dlinkedlists.h

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2007, Digium, Inc.
 *
 * Steve Murphy <[email protected]>
 *
 * Doubly-Linked List Macros--
 * Based on linkedlists.h (to the point of plagiarism!), which is by:
 *
 * 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_DLINKEDLISTS_H
#define ASTERISK_DLINKEDLISTS_H

#include "asterisk/lock.h"

/*!
 * \file dlinkedlists.h
 * \brief A set of macros to manage doubly-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
 * \since 1.6.1
 */
#define AST_DLLIST_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
 * \since 1.6.1
 */
#define AST_RWDLLIST_WRLOCK(head) \
 ast_rwlock_wrlock(&(head)->lock)

/*!
 * \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
 * \since 1.6.1
 */
#define AST_RWDLLIST_RDLOCK(head) \
 ast_rwlock_rdlock(&(head)->lock)

/*!
 * \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
 * \since 1.6.1
 */
#define AST_DLLIST_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
 * \since 1.6.1
 */
#define AST_RWDLLIST_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
 * \since 1.6.1
 */
#define AST_RWDLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_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.
 * \since 1.6.1
 */
#define AST_RWDLLIST_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_DLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_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_RWDLLIST_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.
 * \since 1.6.1
 */
#define AST_RWDLLIST_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_DLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_HEAD_NOLOCK(name, type) \
 struct name { \
 struct type *first; \
 struct type *last; \
 }

/*!
 * \brief Defines initial values for a declaration of AST_DLLIST_HEAD
 * \since 1.6.1
 */
#define AST_DLLIST_HEAD_INIT_VALUE \
 { \
 .first = NULL, \
 .last = NULL, \
 .lock = AST_MUTEX_INIT_VALUE, \
 }

/*!
 * \brief Defines initial values for a declaration of AST_RWDLLIST_HEAD
 * \since 1.6.1
 */
#define AST_RWDLLIST_HEAD_INIT_VALUE \
 { \
 .first = NULL, \
 .last = NULL, \
 .lock = AST_RWLOCK_INIT_VALUE, \
 }

/*!
 * \brief Defines initial values for a declaration of AST_DLLIST_HEAD_NOLOCK
 * \since 1.6.1
 */
#define AST_DLLIST_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_DLLIST_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.
 * \since 1.6.1
 */
#if defined(AST_MUTEX_INIT_W_CONSTRUCTORS)
#define AST_DLLIST_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_DLLIST_HEAD_INIT(&name); \
 } \
 static void __attribute__((destructor)) __fini_##name(void) \
 { \
 AST_DLLIST_HEAD_DESTROY(&name); \
 } \
 struct __dummy_##name
#else
#define AST_DLLIST_HEAD_STATIC(name, type) \
 struct name { \
 struct type *first; \
 struct type *last; \
 ast_mutex_t lock; \
 } name = AST_DLLIST_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_RWDLLIST_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.
 * \since 1.6.1
 */
#ifndef HAVE_PTHREAD_RWLOCK_INITIALIZER
#define AST_RWDLLIST_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_RWDLLIST_HEAD_INIT(&name); \
 } \
 static void __attribute__((destructor)) __fini_##name(void) \
 { \
 AST_RWDLLIST_HEAD_DESTROY(&name); \
 } \
 struct __dummy_##name
#else
#define AST_RWDLLIST_HEAD_STATIC(name, type) \
 struct name { \
 struct type *first; \
 struct type *last; \
 ast_rwlock_t lock; \
 } name = AST_RWDLLIST_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_DLLIST_HEAD_STATIC, except without the lock included.
 * \since 1.6.1
 */
#define AST_DLLIST_HEAD_NOLOCK_STATIC(name, type) \
 struct name { \
 struct type *first; \
 struct type *last; \
 } name = AST_DLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_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.
 * \since 1.6.1
 */
#define AST_RWDLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_HEAD_SET_NOLOCK(head, entry) \
 do { \
 (head)->first = (entry); \
 (head)->last = (entry); \
 } while (0)

/*!
 * \brief Declare previous/forward links inside a list entry.
 * \param type This is the type of each list entry.
 *
 * This macro declares a structure to be used to doubly 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_DLLIST_ENTRY(list_entry) list;
 * }
 * \endcode
 *
 * The field name \a list here is arbitrary, and can be anything you wish.
 * \since 1.6.1
 */
#define AST_DLLIST_ENTRY(type) AST_DLLIST_HEAD_NOLOCK(, type)

