[PATCH] include: document list interface.

[Alan Coopersmith]

On 02/21/11 07:29 PM, Peter Hutterer wrote:
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---
>  include/list.h |  182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 180 insertions(+), 2 deletions(-)
> 
> diff --git a/include/list.h b/include/list.h
> index 4ce20a8..3c8c754 100644
> --- a/include/list.h
> +++ b/include/list.h
> @@ -26,11 +26,102 @@
>  #ifndef _LIST_H_
>  #define _LIST_H_
>  
> -/* classic doubly-link circular list */
> +/**
> + * @file Classic doubly-link circular list implementation.
> + *
> + * Example:
> + * We need to keep a list of struct foo in the parent struct bar, i.e. what
> + * we want is something like this.
> + *
> + *     struct bar {
> + *          ...
> + *          struct foo *foos; -----> struct foo {}, struct foo {}, struct foo{}
> + *          ...
> + *     }
> + *
> + * We need one list head in bar and a list element in all foos (both are of
> + * data type 'struct list').
> + *
> + *     struct bar {
> + *          ...
> + *          struct list foos;
> + *          ...
> + *     }
> + *
> + *     struct foo {
> + *          ...
> + *          struct list entry;
> + *          ...
> + *     }
> + *
> + * Now we initilise the list head:

initilise -> initialize

> + *     struct bar bar;
> + *     ...
> + *     list_init(&bar.foos);
> + *
> + * Then we create the first element and add it to this list:
> + *
> + *     struct foo *foo = malloc(...);
> + *     ....
> + *     list_add(&foo->entry, &bar.foos);
> + *
> + * Repeat the above for each element you want to add to the list. Deleting
> + * works with the element itself.
> + *      list_del(&foo->entry);
> + *      free(foo);
> + *
> + * Note: calling list_del(&bar.foos) will set in bar.foos to an empty
> + * list again.

Seems like the word "in" should be deleted from that sentence.

> + * Looping through the list requires a 'struct foo' as iterator and the
> + * name of the field the subnodes use.

Looks like this should this say:
	a 'struct foo' as iterator, the head of the list, and the
	name of the field the subnodes use.
to parallel the three arguments shown:

> + * struct foo *iterator;
> + * list_for_each_entry(iterator, &bar.foos, entry) {
> + *      if (iterator->something == ...)
> + *             ...
> + * }
> + *
> + * Note: You must not call list_del() on the iterator if you continue the
> + * loop. You need to run the safe for-each loop instead:
> + *
> + * struct foo *iterator, *next;
> + * list_for_each_entry(iterator, next, &bar.foos, entry) {
> + *      if (...)
> + *              list_del(&iterator->entry);
> + * }


Shouldn't that be list_for_each_entry_safe ?

> +
> +/**
> + * The linkage struct for list nodes. This struct must be part of your
> + * to-be-linked struct.
> + *
> + * Example:
> + * struct foo {
> + *      int a;
> + *      void *b;
> + *      struct list *mylist;
> + * }
> + *
> + * Position and name of the struct list field is irrelevant.
> + * There are no requirements that elements of a list are of the same type.
> + * There are no requirements for a list head, any struct list can be a list
> + * head.
> + */
>  struct list {
>      struct list *next, *prev;
>  };
>  
> +/**
> + * Initialize the list as an empty list.
> + *
> + * Example:
> + * list_init(&foo->mylist);
> + *
> + * @param The list to initialized.
> + */
>  static void
>  list_init(struct list *list)
>  {
> @@ -48,6 +139,20 @@ __list_add(struct list *entry,
>      prev->next = entry;
>  }
>  
> +/**
> + * Insert a new element after the given list head.
> + * The list changes from:
> + *      head → some element → ...
> + * to
> + *      head → new element → older element → ...
> + *
> + * Example:
> + * struct foo *newfoo = malloc(...);
> + * list_add(&newfoo->mylist, &foo->mylist);
> + *
> + * @param entry The new element to prepend to the list.
> + * @param head The existing list.
> + */
>  static inline void
>  list_add(struct list *entry, struct list *head)
>  {
> @@ -61,6 +166,20 @@ __list_del(struct list *prev, struct list *next)
>      prev->next = next;
>  }
>  
> +/**
> + * Remove the element from the list it is in. Using this function will reset
> + * the pointers to-fro this element so it is removed from the list. It does

fro -> from ?

