Improve Json serialization

README.md

@@ -48,7 +48,9 @@
 
 - Implement stream producers that emit characters or lines from a stream
   (e.g., a serial port)
--
+- SKEmitter::as_signalk() has been renamed to SKEmitter::as_signalk_json().
+  It now writes its output to a JsonDocument reference instead
+  of returning a String.
 
 ### Migrating Existing Projects
 

src/sensesp/signalk/signalk_delta_queue.cpp

@@ -39,8 +39,13 @@ void SKDeltaQueue::append(const String& val) {
 void SKDeltaQueue::connect_emitters() {
   for (auto const& sk_source : SKEmitter::get_sources()) {
     if (sk_source->get_sk_path() != "") {
-      sk_source->attach(
-          [sk_source, this]() { this->append(sk_source->as_signalk()); });
+      sk_source->attach([sk_source, this]() {
+        String output;
+        JsonDocument doc;
+        sk_source->as_signalk_json(doc);
+        serializeJson(doc, output);
+        this->append(output);
+      });
     }
   }
 }

src/sensesp/signalk/signalk_emitter.h

@@ -29,9 +29,13 @@ class SKEmitter : virtual public Observable {
 
   /**
    * Returns the data to be reported to the server as
-   * a Signal K json string.
+   * a Signal K json object.
    */
-  virtual String as_signalk() { return "not implemented"; }
+  virtual void as_signalk_json(JsonDocument& doc) {
+    ESP_LOGE("SKEmitter", "as_signalk_json() not implemented");
+    JsonVariant obj = doc.as<JsonVariant>();
+    obj.set("ERROR! Not implemented");
+  }
 
   /**
    * Returns a Metadata structure that describes the sk_path this SKEmitter

src/sensesp/signalk/signalk_output.h

@@ -46,13 +46,9 @@ class SKOutput : public SKEmitter, public SymmetricTransform<T> {
     this->ValueProducer<T>::emit(new_value);
   }
 
-  virtual String as_signalk() override {
-    JsonDocument json_doc;
-    String json;
-    json_doc["path"] = this->get_sk_path();
-    json_doc["value"] = ValueProducer<T>::output;
-    serializeJson(json_doc, json);
-    return json;
+  virtual void as_signalk_json(JsonDocument& doc) override {
+    doc["path"] = this->get_sk_path();
+    doc["value"] = ValueProducer<T>::output;
   }
 
   virtual void get_configuration(JsonObject& root) override {
@@ -92,13 +88,9 @@ class SKOutputRawJson : public SKOutput<String> {
                   SKMetadata* meta = NULL)
       : SKOutput<String>(sk_path, config_path, meta) {}
 
-  virtual String as_signalk() override {
-    JsonDocument json_doc;
-    String json;
-    json_doc["path"] = this->get_sk_path();
-    json_doc["value"] = serialized(ValueProducer<String>::output);
-    serializeJson(json_doc, json);
-    return json;
+  virtual void as_signalk_json(JsonDocument& doc) override {
+    doc["path"] = this->get_sk_path();
+    doc["value"] = serialized(ValueProducer<String>::output);
   }
 };
 

src/sensesp/signalk/signalk_time.cpp

@@ -8,13 +8,9 @@ SKOutputTime::SKOutputTime(const String& sk_path, const String& config_path)
   load_configuration();
 }
 
-String SKOutputTime::as_signalk() {
-  JsonDocument json_doc;
-  String json;
-  json_doc["path"] = this->sk_path_;
-  json_doc["value"] = output;
-  serializeJson(json_doc, json);
-  return json;
+void SKOutputTime::as_signalk_json(JsonDocument& doc){
+  doc["path"] = this->sk_path_;
+  doc["value"] = output;
 }
 
 void SKOutputTime::get_configuration(JsonObject& doc) {

src/sensesp/signalk/signalk_time.h

@@ -9,7 +9,7 @@ namespace sensesp {
 class SKOutputTime : public TimeString, public SKEmitter {
  public:
   SKOutputTime(const String& sk_path, const String& config_path = "");
-  virtual String as_signalk() override;
+  virtual void as_signalk_json(JsonDocument& doc) override;
   virtual void get_configuration(JsonObject& doc) override;
   virtual bool set_configuration(const JsonObject& config) override;
   virtual String get_config_schema() override;

src/sensesp/signalk/signalk_types.cpp

@@ -0,0 +1,46 @@
+
+#include "signalk_types.h"
+
+namespace sensesp {
+
+/**
+ * @brief Template specialization for SKOutputPosition::as_signalk_json()
+ *
+ * This specialization allows `Position` objects to be output as Signal K
+ * deltas.
+ *
+ * @tparam
+ * @return String
+ */
+template <>
+void SKOutput<Position>::as_signalk_json(JsonDocument& doc) {
+  doc["path"] = this->get_sk_path();
+  JsonObject value = doc["value"].to<JsonObject>();
+  value["latitude"] = output.latitude;
+  value["longitude"] = output.longitude;
+  if (output.altitude != kPositionInvalidAltitude) {
+    value["altitude"] = output.altitude;
+  }
+}
+
+template <>
+void SKOutput<ENUVector>::as_signalk_json(JsonDocument& doc) {
+  doc["path"] = this->get_sk_path();
+  JsonObject value = doc["value"].to<JsonObject>();
+  value["east"] = output.east;
+  value["north"] = output.north;
+  if (output.up != kPositionInvalidAltitude) {
+    value["up"] = output.up;
+  }
+}
+
+template <>
+void SKOutput<AttitudeVector>::as_signalk_json(JsonDocument& doc) {
+  doc["path"] = this->get_sk_path();
+  JsonObject value = doc["value"].to<JsonObject>();
+  value["roll"] = output.roll;
+  value["pitch"] = output.pitch;
+  value["yaw"] = output.yaw;
+}
+
+}  // namespace sensesp