#define AST_RWDLLIST_ENTRY AST_DLLIST_ENTRY

/*!
 * \brief Returns the first entry contained in a list.
 * \param head This is a pointer to the list head structure
 * \since 1.6.1
 */
#define AST_DLLIST_FIRST(head) ((head)->first)

#define AST_RWDLLIST_FIRST AST_DLLIST_FIRST

/*!
 * \brief Returns the last entry contained in a list.
 * \param head This is a pointer to the list head structure
 * \since 1.6.1
 */
#define AST_DLLIST_LAST(head) ((head)->last)

#define AST_RWDLLIST_LAST AST_DLLIST_LAST

#define AST_DLLIST_NEXT_DIRECTION(elm, field, direction) ((elm)->field.direction)

#define AST_RWDLLIST_NEXT_DIRECTION AST_DLLIST_NEXT_DIRECTION

/*!
 * \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_DLLIST_ENTRY())
 * used to link entries of this list together.
 * \since 1.6.1
 */
#define AST_DLLIST_NEXT(elm, field) AST_DLLIST_NEXT_DIRECTION(elm, field, first)

#define AST_RWDLLIST_NEXT AST_DLLIST_NEXT

/*!
 * \brief Returns the previous entry in the list before 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_DLLIST_ENTRY())
 * used to link entries of this list together.
 * \since 1.6.1
 */
#define AST_DLLIST_PREV(elm, field) AST_DLLIST_NEXT_DIRECTION(elm, field, last)

#define AST_RWDLLIST_PREV AST_DLLIST_PREV

/*!
 * \brief Checks whether the specified list contains any entries.
 * \param head This is a pointer to the list head structure
 *
 * \return non-zero if the list has entries
 * \return zero if not.
 * \since 1.6.1
 */
#define AST_DLLIST_EMPTY(head) (AST_DLLIST_FIRST(head) == NULL)

#define AST_RWDLLIST_EMPTY AST_DLLIST_EMPTY

/*!
 * \brief Checks whether the specified list contains the element.
 * \param head This is a pointer to the list head structure
 * \param elm This is a pointer to the list element to see if in list.
 * \param field List node field for the next node information.
 *
 * \return elm if the list has elm in it.
 * \return NULL if not.
 * \since 11
 */
#define AST_DLLIST_IS_MEMBER(head, elm, field) \
 ({ \
 typeof((head)->first) __cur; \
 typeof((elm)) __elm = (elm); \
 if (!__elm) { \
 __cur = NULL; \
 } else { \
 __cur = (head)->first; \
 while (__cur && __cur != __elm) { \
 __cur = __cur->field.first; \
 } \
 } \
 __cur; \
 })

#define AST_RWDLLIST_IS_MEMBER AST_DLLIST_IS_MEMBER

/*!
 * \brief Traverse a doublly linked list using the specified direction list.
 *
 * \param head List head structure pointer.
 * \param var This is the name of the variable that will hold a pointer to the
 * current list node on each iteration. It must be declared before calling
 * this macro.
 * \param field List node field for the next node information. (declared using AST_DLLIST_ENTRY())
 * \param start Specified list node to start traversal: first or last
 *
 * This macro is use to loop over (traverse) the nodes in a list. It uses a
 * \a for loop, and supplies the enclosed code with a pointer to each list
 * node as it loops. It is typically used as follows:
 * \code
 * static AST_DLLIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
 * ...
 * AST_DLLIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_DLLIST_TRAVERSE_DIRECTION(&entries, current, list, first) {
 * (do something with current here (travers list in forward direction))
 * }
 * ...
 * AST_DLLIST_TRAVERSE_DIRECTION(&entries, current, list, last) {
 * (do something with current here (travers list in reverse direction))
 * }
 * \endcode
 *
 * \since 11
 */
#define AST_DLLIST_TRAVERSE_DIRECTION(head, var, field, start) \
 for ((var) = (head)->start; (var); (var) = AST_DLLIST_NEXT_DIRECTION(var, field, start))

#define AST_RWDLLIST_TRAVERSE_DIRECTION AST_DLLIST_TRAVERSE_DIRECTION

/*!
 * \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_DLLIST_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_DLLIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
 * ...
 * AST_DLLIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_DLLIST_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_DLLIST_TRAVERSE() against the entry pointed to by the \a current pointer without
 * careful consideration of their consequences:
 * \li AST_DLLIST_NEXT() (when used as an lvalue)
 * \li AST_DLLIST_INSERT_AFTER()
 * \li AST_DLLIST_INSERT_HEAD()
 * \li AST_DLLIST_INSERT_TAIL()
 * \since 1.6.1
 */
#define AST_DLLIST_TRAVERSE(head,var,field) \
 AST_DLLIST_TRAVERSE_DIRECTION(head, var, field, first)

