astobj2.c

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/*
 * astobj2 - replacement containers for asterisk data structures.
 *
 * 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.
 */

/*
 * Function implementing astobj2 objects.
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 409567 $")

#include "asterisk/_private.h"
#include "asterisk/astobj2.h"
#include "asterisk/linkedlists.h"
#include "asterisk/utils.h"
#include "asterisk/cli.h"
#define REF_FILE "/tmp/refs"

#if defined(TEST_FRAMEWORK)
/* We are building with the test framework enabled so enable AO2 debug tests as well. */
#define AO2_DEBUG 1
#endif   /* defined(TEST_FRAMEWORK) */

/*!
 * astobj2 objects are always preceded by this data structure,
 * which contains a reference counter,
 * option flags and a pointer to a destructor.
 * The refcount is used to decide when it is time to
 * invoke the destructor.
 * The magic number is used for consistency check.
 */
struct __priv_data {
   int ref_counter;
   ao2_destructor_fn destructor_fn;
   /*! User data size for stats */
   size_t data_size;
   /*! The ao2 object option flags */
   uint32_t options;
   /*! magic number.  This is used to verify that a pointer passed in is a
    *  valid astobj2 */
   uint32_t magic;
};

#define  AO2_MAGIC   0xa570b123

/*!
 * What an astobj2 object looks like: fixed-size private data
 * followed by variable-size user data.
 */
struct astobj2 {
   struct __priv_data priv_data;
   void *user_data[0];
};

struct ao2_lock_priv {
   ast_mutex_t lock;
};

/* AstObj2 with recursive lock. */
struct astobj2_lock {
   struct ao2_lock_priv mutex;
   struct __priv_data priv_data;
   void *user_data[0];
};

struct ao2_rwlock_priv {
   ast_rwlock_t lock;
   /*! Count of the number of threads holding a lock on this object. -1 if it is the write lock. */
   int num_lockers;
};

/* AstObj2 with RW lock. */
struct astobj2_rwlock {
   struct ao2_rwlock_priv rwlock;
   struct __priv_data priv_data;
   void *user_data[0];
};

#ifdef AO2_DEBUG
struct ao2_stats {
   volatile int total_objects;
   volatile int total_mem;
   volatile int total_containers;
   volatile int total_refs;
   volatile int total_locked;
};

static struct ao2_stats ao2;
#endif

#ifndef HAVE_BKTR /* backtrace support */
void ao2_bt(void) {}
#else
#include <execinfo.h>    /* for backtrace */

void ao2_bt(void)
{
   int c, i;
#define N1  20
   void *addresses[N1];
   char **strings;

   c = backtrace(addresses, N1);
   strings = ast_bt_get_symbols(addresses,c);
   ast_verbose("backtrace returned: %d\n", c);
   for(i = 0; i < c; i++) {
      ast_verbose("%d: %p %s\n", i, addresses[i], strings[i]);
   }
   ast_std_free(strings);
}
#endif

#define INTERNAL_OBJ_MUTEX(user_data) \
   ((struct astobj2_lock *) (((char *) (user_data)) - sizeof(struct astobj2_lock)))

#define INTERNAL_OBJ_RWLOCK(user_data) \
   ((struct astobj2_rwlock *) (((char *) (user_data)) - sizeof(struct astobj2_rwlock)))

/*!
 * \brief convert from a pointer _p to a user-defined object
 *
 * \return the pointer to the astobj2 structure
 */
static inline struct astobj2 *INTERNAL_OBJ(void *user_data)
{
   struct astobj2 *p;

   if (!user_data) {
      ast_log(LOG_ERROR, "user_data is NULL\n");
      return NULL;
   }

   p = (struct astobj2 *) ((char *) user_data - sizeof(*p));
   if (AO2_MAGIC != p->priv_data.magic) {
      if (p->priv_data.magic) {
         ast_log(LOG_ERROR, "bad magic number 0x%x for object %p\n",
            p->priv_data.magic, user_data);
      } else {
         ast_log(LOG_ERROR,
            "bad magic number for object %p. Object is likely destroyed.\n",
            user_data);
      }
      ast_assert(0);
      return NULL;
   }

   return p;
}

enum ao2_callback_type {
   DEFAULT,
   WITH_DATA,
};

/*!
 * \brief convert from a pointer _p to an astobj2 object
 *
 * \return the pointer to the user-defined portion.
 */
#define EXTERNAL_OBJ(_p)   ((_p) == NULL ? NULL : (_p)->user_data)

int __ao2_lock(void *user_data, enum ao2_lock_req lock_how, const char *file, const char *func, int line, const char *var)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);
   struct astobj2_lock *obj_mutex;
   struct astobj2_rwlock *obj_rwlock;
   int res = 0;

   if (obj == NULL) {
      return -1;
   }

   switch (obj->priv_data.options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_MUTEX:
      obj_mutex = INTERNAL_OBJ_MUTEX(user_data);
      res = __ast_pthread_mutex_lock(file, line, func, var, &obj_mutex->mutex.lock);
#ifdef AO2_DEBUG
      if (!res) {
         ast_atomic_fetchadd_int(&ao2.total_locked, 1);
      }
#endif
      break;
   case AO2_ALLOC_OPT_LOCK_RWLOCK:
      obj_rwlock = INTERNAL_OBJ_RWLOCK(user_data);
      switch (lock_how) {
      case AO2_LOCK_REQ_MUTEX:
      case AO2_LOCK_REQ_WRLOCK:
         res = __ast_rwlock_wrlock(file, line, func, &obj_rwlock->rwlock.lock, var);
         if (!res) {
            ast_atomic_fetchadd_int(&obj_rwlock->rwlock.num_lockers, -1);
#ifdef AO2_DEBUG
            ast_atomic_fetchadd_int(&ao2.total_locked, 1);
#endif
         }
         break;
      case AO2_LOCK_REQ_RDLOCK:
         res = __ast_rwlock_rdlock(file, line, func, &obj_rwlock->rwlock.lock, var);
         if (!res) {
            ast_atomic_fetchadd_int(&obj_rwlock->rwlock.num_lockers, +1);
#ifdef AO2_DEBUG
            ast_atomic_fetchadd_int(&ao2.total_locked, 1);
#endif
         }
         break;
      }
      break;
   case AO2_ALLOC_OPT_LOCK_NOLOCK:
      /* The ao2 object has no lock. */
      break;
   default:
      ast_log(__LOG_ERROR, file, line, func, "Invalid lock option on ao2 object %p\n",
         user_data);
      return -1;
   }

   return res;
}

int __ao2_unlock(void *user_data, const char *file, const char *func, int line, const char *var)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);
   struct astobj2_lock *obj_mutex;
   struct astobj2_rwlock *obj_rwlock;
   int res = 0;
   int current_value;

