linkedlists.h

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <[email protected]>
 * Kevin P. Fleming <[email protected]>
 *
 * 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.
 */

#ifndef ASTERISK_LINKEDLISTS_H
#define ASTERISK_LINKEDLISTS_H

#include "asterisk/lock.h"

/*!
 * \file linkedlists.h
 * \brief A set of macros to manage forward-linked lists.
 */

/*!
 * \brief Locks a list.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to place an exclusive lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 */
#define AST_LIST_LOCK(head)                  \
   ast_mutex_lock(&(head)->lock)

/*!
 * \brief Write locks a list.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to place an exclusive write lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 */
#define AST_RWLIST_WRLOCK(head)                                         \
        ast_rwlock_wrlock(&(head)->lock)

/*!
 * \brief Write locks a list, with timeout.
 * \param head This is a pointer to the list head structure
 * \param ts Pointer to a timespec structure
 *
 * This macro attempts to place an exclusive write lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 *
 * \since 1.6.1
 */
#define AST_RWLIST_TIMEDWRLOCK(head, ts)  ast_rwlock_timedwrlock(&(head)->lock, ts)

/*!
 * \brief Read locks a list.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to place a read lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 */
#define AST_RWLIST_RDLOCK(head)                                         \
        ast_rwlock_rdlock(&(head)->lock)

/*!
 * \brief Read locks a list, with timeout.
 * \param head This is a pointer to the list head structure
 * \param ts Pointer to a timespec structure
 *
 * This macro attempts to place a read lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 *
 * \since 1.6.1
 */
#define AST_RWLIST_TIMEDRDLOCK(head, ts)                                 \
   ast_rwlock_timedrdlock(&(head)->lock, ts)

/*!
 * \brief Locks a list, without blocking if the list is locked.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to place an exclusive lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 */
#define AST_LIST_TRYLOCK(head)                  \
   ast_mutex_trylock(&(head)->lock)

/*!
 * \brief Write locks a list, without blocking if the list is locked.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to place an exclusive write lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 */
#define AST_RWLIST_TRYWRLOCK(head)                                      \
        ast_rwlock_trywrlock(&(head)->lock)

/*!
 * \brief Read locks a list, without blocking if the list is locked.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to place a read lock in the
 * list head structure pointed to by head.
 * \retval 0 on success
 * \retval non-zero on failure
 */
#define AST_RWLIST_TRYRDLOCK(head)                                      \
        ast_rwlock_tryrdlock(&(head)->lock)

/*!
 * \brief Attempts to unlock a list.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to remove an exclusive lock from the
 * list head structure pointed to by head. If the list
 * was not locked by this thread, this macro has no effect.
 */
#define AST_LIST_UNLOCK(head)                \
   ast_mutex_unlock(&(head)->lock)

/*!
 * \brief Attempts to unlock a read/write based list.
 * \param head This is a pointer to the list head structure
 *
 * This macro attempts to remove a read or write lock from the
 * list head structure pointed to by head. If the list
 * was not locked by this thread, this macro has no effect.
 */
#define AST_RWLIST_UNLOCK(head)                                         \
        ast_rwlock_unlock(&(head)->lock)

/*!
 * \brief Defines a structure to be used to hold a list of specified type.
 * \param name This will be the name of the defined structure.
 * \param type This is the type of each list entry.
 *
 * This macro creates a structure definition that can be used
 * to hold a list of the entries of type \a type. It does not actually
 * declare (allocate) a structure; to do that, either follow this
 * macro with the desired name of the instance you wish to declare,
 * or use the specified \a name to declare instances elsewhere.
 *
 * Example usage:
 * \code
 * static AST_LIST_HEAD(entry_list, entry) entries;
 * \endcode
 *
 * This would define \c struct \c entry_list, and declare an instance of it named
 * \a entries, all intended to hold a list of type \c struct \c entry.
 */
#define AST_LIST_HEAD(name, type)               \
struct name {                       \
   struct type *first;                 \
   struct type *last;                  \
   ast_mutex_t lock;                \
}

