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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 and up. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
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package org.bouncycastle.asn1;

import java.io.IOException;

/**
 * The DLSet encodes ASN.1 SET value without element ordering,
 * and always using definite length form.
 * 
 * X.690
 * 8: Basic encoding rules
 * 8.11 Encoding of a set value 
 * 8.11.1 The encoding of a set value shall be constructed
 * 
 * 8.11.2 The contents octets shall consist of the complete
 * encoding of a data value from each of the types listed in the
 * ASN.1 definition of the set type, in an order chosen by the sender,
 * unless the type was referenced with the keyword
 * OPTIONAL or the keyword DEFAULT.
 * 

 * 8.11.3 The encoding of a data value may, but need not,
 * be present for a type which was referenced with the keyword
 * OPTIONAL or the keyword DEFAULT.
 * 

 * NOTE — The order of data values in a set value is not significant,
 * and places no constraints on the order during transfer
 * 
 * 9: Canonical encoding rules
 * 9.3 Set components
 * The encodings of the component values of a set value shall
 * appear in an order determined by their tags as specified
 * in 8.6 of ITU-T Rec. X.680 | ISO/IEC 8824-1.
 * Additionally, for the purposes of determining the order in which
 * components are encoded when one or more component is an untagged
 * choice type, each untagged choice type is ordered as though it
 * has a tag equal to that of the smallest tag in that choice type
 * or any untagged choice types nested within.
 * 10: Distinguished encoding rules
 * 10.3 Set components
 * The encodings of the component values of a set value shall appear
 * in an order determined by their tags as specified
 * in 8.6 of ITU-T Rec. X.680 | ISO/IEC 8824-1.
 * 
 * NOTE — Where a component of the set is an untagged choice type,
 * the location of that component in the ordering will depend on
 * the tag of the choice component being encoded.
 * 
 * 11: Restrictions on BER employed by both CER and DER
 * 11.5 Set and sequence components with default value 
 * The encoding of a set value or sequence value shall not include
 * an encoding for any component value which is equal to
 * its default value.
 */
public class DLSet
    extends ASN1Set
{
    private int bodyLength = -1;

    /**
     * create an empty set
     */
    public DLSet()
    {
    }

    /**
     * @param element - a single object that makes up the set.
     */
    public DLSet(ASN1Encodable element)
    {
        super(element);
    }

    /**
     * @param elementVector - a vector of objects making up the set.
     */
    public DLSet(ASN1EncodableVector elementVector)
    {
        super(elementVector, false);
    }

    /**
     * create a set from an array of objects.
     */
    public DLSet(ASN1Encodable[] elements)
    {
        super(elements, false);
    }

    DLSet(boolean isSorted, ASN1Encodable[] elements)
    {
        super(isSorted, elements);
    }

    private int getBodyLength() throws IOException
    {
        if (bodyLength < 0)
        {
            int count = elements.length;
            int totalLength = 0;

            for (int i = 0; i < count; ++i)
            {
                ASN1Primitive dlObject = elements[i].toASN1Primitive().toDLObject();
                totalLength += dlObject.encodedLength();
            }

            this.bodyLength = totalLength;
        }

        return bodyLength;
    }

    int encodedLength() throws IOException
    {
        int length = getBodyLength();

        return 1 + StreamUtil.calculateBodyLength(length) + length;
    }

    /**
     * A note on the implementation:
     * 
     * As DL requires the constructed, definite-length model to
     * be used for structured types, this varies slightly from the
     * ASN.1 descriptions given. Rather than just outputting SET,
     * we also have to specify CONSTRUCTED, and the objects length.
     */
    void encode(ASN1OutputStream out, boolean withTag) throws IOException
    {
        if (withTag)
        {
            out.write(BERTags.SET | BERTags.CONSTRUCTED);
        }

        ASN1OutputStream dlOut = out.getDLSubStream();

        int count = elements.length;
        if (bodyLength >= 0 || count > 16)
        {
            out.writeLength(getBodyLength());

            for (int i = 0; i < count; ++i)
            {
                dlOut.writePrimitive(elements[i].toASN1Primitive(), true);
            }
        }
        else
        {
            int totalLength = 0;

            ASN1Primitive[] dlObjects = new ASN1Primitive[count];
            for (int i = 0; i < count; ++i)
            {
                ASN1Primitive dlObject = elements[i].toASN1Primitive().toDLObject();
                dlObjects[i] = dlObject;
                totalLength += dlObject.encodedLength();
            }

            this.bodyLength = totalLength;
            out.writeLength(totalLength);

            for (int i = 0; i < count; ++i)
            {
                dlOut.writePrimitive(dlObjects[i], true);
            }
        }
    }

    ASN1Primitive toDLObject()
    {
        return this;
    }
}