[PATCH v2] include: document list interface.

[Peter Hutterer]

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
Changes since v1:
typos pointed out by Alan
- initilise -> initialize
- "Seems like the word "in" should be deleted from that sentence."
  successfully found the sentence to deleted the work "in" from and executed
  said task. it shall not be missed.
- to-fro → to/from
- list_for_each_entry_safe example fixed to actually use
  list_for_each_entry_safe
- throught he -> through the


 include/list.h |  182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 180 insertions(+), 2 deletions(-)

diff --git a/include/list.h b/include/list.h
index 4ce20a8..5933b97 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 initialize the list head:
+ *
+ *     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 bar.foos to an empty
+ * list again.
+ *
+ * Looping through the list requires a 'struct foo' as iterator and the
+ * name of the field the subnodes use.
+ *
+ * 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_safe(iterator, next, &bar.foos, entry) {
+ *      if (...)
+ *              list_del(&iterator->entry);
+ * }
+ *
+ */
+
+/**
+ * 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/from this element so it is removed from the list. It does
+ * 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 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);		\
-- 
1.7.4