> + * NOT free the element itself or manipulate it otherwise.
> + *
> + * Using list_del on a pure list head (like in the example at the top of
> + * this file) will NOT remove the first element from
> + * the list but rather reset the list as empty list.
> + *
> + * Example:
> + * list_del(&newfoo->mylist);
> + *
> + * @param entry The element to remove.
> + */
>  static inline void
>  list_del(struct list *entry)
>  {
> @@ -68,32 +187,91 @@ list_del(struct list *entry)
>      list_init(entry);
>  }
>  
> +/**
> + * Check if the list is empty.
> + *
> + * Example:
> + * list_is_empty(&foo->mylist);
> + *
> + * @return True if the list contains one or more elements or False otherwise.
> + */
>  static inline Bool
>  list_is_empty(struct list *head)
>  {
>      return head->next == head;
>  }
>  
> +/**
> + * Returns a pointer to the container of this list element.
> + *
> + * Example:
> + * struct foo* f;
> + * f = container_of(&foo->mylist, struct foo, mylist);
> + * assert(f == foo);
> + *
> + * @param ptr Pointer to the struct list.
> + * @param type Data type of the list element.
> + * @param member Member name of the struct list field in the list element.
> + * @return A pointer to the data struct containing the list head.
> + */
>  #ifndef container_of
>  #define container_of(ptr, type, member) \
>      (type *)((char *)(ptr) - (char *) &((type *)0)->member)
>  #endif
>  
> +/**
> + * Alias of container_of
> + */
>  #define list_entry(ptr, type, member) \
>      container_of(ptr, type, member)
>  
> +/**
> + * Retrieve the first list entry for the given list pointer.
> + *
> + * Example:
> + * struct foo *first;
> + * first = list_first_entry(&foo->mylist, struct foo, mylist);
> + *
> + * @param ptr The list head
> + * @param type Data type of the list element to retrieve
> + * @param member Member name of the struct list field in the list element.
> + * @return A pointer to the first list element.
> + */
>  #define list_first_entry(ptr, type, member) \
>      list_entry((ptr)->next, type, member)
>  
>  #define __container_of(ptr, sample, member)				\
>      (void *)((char *)(ptr)						\
>  	     - ((char *)&(sample)->member - (char *)(sample)))
> -
> +/**
> + * Loop through the list given by head and set pos to struct in the list.
> + *
> + * Example:
> + * struct foo *iterator;
> + * list_for_each_entry(iterator, &foo->mylist, mylist) {
> + *      [modify iterator]
> + * }
> + *
> + * This macro is not safe for node deletion. Use list_for_each_entry_safe
> + * instead.
> + *
> + * @param pos Iterator variable of the type of the list elements.
> + * @param head List head
> + * @param member Member name of the struct list in the list elements.
> + *
> + */
>  #define list_for_each_entry(pos, head, member)				\
>      for (pos = __container_of((head)->next, pos, member);		\
>  	 &pos->member != (head);					\
>  	 pos = __container_of(pos->member.next, pos, member))
>  
> +/**
> + * Loop through the list, keeping a backup pointer to the element. This
> + * macro allows for the deletion of a list element while looping throught he

throught he -> through the

> + * list.
> + *
> + * See list_for_each_entry for more details.
> + */
>  #define list_for_each_entry_safe(pos, tmp, head, member)		\
>      for (pos = __container_of((head)->next, pos, member),		\
>  	 tmp = __container_of(pos->member.next, pos, member);		\


-- 
	-Alan Coopersmith-        alan.coopersmith at oracle.com
	 Oracle Solaris Platform Engineering: X Window System