ucx/cx/list.h

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
/**
 * @file list.h
 * @brief Interface for list implementations.
 * @author Mike Becker
 * @author Olaf Wintermann
 * @copyright 2-Clause BSD License
 */

#ifndef UCX_LIST_H
#define UCX_LIST_H

#include "common.h"
#include "collection.h"

#include <assert.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * List class type.
 */
typedef struct cx_list_class_s cx_list_class;

/**
 * Structure for holding the base data of a list.
 */
struct cx_list_s {
    /**
     * Common members for collections.
     */
    CX_COLLECTION_BASE;
    /**
     * The list class definition.
     */
    const cx_list_class *cl;
    /**
     * The actual implementation in case the list class is delegating.
     */
    const cx_list_class *climpl;
};

/**
 * The class definition for arbitrary lists.
 */
struct cx_list_class_s {
    /**
     * Destructor function.
     *
     * Implementations SHALL invoke the content destructor functions if provided
     * and SHALL deallocate the entire list memory.
     */
    void (*deallocate)(struct cx_list_s *list);

    /**
     * Member function for inserting a single element.
     * The data pointer may be @c NULL, in which case the function shall only allocate memory.
     * Returns a pointer to the allocated memory or @c NULL if allocation fails.
     */
    void *(*insert_element)(
            struct cx_list_s *list,
            size_t index,
            const void *data
    );

    /**
     * Member function for inserting multiple elements.
     *
     * @see cx_list_default_insert_array()
     */
    size_t (*insert_array)(
            struct cx_list_s *list,
            size_t index,
            const void *data,
            size_t n
    );

    /**
     * Member function for inserting sorted elements into a sorted list.
     *
     * @see cx_list_default_insert_sorted()
     */
    size_t (*insert_sorted)(
            struct cx_list_s *list,
            const void *sorted_data,
            size_t n
    );

    /**
     * Member function for inserting multiple elements if they do not exist.
     *
     * @see cx_list_default_insert_unique()
     */
    size_t (*insert_unique)(
            struct cx_list_s *list,
            const void *sorted_data,
            size_t n
    );

    /**
     * Member function for inserting an element relative to an iterator position.
     */
    int (*insert_iter)(
            struct cx_iterator_s *iter,
            const void *elem,
            int prepend
    );

    /**
     * Member function for removing elements.
     *
     * Implementations SHALL check if @p targetbuf is set and copy the elements
     * to the buffer without invoking any destructor.
     * When @p targetbuf is not set, the destructors SHALL be invoked.
     *
     * The function SHALL return the actual number of elements removed, which
     * might be lower than @p num when going out of bounds.
     */
    size_t (*remove)(
            struct cx_list_s *list,
            size_t index,
            size_t num,
            void *targetbuf
    );

    /**
     * Member function for removing all elements.
     */
    void (*clear)(struct cx_list_s *list);

    /**
     * Member function for swapping two elements.
     *
     * @see cx_list_default_swap()
     */
    int (*swap)(
            struct cx_list_s *list,
            size_t i,
            size_t j
    );

    /**
     * Member function for element lookup.
     */
    void *(*at)(
            const struct cx_list_s *list,
            size_t index
    );

    /**
     * Member function for finding and optionally removing an element.
     */
    size_t (*find_remove)(
            struct cx_list_s *list,
            const void *elem,
            bool remove
    );

    /**
     * Member function for sorting the list.
     *
     * @see cx_list_default_sort()
     */
    void (*sort)(struct cx_list_s *list);

    /**
     * Optional member function for comparing this list
     * to another list of the same type.
     * If set to @c NULL, the comparison won't be optimized.
     */
    int (*compare)(
            const struct cx_list_s *list,
            const struct cx_list_s *other
    );

    /**
     * Member function for reversing the order of the items.
     */
    void (*reverse)(struct cx_list_s *list);

    /**
     * Member function for returning an iterator pointing to the specified index.
     */
    struct cx_iterator_s (*iterator)(
            const struct cx_list_s *list,
            size_t index,
            bool backward
    );
};

