diff -r 1f40ca07ae1b -r 839fefbdedc7 ucx/cx/iterator.h
--- a/ucx/cx/iterator.h	Sat Apr 20 13:01:58 2024 +0200
+++ b/ucx/cx/iterator.h	Thu May 23 22:35:45 2024 +0200
@@ -30,7 +30,6 @@
  * \brief Interface for iterator implementations.
  * \author Mike Becker
  * \author Olaf Wintermann
- * \version 3.0
  * \copyright 2-Clause BSD License
  */
 
@@ -39,9 +38,6 @@
 
 #include "common.h"
 
-/**
- * The base of mutating and non-mutating iterators.
- */
 struct cx_iterator_base_s {
     /**
      * True iff the iterator points to valid data.
@@ -70,20 +66,10 @@
      */
     __attribute__ ((__nonnull__))
     void (*next)(void *);
-
-    /**
-     * Flag current element for removal, if possible.
-     *
-     * When valid returns false, the behavior of this function is undefined.
-     */
-    __attribute__ ((__nonnull__))
-    bool (*flag_removal)(void *);
-
     /**
      * Indicates whether this iterator may remove elements.
      */
     bool mutating;
-
     /**
      * Internal flag for removing the current element when advancing.
      */
@@ -91,24 +77,34 @@
 };
 
 /**
- * Internal iterator struct - use CxMutIterator.
+ * Declares base attributes for an iterator.
  */
-struct cx_mut_iterator_s {
+#define CX_ITERATOR_BASE struct cx_iterator_base_s base
+
+/**
+ * Internal iterator struct - use CxIterator.
+ */
+struct cx_iterator_s {
+    CX_ITERATOR_BASE;
 
     /**
-     * The base properties of this iterator.
-     */
-    struct cx_iterator_base_s base;
-
-    /**
-     * Handle for the current element, if required.
+     * Handle for the current element.
      */
     void *elem_handle;
 
     /**
      * Handle for the source collection, if any.
      */
-    void *src_handle;
+    union {
+        /**
+         * Access for mutating iterators.
+         */
+        void *m;
+        /**
+         * Access for normal iterators.
+         */
+        void const *c;
+    } src_handle;
 
     /**
      * Field for storing a key-value pair.
@@ -136,83 +132,29 @@
      * Otherwise, this field is usually uninitialized.
      */
     size_t index;
+
+    /**
+     * The size of an individual element.
+     */
+    size_t elem_size;
+
+    /**
+     * May contain the total number of elements, if known.
+     * Shall be set to \c SIZE_MAX when the total number is unknown during iteration.
+     */
+    size_t elem_count;
 };
 
 /**
- * Mutating iterator value type.
- *
- * An iterator points to a certain element in an (possibly unbounded) chain of elements.
- * Iterators that are based on collections (which have a defined "first" element), are supposed
- * to be "position-aware", which means that they keep track of the current index within the collection.
- *
- * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
- * iterator is based on a collection and the underlying collection is mutated by other means than this iterator
- * (e.g. elements added or removed), the iterator becomes invalid (regardless of what cxIteratorValid() returns)
- * and MUST be re-obtained from the collection.
+ * Iterator type.
  *
- * @see CxIterator
- */
-typedef struct cx_mut_iterator_s CxMutIterator;
-
-/**
- * Internal iterator struct - use CxIterator.
- */
-struct cx_iterator_s {
-
-    /**
-     * The base properties of this iterator.
-     */
-    struct cx_iterator_base_s base;
-
-    /**
-     * Handle for the current element, if required.
-     */
-    void *elem_handle;
-
-    /**
-     * Handle for the source collection, if any.
-     */
-    void const *src_handle;
-
-    /**
-     * Field for storing a key-value pair.
-     * May be used by iterators that iterate over k/v-collections.
-     */
-    struct {
-        /**
-         * A pointer to the key.
-         */
-        void const *key;
-        /**
-         * A pointer to the value.
-         */
-        void *value;
-    } kv_data;
-
-    /**
-     * Field for storing a slot number.
-     * May be used by iterators that iterate over multi-bucket collections.
-     */
-    size_t slot;
-
-    /**
-     * If the iterator is position-aware, contains the index of the element in the underlying collection.
-     * Otherwise, this field is usually uninitialized.
-     */
-    size_t index;
-};
-
-/**
- * Iterator value type.
  * An iterator points to a certain element in a (possibly unbounded) chain of elements.
  * Iterators that are based on collections (which have a defined "first" element), are supposed
  * to be "position-aware", which means that they keep track of the current index within the collection.
  *
  * @note Objects that are pointed to by an iterator are always mutable through that iterator. However,
- * this iterator cannot mutate the collection itself (add or remove elements) and any mutation of the
- * collection by other means makes this iterator invalid (regardless of what cxIteratorValid() returns).
- *
- * @see CxMutIterator
+ * any concurrent mutation of the collection other than by this iterator makes this iterator invalid
+ * and it must not be used anymore.
  */
 typedef struct cx_iterator_s CxIterator;
 
@@ -244,12 +186,11 @@
 #define cxIteratorNext(iter) (iter).base.next(&iter)
 
 /**
- * Flags the current element for removal.
+ * Flags the current element for removal, if this iterator is mutating.
  *
  * @param iter the iterator
- * @return false if this iterator cannot remove the element
  */
-#define cxIteratorFlagRemoval(iter) (iter).base.flag_removal(&iter)
+#define cxIteratorFlagRemoval(iter) (iter).base.remove |= (iter).base.mutating
 
 /**
  * Loops over an iterator.
@@ -260,4 +201,55 @@
 #define cx_foreach(type, elem, iter) \
 for (type elem; cxIteratorValid(iter) && (elem = (type)cxIteratorCurrent(iter)) != NULL ; cxIteratorNext(iter))
 
+
+/**
+ * Creates an iterator for the specified plain array.
+ *
+ * The \p array can be \c NULL in which case the iterator will be immediately
+ * initialized such that #cxIteratorValid() returns \c false.
+ *
+ *
+ * @param array a pointer to the array (can be \c NULL)
+ * @param elem_size the size of one array element
+ * @param elem_count the number of elements in the array
+ * @return an iterator for the specified array
+ */
+__attribute__((__warn_unused_result__))
+CxIterator cxIterator(
+        void const *array,
+        size_t elem_size,
+        size_t elem_count
+);
+
+/**
+ * Creates a mutating iterator for the specified plain array.
+ *
+ * While the iterator is in use, the array may only be altered by removing
+ * elements through #cxIteratorFlagRemoval(). Every other change to the array
+ * will bring this iterator to an undefined state.
+ *
+ * When \p remove_keeps_order is set to \c false, removing an element will only
+ * move the last element to the position of the removed element, instead of
+ * moving all subsequent elements by one. Usually, when the order of elements is
+ * not important, this parameter should be set to \c false.
+ *
+ * The \p array can be \c NULL in which case the iterator will be immediately
+ * initialized such that #cxIteratorValid() returns \c false.
+ *
+ *
+ * @param array a pointer to the array (can be \c NULL)
+ * @param elem_size the size of one array element
+ * @param elem_count the number of elements in the array
+ * @param remove_keeps_order \c true if the order of elements must be preserved
+ * when removing an element
+ * @return an iterator for the specified array
+ */
+__attribute__((__warn_unused_result__))
+CxIterator cxMutIterator(
+        void *array,
+        size_t elem_size,
+        size_t elem_count,
+        bool remove_keeps_order
+);
+
 #endif // UCX_ITERATOR_H