/*!
 * \brief Defines a structure to be used to hold a read/write list of specified type.
 * \param name This will be the name of the defined structure.
 * \param type This is the type of each list entry.
 *
 * This macro creates a structure definition that can be used
 * to hold a list of the entries of type \a type. It does not actually
 * declare (allocate) a structure; to do that, either follow this
 * macro with the desired name of the instance you wish to declare,
 * or use the specified \a name to declare instances elsewhere.
 *
 * Example usage:
 * \code
 * static AST_RWLIST_HEAD(entry_list, entry) entries;
 * \endcode
 *
 * This would define \c struct \c entry_list, and declare an instance of it named
 * \a entries, all intended to hold a list of type \c struct \c entry.
 */
#define AST_RWLIST_HEAD(name, type)                                     \
struct name {                                                           \
        struct type *first;                                             \
        struct type *last;                                              \
        ast_rwlock_t lock;                                              \
}

/*!
 * \brief Defines a structure to be used to hold a list of specified type (with no lock).
 * \param name This will be the name of the defined structure.
 * \param type This is the type of each list entry.
 *
 * This macro creates a structure definition that can be used
 * to hold a list of the entries of type \a type. It does not actually
 * declare (allocate) a structure; to do that, either follow this
 * macro with the desired name of the instance you wish to declare,
 * or use the specified \a name to declare instances elsewhere.
 *
 * Example usage:
 * \code
 * static AST_LIST_HEAD_NOLOCK(entry_list, entry) entries;
 * \endcode
 *
 * This would define \c struct \c entry_list, and declare an instance of it named
 * \a entries, all intended to hold a list of type \c struct \c entry.
 */
#define AST_LIST_HEAD_NOLOCK(name, type)           \
struct name {                       \
   struct type *first;                 \
   struct type *last;                  \
}

/*!
 * \brief Defines initial values for a declaration of AST_LIST_HEAD
 */
#define AST_LIST_HEAD_INIT_VALUE {     \
   .first = NULL,             \
   .last = NULL,              \
   .lock = AST_MUTEX_INIT_VALUE,       \
   }

/*!
 * \brief Defines initial values for a declaration of AST_RWLIST_HEAD
 */
#define AST_RWLIST_HEAD_INIT_VALUE      {               \
        .first = NULL,                                  \
        .last = NULL,                                   \
        .lock = AST_RWLOCK_INIT_VALUE,                  \
        }

/*!
 * \brief Defines initial values for a declaration of AST_LIST_HEAD_NOLOCK
 */
#define AST_LIST_HEAD_NOLOCK_INIT_VALUE   {  \
   .first = NULL,             \
   .last = NULL,              \
   }

/*!
 * \brief Defines a structure to be used to hold a list of specified type, statically initialized.
 * \param name This will be the name of the defined structure.
 * \param type This is the type of each list entry.
 *
 * This macro creates a structure definition that can be used
 * to hold a list of the entries of type \a type, and allocates an instance
 * of it, initialized to be empty.
 *
 * Example usage:
 * \code
 * static AST_LIST_HEAD_STATIC(entry_list, entry);
 * \endcode
 *
 * This would define \c struct \c entry_list, intended to hold a list of
 * type \c struct \c entry.
 */
#if defined(AST_MUTEX_INIT_W_CONSTRUCTORS)
#define AST_LIST_HEAD_STATIC(name, type)           \
struct name {                       \
   struct type *first;                 \
   struct type *last;                  \
   ast_mutex_t lock;                \
} name;                          \
static void  __attribute__((constructor)) __init_##name(void)     \
{                          \
        AST_LIST_HEAD_INIT(&name);              \
}                          \
static void  __attribute__((destructor)) __fini_##name(void)      \
{                          \
        AST_LIST_HEAD_DESTROY(&name);              \
}                          \
struct __dummy_##name
#else
#define AST_LIST_HEAD_STATIC(name, type)           \
struct name {                       \
   struct type *first;                 \
   struct type *last;                  \
   ast_mutex_t lock;                \
} name = AST_LIST_HEAD_INIT_VALUE
#endif

