cbzip2inputstream.java

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/*
 *  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.
 *
 */

/*
 * This package is based on the work done by Keiron Liddle, Aftex Software
 * <[e-mail]> to whom the Ant project is very grateful for his
 * great code.
 */
package org.apache.tools.bzip2;

import java.io.InputStream;
import java.io.IOException;

/**
 * An input stream that decompresses from the BZip2 format (without the file
 * header chars) to be read as any other stream.
 *
 * <p>The decompression requires large amounts of memory. Thus you
 * should call the {@link #close() close()} method as soon as
 * possible, to force <tt>CBZip2InputStream</tt> to release the
 * allocated memory.  See {@link CBZip2OutputStream
 * CBZip2OutputStream} for information about memory usage.</p>
 *
 * <p><tt>CBZip2InputStream</tt> reads bytes from the compressed
 * source stream via the single byte {@link java.io.InputStream#read()
 * read()} method exclusively. Thus you should consider to use a
 * buffered source stream.</p>
 * 
 * <p>Instances of this class are not threadsafe.</p>
 */
public class CBZip2InputStream extends InputStream implements BZip2Constants {

    private static void reportCRCError() throws IOException {
        // The clean way would be to throw an exception.
        //throw new IOException("crc error");

        // Just print a message, like the previous versions of this class did
        System.err.println("BZip2 CRC error");
    }

    private void makeMaps() {
        final boolean[] inUse   = this.data.inUse;
        final byte[] seqToUnseq = this.data.seqToUnseq;

        int nInUseShadow = 0;

        for (int i = 0; i < 256; i++) {
            if (inUse[i])
                seqToUnseq[nInUseShadow++] = (byte) i;
        }

        this.nInUse = nInUseShadow;
    }

    /**
     * Index of the last char in the block, so the block size == last + 1.
     */
    private int  last;

    /**
     * Index in zptr[] of original string after sorting.
     */
    private int  origPtr;

    /**
     * always: in the range 0 .. 9.
     * The current block size is 100000 * this number.
     */
    private int blockSize100k;

    private boolean blockRandomised;

    private int bsBuff;
    private int bsLive;
    private final CRC crc = new CRC();

    private int nInUse;

    private InputStream in;

    private int currentChar = -1;

    private static final int EOF                  = 0;
    private static final int START_BLOCK_STATE = 1;
    private static final int RAND_PART_A_STATE = 2;
    private static final int RAND_PART_B_STATE = 3;
    private static final int RAND_PART_C_STATE = 4;
    private static final int NO_RAND_PART_A_STATE = 5;
    private static final int NO_RAND_PART_B_STATE = 6;
    private static final int NO_RAND_PART_C_STATE = 7;

    private int currentState = START_BLOCK_STATE;

    private int storedBlockCRC, storedCombinedCRC;
    private int computedBlockCRC, computedCombinedCRC;

    // Variables used by setup* methods exclusively

    private int su_count;
    private int su_ch2;
    private int su_chPrev;
    private int su_i2;
    private int su_j2;
    private int su_rNToGo;
    private int su_rTPos;
    private int su_tPos;
    private char su_z;

    /**
     * All memory intensive stuff.
     * This field is initialized by initBlock().
     */
    private CBZip2InputStream.Data data;

    /**
     * Constructs a new CBZip2InputStream which decompresses bytes read from
     * the specified stream.
     *
     * <p>Although BZip2 headers are marked with the magic
     * <tt>"Bz"</tt> this constructor expects the next byte in the
     * stream to be the first one after the magic.  Thus callers have
     * to skip the first two bytes. Otherwise this constructor will
     * throw an exception. </p>
     *
     * @throws IOException
     *  if the stream content is malformed or an I/O error occurs.
     * @throws NullPointerException
     *  if <tt>in == null</tt>
     */
    public CBZip2InputStream(final InputStream in) throws IOException {
        super();

        this.in = in;
        init();
    }

    public int read() throws IOException {
        if (this.in != null) {
            return read0();
        } else {
            throw new IOException("stream closed");
        }
    }

    public int read(final byte[] dest, final int offs, final int len)
        throws IOException {
        if (offs < 0) {
            throw new IndexOutOfBoundsException("offs(" + offs + ") < 0.");
        }
        if (len < 0) {
            throw new IndexOutOfBoundsException("len(" + len + ") < 0.");
        }
        if (offs + len > dest.length) {
            throw new IndexOutOfBoundsException("offs(" + offs + ") + len("
                                                + len + ") > dest.length("
                                                + dest.length + ").");
        }
        if (this.in == null) {
            throw new IOException("stream closed");
        }

