LibWeb: Implement a very basic version of TextDecoder

We had a very basic implementation of TextEncoder, let's add a
TextDecoder next to that :^)

1 files changed, 27 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp b/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
new file mode 100644
index 0000000000..28575cd9c7
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Encoding/TextDecoder.cpp
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2022, Ali Mohammad Pur <mpfard@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/FlyString.h>
+#include <LibJS/Runtime/TypedArray.h>
+#include <LibWeb/Bindings/IDLAbstractOperations.h>
+#include <LibWeb/Bindings/Wrapper.h>
+#include <LibWeb/Encoding/TextDecoder.h>
+
+namespace Web::Encoding {
+
+// https://encoding.spec.whatwg.org/#dom-textdecoder-decode
+DOM::ExceptionOr<String> TextDecoder::decode(JS::Handle<JS::Object> const& input) const
+{
+    // FIXME: Implement the streaming stuff.
+
+    auto data_buffer = Bindings::IDL::get_buffer_source_copy(*input.cell());
+    if (!data_buffer.has_value())
+        return DOM::OperationError::create("Failed to copy bytes from ArrayBuffer");
+
+    return m_decoder.to_utf8({ data_buffer->data(), data_buffer->size() });
+}
+
+}