src/sensesp/signalk/signalk_types.h

@@ -0,0 +1,26 @@
+#ifndef SENSESP_SRC_SENSESP_SIGNALK_SIGNALK_TYPES_H_
+#define SENSESP_SRC_SENSESP_SIGNALK_SIGNALK_TYPES_H_
+
+#include <vector>
+
+#include "sensesp/signalk/signalk_output.h"
+#include "sensesp/types/position.h"
+
+namespace sensesp {
+
+template <>
+void SKOutput<Position>::as_signalk_json(JsonDocument& doc);
+
+template <>
+void SKOutput<ENUVector>::as_signalk_json(JsonDocument& doc);
+
+template <>
+void SKOutput<AttitudeVector>::as_signalk_json(JsonDocument& doc);
+
+typedef SKOutput<Position> SKOutputPosition;
+typedef SKOutput<ENUVector> SKOutputENUVector;
+typedef SKOutput<AttitudeVector> SKOutputAttitudeVector;
+
+}  // namespace sensesp
+
+#endif

src/sensesp/system/async_response_handler.h

@@ -6,6 +6,7 @@
 #include <Arduino.h>
 #include <elapsedMillis.h>
 
+#include "sensesp_base_app.h"
 #include "valueproducer.h"
 
 namespace sensesp {
@@ -49,17 +50,18 @@ class AsyncResponseHandler : public ValueConsumer<bool>,
     this->emit(status_);
 
     if (timeout_event_ != nullptr) {
-      reactesp::EventLoop::app->remove(timeout_event_);
+      SensESPBaseApp::get_event_loop()->remove(timeout_event_);
       timeout_event_ = nullptr;
     }
-    timeout_event_ = reactesp::EventLoop::app->onDelay(timeout_, [this]() {
-      if (status_ == AsyncResponseStatus::kPending) {
-        ESP_LOGV("AsyncResponseHandler", "Timeout");
-        status_ = AsyncResponseStatus::kTimeout;
-        this->emit(status_);
-      }
-      this->timeout_event_ = nullptr;
-    });
+    timeout_event_ =
+        SensESPBaseApp::get_event_loop()->onDelay(timeout_, [this]() {
+          if (status_ == AsyncResponseStatus::kPending) {
+            ESP_LOGV("AsyncResponseHandler", "Timeout");
+            status_ = AsyncResponseStatus::kTimeout;
+            this->emit(status_);
+          }
+          this->timeout_event_ = nullptr;
+        });
   }
 
   void set(const bool& success) override {
@@ -72,7 +74,7 @@ class AsyncResponseHandler : public ValueConsumer<bool>,
 
     // Clear the timeout event
     if (timeout_event_ != nullptr) {
-      reactesp::EventLoop::app->remove(timeout_event_);
+      SensESPBaseApp::get_event_loop()->remove(timeout_event_);
       timeout_event_ = nullptr;
     }
 

src/sensesp/system/stream_producer.h

@@ -5,6 +5,7 @@
 
 #include "ReactESP.h"
 #include "sensesp/system/valueproducer.h"
+#include "sensesp_base_app.h"
 
 namespace sensesp {
 
@@ -14,12 +15,13 @@ namespace sensesp {
 class StreamCharProducer : public ValueProducer<char> {
  public:
   StreamCharProducer(Stream* stream) : stream_{stream} {
-    read_event_ = reactesp::EventLoop::app->onAvailable(*stream_, [this]() {
-      while (stream_->available()) {
-        char c = stream_->read();
-        this->emit(c);
-      }
-    });
+    read_event_ =
+        SensESPBaseApp::get_event_loop()->onAvailable(*stream_, [this]() {
+          while (stream_->available()) {
+            char c = stream_->read();
+            this->emit(c);
+          }
+        });
   }
 
  protected:
@@ -36,23 +38,24 @@ class StreamLineProducer : public ValueProducer<String> {
       : stream_{stream}, max_line_length_{max_line_length} {
     static int buf_pos = 0;
     buf_ = new char[max_line_length_ + 1];
-    read_event_ = reactesp::EventLoop::app->onAvailable(*stream_, [this]() {
-      while (stream_->available()) {
-        char c = stream_->read();
-        if (c == '\n') {
-          // Include the newline character in the output
-          buf_[buf_pos++] = c;
-          buf_[buf_pos] = '\0';
-          this->emit(buf_);
-          buf_pos = 0;
-        } else {
-          buf_[buf_pos++] = c;
-          if (buf_pos >= max_line_length_ - 1) {
-            buf_pos = 0;
+    read_event_ =
+        SensESPBaseApp::get_event_loop()->onAvailable(*stream_, [this]() {
+          while (stream_->available()) {
+            char c = stream_->read();
+            if (c == '\n') {
+              // Include the newline character in the output
+              buf_[buf_pos++] = c;
+              buf_[buf_pos] = '\0';
+              this->emit(buf_);
+              buf_pos = 0;
+            } else {
+              buf_[buf_pos++] = c;
+              if (buf_pos >= max_line_length_ - 1) {
+                buf_pos = 0;
+              }
+            }
           }
-        }
-      }
-    });
+        });
   }
 
  protected: