zlistx(3)
=========

NAME
----
zlistx - extended generic list container

SYNOPSIS
--------
----
//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.
// Destroy an item
typedef void (zlistx_destructor_fn) (
    void **item);

// Duplicate an item
typedef void * (zlistx_duplicator_fn) (
    const void *item);

// Compare two items, for sorting
typedef int (zlistx_comparator_fn) (
    const void *item1, const void *item2);

//  Create a new, empty list.
CZMQ_EXPORT zlistx_t *
    zlistx_new (void);

//  Destroy a list. If an item destructor was specified, all items in the
//  list are automatically destroyed as well.                            
CZMQ_EXPORT void
    zlistx_destroy (zlistx_t **self_p);

//  Add an item to the head of the list. Calls the item duplicator, if any,
//  on the item. Resets cursor to list head. Returns an item handle on     
//  success, NULL if memory was exhausted.                                 
CZMQ_EXPORT void *
    zlistx_add_start (zlistx_t *self, void *item);

//  Add an item to the tail of the list. Calls the item duplicator, if any,
//  on the item. Resets cursor to list head. Returns an item handle on     
//  success, NULL if memory was exhausted.                                 
CZMQ_EXPORT void *
    zlistx_add_end (zlistx_t *self, void *item);

//  Return the number of items in the list
CZMQ_EXPORT size_t
    zlistx_size (zlistx_t *self);

//  Return first item in the list, or null, leaves the cursor
CZMQ_EXPORT void *
    zlistx_head (zlistx_t *self);

//  Return last item in the list, or null, leaves the cursor
CZMQ_EXPORT void *
    zlistx_tail (zlistx_t *self);

//  Return the item at the head of list. If the list is empty, returns NULL.
//  Leaves cursor pointing at the head item, or NULL if the list is empty.  
CZMQ_EXPORT void *
    zlistx_first (zlistx_t *self);

//  Return the next item. At the end of the list (or in an empty list),     
//  returns NULL. Use repeated zlistx_next () calls to work through the list
//  from zlistx_first (). First time, acts as zlistx_first().               
CZMQ_EXPORT void *
    zlistx_next (zlistx_t *self);

//  Return the previous item. At the start of the list (or in an empty list),
//  returns NULL. Use repeated zlistx_prev () calls to work through the list 
//  backwards from zlistx_last (). First time, acts as zlistx_last().        
CZMQ_EXPORT void *
    zlistx_prev (zlistx_t *self);

//  Return the item at the tail of list. If the list is empty, returns NULL.
//  Leaves cursor pointing at the tail item, or NULL if the list is empty.  
CZMQ_EXPORT void *
    zlistx_last (zlistx_t *self);

//  Returns the value of the item at the cursor, or NULL if the cursor is
//  not pointing to an item.                                             
CZMQ_EXPORT void *
    zlistx_item (zlistx_t *self);

//  Returns the handle of the item at the cursor, or NULL if the cursor is
//  not pointing to an item.                                              
CZMQ_EXPORT void *
    zlistx_cursor (zlistx_t *self);

//  Returns the item associated with the given list handle, or NULL if passed     
//  in handle is NULL. Asserts that the passed in handle points to a list element.
CZMQ_EXPORT void *
    zlistx_handle_item (void *handle);

//  Find an item in the list, searching from the start. Uses the item     
//  comparator, if any, else compares item values directly. Returns the   
//  item handle found, or NULL. Sets the cursor to the found item, if any.
CZMQ_EXPORT void *
    zlistx_find (zlistx_t *self, void *item);

//  Detach an item from the list, using its handle. The item is not modified, 
//  and the caller is responsible for destroying it if necessary. If handle is
//  null, detaches the first item on the list. Returns item that was detached,
//  or null if none was. If cursor was at item, moves cursor to previous item,
//  so you can detach items while iterating forwards through a list.          
CZMQ_EXPORT void *
    zlistx_detach (zlistx_t *self, void *handle);

