ZLIST(3) CZMQ Manual ZLIST(3) NAME zlist - Class for simple generic list container SYNOPSIS // This is a stable class, and may not change except for emergencies. It // is provided in stable builds. // Comparison function e.g. for sorting and removing. typedef int (zlist_compare_fn) ( void *item1, void *item2); // Callback function for zlist_freefn method typedef void (zlist_free_fn) ( void *data); // Create a new list container CZMQ_EXPORT zlist_t * zlist_new (void); // Destroy a list container CZMQ_EXPORT void zlist_destroy (zlist_t **self_p); // 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 * zlist_first (zlist_t *self); // Return the next item. If the list is empty, returns NULL. To move to // the start of the list call zlist_first (). Advances the cursor. CZMQ_EXPORT void * zlist_next (zlist_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 * zlist_last (zlist_t *self); // Return first item in the list, or null, leaves the cursor CZMQ_EXPORT void * zlist_head (zlist_t *self); // Return last item in the list, or null, leaves the cursor CZMQ_EXPORT void * zlist_tail (zlist_t *self); // Return the current item of list. If the list is empty, returns NULL. // Leaves cursor pointing at the current item, or NULL if the list is empty. CZMQ_EXPORT void * zlist_item (zlist_t *self); // Append an item to the end of the list, return 0 if OK or -1 if this // failed for some reason (out of memory). Note that if a duplicator has // been set, this method will also duplicate the item. CZMQ_EXPORT int zlist_append (zlist_t *self, void *item); // Push an item to the start of the list, return 0 if OK or -1 if this // failed for some reason (out of memory). Note that if a duplicator has // been set, this method will also duplicate the item. CZMQ_EXPORT int zlist_push (zlist_t *self, void *item); // Pop the item off the start of the list, if any CZMQ_EXPORT void * zlist_pop (zlist_t *self); // Checks if an item already is present. Uses compare method to determine if // items are equal. If the compare method is NULL the check will only compare // pointers. Returns true if item is present else false. CZMQ_EXPORT bool zlist_exists (zlist_t *self, void *item); // Remove the specified item from the list if present CZMQ_EXPORT void zlist_remove (zlist_t *self, void *item); // Make a copy of list. If the list has autofree set, the copied list will // duplicate all items, which must be strings. Otherwise, the list will hold // pointers back to the items in the original list. If list is null, returns // NULL. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zlist_t * zlist_dup (zlist_t *self); // Purge all items from list CZMQ_EXPORT void zlist_purge (zlist_t *self); // Return number of items in the list CZMQ_EXPORT size_t zlist_size (zlist_t *self); // Sort the list. If the compare function is null, sorts the list by // ascending key value using a straight ASCII comparison. If you specify // a compare function, this decides how items are sorted. The sort is not // stable, so may reorder items with the same keys. The algorithm used is // combsort, a compromise between performance and simplicity. CZMQ_EXPORT void zlist_sort (zlist_t *self, zlist_compare_fn compare); // Set list for automatic item destruction; item values MUST be strings. // By default a list item refers to a value held elsewhere. When you set // this, each time you append or push a list item, zlist will take a copy // of the string value. Then, when you destroy the list, it will free all // item values automatically. If you use any other technique to allocate // list values, you must free them explicitly before destroying the list. // The usual technique is to pop list items and destroy them, until the // list is empty. CZMQ_EXPORT void zlist_autofree (zlist_t *self); // Sets a compare function for this list. The function compares two items. // It returns an integer less than, equal to, or greater than zero if the // first item is found, respectively, to be less than, to match, or be // greater than the second item. // This function is used for sorting, removal and exists checking. CZMQ_EXPORT void zlist_comparefn (zlist_t *self, zlist_compare_fn fn); // Set a free function for the specified list item. When the item is // destroyed, the free function, if any, is called on that item. // Use this when list items are dynamically allocated, to ensure that // you don't have memory leaks. You can pass 'free' or NULL as a free_fn. // Returns the item, or NULL if there is no such item. CZMQ_EXPORT void * zlist_freefn (zlist_t *self, void *item, zlist_free_fn fn, bool at_tail); // Self test of this class. CZMQ_EXPORT void