Added support for Printable (closes #1444)

extras/tests/Helpers/api/Print.h

@@ -0,0 +1,33 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2021
+// MIT License
+
+#pragma once
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+class Print {
+ public:
+  virtual ~Print() {}
+
+  virtual size_t write(uint8_t) = 0;
+  virtual size_t write(const uint8_t *buffer, size_t size) = 0;
+
+  size_t write(const char *str) {
+    if (!str)
+      return 0;
+    return write(reinterpret_cast<const uint8_t *>(str), strlen(str));
+  }
+
+  size_t write(const char *buffer, size_t size) {
+    return write(reinterpret_cast<const uint8_t *>(buffer), size);
+  }
+};
+
+class Printable {
+ public:
+  virtual ~Printable() {}
+  virtual size_t printTo(Print &p) const = 0;
+};