Initial import of libdpf.

Co-authored-by: Cursor <cursoragent@cursor.com>

thirdparty/json/docs/examples/is_null.cpp

@@ -0,0 +1,30 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create JSON values
+    json j_null;
+    json j_boolean = true;
+    json j_number_integer = 17;
+    json j_number_unsigned_integer = 12345678987654321u;
+    json j_number_float = 23.42;
+    json j_object = {{"one", 1}, {"two", 2}};
+    json j_array = {1, 2, 4, 8, 16};
+    json j_string = "Hello, world";
+    json j_binary = json::binary({1, 2, 3});
+
+    // call is_null()
+    std::cout << std::boolalpha;
+    std::cout << j_null.is_null() << '\n';
+    std::cout << j_boolean.is_null() << '\n';
+    std::cout << j_number_integer.is_null() << '\n';
+    std::cout << j_number_unsigned_integer.is_null() << '\n';
+    std::cout << j_number_float.is_null() << '\n';
+    std::cout << j_object.is_null() << '\n';
+    std::cout << j_array.is_null() << '\n';
+    std::cout << j_string.is_null() << '\n';
+    std::cout << j_binary.is_null() << '\n';
+}