org.xbib.asn1.ASN1BitString Maven / Gradle / Ivy
The newest version!
package org.xbib.asn1;
/**
* Representation of an ASN.1 BIT STRING.
* The BIT STRING type denotes an arbitary string of bits (ones and zeros).
* A BIT STRING value can have any length, including zero. The type is a
* string type.
*/
public final class ASN1BitString extends ASN1Any {
/**
* This constant is the ASN.1 UNIVERSAL tag value for BIT STRING.
*/
public static final int BIT_STRING_TAG = 0x03;
/**
* The values of the BIT STRING are stored in this array of boolean
* values.
*/
private boolean[] bits;
/**
* Constructor for an ASN.1 BIT STRING object. It sets the tag
* to the default value of UNIVERSAL 3, and the bits to the
* given bit values.
*
* @param bitValues - array of booleans representing the bit string.
*/
public ASN1BitString(boolean[] bitValues) {
bits = bitValues;
}
/**
* Constructor for an ASN.1 BIT STRING object from a BER encoding.
*
* @param ber The BER encoding to use.
* @param checkTag If true, it checks the tag. Use false if is implicitly tagged.
* @throws ASN1Exception If the BER encoding is incorrect.
*/
public ASN1BitString(BEREncoding ber, boolean checkTag)
throws ASN1Exception {
super(ber, checkTag); // superclass will call berDecode
}
/**
* Method for initializing the object from a BER encoding.
*
* @param berEncoding The BER encoding to use.
* @param checkTag If true, it checks the tag. Use false if is implicitly tagged.
* @throws ASN1EncodingException If the BER encoding is incorrect.
*/
@Override
public void berDecode(BEREncoding berEncoding, boolean checkTag)
throws ASN1EncodingException {
if (checkTag && (berEncoding.tagGet() != BIT_STRING_TAG || berEncoding.tagTypeGet() != BEREncoding.UNIVERSAL_TAG)) {
throw new ASN1EncodingException("ASN.1 BIT STRING: bad BER: tag=" + berEncoding.tagGet() +
" expected " + BIT_STRING_TAG + "\n");
}
if (berEncoding instanceof BERPrimitive) {
BERPrimitive ber = (BERPrimitive) berEncoding;
int[] encoding = ber.peek();
if (encoding.length < 1) {
throw new ASN1EncodingException("ASN1 BIT STRING: invalid encoding, length = " + encoding.length);
}
int unusedBits = encoding[0] & 0x07;
int numBits = (encoding.length - 1) * 8 - unusedBits;
bits = new boolean[numBits];
for (int bit = 0; bit < numBits; bit++) {
int octet = encoding[bit / 8 + 1];
octet <<= (bit % 8);
bits[bit] = (octet & 0x80) != 0;
}
} else {
throw new ASN1EncodingException("ASN.1 BIT STRING: decoding constructed NOT IMPLEMENTED YET");
}
}
/**
* Returns a BER encoding of the BIT STRING.
* Bit strings can have a primitive encoding and a constructed
* encoding. This method performs the primitive encoding (which
* is the one specified for DER encoding).
*
* @return The BER encoding of the BIT STRING
* @throws ASN1Exception when the BIT STRING is invalid
* and cannot be encoded.
*/
@Override
public BEREncoding berEncode() throws ASN1Exception {
return berEncode(BEREncoding.UNIVERSAL_TAG, BIT_STRING_TAG);
}
/**
* Returns a BER encoding of the BIT STRING.
* Bit strings can have a primitive encoding and a constructed
* encoding. This method performs the primitive encoding (which
* is the one specified for DER encoding).
*
* @return The BER encoding of the BIT STRING
* @throws ASN1Exception when the BIT STRING is invalid
* and cannot be encoded.
*/
@Override
public BEREncoding berEncode(int tagType, int tag) throws ASN1Exception {
int numOctets = (bits.length + 7) / 8;
int[] encoding = new int[numOctets + 1];
encoding[0] = (numOctets * 8) - bits.length;
for (int count = 1; count <= numOctets; count++) {
encoding[count] = 0x00;
int bitBaseIndex = (count - 1) * 8;
for (int bitIndex = 0; bitIndex < 8; bitIndex++) {
int n = bitBaseIndex + bitIndex;
encoding[count] <<= 1;
if (n < bits.length && bits[n]) {
encoding[count] |= 0x01;
}
}
}
return new BERPrimitive(tagType, tag, encoding);
}
/**
* Method to set the bit string's value.
*
* @param newBits the value to set the BIT STRING to.
* @return the object.
*/
public ASN1BitString set(boolean[] newBits) {
bits = newBits;
return this;
}
/**
* Method to get the bit string's value.
*
* @return the BIT STRING's current value.
*/
public boolean[] get() {
return bits;
}
/**
* Returns a new String object representing this ASN.1 object's value.
*
* @return A text string representation of the BitString.
*/
@Override
public String toString() {
StringBuilder str = new StringBuilder();
str.append('\'');
for (boolean bit : bits) {
str.append(bit ? '1' : '0');
}
str.append("'B");
return str.toString();
}
}