From 6b658297d80d849afd11377d18eb6d70c3e8489b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonathan=20M=C3=BCller?= <git@foonathan.net>
Date: Sun, 22 Jan 2017 12:26:28 +0100
Subject: [PATCH] Add visit operation

---
 include/cppast/visitor.hpp | 51 ++++++++++++++++++++++++++++++++++
 src/visitor.cpp            | 57 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 include/cppast/visitor.hpp
 create mode 100644 src/visitor.cpp

diff --git a/include/cppast/visitor.hpp b/include/cppast/visitor.hpp
new file mode 100644
index 0000000..1744392
--- /dev/null
+++ b/include/cppast/visitor.hpp
@@ -0,0 +1,51 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#ifndef CPPAST_VISITOR_HPP_INCLUDED
+#define CPPAST_VISITOR_HPP_INCLUDED
+
+namespace cppast
+{
+    class cpp_entity;
+
+    /// Information about the state of a visit operation.
+    enum class visitor_info
+    {
+        leave_entity, //< Callback called for a leave entity without children.
+
+        container_entity_enter, //< Callback called for a container entity before the children.
+        container_entity_exit,  //< Callback called for a container entity after the children.
+    };
+
+    /// \exclude
+    namespace detail
+    {
+        using visitor_callback_t = bool (*)(void* mem, const cpp_entity&, visitor_info info);
+
+        template <typename Func>
+        bool visitor_callback(void* mem, const cpp_entity& e, visitor_info info)
+        {
+            auto& func = *static_cast<Func*>(mem);
+            return func(e, info);
+        }
+
+        bool visit(const cpp_entity& e, visitor_callback_t cb, void* functor);
+    } // namespace detail
+
+    /// Visits a [cppast::cpp_entity]().
+    /// \effects If the given entity is a container, i.e. if it has child entities,
+    /// calls `f(e, visitor_info::container_entity_enter)`.
+    /// If that returns `true`, recursively calls `visit()` for all child entities,
+    /// followed by a call to `f(e, visitor_info::container_entity_exit)`.
+    /// If the given entity is not a container, calls `f(e, visitor_info::leave_entity)`.
+    /// If the functor returns `false` for [cppast::visitor_info]() other than `container_entity_enter`,
+    /// the visit operation is aborted.
+    template <typename Func>
+    void visit(const cpp_entity& e, Func f)
+    {
+        detail::visit(e, &detail::visitor_callback<Func>, &f);
+    }
+} // namespace cppast
+
+#endif // CPPAST_VISITOR_HPP_INCLUDED
diff --git a/src/visitor.cpp b/src/visitor.cpp
new file mode 100644
index 0000000..9590128
--- /dev/null
+++ b/src/visitor.cpp
@@ -0,0 +1,57 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#include <cppast/visitor.hpp>
+
+#include <cppast/cpp_entity.hpp>
+#include <cppast/cpp_entity_type.hpp>
+#include <cppast/cpp_enum.hpp>
+#include <cppast/cpp_file.hpp>
+#include <cppast/cpp_namespace.hpp>
+
+using namespace cppast;
+
+namespace
+{
+    template <typename T>
+    bool handle_container(const cpp_entity& e, detail::visitor_callback_t cb, void* functor)
+    {
+        auto& container = static_cast<const T&>(e);
+
+        auto handle_children = cb(functor, container, visitor_info::container_entity_enter);
+        if (handle_children)
+        {
+            for (auto& child : container)
+                if (!detail::visit(child, cb, functor))
+                    return false;
+        }
+
+        return cb(functor, container, visitor_info::container_entity_exit);
+    }
+}
+
+bool detail::visit(const cpp_entity& e, detail::visitor_callback_t cb, void* functor)
+{
+    switch (e.type())
+    {
+    case cpp_entity_type::file_t:
+        return handle_container<cpp_file>(e, cb, functor);
+    case cpp_entity_type::namespace_t:
+        return handle_container<cpp_namespace>(e, cb, functor);
+    case cpp_entity_type::enum_t:
+        return handle_container<cpp_enum>(e, cb, functor);
+
+    case cpp_entity_type::namespace_alias_t:
+    case cpp_entity_type::using_directive_t:
+    case cpp_entity_type::using_declaration_t:
+    case cpp_entity_type::enum_value_t:
+        return cb(functor, e, visitor_info::leave_entity);
+
+    case cpp_entity_type::count:
+        break;
+    }
+
+    DEBUG_UNREACHABLE(detail::assert_handler{});
+    return true;
+}