//  Detach item at the cursor, if any, from the list. The item is not modified,
//  and the caller is responsible for destroying it as necessary. Returns item 
//  that was detached, or null if none was. Moves cursor to previous item, so  
//  you can detach items while iterating forwards through a list.              
CZMQ_EXPORT void *
    zlistx_detach_cur (zlistx_t *self);

//  Delete an item, using its handle. Calls the item destructor is any is 
//  set. If handle is null, deletes the first item on the list. Returns 0 
//  if an item was deleted, -1 if not. If cursor was at item, moves cursor
//  to previous item, so you can delete items while iterating forwards    
//  through a list.                                                       
CZMQ_EXPORT int
    zlistx_delete (zlistx_t *self, void *handle);

//  Move an item to the start of the list, via its handle.
CZMQ_EXPORT void
    zlistx_move_start (zlistx_t *self, void *handle);

//  Move an item to the end of the list, via its handle.
CZMQ_EXPORT void
    zlistx_move_end (zlistx_t *self, void *handle);

//  Remove all items from the list, and destroy them if the item destructor
//  is set.                                                                
CZMQ_EXPORT void
    zlistx_purge (zlistx_t *self);

//  Sort the list. If an item comparator was set, calls that to compare    
//  items, otherwise compares on item value. The sort is not stable, so may
//  reorder equal items.                                                   
CZMQ_EXPORT void
    zlistx_sort (zlistx_t *self);

//  Create a new node and insert it into a sorted list. Calls the item        
//  duplicator, if any, on the item. If low_value is true, starts searching   
//  from the start of the list, otherwise searches from the end. Use the item 
//  comparator, if any, to find where to place the new node. Returns a handle 
//  to the new node, or NULL if memory was exhausted. Resets the cursor to the
//  list head.                                                                
CZMQ_EXPORT void *
    zlistx_insert (zlistx_t *self, void *item, bool low_value);

//  Move an item, specified by handle, into position in a sorted list. Uses 
//  the item comparator, if any, to determine the new location. If low_value
//  is true, starts searching from the start of the list, otherwise searches
//  from the end.                                                           
CZMQ_EXPORT void
    zlistx_reorder (zlistx_t *self, void *handle, bool low_value);

//  Make a copy of the list; items are duplicated if you set a duplicator
//  for the list, otherwise not. Copying a null reference returns a null 
//  reference.                                                           
CZMQ_EXPORT zlistx_t *
    zlistx_dup (zlistx_t *self);

//  Set a user-defined deallocator for list items; by default items are not
//  freed when the list is destroyed.                                      
CZMQ_EXPORT void
    zlistx_set_destructor (zlistx_t *self, zlistx_destructor_fn destructor);

//  Set a user-defined duplicator for list items; by default items are not
//  copied when the list is duplicated.                                   
CZMQ_EXPORT void
    zlistx_set_duplicator (zlistx_t *self, zlistx_duplicator_fn duplicator);

//  Set a user-defined comparator for zlistx_find and zlistx_sort; the method 
//  must return -1, 0, or 1 depending on whether item1 is less than, equal to,
//  or greater than, item2.                                                   
CZMQ_EXPORT void
    zlistx_set_comparator (zlistx_t *self, zlistx_comparator_fn comparator);

//  Self test of this class.
CZMQ_EXPORT void
    zlistx_test (bool verbose);

----

DESCRIPTION
-----------

Provides a generic doubly-linked list container. This container provides
hooks for duplicator, comparator, and destructor functions. These tie
into CZMQ and standard C semantics, so e.g. for string items you can
use strdup, strcmp, and zstr_free. To store custom objects, define your
own duplicator and comparator, and use the standard object destructor.

This is a reworking of the simpler zlist container. It is faster to
insert and delete items anywhere in the list, and to keep ordered lists.

