */
static void hash_ao2_destroy(struct ao2_container_hash *self)
{
 int idx;

 /* Check that the container no longer has any nodes */
 for (idx = self->n_buckets; idx--;) {
 if (!AST_DLLIST_EMPTY(&self->buckets[idx].list)) {
 ast_log(LOG_ERROR, "Node ref leak. Hash container still has nodes!\n");
 ast_assert(0);
 break;
 }
 }
}

#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)
 *
 * \return Nothing
 */
static void hash_ao2_dump(struct ao2_container_hash *self, void *where, ao2_prnt_fn *prnt, ao2_prnt_obj_fn *prnt_obj)
{
#define FORMAT "%6s, %16s, %16s, %16s, %16s, %s\n"
#define FORMAT2 "%6d, %16p, %16p, %16p, %16p, "

 int bucket;
 int suppressed_buckets = 0;
 struct hash_bucket_node *node;

 prnt(where, "Number of buckets: %d\n\n", self->n_buckets);

 prnt(where, FORMAT, "Bucket", "Node", "Prev", "Next", "Obj", "Key");
 for (bucket = 0; bucket < self->n_buckets; ++bucket) {
 node = AST_DLLIST_FIRST(&self->buckets[bucket].list);
 if (node) {
 suppressed_buckets = 0;
 do {
 prnt(where, FORMAT2,
 bucket,
 node,
 AST_DLLIST_PREV(node, links),
 AST_DLLIST_NEXT(node, links),
 node->common.obj);
 if (node->common.obj && prnt_obj) {
 prnt_obj(node->common.obj, where, prnt);
 }
 prnt(where, "\n");

 node = AST_DLLIST_NEXT(node, links);
 } while (node);
 } else if (!suppressed_buckets) {
 suppressed_buckets = 1;
 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.
 *
 * \return Nothing
 */
static void hash_ao2_stats(struct ao2_container_hash *self, void *where, ao2_prnt_fn *prnt)
{
#define FORMAT "%10.10s %10.10s %10.10s\n"
#define FORMAT2 "%10d %10d %10d\n"

 int bucket;
 int suppressed_buckets = 0;

 prnt(where, "Number of buckets: %d\n\n", self->n_buckets);

 prnt(where, FORMAT, "Bucket", "Objects", "Max");
 for (bucket = 0; bucket < self->n_buckets; ++bucket) {
 if (self->buckets[bucket].max_elements) {
 suppressed_buckets = 0;
 prnt(where, FORMAT2, bucket, self->buckets[bucket].elements,
 self->buckets[bucket].max_elements);
 } else if (!suppressed_buckets) {
 suppressed_buckets = 1;
 prnt(where, "...\n");
 }
 }

#undef FORMAT
#undef FORMAT2
}
#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 hash_ao2_integrity(struct ao2_container_hash *self)
{
 int bucket_exp;
 int bucket;
 int count_obj;
 int count_total_obj;
 int count_total_node;
 void *obj_last;
 struct hash_bucket_node *node;
 struct hash_bucket_node *prev;
 struct hash_bucket_node *next;

 count_total_obj = 0;
 count_total_node = 0;

 /* For each bucket in the container. */
 for (bucket = 0; bucket < self->n_buckets; ++bucket) {
 if (!AST_DLLIST_FIRST(&self->buckets[bucket].list)
 && !AST_DLLIST_LAST(&self->buckets[bucket].list)) {
 /* The bucket list is empty. */
 continue;
 }

 count_obj = 0;
 obj_last = NULL;

 /* Check bucket list links and nodes. */
 node = AST_DLLIST_LAST(&self->buckets[bucket].list);
 if (!node) {
 ast_log(LOG_ERROR, "Bucket %d list tail is NULL when it should not be!\n",
 bucket);
 return -1;
 }
 if (AST_DLLIST_NEXT(node, links)) {
 ast_log(LOG_ERROR, "Bucket %d list tail node is not the last node!\n",
 bucket);
 return -1;
 }
 node = AST_DLLIST_FIRST(&self->buckets[bucket].list);
 if (!node) {
 ast_log(LOG_ERROR, "Bucket %d list head is NULL when it should not be!\n",
 bucket);
 return -1;
 }
 if (AST_DLLIST_PREV(node, links)) {
 ast_log(LOG_ERROR, "Bucket %d list head node is not the first node!\n",
 bucket);
 return -1;
 }
 for (; node; node = next) {
 /* Check backward link. */
 prev = AST_DLLIST_PREV(node, links);
 if (prev) {
 if (prev == node) {
 ast_log(LOG_ERROR, "Bucket %d list node's prev pointer points to itself!\n",
 bucket);
 return -1;
 }
 if (node != AST_DLLIST_NEXT(prev, links)) {
 ast_log(LOG_ERROR, "Bucket %d list node's prev node does not link back!\n",
 bucket);
 return -1;
 }
 } else if (node != AST_DLLIST_FIRST(&self->buckets[bucket].list)) {
 ast_log(LOG_ERROR, "Bucket %d backward list chain is broken!\n",
 bucket);
 return -1;
 }

 /* Check forward link. */
 next = AST_DLLIST_NEXT(node, links);
 if (next) {
 if (next == node) {
 ast_log(LOG_ERROR, "Bucket %d list node's next pointer points to itself!\n",
 bucket);
 return -1;
 }
 if (node != AST_DLLIST_PREV(next, links)) {
 ast_log(LOG_ERROR, "Bucket %d list node's next node does not link back!\n",
 bucket);
 return -1;
 }
 } else if (node != AST_DLLIST_LAST(&self->buckets[bucket].list)) {
 ast_log(LOG_ERROR, "Bucket %d forward list chain is broken!\n",
 bucket);
 return -1;
 }

 if (bucket != node->my_bucket) {
 ast_log(LOG_ERROR, "Bucket %d node claims to be in bucket %d!\n",
 bucket, node->my_bucket);
 return -1;
 }

