diff -r 921f83a8943f -r d218607f5a7e src/ucx/cx/collection.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ucx/cx/collection.h	Fri May 05 18:02:11 2023 +0200
@@ -0,0 +1,138 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2023 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 collection.h
+ * \brief Common definitions for various collection implementations.
+ * \author Mike Becker
+ * \author Olaf Wintermann
+ * \version 3.0
+ * \copyright 2-Clause BSD License
+ */
+
+#ifndef UCX_COLLECTION_H
+#define UCX_COLLECTION_H
+
+#include "allocator.h"
+#include "iterator.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Special constant used for creating collections that are storing pointers.
+ */
+#define CX_STORE_POINTERS 0
+
+/**
+ * A comparator function comparing two collection elements.
+ */
+typedef int(*cx_compare_func)(
+        void const *left,
+        void const *right
+);
+
+/**
+ * Use this macro to declare common members for a collection structure.
+ */
+#define CX_COLLECTION_MEMBERS \
+    /** \
+     * The allocator to use. \
+     */ \
+    CxAllocator const *allocator; \
+    /** \
+     * The comparator function for the elements. \
+     */ \
+    cx_compare_func cmpfunc; \
+    /** \
+     * The size of each element. \
+     */ \
+    size_t item_size; \
+    /** \
+     * The number of currently stored elements. \
+     */ \
+    size_t size; \
+    /** \
+     * An optional simple destructor for the collection's elements. \
+     * \
+     * @attention Read the documentation of the particular collection implementation \
+     * whether this destructor shall only destroy the contents or also free the memory. \
+     */ \
+    cx_destructor_func simple_destructor; \
+    /** \
+     * An optional advanced destructor for the collection's elements. \
+     * \
+     * @attention Read the documentation of the particular collection implementation \
+     * whether this destructor shall only destroy the contents or also free the memory. \
+     */ \
+    cx_destructor_func2 advanced_destructor; \
+    /** \
+     * The pointer to additional data that is passed to the advanced destructor. \
+     */ \
+    void *destructor_data; \
+    /** \
+     * Indicates if this instance of a collection is supposed to store pointers \
+     * instead of copies of the actual objects. \
+     */ \
+    bool store_pointer;
+
+/**
+ * Invokes the simple destructor function for a specific element.
+ *
+ * Usually only used by collection implementations. There should be no need
+ * to invoke this macro manually.
+ *
+ * @param c the collection
+ * @param e the element
+ */
+#define cx_invoke_simple_destructor(c, e) \
+    (c)->simple_destructor((c)->store_pointer ? (*((void **) (e))) : (e))
+
+/**
+ * Invokes the advanced destructor function for a specific element.
+ *
+ * Usually only used by collection implementations. There should be no need
+ * to invoke this macro manually.
+ *
+ * @param c the collection
+ * @param e the element
+ */
+#define cx_invoke_advanced_destructor(c, e) \
+    (c)->advanced_destructor((c)->destructor_data, \
+    (c)->store_pointer ? (*((void **) (e))) : (e))
+
+
+#define cx_invoke_destructor(c, e) \
+    if ((c)->simple_destructor) cx_invoke_simple_destructor(c,e); \
+    if ((c)->advanced_destructor) cx_invoke_advanced_destructor(c,e)
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif // UCX_COLLECTION_H