    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 * http://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019
    020/*
    021 * This package is based on the work done by Keiron Liddle, Aftex Software
    022 * <keiron@aftexsw.com> to whom the Ant project is very grateful for his
    023 * great code.
    024 */
    025package org.apache.commons.compress.compressors.bzip2;
    026
    027import java.io.IOException;
    028import java.io.InputStream;
    029
    030import org.apache.commons.compress.compressors.CompressorInputStream;
    031
    032/**
    033 * An input stream that decompresses from the BZip2 format to be read as any other stream.
    034 *
    035 * @NotThreadSafe
    036 */
    037public class BZip2CompressorInputStream extends CompressorInputStream implements
    038                                                                          BZip2Constants {
    039
    040    /**
    041     * Index of the last char in the block, so the block size == last + 1.
    042     */
    043    private int last;
    044
    045    /**
    046     * Index in zptr[] of original string after sorting.
    047     */
    048    private int origPtr;
    049
    050    /**
    051     * always: in the range 0 .. 9. The current block size is 100000 * this
    052     * number.
    053     */
    054    private int blockSize100k;
    055
    056    private boolean blockRandomised;
    057
    058    private int bsBuff;
    059    private int bsLive;
    060    private final CRC crc = new CRC();
    061
    062    private int nInUse;
    063
    064    private InputStream in;
    065    private final boolean decompressConcatenated;
    066
    067    private static final int EOF = 0;
    068    private static final int START_BLOCK_STATE = 1;
    069    private static final int RAND_PART_A_STATE = 2;
    070    private static final int RAND_PART_B_STATE = 3;
    071    private static final int RAND_PART_C_STATE = 4;
    072    private static final int NO_RAND_PART_A_STATE = 5;
    073    private static final int NO_RAND_PART_B_STATE = 6;
    074    private static final int NO_RAND_PART_C_STATE = 7;
    075
    076    private int currentState = START_BLOCK_STATE;
    077
    078    private int storedBlockCRC, storedCombinedCRC;
    079    private int computedBlockCRC, computedCombinedCRC;
    080
    081    // Variables used by setup* methods exclusively
    082
    083    private int su_count;
    084    private int su_ch2;
    085    private int su_chPrev;
    086    private int su_i2;
    087    private int su_j2;
    088    private int su_rNToGo;
    089    private int su_rTPos;
    090    private int su_tPos;
    091    private char su_z;
    092
    093    /**
    094     * All memory intensive stuff. This field is initialized by initBlock().
    095     */
    096    private BZip2CompressorInputStream.Data data;
    097
    098    /**
    099     * Constructs a new BZip2CompressorInputStream which decompresses bytes
    100     * read from the specified stream. This doesn't suppprt decompressing
    101     * concatenated .bz2 files.
    102     *
    103     * @param in the InputStream from which this object should be created
    104     * @throws IOException
    105     *             if the stream content is malformed or an I/O error occurs.
    106     * @throws NullPointerException
    107     *             if {@code in == null}
    108     */
    109    public BZip2CompressorInputStream(final InputStream in) throws IOException {
    110        this(in, false);
    111    }
    112
    113    /**
    114     * Constructs a new BZip2CompressorInputStream which decompresses bytes
    115     * read from the specified stream.
    116     *
    117     * @param in the InputStream from which this object should be created
    118     * @param decompressConcatenated
    119     *                     if true, decompress until the end of the input;
    120     *                     if false, stop after the first .bz2 stream and
    121     *                     leave the input position to point to the next
    122     *                     byte after the .bz2 stream
    123     *
    124     * @throws IOException
    125     *             if {@code in == null}, the stream content is malformed, or an I/O error occurs.
