diff -r 809581724cc7 -r 0358f1d9c506 ucx/map.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ucx/map.c	Mon May 22 16:17:26 2023 +0200
@@ -0,0 +1,112 @@
+/*
+ * 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.
+ */
+
+#include "cx/map.h"
+#include <string.h>
+
+// <editor-fold desc="empty map implementation">
+
+static void cx_empty_map_noop(__attribute__((__unused__)) CxMap *map) {
+    // this is a noop, but MUST be implemented
+}
+
+static void *cx_empty_map_get(
+        __attribute__((__unused__)) CxMap const *map,
+        __attribute__((__unused__)) CxHashKey key
+) {
+    return NULL;
+}
+
+static bool cx_empty_map_iter_valid(__attribute__((__unused__)) void const *iter) {
+    return false;
+}
+
+static CxIterator cx_empty_map_iterator(
+        struct cx_map_s const *map,
+        __attribute__((__unused__)) enum cx_map_iterator_type type
+) {
+    CxIterator iter = {0};
+    iter.src_handle = map;
+    iter.base.valid = cx_empty_map_iter_valid;
+    return iter;
+}
+
+static struct cx_map_class_s cx_empty_map_class = {
+        cx_empty_map_noop,
+        cx_empty_map_noop,
+        NULL,
+        cx_empty_map_get,
+        NULL,
+        cx_empty_map_iterator
+};
+
+CxMap cx_empty_map = {
+        NULL,
+        NULL,
+        0,
+        0,
+        NULL,
+        NULL,
+        NULL,
+        false,
+        &cx_empty_map_class
+};
+
+CxMap *const cxEmptyMap = &cx_empty_map;
+
+// </editor-fold>
+
+CxMutIterator cxMapMutIteratorValues(CxMap *map) {
+    CxIterator it = map->cl->iterator(map, CX_MAP_ITERATOR_VALUES);
+    it.base.mutating = true;
+
+    // we know the iterators share the same memory layout
+    CxMutIterator iter;
+    memcpy(&iter, &it, sizeof(CxMutIterator));
+    return iter;
+}
+
+CxMutIterator cxMapMutIteratorKeys(CxMap *map) {
+    CxIterator it = map->cl->iterator(map, CX_MAP_ITERATOR_KEYS);
+    it.base.mutating = true;
+
+    // we know the iterators share the same memory layout
+    CxMutIterator iter;
+    memcpy(&iter, &it, sizeof(CxMutIterator));
+    return iter;
+}
+
+CxMutIterator cxMapMutIterator(CxMap *map) {
+    CxIterator it = map->cl->iterator(map, CX_MAP_ITERATOR_PAIRS);
+    it.base.mutating = true;
+
+    // we know the iterators share the same memory layout
+    CxMutIterator iter;
+    memcpy(&iter, &it, sizeof(CxMutIterator));
+    return iter;
+}