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      1 /*
      2  *  Licensed to the Apache Software Foundation (ASF) under one or more
      3  *  contributor license agreements.  See the NOTICE file distributed with
      4  *  this work for additional information regarding copyright ownership.
      5  *  The ASF licenses this file to You under the Apache License, Version 2.0
      6  *  (the "License"); you may not use this file except in compliance with
      7  *  the License.  You may obtain a copy of the License at
      8  *
      9  *     http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  *  Unless required by applicable law or agreed to in writing, software
     12  *  distributed under the License is distributed on an "AS IS" BASIS,
     13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  *  See the License for the specific language governing permissions and
     15  *  limitations under the License.
     16  */
     17 
     18 /**
     19 * @author Alexey V. Varlamov, Stepan M. Mishura
     20 * @version $Revision$
     21 */
     22 
     23 package org.apache.harmony.security.asn1;
     24 
     25 /**
     26  * Represents ASN.1 bit string value
     27  *
     28  * @see <a href="http://asn1.elibel.tm.fr/en/standards/index.htm">ASN.1</a>
     29  */
     30 public final class BitString {
     31 
     32     private static final byte[] SET_MASK = { (byte) 128, 64, 32, 16, 8, 4, 2, 1 };
     33 
     34     private static final byte[] RESET_MASK = { 0x7f, (byte) 0xbf, (byte) 0xdf,
     35             (byte) 0xef, (byte) 0xf7, (byte) 0xfb, (byte) 0xfd, (byte) 0xfe, };
     36 
     37     /** Sequence of bits padded with unused bits. */
     38     public final byte[] bytes;
     39 
     40     /** Number of unused bits in the last byte. */
     41     public final int unusedBits;
     42 
     43     /**
     44      * @param bytes array of bytes that represents bit string,
     45      *                including unused bits
     46      * @param unusedBits number of unused bits
     47      * @throws IllegalArgumentException - if parameters are invalid
     48      */
     49     public BitString(byte[] bytes, int unusedBits) {
     50         // constraints are set according X.690
     51         if (unusedBits < 0 || unusedBits > 7) {
     52             throw new IllegalArgumentException("Number of unused bits MUST be in range 0-7");
     53         }
     54 
     55         if (bytes.length == 0 && unusedBits != 0) {
     56             throw new IllegalArgumentException("For empty bit string unused bits MUST be 0");
     57         }
     58 
     59         this.bytes = bytes;
     60         this.unusedBits = unusedBits;
     61     }
     62 
     63     public BitString(boolean[] values) {
     64         unusedBits = values.length % 8;
     65         int size = values.length / 8;
     66         if (unusedBits != 0) {
     67             size++;
     68         }
     69         bytes = new byte[size];
     70         for (int i = 0; i < values.length; i++) {
     71             setBit(i, values[i]);
     72         }
     73     }
     74 
     75     public boolean getBit(int bit) {
     76         int offset = bit % 8;
     77         int index = bit / 8;
     78         return (bytes[index] & SET_MASK[offset]) != 0;
     79     }
     80 
     81     public void setBit(int bit, boolean value) {
     82         int offset = bit % 8;
     83         int index = bit / 8;
     84         if (value) {
     85             bytes[index] |= SET_MASK[offset];
     86         } else {
     87             bytes[index] &= RESET_MASK[offset];
     88         }
     89     }
     90 
     91     public boolean[] toBooleanArray() {
     92         boolean[] result = new boolean[bytes.length * 8 - unusedBits];
     93         for (int i = 0; i < result.length; i++) {
     94             result[i] = getBit(i);
     95         }
     96         return result;
     97     }
     98 }
     99