String property limits

src/AIoTC_Config.h

@@ -156,6 +156,21 @@
   #define HAS_TCP
 #endif
 
+#ifdef HAS_TCP
+  #ifndef MQTT_TX_BUFFER_SIZE
+    #define MQTT_TX_BUFFER_SIZE 256
+  #endif // MQTT_TX_BUFFER_SIZE
+
+  #ifndef STRING_PROPERTY_MAX_SIZE
+    // 6 represents the expected overhead of a string property inside a cbor
+    #define STRING_PROPERTY_MAX_SIZE MQTT_TX_BUFFER_SIZE - 6
+  #endif // STRING_PROPERTY_MAX_SIZE
+#else
+  #ifndef STRING_PROPERTY_MAX_SIZE
+    #define STRING_PROPERTY_MAX_SIZE 50
+  #endif // STRING_PROPERTY_MAX_SIZE
+#endif // HAS_TCP
+
 /******************************************************************************
  * CONSTANTS
  ******************************************************************************/

src/ArduinoIoTCloudTCP.h

@@ -106,7 +106,7 @@ class ArduinoIoTCloudTCP: public ArduinoIoTCloudClass
 #endif
 
   private:
-    static const int MQTT_TRANSMIT_BUFFER_SIZE = 256;
+    static const int MQTT_TRANSMIT_BUFFER_SIZE = MQTT_TX_BUFFER_SIZE;
 
     enum class State
     {

src/property/types/CloudWrapperString.h

@@ -23,7 +23,9 @@
  ******************************************************************************/
 
 #include <Arduino.h>
+#include "AIoTC_Config.h"
 #include "CloudWrapperBase.h"
+#include <Arduino_DebugUtils.h>
 
 /******************************************************************************
    CLASS DECLARATION
@@ -50,7 +52,32 @@ class CloudWrapperString : public CloudWrapperBase {
       _cloud_value = _primitive_value;
     }
     virtual CborError appendAttributesToCloud(CborEncoder *encoder) {
-      return appendAttribute(_primitive_value, "", encoder);
+      // check that the string fits mqtt tx buffer
+      if(_name.length() > STRING_PROPERTY_MAX_SIZE) {
+        DEBUG_WARNING(
+          "[WARNING] %s:%s String property name exceedes transmit buffer size, unable to send property",
+          __FILE__, __LINE__);
+
+        /*
+         * If your reached this line it means that you set a preperty name that exceeded the current maximum capabilities
+         * of transmission buffer size. You can either change the buiffer size or the property name can be shortened.
+         * Look below for raising the buffer size
+         */
+
+        return CborErrorOutOfMemory;
+      } else if(_primitive_value.length() + _name.length() > STRING_PROPERTY_MAX_SIZE) {
+        DEBUG_WARNING("[WARNING] %s:%s String property exceedes transmit buffer size", __FILE__, __LINE__);
+
+        /*
+         * If your reached this line it means that the value and the property name exceed the current maximum capabilities
+         * of transmission buffer size. to fix this you can raise the size of the buffer.
+         * you can raise the size of the buffer by setting #define MQTT_TX_BUFFER_SIZE <VALUE> at the beginning of the file
+         */
+
+        return appendAttribute("ERROR_PROPERTY_TOO_LONG", "", encoder);
+      } else {
+        return appendAttribute(_primitive_value, "", encoder);
+      }
     }
     virtual void setAttributesFromCloud() {
       setAttribute(_cloud_value, "");