DerEncoder Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/ssl/pem/PemPrivateKeyParser.java lines 279–344

	static class DerEncoder {

		private final ByteArrayOutputStream stream = new ByteArrayOutputStream();

		void objectIdentifier(@Nullable EncodedOid encodedOid) throws IOException {
			int code = (encodedOid != null) ? 0x06 : 0x05;
			codeLengthBytes(code, (encodedOid != null) ? encodedOid.toByteArray() : null);
		}

		void integer(int... encodedInteger) throws IOException {
			codeLengthBytes(0x02, bytes(encodedInteger));
		}

		void octetString(byte[] bytes) throws IOException {
			codeLengthBytes(0x04, bytes);
		}

		void sequence(byte[] bytes) throws IOException {
			codeLengthBytes(0x30, bytes);
		}

		void codeLengthBytes(int code, byte @Nullable [] bytes) throws IOException {
			this.stream.write(code);
			int length = (bytes != null) ? bytes.length : 0;
			if (length <= 127) {
				this.stream.write(length & 0xFF);
			}
			else {
				ByteArrayOutputStream lengthStream = new ByteArrayOutputStream();
				while (length != 0) {
					lengthStream.write(length & 0xFF);
					length = length >> 8;
				}
				byte[] lengthBytes = lengthStream.toByteArray();
				this.stream.write(0x80 | lengthBytes.length);
				for (int i = lengthBytes.length - 1; i >= 0; i--) {
					this.stream.write(lengthBytes[i]);
				}
			}
			if (bytes != null) {
				this.stream.write(bytes);
			}
		}

		private static byte @Nullable [] bytes(int @Nullable ... elements) {
			if (elements == null) {
				return null;
			}
			byte[] result = new byte[elements.length];
			for (int i = 0; i < elements.length; i++) {
				result[i] = (byte) elements[i];
			}
			return result;
		}

		byte[] toSequence() throws IOException {
			DerEncoder sequenceEncoder = new DerEncoder();
			sequenceEncoder.sequence(toByteArray());
			return sequenceEncoder.toByteArray();
		}

		byte[] toByteArray() {
			return this.stream.toByteArray();
		}

	}