#define AST_RWDLLIST_TRAVERSE AST_DLLIST_TRAVERSE

/*!
 * \brief Loops over (traverses) the entries in a list in reverse order, starting at the end.
 * \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_DLLIST_ENTRY())
 * used to link entries of this list together.
 *
 * This macro is use to loop over (traverse) the entries in a list in reverse order. 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_DLLIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
 * ...
 * AST_DLLIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_DLLIST_TRAVERSE_BACKWARDS(&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_DLLIST_TRAVERSE() against the entry pointed to by the \a current pointer without
 * careful consideration of their consequences:
 * \li AST_DLLIST_PREV() (when used as an lvalue)
 * \li AST_DLLIST_INSERT_BEFORE()
 * \li AST_DLLIST_INSERT_HEAD()
 * \li AST_DLLIST_INSERT_TAIL()
 * \since 1.6.1
 */
#define AST_DLLIST_TRAVERSE_BACKWARDS(head,var,field) \
 AST_DLLIST_TRAVERSE_DIRECTION(head, var, field, last)

#define AST_RWDLLIST_TRAVERSE_BACKWARDS AST_DLLIST_TRAVERSE_BACKWARDS

/*!
 * \brief Safe traversal of a doublly linked list using the specified direction list.
 *
 * \param head List head structure pointer.
 * \param var This is the name of the variable that will hold a pointer to the
 * current list node on each iteration. It must be declared before calling
 * this macro.
 * \param field List node field for the next node information. (declared using AST_DLLIST_ENTRY())
 * \param start Specified list node to start traversal: first or last
 *
 * This macro is used to safely loop over (traverse) the nodes in a list. It
 * uses a \a for loop, and supplies the enclosed code with a pointer to each list
 * node as it loops. It is typically used as follows:
 *
 * \code
 * static AST_DLLIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
 * ...
 * AST_DLLIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_DLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN(&entries, current, list, first) {
 * (do something with current here (travers list in forward direction))
 * }
 * ...
 * AST_DLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN(&entries, current, list, last) {
 * (do something with current here (travers list in reverse direction))
 * }
 * AST_DLLIST_TRAVERSE_DIRECTION_SAFE_END;
 * \endcode
 *
 * It differs from AST_DLLIST_TRAVERSE() in that the code inside the loop can modify
 * (or even free, after calling AST_DLLIST_REMOVE_CURRENT()) the entry pointed to by
 * the \a current pointer without affecting the loop traversal.
 *
 * \since 11
 */
#define AST_DLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN(head, var, field, start) \
 do { \
 typeof((head)) __list_head = (head); \
 typeof(__list_head->first) __list_current; \
 typeof(__list_head->first) __list_first; \
 typeof(__list_head->first) __list_last; \
 typeof(__list_head->first) __list_next; \
 for ((var) = __list_head->start, \
 __list_current = (var), \
 __list_first = (var) ? (var)->field.first : NULL, \
 __list_last = (var) ? (var)->field.last : NULL, \
 __list_next = (var) ? AST_DLLIST_NEXT_DIRECTION(var, field, start) : NULL; \
 (var); \
 (void) __list_current,/* To quiet compiler? */ \
 (void) __list_first,/* To quiet compiler? */ \
 (void) __list_last,/* To quiet compiler? */ \
 (var) = __list_next, \
 __list_current = (var), \
 __list_first = (var) ? (var)->field.first : NULL, \
 __list_last = (var) ? (var)->field.last : NULL, \
 __list_next = (var) ? AST_DLLIST_NEXT_DIRECTION(var, field, start) : NULL \
 )

#define AST_RWDLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN AST_DLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN

/*!
 * \brief Inserts a list node before the current node 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_DLLIST_ENTRY())
 * used to link nodes of this list together.
 *
 * \since 1.6.1
 */
#define AST_DLLIST_INSERT_BEFORE_CURRENT(elm, field) \
 do { \
 typeof((elm)) __elm = (elm); \
 __elm->field.last = __list_last; \
 __elm->field.first = __list_current; \
 if (__list_head->first == __list_current) { \
 __list_head->first = __elm; \
 } else { \
 __list_last->field.first = __elm; \
 } \
 __list_current->field.last = __elm; \
 if (__list_next == __list_last) { \
 __list_next = __elm; \
 } \
 __list_last = __elm; \
 } while (0)

