Added support for std::string_view (closes #1578, closes #1554)

extras/tests/Cpp17/string_view.cpp

@@ -0,0 +1,79 @@
+#include <ArduinoJson.h>
+
+#include <catch.hpp>
+#include <string_view>
+
+#if !ARDUINOJSON_ENABLE_STRING_VIEW
+#  error ARDUINOJSON_ENABLE_STRING_VIEW must be set to 1
+#endif
+
+TEST_CASE("string_view") {
+  StaticJsonDocument<128> doc;
+  JsonVariant variant = doc.to<JsonVariant>();
+
+  SECTION("deserializeJson()") {
+    auto err = deserializeJson(doc, std::string_view("123", 2));
+    REQUIRE(err == DeserializationError::Ok);
+    REQUIRE(doc.as<int>() == 12);
+  }
+
+  SECTION("JsonDocument::set()") {
+    doc.set(std::string_view("123", 2));
+    REQUIRE(doc.as<std::string>() == "12");
+  }
+
+  SECTION("JsonDocument::operator[]() const") {
+    doc["ab"] = "Yes";
+    doc["abc"] = "No";
+    REQUIRE(doc[std::string_view("abc", 2)] == "Yes");
+  }
+
+  SECTION("JsonDocument::operator[]()") {
+    doc[std::string_view("abc", 2)] = "Yes";
+    REQUIRE(doc["ab"] == "Yes");
+  }
+
+  SECTION("JsonVariant::operator==()") {
+    variant.set("A");
+    REQUIRE(variant == std::string_view("AX", 1));
+    REQUIRE_FALSE(variant == std::string_view("BX", 1));
+  }
+
+  SECTION("JsonVariant::operator>()") {
+    variant.set("B");
+    REQUIRE(variant > std::string_view("AX", 1));
+    REQUIRE_FALSE(variant > std::string_view("CX", 1));
+  }
+
+  SECTION("JsonVariant::operator<()") {
+    variant.set("B");
+    REQUIRE(variant < std::string_view("CX", 1));
+    REQUIRE_FALSE(variant < std::string_view("AX", 1));
+  }
+
+  SECTION("String deduplication") {
+    doc.add(std::string_view("example one", 7));
+    REQUIRE(doc.memoryUsage() == JSON_ARRAY_SIZE(1) + 8);
+
+    doc.add(std::string_view("example two", 7));
+    REQUIRE(doc.memoryUsage() == JSON_ARRAY_SIZE(2) + 8);
+  }
+}
+
+using ARDUINOJSON_NAMESPACE::adaptString;
+
+TEST_CASE("StringViewAdapter") {
+  std::string_view str("bravoXXX", 5);
+  auto adapter = adaptString(str);
+
+  CHECK(adapter.compare(NULL) > 0);
+  CHECK(adapter.compare("alpha") > 0);
+  CHECK(adapter.compare("bravo") == 0);
+  CHECK(adapter.compare("charlie") < 0);
+
+  CHECK(adapter.equals("bravo"));
+  CHECK_FALSE(adapter.equals("charlie"));
+  CHECK_FALSE(adapter.equals(NULL));
+
+  CHECK(adapter.size() == 5);
+}