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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.EOFException;
import java.io.IOException;
import java.io.InputStream;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.io.Streams;
/**
* Base class for BIT STRING objects
*/
public abstract class ASN1BitString
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 0;
}
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)
{
if (bitString == 0)
{
return new byte[0];
}
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;
}
protected ASN1BitString(byte data, int padBits)
{
if (padBits > 7 || padBits < 0)
{
throw new IllegalArgumentException("pad bits cannot be greater than 7 or less than 0");
}
this.data = new byte[]{ data };
this.padBits = padBits;
}
/**
* Base constructor.
*
* @param data the octets making up the bit string.
* @param padBits the number of extra bits at the end of the string.
*/
public ASN1BitString(
byte[] data,
int padBits)
{
if (data == null)
{
throw new NullPointerException("'data' cannot be null");
}
if (data.length == 0 && padBits != 0)
{
throw new IllegalArgumentException("zero length data with non-zero pad bits");
}
if (padBits > 7 || padBits < 0)
{
throw new IllegalArgumentException("pad bits cannot be greater than 7 or less than 0");
}
this.data = Arrays.clone(data);
this.padBits = padBits;
}
/**
* Return a String representation of this BIT STRING
*
* @return a String representation.
*/
public String getString()
{
StringBuffer buf = new StringBuffer("#");
byte[] string;
try
{
string = getEncoded();
}
catch (IOException e)
{
throw new ASN1ParsingException("Internal error encoding BitString: " + e.getMessage(), e);
}
for (int i = 0; i != string.length; i++)
{
buf.append(table[(string[i] >>> 4) & 0xf]);
buf.append(table[string[i] & 0xf]);
}
return buf.toString();
}
/**
* @return the value of the bit string as an int (truncating if necessary)
*/
public int intValue()
{
int value = 0;
int end = Math.min(4, data.length - 1);
for (int i = 0; i < end; ++i)
{
value |= (data[i] & 0xFF) << (8 * i);
}
if (0 <= end && end < 4)
{
byte der = (byte)(data[end] & (0xFF << padBits));
value |= (der & 0xFF) << (8 * end);
}
return value;
}
/**
* Return the octets contained in this BIT STRING, checking that this BIT STRING really
* does represent an octet aligned string. Only use this method when the standard you are
* following dictates that the BIT STRING will be octet aligned.
*
* @return a copy of the octet aligned data.
*/
public byte[] getOctets()
{
if (padBits != 0)
{
throw new IllegalStateException("attempt to get non-octet aligned data from BIT STRING");
}
return Arrays.clone(data);
}
public byte[] getBytes()
{
return derForm(data, padBits);
}
public int getPadBits()
{
return padBits;
}
public String toString()
{
return getString();
}
public int hashCode()
{
int end = data.length;
if (--end < 0)
{
return 1;
}
byte der = (byte)(data[end] & (0xFF << padBits));
int hc = Arrays.hashCode(data, 0, end);
hc *= 257;
hc ^= der;
return hc ^ padBits;
}
boolean asn1Equals(
ASN1Primitive o)
{
if (!(o instanceof ASN1BitString))
{
return false;
}
ASN1BitString other = (ASN1BitString)o;
if (padBits != other.padBits)
{
return false;
}
byte[] a = data, b = other.data;
int end = a.length;
if (end != b.length)
{
return false;
}
if (--end < 0)
{
return true;
}
for (int i = 0; i < end; ++i)
{
if (a[i] != b[i])
{
return false;
}
}
byte derA = (byte)(a[end] & (0xFF << padBits));
byte derB = (byte)(b[end] & (0xFF << padBits));
return derA == derB;
}
/**
* @deprecated Will be hidden/removed.
*/
protected static byte[] derForm(byte[] data, int padBits)
{
if (0 == data.length)
{
return data;
}
byte[] rv = Arrays.clone(data);
// DER requires pad bits be zero
rv[data.length - 1] &= (0xFF << padBits);
return rv;
}
static ASN1BitString 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");
}
if (padBits > 0 && padBits < 8)
{
if (data[data.length - 1] != (byte)(data[data.length - 1] & (0xFF << padBits)))
{
return new DLBitString(data, padBits);
}
}
}
return new DERBitString(data, padBits);
}
public ASN1Primitive getLoadedObject()
{
return this.toASN1Primitive();
}
ASN1Primitive toDERObject()
{
return new DERBitString(data, padBits);
}
ASN1Primitive toDLObject()
{
return new DLBitString(data, padBits);
}
abstract void encode(ASN1OutputStream out, boolean withTag) throws IOException;
}
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