org.bouncycastle.asn1.DERBitString Maven / Gradle / Ivy
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);
}
}