LibGLSL: Add initial GLSL parser implementation

Userland/Libraries/LibGLSL/Lexer.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/StringView.h>
+#include <AK/Vector.h>
+#include <LibGLSL/Token.h>
+
+namespace GLSL {
+
+class Lexer {
+public:
+    explicit Lexer(StringView, size_t start_line = 0);
+
+    Vector<Token> lex();
+    template<typename Callback>
+    void lex_iterable(Callback);
+
+    void set_ignore_whitespace(bool value) { m_options.ignore_whitespace = value; }
+
+private:
+    char peek(size_t offset = 0) const;
+    char consume();
+    void lex_impl(Function<void(Token)>);
+
+    StringView m_input;
+    size_t m_index { 0 };
+    Position m_previous_position { 0, 0 };
+    Position m_position { 0, 0 };
+
+    struct Options {
+        bool ignore_whitespace { false };
+    } m_options;
+};
+
+template<typename Callback>
+void Lexer::lex_iterable(Callback callback)
+{
+    return lex_impl(move(callback));
+}
+
+}