LibJS: Start implementing iterable framework, add ArrayIterator

With the addition of symbol keys, work can now be done on starting to
implement the well-known symbol functionality. The most important of
these well-known symbols is by far Symbol.iterator.

This patch adds IteratorPrototype, as well as ArrayIterator and
ArrayIteratorPrototype. In the future, sometime after StringIterator has
also been added, this will allow us to use Symbol.iterator directly in
for..of loops, enabling the use of custom iterator objects. Also makes
adding iterator support to native objects much easier (as will have to
be done for Map and Set, when they get added).

1 files changed, 45 insertions, 0 deletions

diff --git a/Libraries/LibJS/Runtime/IteratorOperations.h b/Libraries/LibJS/Runtime/IteratorOperations.h
new file mode 100644
index 0000000000..9b9caae4e9
--- /dev/null
+++ b/Libraries/LibJS/Runtime/IteratorOperations.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * 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.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+// Common iterator operations defined in ECMA262 7.4
+// https://tc39.es/ecma262/#sec-operations-on-iterator-objects
+
+Object* get_iterator(Object& obj, String hint = "sync", Value method = {});
+bool is_iterator_complete(Object& iterator_result);
+Value create_iterator_result_object(Interpreter&, GlobalObject&, Value value, bool done);
+
+Value iterator_next(Object& iterator, Value value = {});
+Value iterator_value(Object& iterator_result);
+Value iterator_step(Object& iterator);
+void iterator_close(Object& iterator);
+
+}