Import of the watch repository from Pebble

src/libutil/includes/util/iterator.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! Simple utility for enforcing consistent use of the iterator pattern
+//! and facilitate unit testing.
+#pragma once
+
+#include <stdbool.h>
+
+typedef void* IteratorState;
+
+typedef bool (*IteratorCallback)(IteratorState state);
+
+typedef struct {
+  IteratorCallback next;
+  IteratorCallback prev;
+  IteratorState state;
+} Iterator;
+
+#define ITERATOR_EMPTY ((Iterator){ 0, 0, 0 })
+
+void iter_init(Iterator* iter, IteratorCallback next, IteratorCallback prev, IteratorState state);
+
+//! @return true if successfully moved to next node
+bool iter_next(Iterator* iter);
+
+//! @return true if successfully moved to previous node
+bool iter_prev(Iterator* iter);
+
+IteratorState iter_get_state(Iterator* iter);
+