    126     */
    127    public BZip2CompressorInputStream(final InputStream in, final boolean decompressConcatenated) throws IOException {
    128        this.in = in;
    129        this.decompressConcatenated = decompressConcatenated;
    130
    131        init(true);
    132        initBlock();
    133    }
    134
    135    @Override
    136    public int read() throws IOException {
    137        if (this.in != null) {
    138            final int r = read0();
    139            count(r < 0 ? -1 : 1);
    140            return r;
    141        }
    142        throw new IOException("stream closed");
    143    }
    144
    145    /*
    146     * (non-Javadoc)
    147     *
    148     * @see java.io.InputStream#read(byte[], int, int)
    149     */
    150    @Override
    151    public int read(final byte[] dest, final int offs, final int len)
    152        throws IOException {
    153        if (offs < 0) {
    154            throw new IndexOutOfBoundsException("offs(" + offs + ") < 0.");
    155        }
    156        if (len < 0) {
    157            throw new IndexOutOfBoundsException("len(" + len + ") < 0.");
    158        }
    159        if (offs + len > dest.length) {
    160            throw new IndexOutOfBoundsException("offs(" + offs + ") + len("
    161                                                + len + ") > dest.length(" + dest.length + ").");
    162        }
    163        if (this.in == null) {
    164            throw new IOException("stream closed");
    165        }
    166        if (len == 0) {
    167            return 0;
    168        }
    169
    170        final int hi = offs + len;
    171        int destOffs = offs;
    172        int b;
    173        while (destOffs < hi && ((b = read0()) >= 0)) {
    174            dest[destOffs++] = (byte) b;
    175            count(1);
    176        }
    177
    178        final int c = (destOffs == offs) ? -1 : (destOffs - offs);
    179        return c;
    180    }
    181
    182    private void makeMaps() {
    183        final boolean[] inUse = this.data.inUse;
    184        final byte[] seqToUnseq = this.data.seqToUnseq;
    185
    186        int nInUseShadow = 0;
    187
    188        for (int i = 0; i < 256; i++) {
    189            if (inUse[i]) {
    190                seqToUnseq[nInUseShadow++] = (byte) i;
    191            }
    192        }
    193
    194        this.nInUse = nInUseShadow;
    195    }
    196
    197    private int read0() throws IOException {
    198        switch (currentState) {
    199        case EOF:
    200            return -1;
    201
    202        case START_BLOCK_STATE:
    203            return setupBlock();
    204
    205        case RAND_PART_A_STATE:
    206            throw new IllegalStateException();
    207
    208        case RAND_PART_B_STATE:
    209            return setupRandPartB();
    210
    211        case RAND_PART_C_STATE:
    212            return setupRandPartC();
    213
    214        case NO_RAND_PART_A_STATE:
    215            throw new IllegalStateException();
    216
    217        case NO_RAND_PART_B_STATE:
    218            return setupNoRandPartB();
    219
    220        case NO_RAND_PART_C_STATE:
    221            return setupNoRandPartC();
    222
    223        default:
    224            throw new IllegalStateException();
    225        }
    226    }
    227
    228    private boolean init(final boolean isFirstStream) throws IOException {
    229        if (null == in) {
    230            throw new IOException("No InputStream");
    231        }
    232
    233        final int magic0 = this.in.read();
    234        if (magic0 == -1 && !isFirstStream) {
    235            return false;
    236        }
    237        final int magic1 = this.in.read();
    238        final int magic2 = this.in.read();
    239
    240        if (magic0 != 'B' || magic1 != 'Z' || magic2 != 'h') {
    241            throw new IOException(isFirstStream
    242                    ? "Stream is not in the BZip2 format"
    243                    : "Garbage after a valid BZip2 stream");
    244        }
    245
    246        final int blockSize = this.in.read();
    247        if ((blockSize < '1') || (blockSize > '9')) {
    248            throw new IOException("BZip2 block size is invalid");
    249        }
    250
    251        this.blockSize100k = blockSize - '0';
    252
    253        this.bsLive = 0;
    254        this.computedCombinedCRC = 0;
    255
    256        return true;
    257    }
    258
    259    private void initBlock() throws IOException {
    260        char magic0;
    261        char magic1;
    262        char magic2;
    263        char magic3;
    264        char magic4;
    265        char magic5;
    266
    267        while (true) {
    268            // Get the block magic bytes.
    269            magic0 = bsGetUByte();
    270            magic1 = bsGetUByte();
    271            magic2 = bsGetUByte();
    272            magic3 = bsGetUByte();
    273            magic4 = bsGetUByte();
    274            magic5 = bsGetUByte();
    275
    276            // If isn't end of stream magic, break out of the loop.
    277            if (magic0 != 0x17 || magic1 != 0x72 || magic2 != 0x45
    278                    || magic3 != 0x38 || magic4 != 0x50 || magic5 != 0x90) {
    279                break;
    280            }
    281
    282            // End of stream was reached. Check the combined CRC and
    283            // advance to the next .bz2 stream if decoding concatenated
    284            // streams.
