package model.asn1;

/**
 * Represents the class (UNIVERSAL, APPLICATION, PRIVATE, CONTEXT-SPECIFIC) of an ASN.1 tag. See X.680$8.1.
 * The purpose of UNIVERSAL, APPLICATION, PRIVATE, and CONTEXT_SPECIFIC can be found in X.680 spec.
 * For example, UNIVERSAL means tags specified in the core ASN.1 spec.
 * This class also represents the value to the two highest bits of DER-encoded tag values.
 */
public enum TagClass {
    UNIVERSAL(Values.UNIVERSAL),
    APPLICATION(Values.APPLICATION),
    PRIVATE(Values.PRIVATE),
    CONTEXT_SPECIFIC(Values.CONTENT_SPECIFIC);

    private final Byte val;

    /**
     * EFFECT: Constructs the tag class with the given DER tag byte value.
     * REQUIRES: The Byte value must have low 6bits cleared.
     */
    TagClass(Byte val) {
        this.val = val;
    }

    public Byte getVal() {
        return val;
    }

    /**
     * The constants of high-two-bit values for Tag DER encoding.
     */
    public static final class Values {
        // 0b00000000
        public static final Byte UNIVERSAL = 0x0;
        // 0b01000000
        public static final Byte APPLICATION = 0x40;
        // 0b11000000
        public static final Byte PRIVATE = -64;
        // 0b10000000
        public static final Byte CONTENT_SPECIFIC = -128;
    }
}