#define AST_RWDLLIST_INSERT_BEFORE_CURRENT AST_DLLIST_INSERT_BEFORE_CURRENT

/*!
 * \brief Inserts a list node after the current node during a traversal.
 * \param elm This is a pointer to the node to be inserted.
 * \param field This is the name of the field (declared using AST_DLLIST_ENTRY())
 * used to link nodes of this list together.
 *
 * \since 11
 */
#define AST_DLLIST_INSERT_AFTER_CURRENT(elm, field) \
 do { \
 typeof((elm)) __elm = (elm); \
 __elm->field.first = __list_first; \
 __elm->field.last = __list_current; \
 if (__list_head->last == __list_current) { \
 __list_head->last = __elm; \
 } else { \
 __list_first->field.last = __elm; \
 } \
 __list_current->field.first = __elm; \
 if (__list_next == __list_first) { \
 __list_next = __elm; \
 } \
 __list_first = __elm; \
 } while (0)

#define AST_RWDLLIST_INSERT_AFTER_CURRENT AST_DLLIST_INSERT_AFTER_CURRENT

/*!
 * \brief Removes the \a current entry from a list during a traversal.
 * \param field This is the name of the field (declared using AST_DLLIST_ENTRY())
 * used to link entries of this list together.
 *
 * \note This macro can \b only be used inside an AST_DLLIST_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).
 * \since 1.6.1
 */
#define AST_DLLIST_REMOVE_CURRENT(field) \
 do { \
 if (__list_first) { \
 __list_first->field.last = __list_last; \
 } else { \
 __list_head->last = __list_last; \
 } \
 if (__list_last) { \
 __list_last->field.first = __list_first; \
 } else { \
 __list_head->first = __list_first; \
 } \
 __list_current->field.first = NULL; \
 __list_current->field.last = NULL; \
 __list_current = NULL; \
 } while (0)

#define AST_RWDLLIST_REMOVE_CURRENT AST_DLLIST_REMOVE_CURRENT

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

#define AST_RWDLLIST_MOVE_CURRENT AST_DLLIST_MOVE_CURRENT

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

#define AST_RWDLLIST_MOVE_CURRENT_BACKWARDS AST_DLLIST_MOVE_CURRENT_BACKWARDS

#define AST_DLLIST_TRAVERSE_DIRECTION_SAFE_END \
 } while (0)

#define AST_RWDLLIST_TRAVERSE_DIRECTION_SAFE_END AST_DLLIST_TRAVERSE_DIRECTION_SAFE_END

/*!
 * \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_DLLIST_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_DLLIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
 * ...
 * AST_DLLIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_DLLIST_TRAVERSE_SAFE_BEGIN(&entries, current, list) {
 * (do something with current here)
 * }
 * AST_DLLIST_TRAVERSE_SAFE_END;
 * \endcode
 *
 * It differs from AST_DLLIST_TRAVERSE() in that the code inside the loop can modify
 * (or even free, after calling AST_DLLIST_REMOVE_CURRENT()) the entry pointed to by
 * the \a current pointer without affecting the loop traversal.
 * \since 1.6.1
 */
#define AST_DLLIST_TRAVERSE_SAFE_BEGIN(head, var, field) \
 AST_DLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN(head, var, field, first)

#define AST_RWDLLIST_TRAVERSE_SAFE_BEGIN AST_DLLIST_TRAVERSE_SAFE_BEGIN

/*!
 * \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_DLLIST_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_DLLIST_HEAD(entry_list, list_entry) entries;
 * ...
 * struct list_entry {
 * ...
 * AST_DLLIST_ENTRY(list_entry) list;
 * }
 * ...
 * struct list_entry *current;
 * ...
 * AST_DLLIST_TRAVERSE_SAFE_BEGIN(&entries, current, list) {
 * (do something with current here)
 * }
 * AST_DLLIST_TRAVERSE_SAFE_END;
 * \endcode
 *
 * It differs from AST_DLLIST_TRAVERSE() in that the code inside the loop can modify
 * (or even free, after calling AST_DLLIST_REMOVE_CURRENT()) the entry pointed to by
 * the \a current pointer without affecting the loop traversal.
 * \since 1.6.1
 */
#define AST_DLLIST_TRAVERSE_BACKWARDS_SAFE_BEGIN(head, var, field) \
 AST_DLLIST_TRAVERSE_DIRECTION_SAFE_BEGIN(head, var, field, last)