    285            if (complete()) {
    286                return;
    287            }
    288        }
    289
    290        if (magic0 != 0x31 || // '1'
    291            magic1 != 0x41 || // ')'
    292            magic2 != 0x59 || // 'Y'
    293            magic3 != 0x26 || // '&'
    294            magic4 != 0x53 || // 'S'
    295            magic5 != 0x59 // 'Y'
    296            ) {
    297            this.currentState = EOF;
    298            throw new IOException("bad block header");
    299        }
    300        this.storedBlockCRC = bsGetInt();
    301        this.blockRandomised = bsR(1) == 1;
    302
    303        /**
    304         * Allocate data here instead in constructor, so we do not allocate
    305         * it if the input file is empty.
    306         */
    307        if (this.data == null) {
    308            this.data = new Data(this.blockSize100k);
    309        }
    310
    311        // currBlockNo++;
    312        getAndMoveToFrontDecode();
    313
    314        this.crc.initialiseCRC();
    315        this.currentState = START_BLOCK_STATE;
    316    }
    317
    318    private void endBlock() throws IOException {
    319        this.computedBlockCRC = this.crc.getFinalCRC();
    320
    321        // A bad CRC is considered a fatal error.
    322        if (this.storedBlockCRC != this.computedBlockCRC) {
    323            // make next blocks readable without error
    324            // (repair feature, not yet documented, not tested)
    325            this.computedCombinedCRC = (this.storedCombinedCRC << 1)
    326                | (this.storedCombinedCRC >>> 31);
    327            this.computedCombinedCRC ^= this.storedBlockCRC;
    328
    329            throw new IOException("BZip2 CRC error");
    330        }
    331
    332        this.computedCombinedCRC = (this.computedCombinedCRC << 1)
    333            | (this.computedCombinedCRC >>> 31);
    334        this.computedCombinedCRC ^= this.computedBlockCRC;
    335    }
    336
    337    private boolean complete() throws IOException {
    338        this.storedCombinedCRC = bsGetInt();
    339        this.currentState = EOF;
    340        this.data = null;
    341
    342        if (this.storedCombinedCRC != this.computedCombinedCRC) {
    343            throw new IOException("BZip2 CRC error");
    344        }
    345
    346        // Look for the next .bz2 stream if decompressing
    347        // concatenated files.
    348        return !decompressConcatenated || !init(false);
    349    }
    350
    351    @Override
    352    public void close() throws IOException {
    353        final InputStream inShadow = this.in;
    354        if (inShadow != null) {
    355            try {
    356                if (inShadow != System.in) {
    357                    inShadow.close();
    358                }
    359            } finally {
    360                this.data = null;
    361                this.in = null;
    362            }
    363        }
    364    }
    365
    366    private int bsR(final int n) throws IOException {
    367        int bsLiveShadow = this.bsLive;
    368        int bsBuffShadow = this.bsBuff;
    369
    370        if (bsLiveShadow < n) {
    371            final InputStream inShadow = this.in;
    372            do {
    373                final int thech = inShadow.read();
    374
    375                if (thech < 0) {
    376                    throw new IOException("unexpected end of stream");
    377                }
    378
    379                bsBuffShadow = (bsBuffShadow << 8) | thech;
    380                bsLiveShadow += 8;
    381            } while (bsLiveShadow < n);
    382
    383            this.bsBuff = bsBuffShadow;
    384        }
    385
    386        this.bsLive = bsLiveShadow - n;
    387        return (bsBuffShadow >> (bsLiveShadow - n)) & ((1 << n) - 1);
    388    }
    389
    390    private boolean bsGetBit() throws IOException {
    391        return bsR(1) != 0;
    392    }
    393
    394    private char bsGetUByte() throws IOException {
    395        return (char) bsR(8);
    396    }
    397
    398    private int bsGetInt() throws IOException {
    399        return (((((bsR(8) << 8) | bsR(8)) << 8) | bsR(8)) << 8) | bsR(8);
    400    }
    401
    402    /**
    403     * Called by createHuffmanDecodingTables() exclusively.