   if (obj == NULL) {
      return -1;
   }

   switch (obj->priv_data.options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_MUTEX:
      obj_mutex = INTERNAL_OBJ_MUTEX(user_data);
      res = __ast_pthread_mutex_unlock(file, line, func, var, &obj_mutex->mutex.lock);
#ifdef AO2_DEBUG
      if (!res) {
         ast_atomic_fetchadd_int(&ao2.total_locked, -1);
      }
#endif
      break;
   case AO2_ALLOC_OPT_LOCK_RWLOCK:
      obj_rwlock = INTERNAL_OBJ_RWLOCK(user_data);

      current_value = ast_atomic_fetchadd_int(&obj_rwlock->rwlock.num_lockers, -1) - 1;
      if (current_value < 0) {
         /* It was a WRLOCK that we are unlocking.  Fix the count. */
         ast_atomic_fetchadd_int(&obj_rwlock->rwlock.num_lockers, -current_value);
      }
      res = __ast_rwlock_unlock(file, line, func, &obj_rwlock->rwlock.lock, var);
#ifdef AO2_DEBUG
      if (!res) {
         ast_atomic_fetchadd_int(&ao2.total_locked, -1);
      }
#endif
      break;
   case AO2_ALLOC_OPT_LOCK_NOLOCK:
      /* The ao2 object has no lock. */
      break;
   default:
      ast_log(__LOG_ERROR, file, line, func, "Invalid lock option on ao2 object %p\n",
         user_data);
      res = -1;
      break;
   }
   return res;
}

int __ao2_trylock(void *user_data, enum ao2_lock_req lock_how, const char *file, const char *func, int line, const char *var)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);
   struct astobj2_lock *obj_mutex;
   struct astobj2_rwlock *obj_rwlock;
   int res = 0;

   if (obj == NULL) {
      return -1;
   }

   switch (obj->priv_data.options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_MUTEX:
      obj_mutex = INTERNAL_OBJ_MUTEX(user_data);
      res = __ast_pthread_mutex_trylock(file, line, func, var, &obj_mutex->mutex.lock);
#ifdef AO2_DEBUG
      if (!res) {
         ast_atomic_fetchadd_int(&ao2.total_locked, 1);
      }
#endif
      break;
   case AO2_ALLOC_OPT_LOCK_RWLOCK:
      obj_rwlock = INTERNAL_OBJ_RWLOCK(user_data);
      switch (lock_how) {
      case AO2_LOCK_REQ_MUTEX:
      case AO2_LOCK_REQ_WRLOCK:
         res = __ast_rwlock_trywrlock(file, line, func, &obj_rwlock->rwlock.lock, var);
         if (!res) {
            ast_atomic_fetchadd_int(&obj_rwlock->rwlock.num_lockers, -1);
#ifdef AO2_DEBUG
            ast_atomic_fetchadd_int(&ao2.total_locked, 1);
#endif
         }
         break;
      case AO2_LOCK_REQ_RDLOCK:
         res = __ast_rwlock_tryrdlock(file, line, func, &obj_rwlock->rwlock.lock, var);
         if (!res) {
            ast_atomic_fetchadd_int(&obj_rwlock->rwlock.num_lockers, +1);
#ifdef AO2_DEBUG
            ast_atomic_fetchadd_int(&ao2.total_locked, 1);
#endif
         }
         break;
      }
      break;
   case AO2_ALLOC_OPT_LOCK_NOLOCK:
      /* The ao2 object has no lock. */
      return 0;
   default:
      ast_log(__LOG_ERROR, file, line, func, "Invalid lock option on ao2 object %p\n",
         user_data);
      return -1;
   }


   return res;
}

/*!
 * \internal
 * \brief Adjust an object's lock to the requested level.
 *
 * \param user_data An ao2 object to adjust lock level.
 * \param lock_how What level to adjust lock.
 * \param keep_stronger TRUE if keep original lock level if it is stronger.
 *
 * \pre The ao2 object is already locked.
 *
 * \details
 * An ao2 object with a RWLOCK will have its lock level adjusted
 * to the specified level if it is not already there.  An ao2
 * object with a different type of lock is not affected.
 *
 * \return Original lock level.
 */
static enum ao2_lock_req adjust_lock(void *user_data, enum ao2_lock_req lock_how, int keep_stronger)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);
   struct astobj2_rwlock *obj_rwlock;
   enum ao2_lock_req orig_lock;

   switch (obj->priv_data.options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_RWLOCK:
      obj_rwlock = INTERNAL_OBJ_RWLOCK(user_data);
      if (obj_rwlock->rwlock.num_lockers < 0) {
         orig_lock = AO2_LOCK_REQ_WRLOCK;
      } else {
         orig_lock = AO2_LOCK_REQ_RDLOCK;
      }
      switch (lock_how) {
      case AO2_LOCK_REQ_MUTEX:
         lock_how = AO2_LOCK_REQ_WRLOCK;
         /* Fall through */
      case AO2_LOCK_REQ_WRLOCK:
         if (lock_how != orig_lock) {
            /* Switch from read lock to write lock. */
            ao2_unlock(user_data);
            ao2_wrlock(user_data);
         }
         break;
      case AO2_LOCK_REQ_RDLOCK:
         if (!keep_stronger && lock_how != orig_lock) {
            /* Switch from write lock to read lock. */
            ao2_unlock(user_data);
            ao2_rdlock(user_data);
         }
         break;
      }
      break;
   default:
      ast_log(LOG_ERROR, "Invalid lock option on ao2 object %p\n", user_data);
      /* Fall through */
   case AO2_ALLOC_OPT_LOCK_NOLOCK:
   case AO2_ALLOC_OPT_LOCK_MUTEX:
      orig_lock = AO2_LOCK_REQ_MUTEX;
      break;
   }

   return orig_lock;
}

void *ao2_object_get_lockaddr(void *user_data)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);
   struct astobj2_lock *obj_mutex;

   if (obj == NULL) {
      return NULL;
   }

   switch (obj->priv_data.options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_MUTEX:
      obj_mutex = INTERNAL_OBJ_MUTEX(user_data);
      return &obj_mutex->mutex.lock;
   default:
      break;
   }

   return NULL;
}

static int internal_ao2_ref(void *user_data, int delta, const char *file, int line, const char *func)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);
   struct astobj2_lock *obj_mutex;
   struct astobj2_rwlock *obj_rwlock;
   int current_value;
   int ret;

   if (obj == NULL) {
      return -1;
   }

   /* if delta is 0, just return the refcount */
   if (delta == 0) {
      return obj->priv_data.ref_counter;
   }

   /* we modify with an atomic operation the reference counter */
   ret = ast_atomic_fetchadd_int(&obj->priv_data.ref_counter, delta);
   current_value = ret + delta;

#ifdef AO2_DEBUG
   ast_atomic_fetchadd_int(&ao2.total_refs, delta);
#endif

   if (0 < current_value) {
      /* The object still lives. */
      return ret;
   }

   /* this case must never happen */
   if (current_value < 0) {
      ast_log(__LOG_ERROR, file, line, func,
         "Invalid refcount %d on ao2 object %p\n", current_value, user_data);
   }