/**
 * Common type for all list implementations.
 */
typedef struct cx_list_s CxList;

/**
 * A shared instance of an empty list.
 *
 * Writing to that list is not allowed.
 *
 * You can use this as a placeholder for initializing CxList pointers
 * for which you do not want to reserve memory right from the beginning.
 */
cx_attr_export
extern CxList *const cxEmptyList;

/**
 * Default implementation of an array insert.
 *
 * This function uses the element insert function for each element of the array.
 *
 * Use this in your own list class if you do not want to implement an optimized
 * version for your list.
 *
 * @param list the list
 * @param index the index where to insert the data
 * @param data a pointer to the array of data to insert
 * @param n the number of elements to insert
 * @return the number of elements actually inserted
 */
cx_attr_nonnull
cx_attr_export
size_t cx_list_default_insert_array(
        struct cx_list_s *list,
        size_t index,
        const void *data,
        size_t n
);

/**
 * Default implementation of a sorted insert.
 *
 * This function uses the array insert function to insert consecutive groups
 * of sorted data.
 *
 * The source data @em must already be sorted wrt. the list's compare function.
 *
 * Use this in your own list class if you do not want to implement an optimized
 * version for your list.
 *
 * @param list the list
 * @param sorted_data a pointer to the array of pre-sorted data to insert
 * @param n the number of elements to insert
 * @return the number of elements actually inserted
 */
cx_attr_nonnull
cx_attr_export
size_t cx_list_default_insert_sorted(
        struct cx_list_s *list,
        const void *sorted_data,
        size_t n
);

/**
 * Default implementation of an array insert where only elements are inserted when they don't exist in the list.
 *
 * This function is similar to cx_list_default_insert_sorted(), except it skips elements that are already in the list.
 *
 * @note The return value of this function denotes the number of elements from the @p sorted_data that are definitely
 * contained in the list after completing the call. It is @em not the number of elements that were newly inserted.
 * That means, when no error occurred, the return value should be @p n.
 *
 * Use this in your own list class if you do not want to implement an optimized version for your list.
 *
 * @param list the list
 * @param sorted_data a pointer to the array of pre-sorted data to insert
 * @param n the number of elements to insert
 * @return the number of elements from the @p sorted_data that are definitely present in the list after this call
 */
cx_attr_nonnull
cx_attr_export
size_t cx_list_default_insert_unique(
        struct cx_list_s *list,
        const void *sorted_data,
        size_t n
);

/**
 * Default unoptimized sort implementation.
 *
 * This function will copy all data to an array, sort the array with standard
 * qsort, and then copy the data back to the list memory.
 *
 * Use this in your own list class if you do not want to implement an optimized
 * version for your list.
 *
 * @param list the list that shall be sorted
 */
cx_attr_nonnull
cx_attr_export
void cx_list_default_sort(struct cx_list_s *list);

/**
 * Default unoptimized swap implementation.
 *
 * Use this in your own list class if you do not want to implement an optimized
 * version for your list.
 *
 * @param list the list in which to swap
 * @param i index of one element
 * @param j index of the other element
 * @retval zero success
 * @retval non-zero when indices are out of bounds or memory
 * allocation for the temporary buffer fails
 */
cx_attr_nonnull
cx_attr_export
int cx_list_default_swap(struct cx_list_s *list, size_t i, size_t j);

