org.bouncycastle.asn1.DERBitString.java Source code

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Here is the source code for org.bouncycastle.asn1.DERBitString.java

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package org.bouncycastle.asn1;

import java.io.IOException;

/**
 * A BIT STRING with DER encoding - the first byte contains the count of padding bits included in the byte array's last byte.
 */
public class DERBitString extends ASN1BitString {
    /**
     * return a Bit String from the passed in object
     *
     * @param obj a DERBitString or an object that can be converted into one.
     * @exception IllegalArgumentException if the object cannot be converted.
     * @return a DERBitString instance, or null.
     */
    public static DERBitString getInstance(Object obj) {
        if (obj == null || obj instanceof DERBitString) {
            return (DERBitString) obj;
        }
        if (obj instanceof DLBitString) {
            return new DERBitString(((DLBitString) obj).data, ((DLBitString) obj).padBits);
        }
        if (obj instanceof byte[]) {
            try {
                return (DERBitString) fromByteArray((byte[]) obj);
            } catch (Exception e) {
                throw new IllegalArgumentException("encoding error in getInstance: " + e.toString());
            }
        }

        throw new IllegalArgumentException("illegal object in getInstance: " + obj.getClass().getName());
    }

    /**
     * return a Bit String from a tagged object.
     *
     * @param obj the tagged object holding the object we want
     * @param explicit true if the object is meant to be explicitly
     *              tagged false otherwise.
     * @exception IllegalArgumentException if the tagged object cannot
     *               be converted.
     * @return a DERBitString instance, or null.
     */
    public static DERBitString getInstance(ASN1TaggedObject obj, boolean explicit) {
        ASN1Primitive o = obj.getObject();

        if (explicit || o instanceof DERBitString) {
            return getInstance(o);
        } else {
            return fromOctetString(ASN1OctetString.getInstance(o).getOctets());
        }
    }

    protected DERBitString(byte data, int padBits) {
        super(data, padBits);
    }

    /**
     * @param data the octets making up the bit string.
     * @param padBits the number of extra bits at the end of the string.
     */
    public DERBitString(byte[] data, int padBits) {
        super(data, padBits);
    }

    public DERBitString(byte[] data) {
        this(data, 0);
    }

    public DERBitString(int value) {
        super(getBytes(value), getPadBits(value));
    }

    public DERBitString(ASN1Encodable obj) throws IOException {
        super(obj.toASN1Primitive().getEncoded(ASN1Encoding.DER), 0);
    }

    boolean isConstructed() {
        return false;
    }

    int encodedLength() {
        return 1 + StreamUtil.calculateBodyLength(data.length + 1) + data.length + 1;
    }

    void encode(ASN1OutputStream out, boolean withTag) throws IOException {
        int len = data.length;
        if (0 == len || 0 == padBits || (data[len - 1] == (byte) (data[len - 1] & (0xFF << padBits)))) {
            out.writeEncoded(withTag, BERTags.BIT_STRING, (byte) padBits, data);
        } else {
            byte der = (byte) (data[len - 1] & (0xFF << padBits));
            out.writeEncoded(withTag, BERTags.BIT_STRING, (byte) padBits, data, 0, len - 1, der);
        }
    }

    ASN1Primitive toDERObject() {
        return this;
    }

    ASN1Primitive toDLObject() {
        return this;
    }

    static DERBitString fromOctetString(byte[] bytes) {
        if (bytes.length < 1) {
            throw new IllegalArgumentException("truncated BIT STRING detected");
        }

        int padBits = bytes[0];
        byte[] data = new byte[bytes.length - 1];

        if (data.length != 0) {
            System.arraycopy(bytes, 1, data, 0, bytes.length - 1);
        }

        return new DERBitString(data, padBits);
    }
}