Add NULL support to Client DER library

client/src/der.vala

@@ -59,6 +59,8 @@ namespace StudySystemClient.Der {
 			return new Utf8String.from_content(content);
 		case Sequence.TYPE:
 			return new Sequence.from_content(content);
+		case Null.TYPE:
+			return new Null.from_content(content);
 		default:
 			throw new DecodeError.UNKNOWN_TYPE("Unsupported type: %02x",
 											   type);
@@ -287,4 +289,22 @@ namespace StudySystemClient.Der {
 			value = decode(bytes);
 		}
 	}
+
+	public class Null : Datum {
+		internal const uint8 TYPE = 0x05;
+
+		public Null() {
+			type = TYPE;
+			content = new uint8[] {};
+		}
+
+		internal Null.from_content(uint8[] bytes) throws DecodeError {
+			if (bytes.length != 0) {
+				throw new DecodeError.INVALID_CONTENT(
+					"Non-empty content for NULL");
+			}
+			type = TYPE;
+			content = bytes;
+		}
+	}
 }

client/tests/der_tests.vala

@@ -180,6 +180,10 @@ void main(string[] args) {
 			test_encode(choice, expected);
 		});
 
+	Test.add_func("/encode/null", () => {
+			test_encode(new Der.Null(), { 0x05, 0x00 });
+		});
+
 	/*
 	 * Decoding
 	 */
@@ -289,5 +293,23 @@ void main(string[] args) {
 			test_utf8string_value("foo", choice.value);
 		});
 
+	Test.add_func("/decode/null", () => {
+			var bytes = new uint8[] { 0x05, 0x00 };
+			Der.Null @null;
+			try {
+				@null = decode(bytes) as Der.Null;
+			} catch (DecodeError err) {
+				Test.message("Decoding failed: %s", err.message);
+				Test.fail();
+				return;
+			}
+			if (@null == null) {
+				Test.message("Bytes were not decoded as a NULL");
+				Test.fail();
+				return;
+			}
+		});
+
+
 	Test.run();
 }