/**
 * Initializes a list struct.
 *
 * Only use this function if you are creating your own list implementation.
 * The purpose of this function is to be called in the initialization code
 * of your list to set certain members correctly.
 *
 * This is particularly important when you want your list to support
 * #CX_STORE_POINTERS as @p elem_size. This function will wrap the list
 * class accordingly and make sure that you can implement your list as if
 * it was only storing objects, and the wrapper will automatically enable
 * the feature of storing pointers.
 *
 * @par Example
 *
 * @code
 * CxList *myCustomListCreate(
 *         const CxAllocator *allocator,
 *         cx_compare_func comparator,
 *         size_t elem_size
 * ) {
 *     if (allocator == NULL) {
 *         allocator = cxDefaultAllocator;
 *     }
 *
 *     MyCustomList *list = cxCalloc(allocator, 1, sizeof(MyCustomList));
 *     if (list == NULL) return NULL;
 *
 *     // initialize
 *     cx_list_init((CxList*)list, &my_custom_list_class,
 *             allocator, comparator, elem_size);
 *
 *     // ... some more custom stuff ...
 *
 *     return (CxList *) list;
 * }
 * @endcode
 *
 * @param list the list to initialize
 * @param cl the list class
 * @param allocator the allocator for the elements
 * @param comparator a compare function for the elements
 * @param elem_size the size of one element
 */
cx_attr_nonnull_arg(1, 2, 3)
cx_attr_export
void cx_list_init(
    struct cx_list_s *list,
    struct cx_list_class_s *cl,
    const struct cx_allocator_s *allocator,
    cx_compare_func comparator,
    size_t elem_size
);

/**
 * Returns the number of elements currently stored in the list.
 *
 * @param list the list
 * @return the number of currently stored elements
 */
cx_attr_nonnull
static inline size_t cxListSize(const CxList *list) {
    return list->collection.size;
}

/**
 * Adds an item to the end of the list.
 *
 * @param list the list
 * @param elem a pointer to the element to add
 * @retval zero success
 * @retval non-zero memory allocation failure
 * @see cxListAddArray()
 * @see cxListEmplace()
 */
cx_attr_nonnull
static inline int cxListAdd(
        CxList *list,
        const void *elem
) {
    list->collection.sorted = false;
    return list->cl->insert_element(list, list->collection.size, elem) == NULL;
}

/**
 * Adds multiple items to the end of the list.
 *
 * This method is more efficient than invoking cxListAdd() multiple times.
 *
 * If there is not enough memory to add all elements, the returned value is
 * less than @p n.
 *
 * If this list is storing pointers instead of objects, @p array is expected to
 * be an array of pointers.
 *
 * @param list the list
 * @param array a pointer to the elements to add
 * @param n the number of elements to add
 * @return the number of added elements
 */
cx_attr_nonnull
static inline size_t cxListAddArray(
        CxList *list,
        const void *array,
        size_t n
) {
    list->collection.sorted = false;
    return list->cl->insert_array(list, list->collection.size, array, n);
}

/**
 * Inserts an item at the specified index.
 *
 * If the @p index equals the list @c size, this is effectively cxListAdd().
 *
 * @param list the list
 * @param index the index the element shall have
 * @param elem a pointer to the element to add
 * @retval zero success
 * @retval non-zero memory allocation failure or the index is out of bounds
 * @see cxListInsertAfter()
 * @see cxListInsertBefore()
 * @see cxListEmplaceAt()
 */
cx_attr_nonnull
static inline int cxListInsert(
        CxList *list,
        size_t index,
        const void *elem
) {
    list->collection.sorted = false;
    return list->cl->insert_element(list, index, elem) == NULL;
}

/**
 * Allocates memory for an element at the specified index and returns a pointer to that memory.
 *
 * @remark When the list is storing pointers, this will return a @c void**.
 *
 * @param list the list
 * @param index the index where to emplace the element
 * @return a pointer to the allocated memory; @c NULL when the operation fails, or the index is out-of-bounds
 * @see cxListEmplace()
 * @see cxListInsert()
 */
cx_attr_nonnull
static inline void *cxListEmplaceAt(CxList *list, size_t index) {
    list->collection.sorted = false;
    return list->cl->insert_element(list, index, NULL);
}


/**
 * Allocates memory for an element at the end of the list and returns a pointer to that memory.
 *
 * @remark When the list is storing pointers, this will return a @c void**.
 *
 * @param list the list
 * @return a pointer to the allocated memory; @c NULL when the operation fails, or the index is out-of-bounds
 * @see cxListEmplaceAt()
 * @see cxListAdd()
 */
cx_attr_nonnull
static inline void *cxListEmplace(CxList *list) {
    list->collection.sorted = false;
    return list->cl->insert_element(list, list->collection.size, NULL);
}