/*!
 * \brief Defines a structure to be used to hold a read/write list of specified type, statically initialized.
 * \param name This will be the name of the defined structure.
 * \param type This is the type of each list entry.
 *
 * This macro creates a structure definition that can be used
 * to hold a list of the entries of type \a type, and allocates an instance
 * of it, initialized to be empty.
 *
 * Example usage:
 * \code
 * static AST_RWLIST_HEAD_STATIC(entry_list, entry);
 * \endcode
 *
 * This would define \c struct \c entry_list, intended to hold a list of
 * type \c struct \c entry.
 */
#ifndef HAVE_PTHREAD_RWLOCK_INITIALIZER
#define AST_RWLIST_HEAD_STATIC(name, type)                              \
struct name {                                                           \
        struct type *first;                                             \
        struct type *last;                                              \
        ast_rwlock_t lock;                                              \
} name;                                                                 \
static void  __attribute__((constructor)) __init_##name(void)          \
{                                                                       \
        AST_RWLIST_HEAD_INIT(&name);                                    \
}                                                                       \
static void  __attribute__((destructor)) __fini_##name(void)           \
{                                                                       \
        AST_RWLIST_HEAD_DESTROY(&name);                                 \
}                                                                       \
struct __dummy_##name
#else
#define AST_RWLIST_HEAD_STATIC(name, type)                              \
struct name {                                                           \
        struct type *first;                                             \
        struct type *last;                                              \
        ast_rwlock_t lock;                                              \
} name = AST_RWLIST_HEAD_INIT_VALUE
#endif

/*!
 * \brief Defines a structure to be used to hold a list of specified type, statically initialized.
 *
 * This is the same as AST_LIST_HEAD_STATIC, except without the lock included.
 */
#define AST_LIST_HEAD_NOLOCK_STATIC(name, type)          \
struct name {                       \
   struct type *first;                 \
   struct type *last;                  \
} name = AST_LIST_HEAD_NOLOCK_INIT_VALUE

/*!
 * \brief Initializes a list head structure with a specified first entry.
 * \param head This is a pointer to the list head structure
 * \param entry pointer to the list entry that will become the head of the list
 *
 * This macro initializes a list head structure by setting the head
 * entry to the supplied value and recreating the embedded lock.
 */
#define AST_LIST_HEAD_SET(head, entry) do {           \
   (head)->first = (entry);               \
   (head)->last = (entry);                \
   ast_mutex_init(&(head)->lock);               \
} while (0)

/*!
 * \brief Initializes an rwlist head structure with a specified first entry.
 * \param head This is a pointer to the list head structure
 * \param entry pointer to the list entry that will become the head of the list
 *
 * This macro initializes a list head structure by setting the head
 * entry to the supplied value and recreating the embedded lock.
 */
#define AST_RWLIST_HEAD_SET(head, entry) do {                           \
        (head)->first = (entry);                                        \
        (head)->last = (entry);                                         \
        ast_rwlock_init(&(head)->lock);                                 \
} while (0)

/*!
 * \brief Initializes a list head structure with a specified first entry.
 * \param head This is a pointer to the list head structure
 * \param entry pointer to the list entry that will become the head of the list
 *
 * This macro initializes a list head structure by setting the head
 * entry to the supplied value.
 */
#define AST_LIST_HEAD_SET_NOLOCK(head, entry) do {       \
   (head)->first = (entry);               \
   (head)->last = (entry);                \
} while (0)

/*!
 * \brief Declare a forward link structure inside a list entry.
 * \param type This is the type of each list entry.
 *
 * This macro declares a structure to be used to link list entries together.
 * It must be used inside the definition of the structure named in
 * \a type, as follows:
 *
 * \code
 * struct list_entry {
      ...
      AST_LIST_ENTRY(list_entry) list;
 * }
 * \endcode
 *
 * The field name \a list here is arbitrary, and can be anything you wish.
 */
#define AST_LIST_ENTRY(type)                 \
struct {                      \
   struct type *next;                  \
}

#define AST_RWLIST_ENTRY AST_LIST_ENTRY

/*!
 * \brief Returns the first entry contained in a list.
 * \param head This is a pointer to the list head structure
 */
#define AST_LIST_FIRST(head)  ((head)->first)