    404     */
    405    private static void hbCreateDecodeTables(final int[] limit,
    406                                             final int[] base, final int[] perm, final char[] length,
    407                                             final int minLen, final int maxLen, final int alphaSize) {
    408        for (int i = minLen, pp = 0; i <= maxLen; i++) {
    409            for (int j = 0; j < alphaSize; j++) {
    410                if (length[j] == i) {
    411                    perm[pp++] = j;
    412                }
    413            }
    414        }
    415
    416        for (int i = MAX_CODE_LEN; --i > 0;) {
    417            base[i] = 0;
    418            limit[i] = 0;
    419        }
    420
    421        for (int i = 0; i < alphaSize; i++) {
    422            base[length[i] + 1]++;
    423        }
    424
    425        for (int i = 1, b = base[0]; i < MAX_CODE_LEN; i++) {
    426            b += base[i];
    427            base[i] = b;
    428        }
    429
    430        for (int i = minLen, vec = 0, b = base[i]; i <= maxLen; i++) {
    431            final int nb = base[i + 1];
    432            vec += nb - b;
    433            b = nb;
    434            limit[i] = vec - 1;
    435            vec <<= 1;
    436        }
    437
    438        for (int i = minLen + 1; i <= maxLen; i++) {
    439            base[i] = ((limit[i - 1] + 1) << 1) - base[i];
    440        }
    441    }
    442
    443    private void recvDecodingTables() throws IOException {
    444        final Data dataShadow = this.data;
    445        final boolean[] inUse = dataShadow.inUse;
    446        final byte[] pos = dataShadow.recvDecodingTables_pos;
    447        final byte[] selector = dataShadow.selector;
    448        final byte[] selectorMtf = dataShadow.selectorMtf;
    449
    450        int inUse16 = 0;
    451
    452        /* Receive the mapping table */
    453        for (int i = 0; i < 16; i++) {
    454            if (bsGetBit()) {
    455                inUse16 |= 1 << i;
    456            }
    457        }
    458
    459        for (int i = 256; --i >= 0;) {
    460            inUse[i] = false;
    461        }
    462
    463        for (int i = 0; i < 16; i++) {
    464            if ((inUse16 & (1 << i)) != 0) {
    465                final int i16 = i << 4;
    466                for (int j = 0; j < 16; j++) {
    467                    if (bsGetBit()) {
    468                        inUse[i16 + j] = true;
    469                    }
    470                }
    471            }
    472        }
    473
    474        makeMaps();
    475        final int alphaSize = this.nInUse + 2;
    476
    477        /* Now the selectors */
    478        final int nGroups = bsR(3);
    479        final int nSelectors = bsR(15);
    480
    481        for (int i = 0; i < nSelectors; i++) {
    482            int j = 0;
    483            while (bsGetBit()) {
    484                j++;
    485            }
    486            selectorMtf[i] = (byte) j;
    487        }
    488
    489        /* Undo the MTF values for the selectors. */
    490        for (int v = nGroups; --v >= 0;) {
    491            pos[v] = (byte) v;
    492        }
    493
    494        for (int i = 0; i < nSelectors; i++) {
    495            int v = selectorMtf[i] & 0xff;
    496            final byte tmp = pos[v];
    497            while (v > 0) {
    498                // nearly all times v is zero, 4 in most other cases
    499                pos[v] = pos[v - 1];
    500                v--;
    501            }
    502            pos[0] = tmp;
    503            selector[i] = tmp;
    504        }
    505
    506        final char[][] len = dataShadow.temp_charArray2d;
    507
    508        /* Now the coding tables */
    509        for (int t = 0; t < nGroups; t++) {
    510            int curr = bsR(5);
    511            final char[] len_t = len[t];
    512            for (int i = 0; i < alphaSize; i++) {
    513                while (bsGetBit()) {
    514                    curr += bsGetBit() ? -1 : 1;
    515                }
    516                len_t[i] = (char) curr;
    517            }
    518        }
    519
    520        // finally create the Huffman tables
    521        createHuffmanDecodingTables(alphaSize, nGroups);
    522    }
    523
    524    /**
    525     * Called by recvDecodingTables() exclusively.