/**
 * Inserts an item into a sorted list.
 *
 * If the list is not sorted already, the behavior is undefined.
 *
 * @param list the list
 * @param elem a pointer to the element to add
 * @retval zero success
 * @retval non-zero memory allocation failure
 */
cx_attr_nonnull
static inline int cxListInsertSorted(
        CxList *list,
        const void *elem
) {
    assert(list->collection.sorted || list->collection.size == 0);
    list->collection.sorted = true;
    const void *data = list->collection.store_pointer ? &elem : elem;
    return list->cl->insert_sorted(list, data, 1) == 0;
}

/**
 * Inserts an item into a sorted list if it does not exist.
 *
 * If the list is not sorted already, the behavior is undefined.
 *
 * @param list the list
 * @param elem a pointer to the element to add
 * @retval zero success (also when the element was already in the list)
 * @retval non-zero memory allocation failure
 */
cx_attr_nonnull
static inline int cxListInsertUnique(
        CxList *list,
        const void *elem
) {
    assert(list->collection.sorted || list->collection.size == 0);
    list->collection.sorted = true;
    const void *data = list->collection.store_pointer ? &elem : elem;
    return list->cl->insert_unique(list, data, 1) == 0;
}

/**
 * Inserts multiple items to the list at the specified index.
 * If the @p index equals the list size, this is effectively cxListAddArray().
 *
 * This method is usually more efficient than invoking cxListInsert()
 * multiple times.
 *
 * If there is not enough memory to add all elements, the returned value is
 * less than @p n.
 *
 * If this list is storing pointers instead of objects, @p array is expected to
 * be an array of pointers.
 *
 * @param list the list
 * @param index the index where to add the elements
 * @param array a pointer to the elements to add
 * @param n the number of elements to add
 * @return the number of added elements
 */
cx_attr_nonnull
static inline size_t cxListInsertArray(
        CxList *list,
        size_t index,
        const void *array,
        size_t n
) {
    list->collection.sorted = false;
    return list->cl->insert_array(list, index, array, n);
}

/**
 * Inserts a sorted array into a sorted list.
 *
 * This method is usually more efficient than inserting each element separately
 * because consecutive chunks of sorted data are inserted in one pass.
 *
 * If there is not enough memory to add all elements, the returned value is
 * less than @p n.
 *
 * If this list is storing pointers instead of objects, @p array is expected to
 * be an array of pointers.
 *
 * If the list is not sorted already, the behavior is undefined.
 *
 * @param list the list
 * @param array a pointer to the elements to add
 * @param n the number of elements to add
 * @return the number of added elements
 */
cx_attr_nonnull
static inline size_t cxListInsertSortedArray(
        CxList *list,
        const void *array,
        size_t n
) {
    assert(list->collection.sorted || list->collection.size == 0);
    list->collection.sorted = true;
    return list->cl->insert_sorted(list, array, n);
}

/**
 * Inserts a sorted array into a sorted list, skipping duplicates.
 *
 * This method is usually more efficient than inserting each element separately
 * because consecutive chunks of sorted data are inserted in one pass.
 *
 * If there is not enough memory to add all elements, the returned value is
 * less than @p n.
 *
 * @note The return value of this function denotes the number of elements
 * from the @p sorted_data that are definitely contained in the list after
 * completing the call. It is @em not the number of elements that were newly
 * inserted. That means, when no error occurred, the return value should
 * be @p n.
 *
 * If this list is storing pointers instead of objects @p array is expected to
 * be an array of pointers.
 *
 * If the list is not sorted already, the behavior is undefined.
 * This is also the case when the @p array is not sorted.
 *
 * @param list the list
 * @param array a pointer to the elements to add
 * @param n the number of elements to add
 * @return the number of added elements
 *
 * @return the number of elements from the @p sorted_data that are definitely present in the list after this call
 */
cx_attr_nonnull
static inline size_t cxListInsertUniqueArray(
        CxList *list,
        const void *array,
        size_t n
) {
    assert(list->collection.sorted || list->collection.size == 0);
    list->collection.sorted = true;
    return list->cl->insert_unique(list, array, n);
}