   /* last reference, destroy the object */
   if (obj->priv_data.destructor_fn != NULL) {
      obj->priv_data.destructor_fn(user_data);
   }

#ifdef AO2_DEBUG
   ast_atomic_fetchadd_int(&ao2.total_mem, - obj->priv_data.data_size);
   ast_atomic_fetchadd_int(&ao2.total_objects, -1);
#endif

   switch (obj->priv_data.options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_MUTEX:
      obj_mutex = INTERNAL_OBJ_MUTEX(user_data);
      ast_mutex_destroy(&obj_mutex->mutex.lock);

      /*
       * For safety, zero-out the astobj2_lock header and also the
       * first word of the user-data, which we make sure is always
       * allocated.
       */
      memset(obj_mutex, '\0', sizeof(*obj_mutex) + sizeof(void *) );
      ast_free(obj_mutex);
      break;
   case AO2_ALLOC_OPT_LOCK_RWLOCK:
      obj_rwlock = INTERNAL_OBJ_RWLOCK(user_data);
      ast_rwlock_destroy(&obj_rwlock->rwlock.lock);

      /*
       * For safety, zero-out the astobj2_rwlock header and also the
       * first word of the user-data, which we make sure is always
       * allocated.
       */
      memset(obj_rwlock, '\0', sizeof(*obj_rwlock) + sizeof(void *) );
      ast_free(obj_rwlock);
      break;
   case AO2_ALLOC_OPT_LOCK_NOLOCK:
      /*
       * For safety, zero-out the astobj2 header and also the first
       * word of the user-data, which we make sure is always
       * allocated.
       */
      memset(obj, '\0', sizeof(*obj) + sizeof(void *) );
      ast_free(obj);
      break;
   default:
      ast_log(__LOG_ERROR, file, line, func,
         "Invalid lock option on ao2 object %p\n", user_data);
      break;
   }

   return ret;
}

int __ao2_ref_debug(void *user_data, int delta, const char *tag, const char *file, int line, const char *func)
{
   struct astobj2 *obj = INTERNAL_OBJ(user_data);

   if (obj == NULL)
      return -1;

   if (delta != 0) {
      FILE *refo = fopen(REF_FILE, "a");
      if (refo) {
         fprintf(refo, "%p %s%d   %s:%d:%s (%s) [@%d]\n", user_data, (delta < 0 ? "" : "+"),
            delta, file, line, func, tag, obj->priv_data.ref_counter);
         fclose(refo);
      }
   }
   if (obj->priv_data.ref_counter + delta == 0 && obj->priv_data.destructor_fn != NULL) { /* this isn't protected with lock; just for o/p */
      FILE *refo = fopen(REF_FILE, "a");
      if (refo) {
         fprintf(refo, "%p **call destructor** %s:%d:%s (%s)\n", user_data, file, line, func, tag);
         fclose(refo);
      }
   }
   return internal_ao2_ref(user_data, delta, file, line, func);
}

int __ao2_ref(void *user_data, int delta)
{
   return internal_ao2_ref(user_data, delta, __FILE__, __LINE__, __FUNCTION__);
}

static void *internal_ao2_alloc(size_t data_size, ao2_destructor_fn destructor_fn, unsigned int options, const char *file, int line, const char *func)
{
   /* allocation */
   struct astobj2 *obj;
   struct astobj2_lock *obj_mutex;
   struct astobj2_rwlock *obj_rwlock;

   if (data_size < sizeof(void *)) {
      /*
       * We always alloc at least the size of a void *,
       * for debugging purposes.
       */
      data_size = sizeof(void *);
   }

   switch (options & AO2_ALLOC_OPT_LOCK_MASK) {
   case AO2_ALLOC_OPT_LOCK_MUTEX:
#if defined(__AST_DEBUG_MALLOC)
      obj_mutex = __ast_calloc(1, sizeof(*obj_mutex) + data_size, file, line, func);
#else
      obj_mutex = ast_calloc(1, sizeof(*obj_mutex) + data_size);
#endif
      if (obj_mutex == NULL) {
         return NULL;
      }

      ast_mutex_init(&obj_mutex->mutex.lock);
      obj = (struct astobj2 *) &obj_mutex->priv_data;
      break;
   case AO2_ALLOC_OPT_LOCK_RWLOCK:
#if defined(__AST_DEBUG_MALLOC)
      obj_rwlock = __ast_calloc(1, sizeof(*obj_rwlock) + data_size, file, line, func);
#else
      obj_rwlock = ast_calloc(1, sizeof(*obj_rwlock) + data_size);
#endif
      if (obj_rwlock == NULL) {
         return NULL;
      }

      ast_rwlock_init(&obj_rwlock->rwlock.lock);
      obj = (struct astobj2 *) &obj_rwlock->priv_data;
      break;
   case AO2_ALLOC_OPT_LOCK_NOLOCK:
#if defined(__AST_DEBUG_MALLOC)
      obj = __ast_calloc(1, sizeof(*obj) + data_size, file, line, func);
#else
      obj = ast_calloc(1, sizeof(*obj) + data_size);
#endif
      if (obj == NULL) {
         return NULL;
      }
      break;
   default:
      /* Invalid option value. */
      ast_log(__LOG_DEBUG, file, line, func, "Invalid lock option requested\n");
      return NULL;
   }

   /* Initialize common ao2 values. */
   obj->priv_data.ref_counter = 1;
   obj->priv_data.destructor_fn = destructor_fn;   /* can be NULL */
   obj->priv_data.data_size = data_size;
   obj->priv_data.options = options;
   obj->priv_data.magic = AO2_MAGIC;

#ifdef AO2_DEBUG
   ast_atomic_fetchadd_int(&ao2.total_objects, 1);
   ast_atomic_fetchadd_int(&ao2.total_mem, data_size);
   ast_atomic_fetchadd_int(&ao2.total_refs, 1);
#endif

   /* return a pointer to the user data */
   return EXTERNAL_OBJ(obj);
}

void *__ao2_alloc_debug(size_t data_size, ao2_destructor_fn destructor_fn, unsigned int options, const char *tag,
   const char *file, int line, const char *func, int ref_debug)
{
   /* allocation */
   void *obj;
   FILE *refo;

   if ((obj = internal_ao2_alloc(data_size, destructor_fn, options, file, line, func)) == NULL) {
      return NULL;
   }

   if (ref_debug && (refo = fopen(REF_FILE, "a"))) {
      fprintf(refo, "%p =1   %s:%d:%s (%s)\n", obj, file, line, func, tag);
      fclose(refo);
   }

   /* return a pointer to the user data */
   return obj;
}

void *__ao2_alloc(size_t data_size, ao2_destructor_fn destructor_fn, unsigned int options)
{
   return internal_ao2_alloc(data_size, destructor_fn, options, __FILE__, __LINE__, __FUNCTION__);
}


void __ao2_global_obj_release(struct ao2_global_obj *holder, const char *tag, const char *file, int line, const char *func, const char *name)
{
   if (!holder) {
      /* For sanity */
      ast_log(LOG_ERROR, "Must be called with a global object!\n");
      return;
   }
   if (__ast_rwlock_wrlock(file, line, func, &holder->lock, name)) {
      /* Could not get the write lock. */
      return;
   }