    526     */
    527    private void createHuffmanDecodingTables(final int alphaSize,
    528                                             final int nGroups) {
    529        final Data dataShadow = this.data;
    530        final char[][] len = dataShadow.temp_charArray2d;
    531        final int[] minLens = dataShadow.minLens;
    532        final int[][] limit = dataShadow.limit;
    533        final int[][] base = dataShadow.base;
    534        final int[][] perm = dataShadow.perm;
    535
    536        for (int t = 0; t < nGroups; t++) {
    537            int minLen = 32;
    538            int maxLen = 0;
    539            final char[] len_t = len[t];
    540            for (int i = alphaSize; --i >= 0;) {
    541                final char lent = len_t[i];
    542                if (lent > maxLen) {
    543                    maxLen = lent;
    544                }
    545                if (lent < minLen) {
    546                    minLen = lent;
    547                }
    548            }
    549            hbCreateDecodeTables(limit[t], base[t], perm[t], len[t], minLen,
    550                                 maxLen, alphaSize);
    551            minLens[t] = minLen;
    552        }
    553    }
    554
    555    private void getAndMoveToFrontDecode() throws IOException {
    556        this.origPtr = bsR(24);
    557        recvDecodingTables();
    558
    559        final InputStream inShadow = this.in;
    560        final Data dataShadow = this.data;
    561        final byte[] ll8 = dataShadow.ll8;
    562        final int[] unzftab = dataShadow.unzftab;
    563        final byte[] selector = dataShadow.selector;
    564        final byte[] seqToUnseq = dataShadow.seqToUnseq;
    565        final char[] yy = dataShadow.getAndMoveToFrontDecode_yy;
    566        final int[] minLens = dataShadow.minLens;
    567        final int[][] limit = dataShadow.limit;
    568        final int[][] base = dataShadow.base;
    569        final int[][] perm = dataShadow.perm;
    570        final int limitLast = this.blockSize100k * 100000;
    571
    572        /*
    573         * Setting up the unzftab entries here is not strictly necessary, but it
    574         * does save having to do it later in a separate pass, and so saves a
    575         * block's worth of cache misses.
    576         */
    577        for (int i = 256; --i >= 0;) {
    578            yy[i] = (char) i;
    579            unzftab[i] = 0;
    580        }
    581
    582        int groupNo = 0;
    583        int groupPos = G_SIZE - 1;
    584        final int eob = this.nInUse + 1;
    585        int nextSym = getAndMoveToFrontDecode0(0);
    586        int bsBuffShadow = this.bsBuff;
    587        int bsLiveShadow = this.bsLive;
    588        int lastShadow = -1;
    589        int zt = selector[groupNo] & 0xff;
    590        int[] base_zt = base[zt];
    591        int[] limit_zt = limit[zt];
    592        int[] perm_zt = perm[zt];
    593        int minLens_zt = minLens[zt];
    594
    595        while (nextSym != eob) {
    596            if ((nextSym == RUNA) || (nextSym == RUNB)) {
    597                int s = -1;
    598
    599                for (int n = 1; true; n <<= 1) {
    600                    if (nextSym == RUNA) {
    601                        s += n;
    602                    } else if (nextSym == RUNB) {
    603                        s += n << 1;
    604                    } else {
    605                        break;
    606                    }
    607
    608                    if (groupPos == 0) {
    609                        groupPos = G_SIZE - 1;
    610                        zt = selector[++groupNo] & 0xff;
    611                        base_zt = base[zt];
    612                        limit_zt = limit[zt];
    613                        perm_zt = perm[zt];
    614                        minLens_zt = minLens[zt];
    615                    } else {
    616                        groupPos--;
    617                    }
    618
    619                    int zn = minLens_zt;
    620
    621                    // Inlined:
    622                    // int zvec = bsR(zn);
    623                    while (bsLiveShadow < zn) {
    624                        final int thech = inShadow.read();
    625                        if (thech >= 0) {
    626                            bsBuffShadow = (bsBuffShadow << 8) | thech;
    627                            bsLiveShadow += 8;
    628                            continue;
    629                        }
    630                        throw new IOException("unexpected end of stream");
    631                    }
    632                    int zvec = (bsBuffShadow >> (bsLiveShadow - zn))
    633                        & ((1 << zn) - 1);
    634                    bsLiveShadow -= zn;
    635
    636                    while (zvec > limit_zt[zn]) {
    637                        zn++;
    638                        while (bsLiveShadow < 1) {
    639                            final int thech = inShadow.read();
    640                            if (thech >= 0) {
    641                                bsBuffShadow = (bsBuffShadow << 8) | thech;
    642                                bsLiveShadow += 8;
    643                                continue;
    644                            }
    645                            throw new IOException(
    646                                                  "unexpected end of stream");
    647                        }
    648                        bsLiveShadow--;
    649                        zvec = (zvec << 1)
    650                            | ((bsBuffShadow >> bsLiveShadow) & 1);
    651                    }
    652                    nextSym = perm_zt[zvec - base_zt[zn]];
    653                }
    654
    655                final byte ch = seqToUnseq[yy[0]];
    656                unzftab[ch & 0xff] += s + 1;
    657
    658                while (s-- >= 0) {
    659                    ll8[++lastShadow] = ch;
    660                }
    661
    662                if (lastShadow >= limitLast) {
    663                    throw new IOException("block overrun");
    664                }
    665            } else {
    666                if (++lastShadow >= limitLast) {
    667                    throw new IOException("block overrun");
    668                }
    669
    670                final char tmp = yy[nextSym - 1];
    671                unzftab[seqToUnseq[tmp] & 0xff]++;
    672                ll8[lastShadow] = seqToUnseq[tmp];
    673
    674                /*
    675                 * This loop is hammered during decompression, hence avoid
    676                 * native method call overhead of System.arraycopy for very
    677                 * small ranges to copy.