/**
 * Inserts an element after the current location of the specified iterator.
 *
 * The used iterator remains operational, but all other active iterators should
 * be considered invalidated.
 *
 * If @p iter is not a list iterator, the behavior is undefined.
 * If @p iter is a past-the-end iterator, the new element gets appended to the list.
 *
 * @param iter an iterator
 * @param elem the element to insert
 * @retval zero success
 * @retval non-zero memory allocation failure
 * @see cxListInsert()
 * @see cxListInsertBefore()
 */
cx_attr_nonnull
static inline int cxListInsertAfter(
        CxIterator *iter,
        const void *elem
) {
    CxList* list = (CxList*)iter->src_handle.m;
    list->collection.sorted = false;
    return list->cl->insert_iter(iter, elem, 0);
}

/**
 * Inserts an element before the current location of the specified iterator.
 *
 * The used iterator remains operational, but all other active iterators should
 * be considered invalidated.
 *
 * If @p iter is not a list iterator, the behavior is undefined.
 * If @p iter is a past-the-end iterator, the new element gets appended to the list.
 *
 * @param iter an iterator
 * @param elem the element to insert
 * @retval zero success
 * @retval non-zero memory allocation failure
 * @see cxListInsert()
 * @see cxListInsertAfter()
 */
cx_attr_nonnull
static inline int cxListInsertBefore(
        CxIterator *iter,
        const void *elem
) {
    CxList* list = (CxList*)iter->src_handle.m;
    list->collection.sorted = false;
    return list->cl->insert_iter(iter, elem, 1);
}

/**
 * Removes the element at the specified index.
 *
 * If an element destructor function is specified, it is called before
 * removing the element.
 *
 * @param list the list
 * @param index the index of the element
 * @retval zero success
 * @retval non-zero index out of bounds
 */
cx_attr_nonnull
static inline int cxListRemove(
        CxList *list,
        size_t index
) {
    return list->cl->remove(list, index, 1, NULL) == 0;
}

/**
 * Removes and returns the element at the specified index.
 *
 * No destructor is called, and instead the element is copied to the
 * @p targetbuf which MUST be large enough to hold the removed element.
 * If the list is storing pointers, only the pointer is copied to @p targetbuf.
 *
 * @param list the list
 * @param index the index of the element
 * @param targetbuf a buffer where to copy the element
 * @retval zero success
 * @retval non-zero index out of bounds
 */
cx_attr_nonnull
cx_attr_access_w(3)
static inline int cxListRemoveAndGet(
        CxList *list,
        size_t index,
        void *targetbuf
) {
    return list->cl->remove(list, index, 1, targetbuf) == 0;
}

/**
 * Removes and returns the first element of the list.
 *
 * No destructor is called, and instead the element is copied to the
 * @p targetbuf which MUST be large enough to hold the removed element.
 * If the list is storing pointers, only the pointer is copied to @p targetbuf.
 *
 * @param list the list
 * @param targetbuf a buffer where to copy the element
 * @retval zero success
 * @retval non-zero the list is empty
 * @see cxListPopFront()
 * @see cxListRemoveAndGetLast()
 */
cx_attr_nonnull
cx_attr_access_w(2)
static inline int cxListRemoveAndGetFirst(
    CxList *list,
    void *targetbuf
) {
    return list->cl->remove(list, 0, 1, targetbuf) == 0;
}

/**
 * Removes and returns the first element of the list.
 *
 * Alias for cxListRemoveAndGetFirst().
 *
 * No destructor is called, and instead the element is copied to the
 * @p targetbuf which MUST be large enough to hold the removed element.
 * If the list is storing pointers, only the pointer is copied to @p targetbuf.
 *
 * @param list (@c CxList*) the list
 * @param targetbuf (@c void*) a buffer where to copy the element
 * @retval zero success
 * @retval non-zero the list is empty
 * @see cxListRemoveAndGetFirst()
 * @see cxListPop()
 */
#define cxListPopFront(list, targetbuf) cxListRemoveAndGetFirst((list), (targetbuf))