   /* Release the held ao2 object. */
   if (holder->obj) {
      if (tag) {
         __ao2_ref_debug(holder->obj, -1, tag, file, line, func);
      } else {
         __ao2_ref(holder->obj, -1);
      }
      holder->obj = NULL;
   }

   __ast_rwlock_unlock(file, line, func, &holder->lock, name);
}

void *__ao2_global_obj_replace(struct ao2_global_obj *holder, void *obj, const char *tag, const char *file, int line, const char *func, const char *name)
{
   void *obj_old;

   if (!holder) {
      /* For sanity */
      ast_log(LOG_ERROR, "Must be called with a global object!\n");
      return NULL;
   }
   if (__ast_rwlock_wrlock(file, line, func, &holder->lock, name)) {
      /* Could not get the write lock. */
      return NULL;
   }

   if (obj) {
      if (tag) {
         __ao2_ref_debug(obj, +1, tag, file, line, func);
      } else {
         __ao2_ref(obj, +1);
      }
   }
   obj_old = holder->obj;
   holder->obj = obj;

   __ast_rwlock_unlock(file, line, func, &holder->lock, name);

   return obj_old;
}

int __ao2_global_obj_replace_unref(struct ao2_global_obj *holder, void *obj, const char *tag, const char *file, int line, const char *func, const char *name)
{
   void *obj_old;

   obj_old = __ao2_global_obj_replace(holder, obj, tag, file, line, func, name);
   if (obj_old) {
      if (tag) {
         __ao2_ref_debug(obj_old, -1, tag, file, line, func);
      } else {
         __ao2_ref(obj_old, -1);
      }
      return 1;
   }
   return 0;
}

void *__ao2_global_obj_ref(struct ao2_global_obj *holder, const char *tag, const char *file, int line, const char *func, const char *name)
{
   void *obj;

   if (!holder) {
      /* For sanity */
      ast_log(LOG_ERROR, "Must be called with a global object!\n");
      return NULL;
   }

   if (__ast_rwlock_rdlock(file, line, func, &holder->lock, name)) {
      /* Could not get the read lock. */
      return NULL;
   }

   obj = holder->obj;
   if (obj) {
      if (tag) {
         __ao2_ref_debug(obj, +1, tag, file, line, func);
      } else {
         __ao2_ref(obj, +1);
      }
   }

   __ast_rwlock_unlock(file, line, func, &holder->lock, name);

   return obj;
}

/* internal callback to destroy a container. */
static void container_destruct(void *c);

/* internal callback to destroy a container. */
static void container_destruct_debug(void *c);

/*!
 * A structure to create a linked list of entries,
 * used within a bucket.
 * XXX \todo this should be private to the container code
 */
struct bucket_entry {
   AST_LIST_ENTRY(bucket_entry) entry;
   int version;
   struct astobj2 *astobj;/* pointer to internal data */
};

/* each bucket in the container is a tailq. */
AST_LIST_HEAD_NOLOCK(bucket, bucket_entry);

/*!
 * A container; stores the hash and callback functions, information on
 * the size, the hash bucket heads, and a version number, starting at 0
 * (for a newly created, empty container)
 * and incremented every time an object is inserted or deleted.
 * The assumption is that an object is never moved in a container,
 * but removed and readded with the new number.
 * The version number is especially useful when implementing iterators.
 * In fact, we can associate a unique, monotonically increasing number to
 * each object, which means that, within an iterator, we can store the
 * version number of the current object, and easily look for the next one,
 * which is the next one in the list with a higher number.
 * Since all objects have a version >0, we can use 0 as a marker for
 * 'we need the first object in the bucket'.
 *
 * \todo Linking and unlink objects is typically expensive, as it
 * involves a malloc() of a small object which is very inefficient.
 * To optimize this, we allocate larger arrays of bucket_entry's
 * when we run out of them, and then manage our own freelist.
 * This will be more efficient as we can do the freelist management while
 * we hold the lock (that we need anyways).
 */
struct ao2_container {
   ao2_hash_fn *hash_fn;
   ao2_callback_fn *cmp_fn;
   int n_buckets;
   /*! Number of elements in the container */
   int elements;
   /*! described above */
   int version;
   /*! variable size */
   struct bucket buckets[0];
};

/*!
 * \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;
}

/*
 * A container is just an object, after all!
 */
static struct ao2_container *internal_ao2_container_alloc(struct ao2_container *c,
   unsigned int n_buckets, ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn)
{
   /* XXX maybe consistency check on arguments ? */
   /* compute the container size */

   if (!c) {
      return NULL;
   }

   c->version = 1;   /* 0 is a reserved value here */
   c->n_buckets = hash_fn ? n_buckets : 1;
   c->hash_fn = hash_fn ? hash_fn : hash_zero;
   c->cmp_fn = cmp_fn;

#ifdef AO2_DEBUG
   ast_atomic_fetchadd_int(&ao2.total_containers, 1);
#endif

   return c;
}

struct ao2_container *__ao2_container_alloc_debug(unsigned int options,
   unsigned int n_buckets, ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn,
   const char *tag, const char *file, int line, const char *func, int ref_debug)
{
   /* XXX maybe consistency check on arguments ? */
   /* compute the container size */
   unsigned int num_buckets = hash_fn ? n_buckets : 1;
   size_t container_size = sizeof(struct ao2_container) + num_buckets * sizeof(struct bucket);
   struct ao2_container *c = __ao2_alloc_debug(container_size, ref_debug ? container_destruct_debug : container_destruct, options, tag, file, line, func, ref_debug);

   return internal_ao2_container_alloc(c, num_buckets, hash_fn, cmp_fn);
}

struct ao2_container *__ao2_container_alloc(unsigned int options,
   unsigned int n_buckets, ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn)
{
   /* XXX maybe consistency check on arguments ? */
   /* compute the container size */
   const unsigned int num_buckets = hash_fn ? n_buckets : 1;
   size_t container_size = sizeof(struct ao2_container) + num_buckets * sizeof(struct bucket);
   struct ao2_container *c = __ao2_alloc(container_size, container_destruct, options);

   return internal_ao2_container_alloc(c, num_buckets, hash_fn, cmp_fn);
}

/*!
 * return the number of elements in the container
 */
int ao2_container_count(struct ao2_container *c)
{
   return c->elements;
}