EXAMPLE
-------
.From zlistx_test method
----
zlistx_t *list = zlistx_new ();
assert (list);
assert (zlistx_size (list) == 0);

//  Test operations on an empty list
assert (zlistx_first (list) == NULL);
assert (zlistx_last (list) == NULL);
assert (zlistx_next (list) == NULL);
assert (zlistx_prev (list) == NULL);
assert (zlistx_find (list, "hello") == NULL);
assert (zlistx_delete (list, NULL) == -1);
assert (zlistx_detach (list, NULL) == NULL);
assert (zlistx_delete (list, NULL) == -1);
assert (zlistx_detach (list, NULL) == NULL);
zlistx_purge (list);
zlistx_sort (list);

//  Use item handlers
zlistx_set_destructor (list, (zlistx_destructor_fn *) zstr_free);
zlistx_set_duplicator (list, (zlistx_duplicator_fn *) strdup);
zlistx_set_comparator (list, (zlistx_comparator_fn *) strcmp);

//  Try simple insert/sort/delete/next
assert (zlistx_next (list) == NULL);
zlistx_add_end (list, "world");
assert (streq ((char *) zlistx_next (list), "world"));
zlistx_add_end (list, "hello");
assert (streq ((char *) zlistx_prev (list), "hello"));
zlistx_sort (list);
assert (zlistx_size (list) == 2);
void *handle = zlistx_find (list, "hello");
char *item1 = (char *) zlistx_item (list);
char *item2 = (char *) zlistx_handle_item (handle);
assert (item1 == item2);
assert (streq (item1, "hello"));
zlistx_delete (list, handle);
assert (zlistx_size (list) == 1);
char *string = (char *) zlistx_detach (list, NULL);
assert (streq (string, "world"));
free (string);
assert (zlistx_size (list) == 0);

//  Check next/back work
//  Now populate the list with items
zlistx_add_start (list, "five");
zlistx_add_end   (list, "six");
zlistx_add_start (list, "four");
zlistx_add_end   (list, "seven");
zlistx_add_start (list, "three");
zlistx_add_end   (list, "eight");
zlistx_add_start (list, "two");
zlistx_add_end   (list, "nine");
zlistx_add_start (list, "one");
zlistx_add_end   (list, "ten");

//  Test our navigation skills
assert (zlistx_size (list) == 10);
assert (streq ((char *) zlistx_last (list), "ten"));
assert (streq ((char *) zlistx_prev (list), "nine"));
assert (streq ((char *) zlistx_prev (list), "eight"));
assert (streq ((char *) zlistx_prev (list), "seven"));
assert (streq ((char *) zlistx_prev (list), "six"));
assert (streq ((char *) zlistx_prev (list), "five"));
assert (streq ((char *) zlistx_first (list), "one"));
assert (streq ((char *) zlistx_next (list), "two"));
assert (streq ((char *) zlistx_next (list), "three"));
assert (streq ((char *) zlistx_next (list), "four"));

//  Sort by alphabetical order
zlistx_sort (list);
assert (streq ((char *) zlistx_first (list), "eight"));
assert (streq ((char *) zlistx_last (list), "two"));

//  Moving items around
handle = zlistx_find (list, "six");
zlistx_move_start (list, handle);
assert (streq ((char *) zlistx_first (list), "six"));
zlistx_move_end (list, handle);
assert (streq ((char *) zlistx_last (list), "six"));
zlistx_sort (list);
assert (streq ((char *) zlistx_last (list), "two"));

//  Copying a list
zlistx_t *copy = zlistx_dup (list);
assert (copy);
assert (zlistx_size (copy) == 10);
assert (streq ((char *) zlistx_first (copy), "eight"));
assert (streq ((char *) zlistx_last (copy), "two"));
zlistx_destroy (&copy);

//  Delete items while iterating
string = (char *) zlistx_first (list);
assert (streq (string, "eight"));
string = (char *) zlistx_next (list);
assert (streq (string, "five"));
zlistx_delete (list, zlistx_cursor (list));
string = (char *) zlistx_next (list);
assert (streq (string, "four"));

zlistx_purge (list);
zlistx_destroy (&list);
----
