Merge pull request #1950 from FrancoisChabot/issues/1457

templated input adapters

include/nlohmann/detail/input/binary_reader.hpp

@@ -24,6 +24,20 @@ namespace nlohmann
 {
 namespace detail
 {
+
+/*!
+@brief determine system byte order
+
+@return true if and only if system's byte order is little endian
+
+@note from https://stackoverflow.com/a/1001328/266378
+*/
+static bool little_endianess(int num = 1) noexcept
+{
+    return *reinterpret_cast<char*>(&num) == 1;
+}
+
+
 ///////////////////
 // binary reader //
 ///////////////////
@@ -31,7 +45,7 @@ namespace detail
 /*!
 @brief deserialization of CBOR, MessagePack, and UBJSON values
 */
-template<typename BasicJsonType, typename SAX = json_sax_dom_parser<BasicJsonType>>
+template<typename BasicJsonType, typename InputAdapterType, typename SAX = json_sax_dom_parser<BasicJsonType>>
 class binary_reader
 {
     using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -47,10 +61,9 @@ class binary_reader
 
     @param[in] adapter  input adapter to read from
     */
-    explicit binary_reader(input_adapter_t adapter) : ia(std::move(adapter))
+    explicit binary_reader(InputAdapterType&& adapter) : ia(std::move(adapter))
     {
         (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
-        assert(ia);
     }
 
     // make class move-only
@@ -119,18 +132,6 @@ class binary_reader
         return result;
     }
 
-    /*!
-    @brief determine system byte order
-
-    @return true if and only if system's byte order is little endian
-
-    @note from https://stackoverflow.com/a/1001328/266378
-    */
-    static constexpr bool little_endianess(int num = 1) noexcept
-    {
-        return *reinterpret_cast<char*>(&num) == 1;
-    }
-
   private:
     //////////
     // BSON //
@@ -2085,7 +2086,7 @@ class binary_reader
     int get()
     {
         ++chars_read;
-        return current = ia->get_character();
+        return current = ia.get_character();
     }
 
     /*!
@@ -2273,7 +2274,7 @@ class binary_reader
 
   private:
     /// input adapter
-    input_adapter_t ia = nullptr;
+    InputAdapterType ia;
 
     /// the current character
     int current = std::char_traits<char>::eof();

include/nlohmann/detail/input/lexer.hpp

@@ -22,19 +22,9 @@ namespace detail
 // lexer //
 ///////////
 
-/*!
-@brief lexical analysis
-
-This class organizes the lexical analysis during JSON deserialization.
-*/
 template<typename BasicJsonType>
-class lexer
+class lexer_base
 {
-    using number_integer_t = typename BasicJsonType::number_integer_t;
-    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
-    using number_float_t = typename BasicJsonType::number_float_t;
-    using string_t = typename BasicJsonType::string_t;
-
   public:
     /// token types for the parser
     enum class token_type
@@ -75,9 +65,9 @@ class lexer
                 return "null literal";
             case token_type::value_string:
                 return "string literal";
-            case lexer::token_type::value_unsigned:
-            case lexer::token_type::value_integer:
-            case lexer::token_type::value_float:
+            case token_type::value_unsigned:
+            case token_type::value_integer:
+            case token_type::value_float:
                 return "number literal";
             case token_type::begin_array:
                 return "'['";
@@ -103,15 +93,31 @@ class lexer
                 // LCOV_EXCL_STOP
         }
     }
+};
+/*!
+@brief lexical analysis
+
+This class organizes the lexical analysis during JSON deserialization.
+*/
+template<typename BasicJsonType, typename InputAdapterType>
+class lexer : public lexer_base<BasicJsonType>
+{
+    using number_integer_t = typename BasicJsonType::number_integer_t;
+    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
+    using number_float_t = typename BasicJsonType::number_float_t;
+    using string_t = typename BasicJsonType::string_t;
+
+  public:
+    using token_type = typename lexer_base<BasicJsonType>::token_type;
 
-    explicit lexer(detail::input_adapter_t&& adapter)
+    explicit lexer(InputAdapterType&& adapter)
         : ia(std::move(adapter)), decimal_point_char(get_decimal_point()) {}
 