/*
 * link an object to a container
 */
static struct bucket_entry *internal_ao2_link(struct ao2_container *c, void *user_data, int flags, const char *tag, const char *file, int line, const char *func)
{
   int i;
   enum ao2_lock_req orig_lock;
   /* create a new list entry */
   struct bucket_entry *p;
   struct astobj2 *obj = INTERNAL_OBJ(user_data);

   if (obj == NULL) {
      return NULL;
   }

   if (INTERNAL_OBJ(c) == NULL) {
      return NULL;
   }

   p = ast_calloc(1, sizeof(*p));
   if (!p) {
      return NULL;
   }

   i = abs(c->hash_fn(user_data, OBJ_POINTER));

   if (flags & OBJ_NOLOCK) {
      orig_lock = adjust_lock(c, AO2_LOCK_REQ_WRLOCK, 1);
   } else {
      ao2_wrlock(c);
      orig_lock = AO2_LOCK_REQ_MUTEX;
   }

   i %= c->n_buckets;
   p->astobj = obj;
   p->version = ast_atomic_fetchadd_int(&c->version, 1);
   AST_LIST_INSERT_TAIL(&c->buckets[i], p, entry);
   ast_atomic_fetchadd_int(&c->elements, 1);

   if (tag) {
      __ao2_ref_debug(user_data, +1, tag, file, line, func);
   } else {
      __ao2_ref(user_data, +1);
   }

   if (flags & OBJ_NOLOCK) {
      adjust_lock(c, orig_lock, 0);
   } else {
      ao2_unlock(c);
   }

   return p;
}

void *__ao2_link_debug(struct ao2_container *c, void *obj_new, int flags, const char *tag, const char *file, int line, const char *func)
{
   return internal_ao2_link(c, obj_new, flags, tag, file, line, func);
}

void *__ao2_link(struct ao2_container *c, void *obj_new, int flags)
{
   return internal_ao2_link(c, obj_new, flags, NULL, __FILE__, __LINE__, __PRETTY_FUNCTION__);
}

/*!
 * \brief another convenience function is a callback that matches on address
 */
int ao2_match_by_addr(void *user_data, void *arg, int flags)
{
   return (user_data == arg) ? (CMP_MATCH | CMP_STOP) : 0;
}

/*
 * Unlink an object from the container
 * and destroy the associated * bucket_entry structure.
 */
void *__ao2_unlink_debug(struct ao2_container *c, void *user_data, int flags,
   const char *tag, const char *file, int line, const char *func)
{
   if (INTERNAL_OBJ(user_data) == NULL) { /* safety check on the argument */
      return NULL;
   }

   flags |= (OBJ_UNLINK | OBJ_POINTER | OBJ_NODATA);
   __ao2_callback_debug(c, flags, ao2_match_by_addr, user_data, tag, file, line, func);

   return NULL;
}

void *__ao2_unlink(struct ao2_container *c, void *user_data, int flags)
{
   if (INTERNAL_OBJ(user_data) == NULL) { /* safety check on the argument */
      return NULL;
   }

   flags |= (OBJ_UNLINK | OBJ_POINTER | OBJ_NODATA);
   __ao2_callback(c, flags, ao2_match_by_addr, user_data);

   return NULL;
}

/*!
 * \brief special callback that matches all
 */
static int cb_true(void *user_data, void *arg, int flags)
{
   return CMP_MATCH;
}

/*!
 * \brief similar to cb_true, but is an ao2_callback_data_fn instead
 */
static int cb_true_data(void *user_data, void *arg, void *data, int flags)
{
   return CMP_MATCH;
}

/*!
 * Browse the container using different stategies accoding the flags.
 * \return Is a pointer to an object or to a list of object if OBJ_MULTIPLE is
 * specified.
 * Luckily, for debug purposes, the added args (tag, file, line, func)
 * aren't an excessive load to the system, as the callback should not be
 * called as often as, say, the ao2_ref func is called.
 */
static void *internal_ao2_callback(struct ao2_container *c, enum search_flags flags,
   void *cb_fn, void *arg, void *data, enum ao2_callback_type type, const char *tag,
   const char *file, int line, const char *func)
{
   int i, start, last;  /* search boundaries */
   enum ao2_lock_req orig_lock;
   void *ret = NULL;
   ao2_callback_fn *cb_default = NULL;
   ao2_callback_data_fn *cb_withdata = NULL;
   struct ao2_container *multi_container = NULL;
   struct ao2_iterator *multi_iterator = NULL;

   if (INTERNAL_OBJ(c) == NULL) {   /* safety check on the argument */
      return NULL;
   }

   /*
    * This logic is used so we can support OBJ_MULTIPLE with OBJ_NODATA
    * turned off.  This if statement checks for the special condition
    * where multiple items may need to be returned.
    */
   if ((flags & (OBJ_MULTIPLE | OBJ_NODATA)) == OBJ_MULTIPLE) {
      /* we need to return an ao2_iterator with the results,
       * as there could be more than one. the iterator will
       * hold the only reference to a container that has all the
       * matching objects linked into it, so when the iterator
       * is destroyed, the container will be automatically
       * destroyed as well.
       */
      multi_container = __ao2_container_alloc(AO2_ALLOC_OPT_LOCK_NOLOCK, 1, NULL, NULL);
      if (!multi_container) {
         return NULL;
      }
      if (!(multi_iterator = ast_calloc(1, sizeof(*multi_iterator)))) {
         ao2_ref(multi_container, -1);
         return NULL;
      }
   }

   /* override the match function if necessary */
   if (cb_fn == NULL) { /* if NULL, match everything */
      if (type == WITH_DATA) {
         cb_withdata = cb_true_data;
      } else {
         cb_default = cb_true;
      }
   } else {
      /* We do this here to avoid the per object casting penalty (even though
         that is probably optimized away anyway). */
      if (type == WITH_DATA) {
         cb_withdata = cb_fn;
      } else {
         cb_default = cb_fn;
      }
   }

   /*
    * XXX this can be optimized.
    * If we have a hash function and lookup by pointer,
    * run the hash function. Otherwise, scan the whole container
    * (this only for the time being. We need to optimize this.)
    */
   if ((flags & (OBJ_POINTER | OBJ_KEY))) {
      /* we know hash can handle this case */
      start = i = c->hash_fn(arg, flags & (OBJ_POINTER | OBJ_KEY)) % c->n_buckets;
   } else {
      /* don't know, let's scan all buckets */
      start = i = -1;      /* XXX this must be fixed later. */
   }

   /* determine the search boundaries: i..last-1 */
   if (i < 0) {
      start = i = 0;
      last = c->n_buckets;
   } else if ((flags & OBJ_CONTINUE)) {
      last = c->n_buckets;
   } else {
      last = i + 1;
   }

   /* avoid modifications to the content */
   if (flags & OBJ_NOLOCK) {
      if (flags & OBJ_UNLINK) {
         orig_lock = adjust_lock(c, AO2_LOCK_REQ_WRLOCK, 1);
      } else {
         orig_lock = adjust_lock(c, AO2_LOCK_REQ_RDLOCK, 1);
      }
   } else {
      orig_lock = AO2_LOCK_REQ_MUTEX;
      if (flags & OBJ_UNLINK) {
         ao2_wrlock(c);
      } else {
         ao2_rdlock(c);
      }
   }

   for (; i < last ; i++) {
      /* scan the list with prev-cur pointers */
      struct bucket_entry *cur;