    678                 */
    679                if (nextSym <= 16) {
    680                    for (int j = nextSym - 1; j > 0;) {
    681                        yy[j] = yy[--j];
    682                    }
    683                } else {
    684                    System.arraycopy(yy, 0, yy, 1, nextSym - 1);
    685                }
    686
    687                yy[0] = tmp;
    688
    689                if (groupPos == 0) {
    690                    groupPos = G_SIZE - 1;
    691                    zt = selector[++groupNo] & 0xff;
    692                    base_zt = base[zt];
    693                    limit_zt = limit[zt];
    694                    perm_zt = perm[zt];
    695                    minLens_zt = minLens[zt];
    696                } else {
    697                    groupPos--;
    698                }
    699
    700                int zn = minLens_zt;
    701
    702                // Inlined:
    703                // int zvec = bsR(zn);
    704                while (bsLiveShadow < zn) {
    705                    final int thech = inShadow.read();
    706                    if (thech >= 0) {
    707                        bsBuffShadow = (bsBuffShadow << 8) | thech;
    708                        bsLiveShadow += 8;
    709                        continue;
    710                    }
    711                    throw new IOException("unexpected end of stream");
    712                }
    713                int zvec = (bsBuffShadow >> (bsLiveShadow - zn))
    714                    & ((1 << zn) - 1);
    715                bsLiveShadow -= zn;
    716
    717                while (zvec > limit_zt[zn]) {
    718                    zn++;
    719                    while (bsLiveShadow < 1) {
    720                        final int thech = inShadow.read();
    721                        if (thech >= 0) {
    722                            bsBuffShadow = (bsBuffShadow << 8) | thech;
    723                            bsLiveShadow += 8;
    724                            continue;
    725                        }
    726                        throw new IOException("unexpected end of stream");
    727                    }
    728                    bsLiveShadow--;
    729                    zvec = (zvec << 1) | ((bsBuffShadow >> bsLiveShadow) & 1);
    730                }
    731                nextSym = perm_zt[zvec - base_zt[zn]];
    732            }
    733        }
    734
    735        this.last = lastShadow;
    736        this.bsLive = bsLiveShadow;
    737        this.bsBuff = bsBuffShadow;
    738    }
    739
    740    private int getAndMoveToFrontDecode0(final int groupNo) throws IOException {
    741        final InputStream inShadow = this.in;
    742        final Data dataShadow = this.data;
    743        final int zt = dataShadow.selector[groupNo] & 0xff;
    744        final int[] limit_zt = dataShadow.limit[zt];
    745        int zn = dataShadow.minLens[zt];
    746        int zvec = bsR(zn);
    747        int bsLiveShadow = this.bsLive;
    748        int bsBuffShadow = this.bsBuff;
    749
    750        while (zvec > limit_zt[zn]) {
    751            zn++;
    752            while (bsLiveShadow < 1) {
    753                final int thech = inShadow.read();
    754
    755                if (thech >= 0) {
    756                    bsBuffShadow = (bsBuffShadow << 8) | thech;
    757                    bsLiveShadow += 8;
    758                    continue;
    759                }
    760                throw new IOException("unexpected end of stream");
    761            }
    762            bsLiveShadow--;
    763            zvec = (zvec << 1) | ((bsBuffShadow >> bsLiveShadow) & 1);
    764        }
    765
    766        this.bsLive = bsLiveShadow;
    767        this.bsBuff = bsBuffShadow;
    768
    769        return dataShadow.perm[zt][zvec - dataShadow.base[zt][zn]];
    770    }
    771
    772    private int setupBlock() throws IOException {
    773        if (currentState == EOF || this.data == null) {
    774            return -1;
    775        }
    776
    777        final int[] cftab = this.data.cftab;
    778        final int[] tt = this.data.initTT(this.last + 1);
    779        final byte[] ll8 = this.data.ll8;
    780        cftab[0] = 0;
    781        System.arraycopy(this.data.unzftab, 0, cftab, 1, 256);
    782
    783        for (int i = 1, c = cftab[0]; i <= 256; i++) {