zlist_test (bool verbose); Please add '@interface' section in './../src/zlist.c'. DESCRIPTION Provides a generic container implementing a fast singly-linked list. You can use this to construct multi-dimensional lists, and other structures to- gether with other generic containers like zhash. This is a simple class. For demanding applications we recommend using zlistx. To iterate through a list, use zlist_first to get the first item, then loop while not null, and do zlist_next at the end of each iteration. EXAMPLE From zlist_test method. zlist_t *list = zlist_new (); assert (list); assert (zlist_size (list) == 0); // Three items we'll use as test data // List items are void *, not particularly strings char *cheese = "boursin"; char *bread = "baguette"; char *wine = "bordeaux"; zlist_append (list, cheese); assert (zlist_size (list) == 1); assert ( zlist_exists (list, cheese)); assert (!zlist_exists (list, bread)); assert (!zlist_exists (list, wine)); zlist_append (list, bread); assert (zlist_size (list) == 2); assert ( zlist_exists (list, cheese)); assert ( zlist_exists (list, bread)); assert (!zlist_exists (list, wine)); zlist_append (list, wine); assert (zlist_size (list) == 3); assert ( zlist_exists (list, cheese)); assert ( zlist_exists (list, bread)); assert ( zlist_exists (list, wine)); assert (zlist_head (list) == cheese); assert (zlist_next (list) == cheese); assert (zlist_first (list) == cheese); assert (zlist_tail (list) == wine); assert (zlist_next (list) == bread); assert (zlist_first (list) == cheese); assert (zlist_next (list) == bread); assert (zlist_next (list) == wine); assert (zlist_next (list) == NULL); // After we reach end of list, next wraps around assert (zlist_next (list) == cheese); assert (zlist_size (list) == 3); zlist_remove (list, wine); assert (zlist_size (list) == 2); assert (zlist_first (list) == cheese); zlist_remove (list, cheese); assert (zlist_size (list) == 1); assert (zlist_first (list) == bread); zlist_remove (list, bread); assert (zlist_size (list) == 0); zlist_append (list, cheese); zlist_append (list, bread); assert (zlist_last (list) == bread); zlist_remove (list, bread); assert (zlist_last (list) == cheese); zlist_remove (list, cheese); assert (zlist_last (list) == NULL); zlist_push (list, cheese); assert (zlist_size (list) == 1); assert (zlist_first (list) == cheese); zlist_push (list, bread); assert (zlist_size (list) == 2); assert (zlist_first (list) == bread); assert (zlist_item (list) == bread); zlist_append (list, wine); assert (zlist_size (list) == 3); assert (zlist_first (list) == bread); zlist_t *sub_list = zlist_dup (list); assert (sub_list); assert (zlist_size (sub_list) == 3); zlist_sort (list, NULL); char *item; item = (char *) zlist_pop (list); assert (item == bread); item = (char *) zlist_pop (list); assert (item == wine); item = (char *) zlist_pop (list); assert (item == cheese); assert (zlist_size (list) == 0); assert (zlist_size (sub_list) == 3); zlist_push (list, sub_list); zlist_t *sub_list_2 = zlist_dup (sub_list); zlist_append (list, sub_list_2); assert (zlist_freefn (list, sub_list, &s_zlist_free, false) == sub_list); assert (zlist_freefn (list, sub_list_2, &s_zlist_free, true) == sub_list_2); zlist_destroy (&list); // Test autofree functionality list = zlist_new (); assert (list); zlist_autofree (list); // Set equals function otherwise equals will not work as autofree copies strings zlist_comparefn (list, (zlist_compare_fn *) strcmp); zlist_push (list, bread); zlist_append (list, cheese); assert (zlist_size (list) == 2); zlist_append (list, wine); assert (zlist_exists (list, wine)); zlist_remove (list, wine); assert (!zlist_exists (list, wine)); assert (streq ((const char *) zlist_first (list), bread)); item = (char *) zlist_pop (list); assert (streq (item, bread)); freen (item); item = (char *) zlist_pop (list); assert (streq (item, cheese)); freen (item); zlist_destroy (&list); assert (list == NULL); #if defined (__WINDOWS__) zsys_shutdown(); #endif AUTHORS The czmq manual was written by the authors in the AUTHORS file. RESOURCES Main web site: Report bugs to the email <zeromq-dev@lists.zeromq.org[1]> COPYRIGHT Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: http://czmq.zeromq.org. This Source Code Form is subject to the terms of the Mozilla Public Li- cense, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/. LICENSE included with the czmq distribution. NOTES 1. zeromq-dev@lists.zeromq.org mailto:zeromq-dev@lists.zeromq.org CZMQ 4.2.1 08/27/2026 ZLIST(3)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | AUTHORS | RESOURCES | COPYRIGHT | NOTES
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