/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @author Alexey V. Varlamov, Stepan M. Mishura
* @version $Revision$
*/
package org.apache.harmony.security.asn1;
/**
* Represents ASN.1 bit string value
*
* @see <a href="http://asn1.elibel.tm.fr/en/standards/index.htm">ASN.1</a>
*/
public final class BitString {
private static final byte[] SET_MASK = { (byte) 128, 64, 32, 16, 8, 4, 2, 1 };
private static final byte[] RESET_MASK = { 0x7f, (byte) 0xbf, (byte) 0xdf,
(byte) 0xef, (byte) 0xf7, (byte) 0xfb, (byte) 0xfd, (byte) 0xfe, };
/** Sequence of bits padded with unused bits. */
public final byte[] bytes;
/** Number of unused bits in the last byte. */
public final int unusedBits;
/**
* @param bytes array of bytes that represents bit string,
* including unused bits
* @param unusedBits number of unused bits
* @throws IllegalArgumentException - if parameters are invalid
*/
public BitString(byte[] bytes, int unusedBits) {
// constraints are set according X.690
if (unusedBits < 0 || unusedBits > 7) {
throw new IllegalArgumentException("Number of unused bits MUST be in range 0-7");
}
if (bytes.length == 0 && unusedBits != 0) {
throw new IllegalArgumentException("For empty bit string unused bits MUST be 0");
}
this.bytes = bytes;
this.unusedBits = unusedBits;
}
public BitString(boolean[] values) {
unusedBits = values.length % 8;
int size = values.length / 8;
if (unusedBits != 0) {
size++;
}
bytes = new byte[size];
for (int i = 0; i < values.length; i++) {
setBit(i, values[i]);
}
}
public boolean getBit(int bit) {
int offset = bit % 8;
int index = bit / 8;
return (bytes[index] & SET_MASK[offset]) != 0;
}
public void setBit(int bit, boolean value) {
int offset = bit % 8;
int index = bit / 8;
if (value) {
bytes[index] |= SET_MASK[offset];
} else {
bytes[index] &= RESET_MASK[offset];
}
}
public boolean[] toBooleanArray() {
boolean[] result = new boolean[bytes.length * 8 - unusedBits];
for (int i = 0; i < result.length; i++) {
result[i] = getBit(i);
}
return result;
}
}