luni/src/main/java/org/apache/harmony/security/asn1/ASN1BitString.java

/*
 *  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 Vladimir N. Molotkov, Stepan M. Mishura
* @version $Revision$
*/

package org.apache.harmony.security.asn1;

import java.io.IOException;
import libcore.util.EmptyArray;

/**
 * This class represents ASN.1 Bitstring type.
 *
 * @see <a href="http://asn1.elibel.tm.fr/en/standards/index.htm">ASN.1</a>
 */
public class ASN1BitString extends ASN1StringType {

    // default implementation
    private static final ASN1BitString ASN1 = new ASN1BitString();

    /**
     * Constructs ASN.1 Bitstring type
     *
     * The constructor is provided for inheritance purposes
     * when there is a need to create a custom ASN.1 Bitstring type.
     * To get a default implementation it is recommended to use
     * getInstance() method.
     */
    public ASN1BitString() {
        super(TAG_BITSTRING);
    }

    /**
     * Returns ASN.1 Bitstring type default implementation
     *
     * The default implementation works with encoding
     * that is represented as BitString object.
     *
     * @return ASN.1 Bitstring type default implementation
     * @see org.apache.harmony.security.asn1.BitString
     */
    public static ASN1BitString getInstance() {
        return ASN1;
    }

    @Override public Object decode(BerInputStream in) throws IOException {
        in.readBitString();

        if (in.isVerify) {
            return null;
        }
        return getDecodedObject(in);
    }

    /**
     * Extracts BitString object from BER input stream.
     *
     * @param in - BER input stream
     * @return BitString object
     */
    @Override public Object getDecodedObject(BerInputStream in) throws IOException {
        byte[] bytes = new byte[in.length - 1];
        System.arraycopy(in.buffer, in.contentOffset + 1, bytes, 0,
                in.length - 1);
        return new BitString(bytes, in.buffer[in.contentOffset]);
    }

    @Override public void encodeContent(BerOutputStream out) {
        out.encodeBitString();
    }

    @Override public void setEncodingContent(BerOutputStream out) {
        out.length = ((BitString) out.content).bytes.length + 1;
    }

    /**
     * Default implementation for ASN.1 Named Bitstring type
     *
     * The default implementation works with encoding
     * that is mapped to array of boolean.
     */
    public static class ASN1NamedBitList extends ASN1BitString {
        private static final byte[] SET_MASK = { (byte) 128, 64, 32, 16, 8, 4, 2, 1};
        private static final BitString emptyString = new BitString(EmptyArray.BYTE, 0);
        private static final int INDEFINITE_SIZE = -1;

        private final int minBits;
        private final int maxBits;

        public ASN1NamedBitList(int minBits) {
            this.minBits = minBits;
            this.maxBits = INDEFINITE_SIZE;
        }

        @Override public Object getDecodedObject(BerInputStream in) throws IOException {
            boolean[] value;

            int unusedBits = in.buffer[in.contentOffset];
            int bitsNumber = (in.length - 1) * 8 - unusedBits;

            if (maxBits == INDEFINITE_SIZE) {
                if (minBits == INDEFINITE_SIZE) {
                    value = new boolean[bitsNumber];
                } else {
                    if (bitsNumber > minBits) {
                        value = new boolean[bitsNumber];
                    } else {
                        value = new boolean[minBits];
                    }
                }
            } else {
                if (bitsNumber > maxBits) {
                    throw new ASN1Exception("ASN.1 Named Bitstring: size constraints");
                }
                value = new boolean[maxBits];
            }

            if (bitsNumber == 0) {
                // empty bit string
                return value;
            }

            int i = 1;
            int j = 0;
            byte octet = in.buffer[in.contentOffset + i];
            for (int size = in.length - 1; i < size; i++) {
                for (int k = 0; k < 8; k++, j++) {
                    value[j] = (SET_MASK[k] & octet) != 0;
                }
                i++;
                octet = in.buffer[in.contentOffset + i];
            }

            // final octet
            for (int k = 0; k < (8 - unusedBits); k++, j++) {
                value[j] = (SET_MASK[k] & octet) != 0;
            }

            return value;
        }

        @Override public void setEncodingContent(BerOutputStream out) {
            boolean[] toEncode = (boolean[]) out.content;

            int index = toEncode.length - 1;
            while (index > -1 && !toEncode[index]) {
                index--;
            }

            if (index == -1) {
                out.content = emptyString;
                out.length = 1;
            } else {
                int unusedBits = 7 - index % 8;
                byte[] bytes = new byte[index / 8 + 1];

                int j = 0;
                index = bytes.length - 1;
                for (int i = 0; i < index; i++) {
                    for (int k = 0; k < 8; k++, j++) {
                        if (toEncode[j]) {
                            bytes[i] = (byte) (bytes[i] | SET_MASK[k]);
                        }
                    }
                }

                //final octet
                for (int k = 0; k < (8 - unusedBits); k++, j++) {
                    if (toEncode[j]) {
                        bytes[index] = (byte) (bytes[index] | SET_MASK[k]);
                    }
                }

                out.content = new BitString(bytes, unusedBits);
                out.length = bytes.length + 1;
            }
        }
    }
}