        final int hi = offs + len;
        int destOffs = offs;
        for (int b; (destOffs < hi) && ((b = read0()) >= 0);) {
            dest[destOffs++] = (byte) b;
        }

        return (destOffs == offs) ? -1 : (destOffs - offs);
    }

    private int read0() throws IOException {
        final int retChar = this.currentChar;

        switch (this.currentState) {
        case EOF:
            return -1;

        case START_BLOCK_STATE:
            throw new IllegalStateException();

        case RAND_PART_A_STATE:
            throw new IllegalStateException();

        case RAND_PART_B_STATE:
            setupRandPartB();
            break;

        case RAND_PART_C_STATE:
            setupRandPartC();
            break;

        case NO_RAND_PART_A_STATE:
            throw new IllegalStateException();

        case NO_RAND_PART_B_STATE:
            setupNoRandPartB();
            break;

        case NO_RAND_PART_C_STATE:
            setupNoRandPartC();
            break;

        default:
            throw new IllegalStateException();
        }

        return retChar;
    }

    private void init() throws IOException {
        int magic2 = this.in.read();
        if (magic2 != 'h') {
            throw new IOException("Stream is not BZip2 formatted: expected 'h'"
                                  + " as first byte but got '" + (char) magic2
                                  + "'");
        }

        int blockSize = this.in.read();
        if ((blockSize < '1') || (blockSize > '9')) {
            throw new IOException("Stream is not BZip2 formatted: illegal "
                                  + "blocksize " + (char) blockSize);
        }

        this.blockSize100k = blockSize - '0';

        initBlock();
        setupBlock();
    }

    private void initBlock() throws IOException {
        char magic0 = bsGetUByte();
        char magic1 = bsGetUByte();
        char magic2 = bsGetUByte();
        char magic3 = bsGetUByte();
        char magic4 = bsGetUByte();
        char magic5 = bsGetUByte();

        if (magic0 == 0x17 &&
            magic1 == 0x72 &&
            magic2 == 0x45 &&
            magic3 == 0x38 &&
            magic4 == 0x50 &&
            magic5 == 0x90) {
            complete(); // end of file
        } else if (magic0 != 0x31 || // '1'
                   magic1 != 0x41 || // ')'
                   magic2 != 0x59 || // 'Y'
                   magic3 != 0x26 || // '&'
                   magic4 != 0x53 || // 'S'
                   magic5 != 0x59   // 'Y'
                   ) {
            this.currentState = EOF;
            throw new IOException("bad block header");
        } else {
            this.storedBlockCRC = bsGetInt();
            this.blockRandomised = bsR(1) == 1;

            /**
             * Allocate data here instead in constructor, so we do not
             * allocate it if the input file is empty.
             */
            if (this.data == null) {
                this.data = new Data(this.blockSize100k);
            }

            // currBlockNo++;
            getAndMoveToFrontDecode();

            this.crc.initialiseCRC();
            this.currentState = START_BLOCK_STATE;
        }
    }

    private void endBlock() throws IOException {
        this.computedBlockCRC = this.crc.getFinalCRC();

        // A bad CRC is considered a fatal error.
        if (this.storedBlockCRC != this.computedBlockCRC) {
            // make next blocks readable without error
            // (repair feature, not yet documented, not tested)
            this.computedCombinedCRC
                = (this.storedCombinedCRC << 1)
                | (this.storedCombinedCRC >>> 31);
            this.computedCombinedCRC ^= this.storedBlockCRC;

            reportCRCError();
        }

        this.computedCombinedCRC
            = (this.computedCombinedCRC << 1)
            | (this.computedCombinedCRC >>> 31);
        this.computedCombinedCRC ^= this.computedBlockCRC;
    }

    private void complete() throws IOException {
        this.storedCombinedCRC = bsGetInt();
        this.currentState = EOF;
        this.data = null;

        if (this.storedCombinedCRC != this.computedCombinedCRC) {
            reportCRCError();
        }
    }

    public void close() throws IOException {
        InputStream inShadow = this.in;
        if (inShadow != null) {
            try {
                if (inShadow != System.in) {
                    inShadow.close();
                }