#define AST_RWLIST_FIRST AST_LIST_FIRST

/*!
 * \brief Returns the last entry contained in a list.
 * \param head This is a pointer to the list head structure
 */
#define AST_LIST_LAST(head)   ((head)->last)

#define AST_RWLIST_LAST AST_LIST_LAST

/*!
 * \brief Returns the next entry in the list after the given entry.
 * \param elm This is a pointer to the current entry.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 */
#define AST_LIST_NEXT(elm, field)   ((elm)->field.next)

#define AST_RWLIST_NEXT AST_LIST_NEXT

/*!
 * \brief Checks whether the specified list contains any entries.
 * \param head This is a pointer to the list head structure
 *
 * \return zero if the list has entries
 * \return non-zero if not.
 */
#define AST_LIST_EMPTY(head)  (AST_LIST_FIRST(head) == NULL)

#define AST_RWLIST_EMPTY AST_LIST_EMPTY

/*!
 * \brief Loops over (traverses) the entries in a list.
 * \param head This is a pointer to the list head structure
 * \param var This is the name of the variable that will hold a pointer to the
 * current list entry on each iteration. It must be declared before calling
 * this macro.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * This macro is use to loop over (traverse) the entries in a list. It uses a
 * \a for loop, and supplies the enclosed code with a pointer to each list
 * entry as it loops. It is typically used as follows:
 * \code
 * static AST_LIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
      ...
      AST_LIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_LIST_TRAVERSE(&entries, current, list) {
     (do something with current here)
 * }
 * \endcode
 * \warning If you modify the forward-link pointer contained in the \a current entry while
 * inside the loop, the behavior will be unpredictable. At a minimum, the following
 * macros will modify the forward-link pointer, and should not be used inside
 * AST_LIST_TRAVERSE() against the entry pointed to by the \a current pointer without
 * careful consideration of their consequences:
 * \li AST_LIST_NEXT() (when used as an lvalue)
 * \li AST_LIST_INSERT_AFTER()
 * \li AST_LIST_INSERT_HEAD()
 * \li AST_LIST_INSERT_TAIL()
 * \li AST_LIST_INSERT_SORTALPHA()
 */
#define AST_LIST_TRAVERSE(head,var,field)             \
   for((var) = (head)->first; (var); (var) = (var)->field.next)

#define AST_RWLIST_TRAVERSE AST_LIST_TRAVERSE

/*!
 * \brief Loops safely over (traverses) the entries in a list.
 * \param head This is a pointer to the list head structure
 * \param var This is the name of the variable that will hold a pointer to the
 * current list entry on each iteration. It must be declared before calling
 * this macro.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * This macro is used to safely loop over (traverse) the entries in a list. It
 * uses a \a for loop, and supplies the enclosed code with a pointer to each list
 * entry as it loops. It is typically used as follows:
 *
 * \code
 * static AST_LIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
      ...
      AST_LIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_LIST_TRAVERSE_SAFE_BEGIN(&entries, current, list) {
     (do something with current here)
 * }
 * AST_LIST_TRAVERSE_SAFE_END;
 * \endcode
 *
 * It differs from AST_LIST_TRAVERSE() in that the code inside the loop can modify
 * (or even free, after calling AST_LIST_REMOVE_CURRENT()) the entry pointed to by
 * the \a current pointer without affecting the loop traversal.
 */
#define AST_LIST_TRAVERSE_SAFE_BEGIN(head, var, field) {          \
   typeof((head)) __list_head = head;                          \
   typeof(__list_head->first) __list_next;                        \
   typeof(__list_head->first) __list_prev = NULL;                 \
   typeof(__list_head->first) __list_current;                     \
   for ((var) = __list_head->first,                         \
      __list_current = (var),                               \
      __list_next = (var) ? (var)->field.next : NULL;             \
      (var);                                             \
      __list_prev = __list_current,                         \
      (var) = __list_next,                               \
      __list_current = (var),                               \
      __list_next = (var) ? (var)->field.next : NULL,             \
      (void) __list_prev /* To quiet compiler? */                 \
      )