/**
 * Removes and returns the last element of the list.
 *
 * No destructor is called, and instead the element is copied to the
 * @p targetbuf which MUST be large enough to hold the removed element.
 * If the list is storing pointers, only the pointer is copied to @p targetbuf.
 *
 * @param list the list
 * @param targetbuf a buffer where to copy the element
 * @retval zero success
 * @retval non-zero the list is empty
 */
cx_attr_nonnull
cx_attr_access_w(2)
static inline int cxListRemoveAndGetLast(
    CxList *list,
    void *targetbuf
) {
    // note: index may wrap - member function will catch that
    return list->cl->remove(list, list->collection.size - 1, 1, targetbuf) == 0;
}

/**
 * Removes and returns the last element of the list.
 *
 * Alias for cxListRemoveAndGetLast().
 *
 * No destructor is called, and instead the element is copied to the
 * @p targetbuf which MUST be large enough to hold the removed element.
 * If the list is storing pointers, only the pointer is copied to @p targetbuf.
 *
 * @param list (@c CxList*) the list
 * @param targetbuf (@c void*) a buffer where to copy the element
 * @retval zero success
 * @retval non-zero the list is empty
 * @see cxListRemoveAndGetLast()
 * @see cxListPopFront()
 */
#define cxListPop(list, targetbuf) cxListRemoveAndGetLast((list), (targetbuf))

/**
 * Removes multiple element starting at the specified index.
 *
 * If an element destructor function is specified, it is called for each
 * element. It is guaranteed that the destructor is called before removing
 * the element. However, due to possible optimizations, it is neither guaranteed
 * that the destructors are invoked for all elements before starting to remove
 * them, nor that the element is removed immediately after the destructor call
 * before proceeding to the next element.
 *
 * @param list the list
 * @param index the index of the element
 * @param num the number of elements to remove
 * @return the actual number of removed elements
 */
cx_attr_nonnull
static inline size_t cxListRemoveArray(
        CxList *list,
        size_t index,
        size_t num
) {
    return list->cl->remove(list, index, num, NULL);
}

/**
 * Removes and returns multiple elements starting at the specified index.
 *
 * No destructor is called, and instead the elements are copied to the
 * @p targetbuf which MUST be large enough to hold all removed elements.
 * If the list is storing pointers, @p targetbuf is expected to be an array of pointers.
 *
 * @param list the list
 * @param index the index of the element
 * @param num the number of elements to remove
 * @param targetbuf a buffer where to copy the elements
 * @return the actual number of removed elements
 */
cx_attr_nonnull
cx_attr_access_w(4)
static inline size_t cxListRemoveArrayAndGet(
        CxList *list,
        size_t index,
        size_t num,
        void *targetbuf
) {
    return list->cl->remove(list, index, num, targetbuf);
}

/**
 * Removes all elements from this list.
 *
 * If element destructor functions are specified, they are called for each
 * element before removing them.
 *
 * @param list the list
 */
cx_attr_nonnull
static inline void cxListClear(CxList *list) {
    list->cl->clear(list);
    list->collection.sorted = true; // empty lists are always sorted
}

/**
 * Swaps two items in the list.
 *
 * Implementations should only allocate temporary memory for the swap if
 * it is necessary.
 *
 * @param list the list
 * @param i the index of the first element
 * @param j the index of the second element
 * @retval zero success
 * @retval non-zero one of the indices is out of bounds,
 * or the swap needed extra memory, but allocation failed
 */
cx_attr_nonnull
static inline int cxListSwap(
        CxList *list,
        size_t i,
        size_t j
) {
    list->collection.sorted = false;
    return list->cl->swap(list, i, j);
}