#define AST_RWDLLIST_TRAVERSE_BACKWARDS_SAFE_BEGIN AST_DLLIST_TRAVERSE_BACKWARDS_SAFE_BEGIN

/*!
 * \brief Inserts a list entry after the current entry during a backwards traversal. Since
 * this is a backwards traversal, this will insert the entry AFTER the current
 * element. Since this is a backwards traveral, though, this would be BEFORE
 * the current entry in traversal order. Confusing?
 * \param elm This is a pointer to the entry to be inserted.
 * \param field This is the name of the field (declared using AST_DLLIST_ENTRY())
 * used to link entries of this list together.
 *
 * \since 1.6.1
 */
#define AST_DLLIST_INSERT_BEFORE_CURRENT_BACKWARDS(elm, field) \
 AST_DLLIST_INSERT_AFTER_CURRENT(elm, field)

#define AST_RWDLLIST_INSERT_BEFORE_CURRENT_BACKWARDS AST_DLLIST_INSERT_BEFORE_CURRENT_BACKWARDS

/*!
 * \brief Closes a safe loop traversal block.
 * \since 1.6.1
 */
#define AST_DLLIST_TRAVERSE_SAFE_END AST_DLLIST_TRAVERSE_DIRECTION_SAFE_END

#define AST_RWDLLIST_TRAVERSE_SAFE_END AST_DLLIST_TRAVERSE_SAFE_END

/*!
 * \brief Closes a safe loop traversal block.
 * \since 1.6.1
 */
#define AST_DLLIST_TRAVERSE_BACKWARDS_SAFE_END AST_DLLIST_TRAVERSE_DIRECTION_SAFE_END

#define AST_RWDLLIST_TRAVERSE_BACKWARDS_SAFE_END AST_DLLIST_TRAVERSE_BACKWARDS_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.
 * \since 1.6.1
 */
#define AST_DLLIST_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.
 * \since 1.6.1
 */
#define AST_RWDLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_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.
 * \since 1.6.1
 */
#define AST_RWDLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_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_DLLIST_ENTRY())
 * used to link entries of this list together.
 * \since 1.6.1
 */
#define AST_DLLIST_INSERT_AFTER(head, listelm, elm, field) \
 do { \
 typeof((listelm)) __listelm = (listelm); \
 typeof((elm)) __elm = (elm); \
 __elm->field.first = __listelm->field.first; \
 __elm->field.last = __listelm; \
 if ((head)->last == __listelm) { \
 (head)->last = __elm; \
 } else { \
 __listelm->field.first->field.last = __elm; \
 } \
 __listelm->field.first = __elm; \
 } while (0)

#define AST_RWDLLIST_INSERT_AFTER AST_DLLIST_INSERT_AFTER

/*!
 * \brief Inserts a list entry before a given entry.
 * \param head This is a pointer to the list head structure
 * \param listelm This is a pointer to the entry before 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_DLLIST_ENTRY())
 * used to link entries of this list together.
 * \since 1.6.1
 */
#define AST_DLLIST_INSERT_BEFORE(head, listelm, elm, field) \
 do { \
 typeof((listelm)) __listelm = (listelm); \
 typeof((elm)) __elm = (elm); \
 __elm->field.last = __listelm->field.last; \
 __elm->field.first = __listelm; \
 if ((head)->first == __listelm) { \
 (head)->first = __elm; \
 } else { \
 __listelm->field.last->field.first = __elm; \
 } \
 __listelm->field.last = __elm; \
 } while (0)

#define AST_RWDLLIST_INSERT_BEFORE AST_DLLIST_INSERT_BEFORE

/*!
 * \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_DLLIST_ENTRY())
 * used to link entries of this list together.
 * \since 1.6.1
 */
#define AST_DLLIST_INSERT_HEAD(head, elm, field) \
 do { \
 typeof((elm)) __elm = (elm); \
 __elm->field.last = NULL; \
 __elm->field.first = (head)->first; \
 if (!(head)->first) { \
 (head)->last = __elm; \
 } else { \
 (head)->first->field.last = __elm; \
 } \
 (head)->first = __elm; \
 } while (0)