#define AST_RWLIST_TRAVERSE_SAFE_BEGIN AST_LIST_TRAVERSE_SAFE_BEGIN

/*!
 * \brief Removes the \a current entry from a list during a traversal.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * \note This macro can \b only be used inside an AST_LIST_TRAVERSE_SAFE_BEGIN()
 * block; it is used to unlink the current entry from the list without affecting
 * the list traversal (and without having to re-traverse the list to modify the
 * previous entry, if any).
 */
#define AST_LIST_REMOVE_CURRENT(field) do {                    \
      __list_current->field.next = NULL;                       \
      __list_current = __list_prev;                         \
      if (__list_prev) {                                    \
         __list_prev->field.next = __list_next;                \
      } else {                                        \
         __list_head->first = __list_next;                     \
      }                                               \
      if (!__list_next) {                                   \
         __list_head->last = __list_prev;                   \
      }                                               \
   } while (0)

#define AST_RWLIST_REMOVE_CURRENT AST_LIST_REMOVE_CURRENT

/*!
 * \brief Move the current list entry to another list.
 *
 * \note This is a silly macro.  It should be done explicitly
 * otherwise the field parameter must be the same for the two
 * lists.
 *
 * AST_LIST_REMOVE_CURRENT(field);
 * AST_LIST_INSERT_TAIL(newhead, var, other_field);
 */
#define AST_LIST_MOVE_CURRENT(newhead, field) do {       \
   typeof ((newhead)->first) __extracted = __list_current;  \
   AST_LIST_REMOVE_CURRENT(field);                    \
   AST_LIST_INSERT_TAIL((newhead), __extracted, field);  \
   } while (0)

#define AST_RWLIST_MOVE_CURRENT AST_LIST_MOVE_CURRENT

/*!
 * \brief Inserts a list entry before the current entry during a traversal.
 * \param elm This is a pointer to the entry to be inserted.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * \note This macro can \b only be used inside an AST_LIST_TRAVERSE_SAFE_BEGIN()
 * block.
 */
#define AST_LIST_INSERT_BEFORE_CURRENT(elm, field) do {     \
   if (__list_prev) {                              \
      (elm)->field.next = __list_prev->field.next;    \
      __list_prev->field.next = elm;                  \
   } else {                                  \
      (elm)->field.next = __list_head->first;            \
      __list_head->first = (elm);                     \
   }                                         \
   __list_prev = (elm);                         \
} while (0)

#define AST_RWLIST_INSERT_BEFORE_CURRENT AST_LIST_INSERT_BEFORE_CURRENT

/*!
 * \brief Closes a safe loop traversal block.
 */
#define AST_LIST_TRAVERSE_SAFE_END  }

#define AST_RWLIST_TRAVERSE_SAFE_END AST_LIST_TRAVERSE_SAFE_END

/*!
 * \brief Initializes a list head structure.
 * \param head This is a pointer to the list head structure
 *
 * This macro initializes a list head structure by setting the head
 * entry to \a NULL (empty list) and recreating the embedded lock.
 */
#define AST_LIST_HEAD_INIT(head) {              \
   (head)->first = NULL;                  \
   (head)->last = NULL;                \
   ast_mutex_init(&(head)->lock);               \
}

/*!
 * \brief Initializes an rwlist head structure.
 * \param head This is a pointer to the list head structure
 *
 * This macro initializes a list head structure by setting the head
 * entry to \a NULL (empty list) and recreating the embedded lock.
 */
#define AST_RWLIST_HEAD_INIT(head) {                                    \
        (head)->first = NULL;                                           \
        (head)->last = NULL;                                            \
        ast_rwlock_init(&(head)->lock);                                 \
}

/*!
 * \brief Destroys a list head structure.
 * \param head This is a pointer to the list head structure
 *
 * This macro destroys a list head structure by setting the head
 * entry to \a NULL (empty list) and destroying the embedded lock.
 * It does not free the structure from memory.
 */
#define AST_LIST_HEAD_DESTROY(head) {              \
   (head)->first = NULL;                  \
   (head)->last = NULL;                \
   ast_mutex_destroy(&(head)->lock);            \
}

