security/src/main/java/io/airlift/security/der/DerUtils.java
public static byte[] decodeSequenceOptionalElement(byte[] element)
    {
        int index = 0;

        // check tag
        checkArgument((element[0] & 0xE0) == 0xA0, "Expected optional sequence element tag");
        index++;

        // read length
        int length = decodeLength(element, index);
        index += encodedLengthSize(length);
        checkArgument(length + index == element.length, "Invalid optional sequence element");

        return Arrays.copyOfRange(element, index, index + length);
    }
public static byte[] decodeSequenceOptionalElement(byte[] element)
    {
        int index = 0;

        // check tag
        checkArgument((element[0] & 0xE0) == 0xA0, "Expected optional sequence element tag");
        index++;

        // read length
        int length = decodeLength(element, index);
        index += encodedLengthSize(length);
        checkArgument(length + index == element.length, "Invalid optional sequence element");

        return Arrays.copyOfRange(element, index, index + length);
    }
Decodes a optional element of a sequence.