Added support for Printable (closes #1444)

extras/tests/Misc/printable.cpp

@@ -0,0 +1,112 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2021
+// MIT License
+
+#include <Arduino.h>
+#include <catch.hpp>
+
+#define ARDUINOJSON_ENABLE_ARDUINO_STREAM 1
+#include <ArduinoJson.h>
+
+struct PrintOneCharacterAtATime {
+  static size_t printStringTo(const std::string& s, Print& p) {
+    size_t result = 0;
+    for (std::string::const_iterator it = s.begin(); it != s.end(); ++it) {
+      size_t n = p.write(uint8_t(*it));
+      if (n == 0)
+        break;
+      result += n;
+    }
+    return result;
+  }
+};
+
+struct PrintAllAtOnce {
+  static size_t printStringTo(const std::string& s, Print& p) {
+    return p.write(s.data(), s.size());
+  }
+};
+
+template <typename PrintPolicy>
+struct PrintableString : public Printable {
+  PrintableString(const char* s) : _str(s), _total(0) {}
+
+  virtual size_t printTo(Print& p) const {
+    size_t result = PrintPolicy::printStringTo(_str, p);
+    _total += result;
+    return result;
+  }
+
+  size_t totalBytesWritten() const {
+    return _total;
+  }
+
+ private:
+  std::string _str;
+  mutable size_t _total;
+};
+
+TEST_CASE("Printable") {
+  SECTION("Enough space for the whole string") {
+    StaticJsonDocument<64> doc;
+    doc.set(666);
+
+    SECTION("Via Print::write(char)") {
+      PrintableString<PrintOneCharacterAtATime> printable = "Hello World!";
+      CHECK(doc.set(printable) == true);
+      CHECK(doc.as<std::string>() == "Hello World!");
+      CHECK(printable.totalBytesWritten() == 12);
+      CHECK(doc.overflowed() == false);
+      CHECK(doc.memoryUsage() == 13);
+    }
+
+    SECTION("Via Print::write(const char* size_t)") {
+      PrintableString<PrintAllAtOnce> printable = "Hello World!";
+      CHECK(doc.set(printable) == true);
+      CHECK(doc.as<std::string>() == "Hello World!");
+      CHECK(printable.totalBytesWritten() == 12);
+      CHECK(doc.overflowed() == false);
+      CHECK(doc.memoryUsage() == 13);
+    }
+  }
+
+  SECTION("Too small memory pool") {
+    StaticJsonDocument<8> doc;
+
+    SECTION("Via Print::write(char)") {
+      PrintableString<PrintOneCharacterAtATime> printable = "Hello World!";
+      CHECK(doc.set(printable) == false);
+      CHECK(doc.isNull());
+      CHECK(printable.totalBytesWritten() == 8);
+      CHECK(doc.overflowed() == true);
+      CHECK(doc.memoryUsage() == 0);
+    }
+
+    SECTION("Via Print::write(const char* size_t)") {
+      PrintableString<PrintAllAtOnce> printable = "Hello World!";
+      CHECK(doc.set(printable) == false);
+      CHECK(doc.isNull());
+      CHECK(printable.totalBytesWritten() == 0);
+      CHECK(doc.overflowed() == true);
+      CHECK(doc.memoryUsage() == 0);
+    }
+  }
+
+  SECTION("Null variant") {
+    JsonVariant var;
+    PrintableString<PrintOneCharacterAtATime> printable = "Hello World!";
+    CHECK(var.set(printable) == false);
+    CHECK(var.isNull());
+    CHECK(printable.totalBytesWritten() == 0);
+  }
+
+  SECTION("String deduplication") {
+    StaticJsonDocument<128> doc;
+    doc.add(PrintableString<PrintOneCharacterAtATime>("Hello World!"));
+    doc.add(PrintableString<PrintAllAtOnce>("Hello World!"));
+    REQUIRE(doc.size() == 2);
+    CHECK(doc[0] == "Hello World!");
+    CHECK(doc[1] == "Hello World!");
+    CHECK(doc.memoryUsage() == JSON_ARRAY_SIZE(2) + 13);
+  }
+}