/*!
 * \brief Destroys an rwlist head structure.
 * \param head This is a pointer to the list head structure
 *
 * This macro destroys a list head structure by setting the head
 * entry to \a NULL (empty list) and destroying the embedded lock.
 * It does not free the structure from memory.
 */
#define AST_RWLIST_HEAD_DESTROY(head) {                                 \
        (head)->first = NULL;                                           \
        (head)->last = NULL;                                            \
        ast_rwlock_destroy(&(head)->lock);                              \
}

/*!
 * \brief Initializes a list head structure.
 * \param head This is a pointer to the list head structure
 *
 * This macro initializes a list head structure by setting the head
 * entry to \a NULL (empty list). There is no embedded lock handling
 * with this macro.
 */
#define AST_LIST_HEAD_INIT_NOLOCK(head) {          \
   (head)->first = NULL;                  \
   (head)->last = NULL;                \
}

/*!
 * \brief Inserts a list entry after a given entry.
 * \param head This is a pointer to the list head structure
 * \param listelm This is a pointer to the entry after which the new entry should
 * be inserted.
 * \param elm This is a pointer to the entry to be inserted.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 */
#define AST_LIST_INSERT_AFTER(head, listelm, elm, field) do {     \
   (elm)->field.next = (listelm)->field.next;         \
   (listelm)->field.next = (elm);               \
   if ((head)->last == (listelm))               \
      (head)->last = (elm);               \
} while (0)

#define AST_RWLIST_INSERT_AFTER AST_LIST_INSERT_AFTER

/*!
 * \brief Inserts a list entry at the head of a list.
 * \param head This is a pointer to the list head structure
 * \param elm This is a pointer to the entry to be inserted.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 */
#define AST_LIST_INSERT_HEAD(head, elm, field) do {         \
      (elm)->field.next = (head)->first;        \
      (head)->first = (elm);              \
      if (!(head)->last)               \
         (head)->last = (elm);            \
} while (0)

#define AST_RWLIST_INSERT_HEAD AST_LIST_INSERT_HEAD

/*!
 * \brief Appends a list entry to the tail of a list.
 * \param head This is a pointer to the list head structure
 * \param elm This is a pointer to the entry to be appended.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * Note: The link field in the appended entry is \b not modified, so if it is
 * actually the head of a list itself, the entire list will be appended
 * temporarily (until the next AST_LIST_INSERT_TAIL is performed).
 */
#define AST_LIST_INSERT_TAIL(head, elm, field) do {         \
      if (!(head)->first) {                  \
      (head)->first = (elm);              \
      (head)->last = (elm);               \
      } else {                      \
      (head)->last->field.next = (elm);         \
      (head)->last = (elm);               \
      }                          \
} while (0)

#define AST_RWLIST_INSERT_TAIL AST_LIST_INSERT_TAIL

/*!
 * \brief Inserts a list entry into a alphabetically sorted list
 * \param head Pointer to the list head structure
 * \param elm Pointer to the entry to be inserted
 * \param field Name of the list entry field (declared using AST_LIST_ENTRY())
 * \param sortfield Name of the field on which the list is sorted
 * \since 1.6.1
 */
#define AST_LIST_INSERT_SORTALPHA(head, elm, field, sortfield) do {     \
   if (!(head)->first) {                                               \
      (head)->first = (elm);                                          \
      (head)->last = (elm);                                           \
   } else {                                                            \
      typeof((head)->first) __cur = (head)->first, __prev = NULL;     \
      while (__cur && strcmp(__cur->sortfield, elm->sortfield) < 0) { \
         __prev = __cur;                                             \
         __cur = __cur->field.next;                                  \
      }                                                               \
      if (!__prev) {                                                  \
         AST_LIST_INSERT_HEAD(head, elm, field);                     \
      } else if (!__cur) {                                            \
         AST_LIST_INSERT_TAIL(head, elm, field);                     \
      } else {                                                        \
         AST_LIST_INSERT_AFTER(head, __prev, elm, field);            \
      }                                                               \
   }                                                                   \
} while (0)

