Add a distinct Buffer type for encoding binary data in JSON responses. Treated like a string, but allows other consumers (a-la node-osrm) to recognize and not break string encodings.

include/engine/plugins/tile.hpp

@@ -333,7 +333,7 @@ template <class DataFacadeT> class TilePlugin final : public BasePlugin
             }
         }
 
-        json_result.values["pbf"] = buffer;
+        json_result.values["pbf"] = osrm::util::json::Buffer(buffer);
 
         return Status::Ok;
     }

include/util/json_container.hpp

@@ -50,6 +50,15 @@ namespace json
 struct Object;
 struct Array;
 
+// For encoding raw binary data in a JSON response
+struct Buffer
+{
+    Buffer() {}
+    Buffer(const char *value) : value(value) {}
+    Buffer(std::string value) : value(std::move(value)) {}
+    std::string value;
+};
+
 struct String
 {
     String() = default;
@@ -78,6 +87,7 @@ struct Null
 };
 
 using Value = mapbox::util::variant<String,
+                                    Buffer,
                                     Number,
                                     mapbox::util::recursive_wrapper<Object>,
                                     mapbox::util::recursive_wrapper<Array>,

include/util/json_renderer.hpp

@@ -25,6 +25,13 @@ struct Renderer
 {
     explicit Renderer(std::ostream &_out) : out(_out) {}
 
+    void operator()(const Buffer &buffer) const
+    {
+        out << "\"";
+        out << escape_JSON(buffer.value);
+        out << "\"";
+    }
+
     void operator()(const String &string) const
     {
         out << "\"";
@@ -81,6 +88,14 @@ struct ArrayRenderer
 {
     explicit ArrayRenderer(std::vector<char> &_out) : out(_out) {}
 
+    void operator()(const Buffer &buffer) const
+    {
+        out.push_back('\"');
+        const auto string_to_insert = escape_JSON(buffer.value);
+        out.insert(std::end(out), std::begin(string_to_insert), std::end(string_to_insert));
+        out.push_back('\"');
+    }
+
     void operator()(const String &string) const
     {
         out.push_back('\"');