     // delete because of pointer members
     lexer(const lexer&) = delete;
-    lexer(lexer&&) = delete;
+    lexer(lexer&&) = default;
     lexer& operator=(lexer&) = delete;
-    lexer& operator=(lexer&&) = delete;
+    lexer& operator=(lexer&&) = default;
     ~lexer() = default;
 
   private:
@@ -1256,7 +1262,7 @@ scan_number_done:
         }
         else
         {
-            current = ia->get_character();
+            current = ia.get_character();
         }
 
         if (JSON_HEDLEY_LIKELY(current != std::char_traits<char>::eof()))
@@ -1480,7 +1486,7 @@ scan_number_done:
 
   private:
     /// input adapter
-    detail::input_adapter_t ia = nullptr;
+    InputAdapterType ia;
 
     /// the current character
     std::char_traits<char>::int_type current = std::char_traits<char>::eof();

include/nlohmann/detail/input/parser.hpp

@@ -24,44 +24,45 @@ namespace detail
 // parser //
 ////////////
 
+enum class parse_event_t : uint8_t
+{
+    /// the parser read `{` and started to process a JSON object
+    object_start,
+    /// the parser read `}` and finished processing a JSON object
+    object_end,
+    /// the parser read `[` and started to process a JSON array
+    array_start,
+    /// the parser read `]` and finished processing a JSON array
+    array_end,
+    /// the parser read a key of a value in an object
+    key,
+    /// the parser finished reading a JSON value
+    value
+};
+
+template<typename BasicJsonType>
+using parser_callback_t =
+    std::function<bool(int depth, parse_event_t event, BasicJsonType& parsed)>;
+
 /*!
 @brief syntax analysis
 
 This class implements a recursive descent parser.
 */
-template<typename BasicJsonType>
+template<typename BasicJsonType, typename InputAdapterType>
 class parser
 {
     using number_integer_t = typename BasicJsonType::number_integer_t;
     using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
     using number_float_t = typename BasicJsonType::number_float_t;
     using string_t = typename BasicJsonType::string_t;
-    using lexer_t = lexer<BasicJsonType>;
+    using lexer_t = lexer<BasicJsonType, InputAdapterType>;
     using token_type = typename lexer_t::token_type;
 
   public:
-    enum class parse_event_t : uint8_t
-    {
-        /// the parser read `{` and started to process a JSON object
-        object_start,
-        /// the parser read `}` and finished processing a JSON object
-        object_end,
-        /// the parser read `[` and started to process a JSON array
-        array_start,
-        /// the parser read `]` and finished processing a JSON array
-        array_end,
-        /// the parser read a key of a value in an object
-        key,
-        /// the parser finished reading a JSON value
-        value
-    };
-
-    using parser_callback_t =
-        std::function<bool(int depth, parse_event_t event, BasicJsonType& parsed)>;
-
     /// a parser reading from an input adapter
-    explicit parser(detail::input_adapter_t&& adapter,
-                    const parser_callback_t cb = nullptr,
+    explicit parser(InputAdapterType&& adapter,
+                    const parser_callback_t<BasicJsonType> cb = nullptr,
                     const bool allow_exceptions_ = true)
         : callback(cb), m_lexer(std::move(adapter)), allow_exceptions(allow_exceptions_)
     {
@@ -486,7 +487,7 @@ class parser
 
   private:
     /// callback function
-    const parser_callback_t callback = nullptr;
+    const parser_callback_t<BasicJsonType> callback = nullptr;
     /// the type of the last read token
     token_type last_token = token_type::uninitialized;
     /// the lexer

include/nlohmann/detail/output/binary_writer.hpp

@@ -1538,7 +1538,7 @@ class binary_writer
 
   private:
     /// whether we can assume little endianess
-    const bool is_little_endian = binary_reader<BasicJsonType>::little_endianess();
+    const bool is_little_endian = little_endianess();
 
     /// the output
     output_adapter_t<CharType> oa = nullptr;

test/src/unit-class_lexer.cpp

@@ -40,7 +40,8 @@ namespace
 json::lexer::token_type scan_string(const char* s);
 json::lexer::token_type scan_string(const char* s)
 {
-    return json::lexer(nlohmann::detail::input_adapter(s)).scan();
+    auto ia = nlohmann::detail::input_adapter(s);
+    return nlohmann::detail::lexer<json, decltype(ia)>(std::move(ia)).scan();
 }
 }