🔨 added a SAX-DOM-Parser

test/src/unit-class_parser.cpp

@@ -34,7 +34,7 @@ using nlohmann::json;
 
 #include <valarray>
 
-class SaxEventLogger : public nlohmann::json::json_sax
+class SaxEventLogger : public nlohmann::json::json_sax_t
 {
   public:
     bool null() override
@@ -67,7 +67,7 @@ class SaxEventLogger : public nlohmann::json::json_sax
         return true;
     }
 
-    bool string(const std::string& val) override
+    bool string(std::string&& val) override
     {
         events.push_back("string(" + val + ")");
         return true;
@@ -75,7 +75,7 @@ class SaxEventLogger : public nlohmann::json::json_sax
 
     bool start_object(std::size_t elements) override
     {
-        if (elements == std::size_t(-1))
+        if (elements == no_limit)
         {
             events.push_back("start_object()");
         }
@@ -86,13 +86,13 @@ class SaxEventLogger : public nlohmann::json::json_sax
         return true;
     }
 
-    bool key(const std::string& val) override
+    bool key(std::string&& val) override
     {
         events.push_back("key(" + val + ")");
         return true;
     }
 
-    bool end_object()override
+    bool end_object() override
     {
         events.push_back("end_object()");
         return true;
@@ -100,7 +100,7 @@ class SaxEventLogger : public nlohmann::json::json_sax
 
     bool start_array(std::size_t elements) override
     {
-        if (elements == std::size_t(-1))
+        if (elements == no_limit)
         {
             events.push_back("start_array()");
         }
@@ -134,6 +134,129 @@ class SaxEventLogger : public nlohmann::json::json_sax
     bool errored = false;
 };
 
+class SaxDomParser : public nlohmann::json::json_sax_t
+{
+  public:
+    bool null() override
+    {
+        handle_value(nullptr);
+        return true;
+    }
+
+    bool boolean(bool val) override
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_integer(json::number_integer_t val) override
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_unsigned(json::number_unsigned_t val) override
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool number_float(json::number_float_t val, const std::string&) override
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool string(std::string&& val) override
+    {
+        handle_value(val);
+        return true;
+    }
+
+    bool start_object(std::size_t) override
+    {
+        ref_stack.push_back(handle_value(json::value_t::object));
+        return true;
+    }
+
+    bool key(std::string&& val) override
+    {
+        last_key = val;
+        return true;
+    }
+
+    bool end_object() override
+    {
+        ref_stack.pop_back();
+        return true;
+    }
+
+    bool start_array(std::size_t) override
+    {
+        ref_stack.push_back(handle_value(json::value_t::array));
+        return true;
+    }
+
+    bool end_array() override
+    {
+        ref_stack.pop_back();
+        return true;
+    }
+
+    bool binary(const std::vector<uint8_t>&) override
+    {
+        return true;
+    }
+
+    bool parse_error(std::size_t position, const std::string&) override
+    {
+        return false;
+    }
+
+    json& get_value()
+    {
+        return root;
+    }
+
+  private:
+    /// the parsed JSON value
+    json root;
+    /// stack to model hierarchy of values
+    std::vector<json*> ref_stack;
+    /// helper variable for object keys
+    std::string last_key;
+
+    /*!
+    @invariant If the ref stack is empty, then the passed value will be the new
+               root.
+    @invariant If the ref stack contains a value, then it is an array or an
+               object to which we can add elements
+    */
+    json* handle_value(json&& j)
+    {
+        if (ref_stack.empty())
+        {
+            assert(root.is_null());
+            root = j;
+            return &root;
+        }
+        else
+        {
+            assert(ref_stack.back()->is_array() or ref_stack.back()->is_object());
+            if (ref_stack.back()->is_array())
+            {
+                ref_stack.back()->push_back(j);
+                return &(ref_stack.back()->back());
+            }
+            else
+            {
+                json& r = ref_stack.back()->operator[](last_key) = j;
+                return &r;
+            }
+        }
+    }
+};
+
 json parser_helper(const std::string& s);
 bool accept_helper(const std::string& s);
 
@@ -148,6 +271,10 @@ json parser_helper(const std::string& s)
     CHECK_NOTHROW(json::parser(nlohmann::detail::input_adapter(s), nullptr, false).parse(true, j_nothrow));
     CHECK(j_nothrow == j);
 
+    SaxDomParser sdp;
+    json::sax_parse(s, &sdp);
+    CHECK(sdp.get_value() == j);
+
     return j;
 }