      AST_LIST_TRAVERSE_SAFE_BEGIN(&c->buckets[i], cur, entry) {
         int match = (CMP_MATCH | CMP_STOP);

         if (type == WITH_DATA) {
            match &= cb_withdata(EXTERNAL_OBJ(cur->astobj), arg, data, flags);
         } else {
            match &= cb_default(EXTERNAL_OBJ(cur->astobj), arg, flags);
         }

         /* we found the object, performing operations according flags */
         if (match == 0) { /* no match, no stop, continue */
            continue;
         } else if (match == CMP_STOP) {  /* no match but stop, we are done */
            i = last;
            break;
         }

         /* we have a match (CMP_MATCH) here */
         if (!(flags & OBJ_NODATA)) {  /* if must return the object, record the value */
            /* it is important to handle this case before the unlink */
            ret = EXTERNAL_OBJ(cur->astobj);
            if (!(flags & (OBJ_UNLINK | OBJ_MULTIPLE))) {
               if (tag) {
                  __ao2_ref_debug(ret, 1, tag, file, line, func);
               } else {
                  __ao2_ref(ret, 1);
               }
            }
         }

         /* If we are in OBJ_MULTIPLE mode and OBJ_NODATA is off,
          * link the object into the container that will hold the results.
          */
         if (ret && (multi_container != NULL)) {
            if (tag) {
               __ao2_link_debug(multi_container, ret, flags, tag, file, line, func);
            } else {
               __ao2_link(multi_container, ret, flags);
            }
            ret = NULL;
         }

         if (flags & OBJ_UNLINK) {  /* must unlink */
            /* we are going to modify the container, so update version */
            ast_atomic_fetchadd_int(&c->version, 1);
            AST_LIST_REMOVE_CURRENT(entry);
            /* update number of elements */
            ast_atomic_fetchadd_int(&c->elements, -1);

            /* - When unlinking and not returning the result, (OBJ_NODATA), the ref from the container
             * must be decremented.
             * - When unlinking with OBJ_MULTIPLE the ref from the original container
             * must be decremented regardless if OBJ_NODATA is used. This is because the result is
             * returned in a new container that already holds its own ref for the object. If the ref
             * from the original container is not accounted for here a memory leak occurs. */
            if (flags & (OBJ_NODATA | OBJ_MULTIPLE)) {
               if (tag)
                  __ao2_ref_debug(EXTERNAL_OBJ(cur->astobj), -1, tag, file, line, func);
               else
                  __ao2_ref(EXTERNAL_OBJ(cur->astobj), -1);
            }
            ast_free(cur); /* free the link record */
         }

         if ((match & CMP_STOP) || !(flags & OBJ_MULTIPLE)) {
            /* We found our only (or last) match, so force an exit from
               the outside loop. */
            i = last;
            break;
         }
      }
      AST_LIST_TRAVERSE_SAFE_END;

      if (ret) {
         break;
      }

      if (i == c->n_buckets - 1 && (flags & OBJ_POINTER) && (flags & OBJ_CONTINUE)) {
         /* Move to the beginning to ensure we check every bucket */
         i = -1;
         last = start;
      }
   }

   if (flags & OBJ_NOLOCK) {
      adjust_lock(c, orig_lock, 0);
   } else {
      ao2_unlock(c);
   }

   /* if multi_container was created, we are returning multiple objects */
   if (multi_container != NULL) {
      *multi_iterator = ao2_iterator_init(multi_container,
         AO2_ITERATOR_UNLINK | AO2_ITERATOR_MALLOCD);
      ao2_ref(multi_container, -1);
      return multi_iterator;
   } else {
      return ret;
   }
}

void *__ao2_callback_debug(struct ao2_container *c, enum search_flags flags,
   ao2_callback_fn *cb_fn, void *arg, const char *tag, const char *file, int line,
   const char *func)
{
   return internal_ao2_callback(c,flags, cb_fn, arg, NULL, DEFAULT, tag, file, line, func);
}

void *__ao2_callback(struct ao2_container *c, enum search_flags flags,
   ao2_callback_fn *cb_fn, void *arg)
{
   return internal_ao2_callback(c,flags, cb_fn, arg, NULL, DEFAULT, NULL, NULL, 0, NULL);
}

void *__ao2_callback_data_debug(struct ao2_container *c, enum search_flags flags,
   ao2_callback_data_fn *cb_fn, void *arg, void *data, const char *tag, const char *file,
   int line, const char *func)
{
   return internal_ao2_callback(c, flags, cb_fn, arg, data, WITH_DATA, tag, file, line, func);
}

void *__ao2_callback_data(struct ao2_container *c, enum search_flags flags,
   ao2_callback_data_fn *cb_fn, void *arg, void *data)
{
   return internal_ao2_callback(c, flags, cb_fn, arg, data, WITH_DATA, NULL, NULL, 0, NULL);
}

/*!
 * the find function just invokes the default callback with some reasonable flags.
 */
void *__ao2_find_debug(struct ao2_container *c, const void *arg, enum search_flags flags,
   const char *tag, const char *file, int line, const char *func)
{
   void *arged = (void *) arg;/* Done to avoid compiler const warning */

   return __ao2_callback_debug(c, flags, c->cmp_fn, arged, tag, file, line, func);
}

void *__ao2_find(struct ao2_container *c, const void *arg, enum search_flags flags)
{
   void *arged = (void *) arg;/* Done to avoid compiler const warning */

   return __ao2_callback(c, flags, c->cmp_fn, arged);
}

/*!
 * initialize an iterator so we start from the first object
 */
struct ao2_iterator ao2_iterator_init(struct ao2_container *c, int flags)
{
   struct ao2_iterator a = {
      .c = c,
      .flags = flags
   };

   ao2_ref(c, +1);

   return a;
}

/*!
 * destroy an iterator
 */
void ao2_iterator_destroy(struct ao2_iterator *iter)
{
   ao2_ref(iter->c, -1);
   if (iter->flags & AO2_ITERATOR_MALLOCD) {
      ast_free(iter);
   } else {
      iter->c = NULL;
   }
}

/*
 * move to the next element in the container.
 */
static void *internal_ao2_iterator_next(struct ao2_iterator *iter, const char *tag, const char *file, int line, const char *func)
{
   int lim;
   enum ao2_lock_req orig_lock;
   struct bucket_entry *p = NULL;
   void *ret;

   if (INTERNAL_OBJ(iter->c) == NULL) {
      return NULL;
   }

   if (iter->flags & AO2_ITERATOR_DONTLOCK) {
      if (iter->flags & AO2_ITERATOR_UNLINK) {
         orig_lock = adjust_lock(iter->c, AO2_LOCK_REQ_WRLOCK, 1);
      } else {
         orig_lock = adjust_lock(iter->c, AO2_LOCK_REQ_RDLOCK, 1);
      }
   } else {
      orig_lock = AO2_LOCK_REQ_MUTEX;
      if (iter->flags & AO2_ITERATOR_UNLINK) {
         ao2_wrlock(iter->c);
      } else {
         ao2_rdlock(iter->c);
      }
   }