/**
 * Returns a pointer to the element at the specified index.
 *
 * If the list is storing pointers, returns the pointer stored at the specified index.
 *
 * @param list the list
 * @param index the index of the element
 * @return a pointer to the element or @c NULL if the index is out of bounds
 */
cx_attr_nonnull
static inline void *cxListAt(
        const CxList *list,
        size_t index
) {
    return list->cl->at(list, index);
}

/**
 * Returns a pointer to the first element.
 *
 * If the list is storing pointers, returns the first pointer stored in the list.
 *
 * @param list the list
 * @return a pointer to the first element or @c NULL if the list is empty
 */
cx_attr_nonnull
static inline void *cxListFirst(const CxList *list) {
    return list->cl->at(list, 0);
}

/**
 * Returns a pointer to the last element.
 *
 * If the list is storing pointers, returns the last pointer stored in the list.
 *
 * @param list the list
 * @return a pointer to the last element or @c NULL if the list is empty
 */
cx_attr_nonnull
static inline void *cxListLast(const CxList *list) {
    return list->cl->at(list, list->collection.size - 1);
}

/**
 * Sets the element at the specified index in the list
 *
 * @param list the list to set the element in
 * @param index the index to set the element at
 * @param elem element to set
 * @retval zero on success
 * @retval non-zero when index is out of bounds
 */
cx_attr_nonnull
cx_attr_export
int cxListSet(
        CxList *list,
        size_t index,
        const void *elem
);

/**
 * Returns an iterator pointing to the item at the specified index.
 *
 * The returned iterator is position-aware.
 *
 * If the index is out of range or @p list is @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @param index the index where the iterator shall point at
 * @return a new iterator
 */
cx_attr_nodiscard
static inline CxIterator cxListIteratorAt(
        const CxList *list,
        size_t index
) {
    if (list == NULL) list = cxEmptyList;
    return list->cl->iterator(list, index, false);
}

/**
 * Returns a backwards iterator pointing to the item at the specified index.
 *
 * The returned iterator is position-aware.
 *
 * If the index is out of range or @p list is @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @param index the index where the iterator shall point at
 * @return a new iterator
 */
cx_attr_nodiscard
static inline CxIterator cxListBackwardsIteratorAt(
        const CxList *list,
        size_t index
) {
    if (list == NULL) list = cxEmptyList;
    return list->cl->iterator(list, index, true);
}

/**
 * Returns a mutating iterator pointing to the item at the specified index.
 *
 * The returned iterator is position-aware.
 *
 * If the index is out of range or @p list is @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @param index the index where the iterator shall point at
 * @return a new iterator
 */
cx_attr_nodiscard
cx_attr_export
CxIterator cxListMutIteratorAt(
        CxList *list,
        size_t index
);

/**
 * Returns a mutating backwards iterator pointing to the item at the
 * specified index.
 *
 * The returned iterator is position-aware.
 *
 * If the index is out of range or @p list is @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @param index the index where the iterator shall point at
 * @return a new iterator
 */
cx_attr_nodiscard
cx_attr_export
CxIterator cxListMutBackwardsIteratorAt(
        CxList *list,
        size_t index
);

/**
 * Returns an iterator pointing to the first item of the list.
 *
 * The returned iterator is position-aware.
 *
 * If the list is empty or @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @return a new iterator
 */
cx_attr_nodiscard
static inline CxIterator cxListIterator(const CxList *list) {
    if (list == NULL) list = cxEmptyList;
    return list->cl->iterator(list, 0, false);
}

/**
 * Returns a mutating iterator pointing to the first item of the list.
 *
 * The returned iterator is position-aware.
 *
 * If the list is empty or @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @return a new iterator
 */
cx_attr_nodiscard
static inline CxIterator cxListMutIterator(CxList *list) {
    if (list == NULL) list = cxEmptyList;
    return cxListMutIteratorAt(list, 0);
}