 ++count_total_node;
 if (!node->common.obj) {
 /* Node is empty. */
 continue;
 }
 ++count_obj;

 /* Check container hash key for expected bucket. */
 bucket_exp = abs(self->hash_fn(node->common.obj, OBJ_SEARCH_OBJECT)
 % self->n_buckets);
 if (bucket != bucket_exp) {
 ast_log(LOG_ERROR, "Bucket %d node hashes to bucket %d!\n",
 bucket, bucket_exp);
 return -1;
 }

 /* Check sort if configured. */
 if (self->common.sort_fn) {
 if (obj_last
 && self->common.sort_fn(obj_last, node->common.obj, OBJ_SEARCH_OBJECT) > 0) {
 ast_log(LOG_ERROR, "Bucket %d nodes out of sorted order!\n",
 bucket);
 return -1;
 }
 obj_last = node->common.obj;
 }
 }

 /* Check bucket obj count statistic. */
 if (count_obj != self->buckets[bucket].elements) {
 ast_log(LOG_ERROR, "Bucket %d object count of %d does not match stat of %d!\n",
 bucket, count_obj, self->buckets[bucket].elements);
 return -1;
 }

 /* Accumulate found object counts. */
 count_total_obj += count_obj;
 }

 /* Check total obj count. */
 if (count_total_obj != ao2_container_count(&self->common)) {
 ast_log(LOG_ERROR,
 "Total object count of %d does not match ao2_container_count() of %d!\n",
 count_total_obj, ao2_container_count(&self->common));
 return -1;
 }

 /* Check total node count. */
 if (count_total_node != self->common.nodes) {
 ast_log(LOG_ERROR, "Total node count of %d does not match stat of %d!\n",
 count_total_node, self->common.nodes);
 return -1;
 }

 return 0;
}
#endif /* defined(AO2_DEBUG) */

/*! Hash container virtual method table. */
static const struct ao2_container_methods v_table_hash = {
 .alloc_empty_clone = (ao2_container_alloc_empty_clone_fn) hash_ao2_alloc_empty_clone,
 .new_node = (ao2_container_new_node_fn) hash_ao2_new_node,
 .insert = (ao2_container_insert_fn) hash_ao2_insert_node,
 .traverse_first = (ao2_container_find_first_fn) hash_ao2_find_first,
 .traverse_next = (ao2_container_find_next_fn) hash_ao2_find_next,
 .iterator_next = (ao2_iterator_next_fn) hash_ao2_iterator_next,
 .destroy = (ao2_container_destroy_fn) hash_ao2_destroy,
#if defined(AO2_DEBUG)
 .link_stat = hash_ao2_link_node_stat,
 .unlink_stat = hash_ao2_unlink_node_stat,
 .dump = (ao2_container_display) hash_ao2_dump,
 .stats = (ao2_container_statistics) hash_ao2_stats,
 .integrity = (ao2_container_integrity) hash_ao2_integrity,
#endif /* defined(AO2_DEBUG) */
};

/*!
 * \brief always zero hash function
 *
 * it is convenient to have a hash function that always returns 0.
 * This is basically used when we want to have a container that is
 * a simple linked list.
 *
 * \returns 0
 */
static int hash_zero(const void *user_obj, const int flags)
{
 return 0;
}

/*!
 * \brief Initialize a hash container with the desired number of buckets.
 *
 * \param self Container to initialize.
 * \param options Container behaviour options (See enum ao2_container_opts)
 * \param n_buckets Number of buckets for hash
 * \param hash_fn Pointer to a function computing a hash value.
 * \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 *hash_ao2_container_init(
 struct ao2_container_hash *self, unsigned int options, unsigned int n_buckets,
 ao2_hash_fn *hash_fn, ao2_sort_fn *sort_fn, ao2_callback_fn *cmp_fn)
{
 if (!self) {
 return NULL;
 }

 self->common.v_table = &v_table_hash;
 self->common.sort_fn = sort_fn;
 self->common.cmp_fn = cmp_fn;
 self->common.options = options;
 self->hash_fn = hash_fn ? hash_fn : hash_zero;
 self->n_buckets = n_buckets;

#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_hash(unsigned int ao2_options,
 unsigned int container_options, unsigned int n_buckets, ao2_hash_fn *hash_fn,
 ao2_sort_fn *sort_fn, ao2_callback_fn *cmp_fn,
 const char *tag, const char *file, int line, const char *func)
{
 unsigned int num_buckets;
 size_t container_size;
 struct ao2_container_hash *self;

 num_buckets = hash_fn ? n_buckets : 1;
 container_size = sizeof(struct ao2_container_hash) + num_buckets * sizeof(struct hash_bucket);

 self = __ao2_alloc(container_size, container_destruct, ao2_options,
 tag ?: __PRETTY_FUNCTION__, file, line, func);
 return hash_ao2_container_init(self, container_options, num_buckets, hash_fn,
 sort_fn, cmp_fn);
}

struct ao2_container *__ao2_container_alloc_list(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)
{
 return __ao2_container_alloc_hash(ao2_options, container_options, 1, NULL,
 sort_fn, cmp_fn, tag, file, line, func);
}