    784            c += cftab[i];
    785            cftab[i] = c;
    786        }
    787
    788        for (int i = 0, lastShadow = this.last; i <= lastShadow; i++) {
    789            tt[cftab[ll8[i] & 0xff]++] = i;
    790        }
    791
    792        if ((this.origPtr < 0) || (this.origPtr >= tt.length)) {
    793            throw new IOException("stream corrupted");
    794        }
    795
    796        this.su_tPos = tt[this.origPtr];
    797        this.su_count = 0;
    798        this.su_i2 = 0;
    799        this.su_ch2 = 256; /* not a char and not EOF */
    800
    801        if (this.blockRandomised) {
    802            this.su_rNToGo = 0;
    803            this.su_rTPos = 0;
    804            return setupRandPartA();
    805        }
    806        return setupNoRandPartA();
    807    }
    808
    809    private int setupRandPartA() throws IOException {
    810        if (this.su_i2 <= this.last) {
    811            this.su_chPrev = this.su_ch2;
    812            int su_ch2Shadow = this.data.ll8[this.su_tPos] & 0xff;
    813            this.su_tPos = this.data.tt[this.su_tPos];
    814            if (this.su_rNToGo == 0) {
    815                this.su_rNToGo = Rand.rNums(this.su_rTPos) - 1;
    816                if (++this.su_rTPos == 512) {
    817                    this.su_rTPos = 0;
    818                }
    819            } else {
    820                this.su_rNToGo--;
    821            }
    822            this.su_ch2 = su_ch2Shadow ^= (this.su_rNToGo == 1) ? 1 : 0;
    823            this.su_i2++;
    824            this.currentState = RAND_PART_B_STATE;
    825            this.crc.updateCRC(su_ch2Shadow);
    826            return su_ch2Shadow;
    827        }
    828        endBlock();
    829        initBlock();
    830        return setupBlock();
    831    }
    832
    833    private int setupNoRandPartA() throws IOException {
    834        if (this.su_i2 <= this.last) {
    835            this.su_chPrev = this.su_ch2;
    836            final int su_ch2Shadow = this.data.ll8[this.su_tPos] & 0xff;
    837            this.su_ch2 = su_ch2Shadow;
    838            this.su_tPos = this.data.tt[this.su_tPos];
    839            this.su_i2++;
    840            this.currentState = NO_RAND_PART_B_STATE;
    841            this.crc.updateCRC(su_ch2Shadow);
    842            return su_ch2Shadow;
    843        }
    844        this.currentState = NO_RAND_PART_A_STATE;
    845        endBlock();
    846        initBlock();
    847        return setupBlock();
    848    }
    849
    850    private int setupRandPartB() throws IOException {
    851        if (this.su_ch2 != this.su_chPrev) {
    852            this.currentState = RAND_PART_A_STATE;
    853            this.su_count = 1;
    854            return setupRandPartA();
    855        } else if (++this.su_count >= 4) {
    856            this.su_z = (char) (this.data.ll8[this.su_tPos] & 0xff);
    857            this.su_tPos = this.data.tt[this.su_tPos];
    858            if (this.su_rNToGo == 0) {
    859                this.su_rNToGo = Rand.rNums(this.su_rTPos) - 1;
    860                if (++this.su_rTPos == 512) {
    861                    this.su_rTPos = 0;
    862                }
    863            } else {
    864                this.su_rNToGo--;
    865            }
    866            this.su_j2 = 0;
    867            this.currentState = RAND_PART_C_STATE;
    868            if (this.su_rNToGo == 1) {
    869                this.su_z ^= 1;
    870            }
    871            return setupRandPartC();
    872        } else {
    873            this.currentState = RAND_PART_A_STATE;
    874            return setupRandPartA();
    875        }
    876    }
    877
    878    private int setupRandPartC() throws IOException {
    879        if (this.su_j2 < this.su_z) {
    880            this.crc.updateCRC(this.su_ch2);
    881            this.su_j2++;
    882            return this.su_ch2;
    883        }
    884        this.currentState = RAND_PART_A_STATE;
    885        this.su_i2++;
    886        this.su_count = 0;
    887        return setupRandPartA();
    888    }
    889
    890    private int setupNoRandPartB() throws IOException {
    891        if (this.su_ch2 != this.su_chPrev) {
    892            this.su_count = 1;
    893            return setupNoRandPartA();
    894        } else if (++this.su_count >= 4) {
