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