/**
 * Returns a backwards iterator pointing to the last item of the list.
 *
 * The returned iterator is position-aware.
 *
 * If the list is empty or @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @return a new iterator
 */
cx_attr_nodiscard
static inline CxIterator cxListBackwardsIterator(const CxList *list) {
    if (list == NULL) list = cxEmptyList;
    return list->cl->iterator(list, list->collection.size - 1, true);
}

/**
 * Returns a mutating backwards iterator pointing to the last item of the list.
 *
 * The returned iterator is position-aware.
 *
 * If the list is empty or @c NULL, a past-the-end iterator will be returned.
 *
 * @param list the list
 * @return a new iterator
 */
cx_attr_nodiscard
static inline CxIterator cxListMutBackwardsIterator(CxList *list) {
    if (list == NULL) list = cxEmptyList;
    return cxListMutBackwardsIteratorAt(list, list->collection.size - 1);
}

/**
 * Returns the index of the first element that equals @p elem.
 *
 * Determining equality is performed by the list's comparator function.
 *
 * @param list the list
 * @param elem the element to find
 * @return the index of the element or the size of the list when the element is not found
 * @see cxListIndexValid()
 * @see cxListContains()
 */
cx_attr_nonnull
cx_attr_nodiscard
static inline size_t cxListFind(
        const CxList *list,
        const void *elem
) {
    return list->cl->find_remove((CxList*)list, elem, false);
}

/**
 * Checks if the list contains the specified element.
 *
 * The elements are compared with the list's comparator function.
 *
 * @param list the list
 * @param elem the element to find
 * @retval true if the element is contained
 * @retval false if the element is not contained
 * @see cxListFind()
 */
cx_attr_nonnull
cx_attr_nodiscard
static inline bool cxListContains(
    const CxList* list,
    const void* elem
) {
    return list->cl->find_remove((CxList*)list, elem, false) < list->collection.size;
}

/**
 * Checks if the specified index is within bounds.
 *
 * @param list the list
 * @param index the index
 * @retval true if the index is within bounds
 * @retval false if the index is out of bounds
 */
cx_attr_nonnull
cx_attr_nodiscard
static inline bool cxListIndexValid(const CxList *list, size_t index) {
    return index < list->collection.size;
}

/**
 * Removes and returns the index of the first element that equals @p elem.
 *
 * Determining equality is performed by the list's comparator function.
 *
 * @param list the list
 * @param elem the element to find and remove
 * @return the index of the now removed element or the list size
 * when the element is not found or could not be removed
 * @see cxListIndexValid()
 */
cx_attr_nonnull
static inline size_t cxListFindRemove(
        CxList *list,
        const void *elem
) {
    return list->cl->find_remove(list, elem, true);
}

/**
 * Sorts the list.
 *
 * @remark The underlying sort algorithm is implementation defined.
 *
 * @param list the list
 */
cx_attr_nonnull
static inline void cxListSort(CxList *list) {
    if (list->collection.sorted) return;
    list->cl->sort(list);
    list->collection.sorted = true;
}

/**
 * Reverses the order of the items.
 *
 * @param list the list
 */
cx_attr_nonnull
static inline void cxListReverse(CxList *list) {
    // still sorted, but not according to the cmp_func
    list->collection.sorted = false;
    list->cl->reverse(list);
}

/**
 * Compares a list to another list of the same type.
 *
 * First, the list sizes are compared.
 * If they match, the lists are compared element-wise.
 *
 * @param list the list
 * @param other the list to compare to
 * @retval zero both lists are equal element wise
 * @retval negative the first list is smaller
 * or the first non-equal element in the first list is smaller
 * @retval positive the first list is larger
 * or the first non-equal element in the first list is larger
 */
cx_attr_nonnull
cx_attr_nodiscard
cx_attr_export
int cxListCompare(
        const CxList *list,
        const CxList *other
);

/**
 * Deallocates the memory of the specified list structure.
 *
 * Also calls the content destructor functions for each element, if specified.
 *
 * @param list the list that shall be freed
 */
cx_attr_export
void cxListFree(CxList *list);


#ifdef __cplusplus
} // extern "C"
#endif

#endif // UCX_LIST_H