#define AST_RWLIST_INSERT_SORTALPHA AST_LIST_INSERT_SORTALPHA

/*!
 * \brief Appends a whole list to the tail of a list.
 * \param head This is a pointer to the list head structure
 * \param list This is a pointer to the list to be appended.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * Note: The source list (the \a list parameter) will be empty after
 * calling this macro (the list entries are \b moved to the target list).
 */
#define AST_LIST_APPEND_LIST(head, list, field) do {        \
   if (!(list)->first) {                  \
      break;                     \
   }                       \
   if (!(head)->first) {                  \
      (head)->first = (list)->first;            \
      (head)->last = (list)->last;           \
   } else {                   \
      (head)->last->field.next = (list)->first;    \
      (head)->last = (list)->last;           \
   }                       \
   (list)->first = NULL;                  \
   (list)->last = NULL;                \
} while (0)

#define AST_RWLIST_APPEND_LIST AST_LIST_APPEND_LIST

/*!
  \brief Inserts a whole list after a specific entry in a list
  \param head This is a pointer to the list head structure
  \param list This is a pointer to the list to be inserted.
  \param elm This is a pointer to the entry after which the new list should
  be inserted.
  \param field This is the name of the field (declared using AST_LIST_ENTRY())
  used to link entries of the lists together.

  Note: The source list (the \a list parameter) will be empty after
  calling this macro (the list entries are \b moved to the target list).
 */
#define AST_LIST_INSERT_LIST_AFTER(head, list, elm, field) do {      \
   (list)->last->field.next = (elm)->field.next;         \
   (elm)->field.next = (list)->first;           \
   if ((head)->last == elm) {             \
      (head)->last = (list)->last;           \
   }                       \
   (list)->first = NULL;                  \
   (list)->last = NULL;                \
} while(0)

#define AST_RWLIST_INSERT_LIST_AFTER AST_LIST_INSERT_LIST_AFTER

/*!
 * \brief Removes and returns the head entry from a list.
 * \param head This is a pointer to the list head structure
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 *
 * Removes the head entry from the list, and returns a pointer to it.
 * This macro is safe to call on an empty list.
 */
#define AST_LIST_REMOVE_HEAD(head, field) ({          \
      typeof((head)->first) __cur = (head)->first;    \
      if (__cur) {                  \
         (head)->first = __cur->field.next;     \
         __cur->field.next = NULL;        \
         if ((head)->last == __cur)       \
            (head)->last = NULL;       \
      }                    \
      __cur;                     \
   })

#define AST_RWLIST_REMOVE_HEAD AST_LIST_REMOVE_HEAD

/*!
 * \brief Removes a specific entry from a list.
 * \param head This is a pointer to the list head structure
 * \param elm This is a pointer to the entry to be removed.
 * \param field This is the name of the field (declared using AST_LIST_ENTRY())
 * used to link entries of this list together.
 * \retval elm if elm was in the list.
 * \retval NULL if elm was not in the list or elm was NULL.
 * \warning The removed entry is \b not freed.
 */
#define AST_LIST_REMOVE(head, elm, field)                \
   ({                                           \
      typeof(elm) __elm = (elm);                      \
      if (__elm) {                                 \
         if ((head)->first == __elm) {                \
            (head)->first = __elm->field.next;           \
            __elm->field.next = NULL;                 \
            if ((head)->last == __elm) {              \
               (head)->last = NULL;                \
            }                                   \
         } else {                               \
            typeof(elm) __prev = (head)->first;          \
            while (__prev && __prev->field.next != __elm) { \
               __prev = __prev->field.next;           \
            }                                   \
            if (__prev) {                          \
               __prev->field.next = __elm->field.next;      \
               __elm->field.next = NULL;              \
               if ((head)->last == __elm) {           \
                  (head)->last = __prev;              \
               }                                \
            } else {                            \
               __elm = NULL;                       \
            }                                   \
         }                                      \
      }                                         \
      __elm;                                       \
   })

#define AST_RWLIST_REMOVE AST_LIST_REMOVE

#endif /* _ASTERISK_LINKEDLISTS_H */