   /* optimization. If the container is unchanged and
    * we have a pointer, try follow it
    */
   if (iter->c->version == iter->c_version && (p = iter->obj)) {
      if ((p = AST_LIST_NEXT(p, entry))) {
         goto found;
      }
      /* nope, start from the next bucket */
      iter->bucket++;
      iter->version = 0;
      iter->obj = NULL;
   }

   lim = iter->c->n_buckets;

   /* Browse the buckets array, moving to the next
    * buckets if we don't find the entry in the current one.
    * Stop when we find an element with version number greater
    * than the current one (we reset the version to 0 when we
    * switch buckets).
    */
   for (; iter->bucket < lim; iter->bucket++, iter->version = 0) {
      /* scan the current bucket */
      AST_LIST_TRAVERSE(&iter->c->buckets[iter->bucket], p, entry) {
         if (p->version > iter->version) {
            goto found;
         }
      }
   }

found:
   if (p) {
      ret = EXTERNAL_OBJ(p->astobj);
      if (iter->flags & AO2_ITERATOR_UNLINK) {
         /* we are going to modify the container, so update version */
         ast_atomic_fetchadd_int(&iter->c->version, 1);
         AST_LIST_REMOVE(&iter->c->buckets[iter->bucket], p, entry);
         /* update number of elements */
         ast_atomic_fetchadd_int(&iter->c->elements, -1);
         iter->version = 0;
         iter->obj = NULL;
         iter->c_version = iter->c->version;
         ast_free(p);
      } else {
         iter->version = p->version;
         iter->obj = p;
         iter->c_version = iter->c->version;

         /* inc refcount of returned object */
         if (tag) {
            __ao2_ref_debug(ret, 1, tag, file, line, func);
         } else {
            __ao2_ref(ret, 1);
         }
      }
   } else {
      ret = NULL;
   }

   if (iter->flags & AO2_ITERATOR_DONTLOCK) {
      adjust_lock(iter->c, orig_lock, 0);
   } else {
      ao2_unlock(iter->c);
   }

   return ret;
}

void *__ao2_iterator_next_debug(struct ao2_iterator *iter, const char *tag, const char *file, int line, const char *func)
{
   return internal_ao2_iterator_next(iter, tag, file, line, func);
}

void *__ao2_iterator_next(struct ao2_iterator *iter)
{
   return internal_ao2_iterator_next(iter, NULL, __FILE__, __LINE__, __PRETTY_FUNCTION__);
}

/* callback for destroying container.
 * we can make it simple as we know what it does
 */
static int cd_cb(void *obj, void *arg, int flag)
{
   __ao2_ref(obj, -1);
   return 0;
}

static int cd_cb_debug(void *obj, void *arg, int flag)
{
   __ao2_ref_debug(obj, -1, "deref object via container destroy",  __FILE__, __LINE__, __PRETTY_FUNCTION__);
   return 0;
}

static void container_destruct(void *_c)
{
   struct ao2_container *c = _c;
   int i;

   __ao2_callback(c, OBJ_UNLINK, cd_cb, NULL);

   for (i = 0; i < c->n_buckets; i++) {
      struct bucket_entry *current;

      while ((current = AST_LIST_REMOVE_HEAD(&c->buckets[i], entry))) {
         ast_free(current);
      }
   }

#ifdef AO2_DEBUG
   ast_atomic_fetchadd_int(&ao2.total_containers, -1);
#endif
}

static void container_destruct_debug(void *_c)
{
   struct ao2_container *c = _c;
   int i;

   __ao2_callback_debug(c, OBJ_UNLINK, cd_cb_debug, NULL, "container_destruct_debug called", __FILE__, __LINE__, __PRETTY_FUNCTION__);

   for (i = 0; i < c->n_buckets; i++) {
      struct bucket_entry *current;

      while ((current = AST_LIST_REMOVE_HEAD(&c->buckets[i], entry))) {
         ast_free(current);
      }
   }

#ifdef AO2_DEBUG
   ast_atomic_fetchadd_int(&ao2.total_containers, -1);
#endif
}

/*!
 * \internal
 * \brief Put obj into the arg container.
 * \since 11.0
 *
 * \param obj  pointer to the (user-defined part) of an object.
 * \param arg callback argument from ao2_callback()
 * \param flags flags from ao2_callback()
 *
 * \retval 0 on success.
 * \retval CMP_STOP|CMP_MATCH on error.
 */
static int dup_obj_cb(void *obj, void *arg, int flags)
{
   struct ao2_container *dest = arg;

   return __ao2_link(dest, obj, OBJ_NOLOCK) ? 0 : (CMP_MATCH | CMP_STOP);
}

int ao2_container_dup(struct ao2_container *dest, struct ao2_container *src, enum search_flags flags)
{
   void *obj;
   int res = 0;

   if (!(flags & OBJ_NOLOCK)) {
      ao2_rdlock(src);
      ao2_wrlock(dest);
   }
   obj = __ao2_callback(src, OBJ_NOLOCK, dup_obj_cb, dest);
   if (obj) {
      /* Failed to put this obj into the dest container. */
      __ao2_ref(obj, -1);

      /* Remove all items from the dest container. */
      __ao2_callback(dest, OBJ_NOLOCK | OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, NULL,
         NULL);
      res = -1;
   }
   if (!(flags & OBJ_NOLOCK)) {
      ao2_unlock(dest);
      ao2_unlock(src);
   }

   return res;
}

struct ao2_container *__ao2_container_clone(struct ao2_container *orig, enum search_flags flags)
{
   struct ao2_container *clone;
   struct astobj2 *orig_obj;
   unsigned int options;
   int failed;

   orig_obj = INTERNAL_OBJ(orig);
   if (!orig_obj) {
      return NULL;
   }
   options = orig_obj->priv_data.options;

   /* Create the clone container with the same properties as the original. */
   clone = __ao2_container_alloc(options, orig->n_buckets, orig->hash_fn, orig->cmp_fn);
   if (!clone) {
      return NULL;
   }

   if (flags & OBJ_NOLOCK) {
      ao2_wrlock(clone);
   }
   failed = ao2_container_dup(clone, orig, flags);
   if (flags & OBJ_NOLOCK) {
      ao2_unlock(clone);
   }
   if (failed) {
      /* Object copy into the clone container failed. */
      __ao2_ref(clone, -1);
      clone = NULL;
   }
   return clone;
}

struct ao2_container *__ao2_container_clone_debug(struct ao2_container *orig, enum search_flags flags, const char *tag, const char *file, int line, const char *func, int ref_debug)
{
   struct ao2_container *clone;
   struct astobj2 *orig_obj;
   unsigned int options;
   int failed;

   orig_obj = INTERNAL_OBJ(orig);
   if (!orig_obj) {
      return NULL;
   }
   options = orig_obj->priv_data.options;

