Improve performance of JSON rendering (#6380)

src/benchmarks/CMakeLists.txt

@@ -30,6 +30,18 @@ target_link_libraries(match-bench
 	${TBB_LIBRARIES}
 	${MAYBE_SHAPEFILE})
 
+add_executable(json-render-bench
+	EXCLUDE_FROM_ALL
+	json_render.cpp
+	$<TARGET_OBJECTS:UTIL>)
+
+target_link_libraries(json-render-bench
+	osrm
+	${BOOST_BASE_LIBRARIES}
+	${CMAKE_THREAD_LIBS_INIT}
+	${TBB_LIBRARIES}
+	${MAYBE_SHAPEFILE})
+
 add_executable(alias-bench
 	EXCLUDE_FROM_ALL
     ${AliasBenchmarkSources}
@@ -41,6 +53,8 @@ target_link_libraries(alias-bench
 	${TBB_LIBRARIES}
 	${MAYBE_SHAPEFILE})
 
+
+
 add_executable(packedvector-bench
 	EXCLUDE_FROM_ALL
     ${PackedVectorBenchmarkSources}
@@ -58,4 +72,5 @@ add_custom_target(benchmarks
 	rtree-bench
 	packedvector-bench
 	match-bench
+	json-render-bench
     alias-bench)

src/benchmarks/json_render.cpp

@@ -0,0 +1,128 @@
+
+#include "osrm/json_container.hpp"
+#include "util/json_container.hpp"
+#include "util/json_renderer.hpp"
+#include "util/timing_util.hpp"
+#include <cstdlib>
+#include <fstream>
+#include <iostream>
+#include <rapidjson/document.h>
+#include <sstream>
+#include <stdexcept>
+
+using namespace osrm;
+
+namespace
+{
+
+void convert(const rapidjson::Value &value, json::Value &result)
+{
+    if (value.IsString())
+    {
+        result = json::String{value.GetString()};
+    }
+    else if (value.IsNumber())
+    {
+        result = json::Number{value.GetDouble()};
+    }
+    else if (value.IsObject())
+    {
+        json::Object object;
+        for (auto itr = value.MemberBegin(); itr != value.MemberEnd(); ++itr)
+        {
+            json::Value member;
+            convert(itr->value, member);
+            object.values.emplace(itr->name.GetString(), std::move(member));
+        }
+        result = std::move(object);
+    }
+    else if (value.IsArray())
+    {
+        json::Array array;
+        for (auto itr = value.Begin(); itr != value.End(); ++itr)
+        {
+            json::Value member;
+            convert(*itr, member);
+            array.values.push_back(std::move(member));
+        }
+        result = std::move(array);
+    }
+    else if (value.IsBool())
+    {
+        if (value.GetBool())
+        {
+            result = json::True{};
+        }
+        else
+        {
+            result = json::False{};
+        }
+    }
+    else if (value.IsNull())
+    {
+        result = json::Null{};
+    }
+    else
+    {
+        throw std::runtime_error("unknown type");
+    }
+}
+
+json::Object load(const char *filename)
+{
+    // load file to std string
+    std::ifstream file(filename);
+    std::stringstream buffer;
+    buffer << file.rdbuf();
+    std::string json = buffer.str();
+
+    // load rapidjson document
+    rapidjson::Document document;
+    document.Parse(json.c_str());
+    if (document.HasParseError())
+    {
+        throw std::runtime_error("Failed to parse JSON");
+    }
+
+    json::Value result;
+    convert(document, result);
+    return result.get<json::Object>();
+}
+
+} // namespace
+
+int main(int argc, char **argv)
+{
+    if (argc < 2)
+    {
+        std::cerr << "Usage: " << argv[0] << " file.json\n";
+        return EXIT_FAILURE;
+    }
+
+    const auto obj = load(argv[1]);
+
+    TIMER_START(string);
+    std::string out_str;
+    json::render(out_str, obj);
+    TIMER_STOP(string);
+    std::cout << "String: " << TIMER_MSEC(string) << "ms" << std::endl;
+
+    TIMER_START(stringstream);
+    std::stringstream ss;
+    json::render(ss, obj);
+    std::string out_ss_str{ss.str()};
+    TIMER_STOP(stringstream);
+
+    std::cout << "Stringstream: " << TIMER_MSEC(stringstream) << "ms" << std::endl;
+    TIMER_START(vector);
+    std::vector<char> out_vec;
+    json::render(out_vec, obj);
+    TIMER_STOP(vector);
+    std::cout << "Vector: " << TIMER_MSEC(vector) << "ms" << std::endl;
+
+    if (std::string{out_vec.begin(), out_vec.end()} != out_str || out_str != out_ss_str)
+    {
+        throw std::logic_error("Vector/stringstream/string results are not equal");
+    }
+    return EXIT_SUCCESS;
+}

src/nodejs/node_osrm.cpp

@@ -167,13 +167,13 @@ inline void async(const Nan::FunctionCallbackInfo<v8::Value> &info,
                 ParseResult(status, json_result);
                 if (pluginParams.renderToBuffer)
                 {
-                    std::ostringstream buf;
-                    osrm::util::json::render(buf, json_result);
-                    result = buf.str();
+                    std::string json_string;
+                    osrm::util::json::render(json_string, json_result);
+                    result = std::move(json_string);
                 }
                 else
                 {
-                    result = json_result;
+                    result = std::move(json_result);
                 }
             }
             break;