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