    895            this.su_z = (char) (this.data.ll8[this.su_tPos] & 0xff);
    896            this.su_tPos = this.data.tt[this.su_tPos];
    897            this.su_j2 = 0;
    898            return setupNoRandPartC();
    899        } else {
    900            return setupNoRandPartA();
    901        }
    902    }
    903
    904    private int setupNoRandPartC() throws IOException {
    905        if (this.su_j2 < this.su_z) {
    906            final int su_ch2Shadow = this.su_ch2;
    907            this.crc.updateCRC(su_ch2Shadow);
    908            this.su_j2++;
    909            this.currentState = NO_RAND_PART_C_STATE;
    910            return su_ch2Shadow;
    911        }
    912        this.su_i2++;
    913        this.su_count = 0;
    914        return setupNoRandPartA();
    915    }
    916
    917    private static final class Data {
    918
    919        // (with blockSize 900k)
    920        final boolean[] inUse = new boolean[256]; // 256 byte
    921
    922        final byte[] seqToUnseq = new byte[256]; // 256 byte
    923        final byte[] selector = new byte[MAX_SELECTORS]; // 18002 byte
    924        final byte[] selectorMtf = new byte[MAX_SELECTORS]; // 18002 byte
    925
    926        /**
    927         * Freq table collected to save a pass over the data during
    928         * decompression.
    929         */
    930        final int[] unzftab = new int[256]; // 1024 byte
    931
    932        final int[][] limit = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
    933        final int[][] base = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
    934        final int[][] perm = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
    935        final int[] minLens = new int[N_GROUPS]; // 24 byte
    936
    937        final int[] cftab = new int[257]; // 1028 byte
    938        final char[] getAndMoveToFrontDecode_yy = new char[256]; // 512 byte
    939        final char[][] temp_charArray2d = new char[N_GROUPS][MAX_ALPHA_SIZE]; // 3096
    940        // byte
    941        final byte[] recvDecodingTables_pos = new byte[N_GROUPS]; // 6 byte
    942        // ---------------
    943        // 60798 byte
    944
    945        int[] tt; // 3600000 byte
    946        byte[] ll8; // 900000 byte
    947
    948        // ---------------
    949        // 4560782 byte
    950        // ===============
    951
    952        Data(final int blockSize100k) {
    953            this.ll8 = new byte[blockSize100k * BZip2Constants.BASEBLOCKSIZE];
    954        }
    955
    956        /**
    957         * Initializes the {@link #tt} array.
    958         *
    959         * This method is called when the required length of the array is known.
    960         * I don't initialize it at construction time to avoid unneccessary
    961         * memory allocation when compressing small files.
    962         */
    963        int[] initTT(final int length) {
    964            int[] ttShadow = this.tt;
    965
    966            // tt.length should always be >= length, but theoretically
    967            // it can happen, if the compressor mixed small and large
    968            // blocks. Normally only the last block will be smaller
    969            // than others.
    970            if ((ttShadow == null) || (ttShadow.length < length)) {
    971                this.tt = ttShadow = new int[length];
    972            }
    973
    974            return ttShadow;
    975        }
    976
    977    }
    978
    979    /**
    980     * Checks if the signature matches what is expected for a bzip2 file.
    981     *
    982     * @param signature
    983     *            the bytes to check
    984     * @param length
    985     *            the number of bytes to check
    986     * @return true, if this stream is a bzip2 compressed stream, false otherwise
    987     *
    988     * @since 1.1
    989     */
    990    public static boolean matches(final byte[] signature, final int length) {
    991
    992        if (length < 3) {
    993            return false;
    994        }
    995
    996        if (signature[0] != 'B') {
    997            return false;
    998        }
    999
    1000        if (signature[1] != 'Z') {
    1001            return false;
    1002        }
    1003
    1004        if (signature[2] != 'h') {
    1005            return false;
    1006        }
    1007
    1008        return true;
    1009    }
    1010}