   /* Create the clone container with the same properties as the original. */
   clone = __ao2_container_alloc_debug(options, orig->n_buckets, orig->hash_fn,
      orig->cmp_fn, tag, file, line, func, ref_debug);
   if (!clone) {
      return NULL;
   }

   if (flags & OBJ_NOLOCK) {
      ao2_wrlock(clone);
   }
   failed = ao2_container_dup(clone, orig, flags);
   if (flags & OBJ_NOLOCK) {
      ao2_unlock(clone);
   }
   if (failed) {
      /* Object copy into the clone container failed. */
      if (ref_debug) {
         __ao2_ref_debug(clone, -1, tag, file, line, func);
      } else {
         __ao2_ref(clone, -1);
      }
      clone = NULL;
   }
   return clone;
}

void __ao2_cleanup_debug(void *obj, const char *file, int line, const char *function)
{
   if (obj) {
      __ao2_ref_debug(obj, -1, "ao2_cleanup", file, line, function);
   }
}

void __ao2_cleanup(void *obj)
{
   if (obj) {
      ao2_ref(obj, -1);
   }
}

void ao2_iterator_cleanup(struct ao2_iterator *iter)
{
   if (iter) {
      ao2_iterator_destroy(iter);
   }
}

#ifdef AO2_DEBUG
static int print_cb(void *obj, void *arg, int flag)
{
   struct ast_cli_args *a = (struct ast_cli_args *) arg;
   char *s = (char *)obj;

   ast_cli(a->fd, "string <%s>\n", s);
   return 0;
}

/*
 * Print stats
 */
static char *handle_astobj2_stats(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   switch (cmd) {
   case CLI_INIT:
      e->command = "astobj2 show stats";
      e->usage = "Usage: astobj2 show stats\n"
            "       Show astobj2 show stats\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }
   ast_cli(a->fd, "Objects    : %d\n", ao2.total_objects);
   ast_cli(a->fd, "Containers : %d\n", ao2.total_containers);
   ast_cli(a->fd, "Memory     : %d\n", ao2.total_mem);
   ast_cli(a->fd, "Locked     : %d\n", ao2.total_locked);
   ast_cli(a->fd, "Refs       : %d\n", ao2.total_refs);
   return CLI_SUCCESS;
}

/*
 * This is testing code for astobj
 */
static char *handle_astobj2_test(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct ao2_container *c1;
   struct ao2_container *c2;
   int i, lim;
   char *obj;
   static int prof_id = -1;
   struct ast_cli_args fake_args = { a->fd, 0, NULL };

   switch (cmd) {
   case CLI_INIT:
      e->command = "astobj2 test";
      e->usage = "Usage: astobj2 test <num>\n"
            "       Runs astobj2 test. Creates 'num' objects,\n"
            "       and test iterators, callbacks and may be other stuff\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc != 3) {
      return CLI_SHOWUSAGE;
   }

   if (prof_id == -1)
      prof_id = ast_add_profile("ao2_alloc", 0);

   ast_cli(a->fd, "argc %d argv %s %s %s\n", a->argc, a->argv[0], a->argv[1], a->argv[2]);
   lim = atoi(a->argv[2]);
   ast_cli(a->fd, "called astobj_test\n");

   handle_astobj2_stats(e, CLI_HANDLER, &fake_args);
   /*
    * allocate a container with no default callback, and no hash function.
    * No hash means everything goes in the same bucket.
    */
   c1 = ao2_t_container_alloc(100, NULL /* no callback */, NULL /* no hash */,"test");
   ast_cli(a->fd, "container allocated as %p\n", c1);

   /*
    * fill the container with objects.
    * ao2_alloc() gives us a reference which we pass to the
    * container when we do the insert.
    */
   for (i = 0; i < lim; i++) {
      ast_mark(prof_id, 1 /* start */);
      obj = ao2_t_alloc(80, NULL,"test");
      ast_mark(prof_id, 0 /* stop */);
      ast_cli(a->fd, "object %d allocated as %p\n", i, obj);
      sprintf(obj, "-- this is obj %d --", i);
      ao2_link(c1, obj);
      /* At this point, the refcount on obj is 2 due to the allocation
       * and linking. We can go ahead and reduce the refcount by 1
       * right here so that when the container is unreffed later, the
       * objects will be freed
       */
      ao2_t_ref(obj, -1, "test");
   }

   ast_cli(a->fd, "testing callbacks\n");
   ao2_t_callback(c1, 0, print_cb, a, "test callback");

   ast_cli(a->fd, "testing container cloning\n");
   c2 = ao2_container_clone(c1, 0);
   if (ao2_container_count(c1) != ao2_container_count(c2)) {
      ast_cli(a->fd, "Cloned container does not have the same number of objects!\n");
   }
   ao2_t_callback(c2, 0, print_cb, a, "test callback");

   ast_cli(a->fd, "testing iterators, remove every second object\n");
   {
      struct ao2_iterator ai;
      int x = 0;

      ai = ao2_iterator_init(c1, 0);
      while ( (obj = ao2_t_iterator_next(&ai,"test")) ) {
         ast_cli(a->fd, "iterator on <%s>\n", obj);
         if (x++ & 1)
            ao2_t_unlink(c1, obj,"test");
         ao2_t_ref(obj, -1,"test");
      }
      ao2_iterator_destroy(&ai);
      ast_cli(a->fd, "testing iterators again\n");
      ai = ao2_iterator_init(c1, 0);
      while ( (obj = ao2_t_iterator_next(&ai,"test")) ) {
         ast_cli(a->fd, "iterator on <%s>\n", obj);
         ao2_t_ref(obj, -1,"test");
      }
      ao2_iterator_destroy(&ai);
   }

   ast_cli(a->fd, "testing callbacks again\n");
   ao2_t_callback(c1, 0, print_cb, a, "test callback");

   ast_verbose("now you should see an error message:\n");
   ao2_t_ref(&i, -1, "");  /* i is not a valid object so we print an error here */

   ast_cli(a->fd, "destroy container\n");
   ao2_t_ref(c1, -1, "");  /* destroy container */
   ao2_t_ref(c2, -1, "");  /* destroy container */
   handle_astobj2_stats(e, CLI_HANDLER, &fake_args);
   return CLI_SUCCESS;
}

static struct ast_cli_entry cli_astobj2[] = {
   AST_CLI_DEFINE(handle_astobj2_stats, "Print astobj2 statistics"),
   AST_CLI_DEFINE(handle_astobj2_test, "Test astobj2"),
};

static void astobj2_cleanup(void)
{
   ast_cli_unregister_multiple(cli_astobj2, ARRAY_LEN(cli_astobj2));
}
#endif /* AO2_DEBUG */

int astobj2_init(void)
{
#ifdef AO2_DEBUG
   ast_cli_register_multiple(cli_astobj2, ARRAY_LEN(cli_astobj2));
   ast_register_atexit(astobj2_cleanup);
#endif

   return 0;
}