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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.4.
package org.bouncycastle.asn1;
import java.io.ByteArrayOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.io.Streams;
public class DERBitString
extends ASN1Primitive
implements ASN1String
{
private static final char[] table = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
protected final byte[] data;
protected final int padBits;
/**
* @param bitString an int containing the BIT STRING
* @return the correct number of pad bits for a bit string defined in
* a 32 bit constant
*/
static protected int getPadBits(
int bitString)
{
int val = 0;
for (int i = 3; i >= 0; i--)
{
//
// this may look a little odd, but if it isn't done like this pre jdk1.2
// JVM's break!
//
if (i != 0)
{
if ((bitString >> (i * 8)) != 0)
{
val = (bitString >> (i * 8)) & 0xFF;
break;
}
}
else
{
if (bitString != 0)
{
val = bitString & 0xFF;
break;
}
}
}
if (val == 0)
{
return 7;
}
int bits = 1;
while (((val <<= 1) & 0xFF) != 0)
{
bits++;
}
return 8 - bits;
}
/**
* @param bitString an int containing the BIT STRING
* @return the correct number of bytes for a bit string defined in
* a 32 bit constant
*/
static protected byte[] getBytes(int bitString)
{
int bytes = 4;
for (int i = 3; i >= 1; i--)
{
if ((bitString & (0xFF << (i * 8))) != 0)
{
break;
}
bytes--;
}
byte[] result = new byte[bytes];
for (int i = 0; i < bytes; i++)
{
result[i] = (byte) ((bitString >> (i * 8)) & 0xFF);
}
return result;
}
/**
* 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;
}
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)o).getOctets());
}
}
protected DERBitString(
byte data,
int padBits)
{
this.data = new byte[1];
this.data[0] = data;
this.padBits = 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)
{
this.data = data;
this.padBits = padBits;
}
public DERBitString(
byte[] data)
{
this(data, 0);
}
public DERBitString(
int value)
{
this.data = getBytes(value);
this.padBits = getPadBits(value);
}
public DERBitString(
ASN1Encodable obj)
throws IOException
{
this.data = obj.toASN1Primitive().getEncoded(ASN1Encoding.DER);
this.padBits = 0;
}
public byte[] getBytes()
{
return data;
}
public int getPadBits()
{
return padBits;
}
/**
* @return the value of the bit string as an int (truncating if necessary)
*/
public int intValue()
{
int value = 0;
for (int i = 0; i != data.length && i != 4; i++)
{
value |= (data[i] & 0xff) << (8 * i);
}
return value;
}
boolean isConstructed()
{
return false;
}
int encodedLength()
{
return 1 + StreamUtil.calculateBodyLength(data.length + 1) + data.length + 1;
}
void encode(
ASN1OutputStream out)
throws IOException
{
byte[] bytes = new byte[getBytes().length + 1];
bytes[0] = (byte)getPadBits();
System.arraycopy(getBytes(), 0, bytes, 1, bytes.length - 1);
out.writeEncoded(BERTags.BIT_STRING, bytes);
}
public int hashCode()
{
return padBits ^ Arrays.hashCode(data);
}
protected boolean asn1Equals(
ASN1Primitive o)
{
if (!(o instanceof DERBitString))
{
return false;
}
DERBitString other = (DERBitString)o;
return this.padBits == other.padBits
&& Arrays.areEqual(this.data, other.data);
}
public String getString()
{
StringBuffer buf = new StringBuffer("#");
ByteArrayOutputStream bOut = new ByteArrayOutputStream();
ASN1OutputStream aOut = new ASN1OutputStream(bOut);
try
{
aOut.writeObject(this);
}
catch (IOException e)
{
throw new ASN1ParsingException("Internal error encoding BitString: " + e.getMessage(), e);
}
byte[] string = bOut.toByteArray();
for (int i = 0; i != string.length; i++)
{
buf.append(table[(string[i] >>> 4) & 0xf]);
buf.append(table[string[i] & 0xf]);
}
return buf.toString();
}
public String toString()
{
return getString();
}
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);
}
static DERBitString fromInputStream(int length, InputStream stream)
throws IOException
{
if (length < 1)
{
throw new IllegalArgumentException("truncated BIT STRING detected");
}
int padBits = stream.read();
byte[] data = new byte[length - 1];
if (data.length != 0)
{
if (Streams.readFully(stream, data) != data.length)
{
throw new EOFException("EOF encountered in middle of BIT STRING");
}
}
return new DERBitString(data, padBits);
}
}
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