#define AST_RWDLLIST_INSERT_HEAD AST_DLLIST_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_DLLIST_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_DLLIST_INSERT_TAIL is performed).
 * \since 1.6.1
 */
#define AST_DLLIST_INSERT_TAIL(head, elm, field) \
 do { \
 typeof((elm)) __elm = (elm); \
 __elm->field.first = NULL; \
 if (!(head)->first) { \
 __elm->field.last = NULL; \
 (head)->first = __elm; \
 } else { \
 __elm->field.last = (head)->last; \
 (head)->last->field.first = __elm; \
 } \
 (head)->last = __elm; \
 } while (0)

#define AST_RWDLLIST_INSERT_TAIL AST_DLLIST_INSERT_TAIL

/*!
 * \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_DLLIST_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).
 * \since 1.6.1
 */
#define AST_DLLIST_APPEND_DLLIST(head, list, field) \
 do { \
 if (!(head)->first) { \
 (head)->first = (list)->first; \
 (head)->last = (list)->last; \
 } else { \
 (head)->last->field.first = (list)->first; \
 (list)->first->field.last = (head)->last; \
 (head)->last = (list)->last; \
 } \
 (list)->first = NULL; \
 (list)->last = NULL; \
 } while (0)

#define AST_RWDLLIST_APPEND_DLLIST AST_DLLIST_APPEND_DLLIST

/*!
 * \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_DLLIST_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.
 * \since 1.6.1
 */
#define AST_DLLIST_REMOVE_HEAD(head, field) \
 ({ \
 typeof((head)->first) cur = (head)->first; \
 if (cur) { \
 (head)->first = cur->field.first; \
 if ((head)->first) { \
 (head)->first->field.last = NULL; \
 } \
 cur->field.first = NULL; \
 cur->field.last = NULL; \
 if ((head)->last == cur) { \
 (head)->last = NULL; \
 } \
 } \
 cur; \
 })

#define AST_RWDLLIST_REMOVE_HEAD AST_DLLIST_REMOVE_HEAD

/*!
 * \brief Removes and returns the tail node 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_DLLIST_ENTRY())
 * used to link nodes of this list together.
 *
 * Removes the tail entry from the list, and returns a pointer to it.
 * This macro is safe to call on an empty list.
 * \since 11
 */
#define AST_DLLIST_REMOVE_TAIL(head, field) \
 ({ \
 typeof((head)->last) cur = (head)->last; \
 if (cur) { \
 (head)->last = cur->field.last; \
 if ((head)->last) { \
 (head)->last->field.first = NULL; \
 } \
 cur->field.first = NULL; \
 cur->field.last = NULL; \
 if ((head)->first == cur) { \
 (head)->first = NULL; \
 } \
 } \
 cur; \
 })

#define AST_RWDLLIST_REMOVE_TAIL AST_DLLIST_REMOVE_TAIL

/*!
 * \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_DLLIST_ENTRY())
 * used to link entries of this list together.
 * \warning The removed entry is \b not freed.
 * \since 1.6.1
 */
#define AST_DLLIST_REMOVE(head, elm, field) \
 do { \
 typeof((elm)) __elm = (elm); \
 if (__elm) { \
 if (__elm->field.first) { \
 __elm->field.first->field.last = __elm->field.last; \
 } else { \
 (head)->last = __elm->field.last; \
 } \
 if (__elm->field.last) { \
 __elm->field.last->field.first = __elm->field.first; \
 } else { \
 (head)->first = __elm->field.first; \
 } \
 __elm->field.first = NULL; \
 __elm->field.last = NULL; \
 } \
 } while (0)

#define AST_RWDLLIST_REMOVE AST_DLLIST_REMOVE

/*!
 * \brief Removes a specific node from a list if it is in the list.
 * \param head This is a pointer to the list head structure
 * \param elm This is a pointer to the node to be removed.
 * \param field This is the name of the field (declared using AST_DLLIST_ENTRY())
 * used to link nodes of this list together.
 * \warning The removed node is \b not freed.
 * \return elm if the list had elm in it.
 * \return NULL if not.
 * \since 11
 */
#define AST_DLLIST_REMOVE_VERIFY(head, elm, field) \
 ({ \
 typeof((elm)) __res = AST_DLLIST_IS_MEMBER(head, elm, field); \
 AST_DLLIST_REMOVE(head, __res, field); \
 __res; \
 })

#define AST_RWDLLIST_REMOVE_VERIFY AST_DLLIST_REMOVE_VERIFY

#endif /* _ASTERISK_DLINKEDLISTS_H */