Creates reader type for converting from JSON source to AST node seq…

…uence

A `jsonv::reader` instance reads from some form of JSON source (probably
a string, but the `jsonv::ast_index` type can theoretically read from
anything JSON-like) and converts it into `jsonv::ast_node`s. These
abstract reading from JSON source to normalize `extract` implementations,
which is needed for #150.

- Resolves #171

include/jsonv/all.hpp

@@ -731,6 +731,7 @@ namespace jsonv
 #include "parse.hpp"
 #include "parse_index.hpp"
 #include "path.hpp"
+#include "reader.hpp"
 #include "result.hpp"
 #include "serialization.hpp"
 #include "serialization_builder.hpp"

include/jsonv/ast.hpp

@@ -134,7 +134,7 @@ enum class ast_error : std::uint64_t
     expected_key_delimiter,
     unexpected_token,
     unexpected_comma,
-    eof,
+    unexpected_eof,
     expected_eof,
     depth_exceeded,
     extra_close,
@@ -164,7 +164,7 @@ class ast_node final
     {
     public:
         /// Get the \c ast_node_type type.
-        constexpr ast_node_type type() const
+        static constexpr ast_node_type type()
         {
             return KIndexToken;
         }
@@ -430,7 +430,8 @@ class ast_node final
                                       literal_null,
                                       integer,
                                       decimal,
-                                      error>;
+                                      error
+                                     >;
 
 public:
     ast_node(const storage_type& value) :
@@ -457,6 +458,13 @@ class ast_node final
         return std::visit(std::forward<FVisitor>(visitor), _impl);
     }
 
+    /// Convenience function for calling \c std::visit on a key (see \c as_key).
+    template <typename FVisitor>
+    auto visit_key(FVisitor&& visitor) const
+    {
+        return std::visit(std::forward<FVisitor>(visitor), as_key());
+    }
+
     /// Get the \c ast_node_type that tells the underlying type of this instance.
     ast_node_type type() const
     {
@@ -479,6 +487,17 @@ class ast_node final
         return std::get<T>(_impl);
     }
 
+    /// Get the underlying data of this node as one of the key types: \c key_canonical or \c key_escaped.
+    ///
+    /// \throw std::bad_variant_access if the \c type of this instance is neither \c key_canonical nor \c key_escaped.
+    std::variant<key_canonical, key_escaped> as_key() const
+    {
+        if (type() == ast_node_type::key_canonical)
+            return as<key_canonical>();
+        else
+            return as<key_escaped>();
+    }
+
 private:
     storage_type _impl;
 };

include/jsonv/detail/scope_exit.hpp

@@ -1,24 +1,20 @@
-/** \file jsonv/detail/scope_exit.hpp
- *  Definition of the \c on_scope_exit utility.
- *  
- *  Copyright (c) 2015 by Travis Gockel. All rights reserved.
- *
- *  This program is free software: you can redistribute it and/or modify it under the terms of the Apache License
- *  as published by the Apache Software Foundation, either version 2 of the License, or (at your option) any later
- *  version.
- *
- *  \author Travis Gockel ([email protected])
-**/
-#ifndef __JSONV_DETAIL_SCOPE_EXIT_HPP_INCLUDED__
-#define __JSONV_DETAIL_SCOPE_EXIT_HPP_INCLUDED__
+/// \file jsonv/detail/scope_exit.hpp
+/// Definition of the \c on_scope_exit utility.
+///
+/// Copyright (c) 2015 by Travis Gockel. All rights reserved.
+///
+/// This program is free software: you can redistribute it and/or modify it under the terms of the Apache License
+/// as published by the Apache Software Foundation, either version 2 of the License, or (at your option) any later
+/// version.
+///
+/// \author Travis Gockel ([email protected])
+#pragma once
 
 #include <jsonv/config.hpp>
 
 #include <utility>
 
-namespace jsonv
-{
-namespace detail
+namespace jsonv::detail
 {
 
 template <typename Function>
@@ -29,29 +25,29 @@ class scope_exit_invoker
             _func(std::move(func)),
             _responsible(true)
     { }
-    
+
     scope_exit_invoker(scope_exit_invoker&& src) :
             _func(std::move(src._func)),
             _responsible(src._responsible)
     {
         src._responsible = false;
     }
-    
+
     scope_exit_invoker(const scope_exit_invoker&) = delete;
     scope_exit_invoker& operator=(const scope_exit_invoker&) = delete;
     scope_exit_invoker& operator=(scope_exit_invoker&&) = delete;
-    
+
     ~scope_exit_invoker()
     {
         if (_responsible)
             _func();
     }
-    
+
     void release()
     {
         _responsible = false;
     }
-    
+
 private:
     Function _func;
     bool     _responsible;
@@ -64,6 +60,3 @@ scope_exit_invoker<Function> on_scope_exit(Function func)
 }
 
 }
-}
-
-#endif/*__JSONV_DETAIL_SCOPE_EXIT_HPP_INCLUDED__*/

include/jsonv/forward.hpp

@@ -37,6 +37,7 @@ class path;
 class path_element;
 enum class path_element_kind : unsigned char;
 template <typename TPointer> class polymorphic_adapter_builder;
+class reader;
 template <typename TValue, typename TError> class result;
 class serializer;
 class serialization_context;