    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 *   https://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;
    029import java.nio.ByteOrder;
    030import java.util.Arrays;
    031
    032import org.apache.commons.compress.compressors.CompressorInputStream;
    033import org.apache.commons.compress.utils.BitInputStream;
    034import org.apache.commons.compress.utils.InputStreamStatistics;
    035import org.apache.commons.io.input.CloseShieldInputStream;
    036
    037/**
    038 * An input stream that decompresses from the BZip2 format to be read as any other stream.
    039 *
    040 * @NotThreadSafe
    041 */
    042public class BZip2CompressorInputStream extends CompressorInputStream implements BZip2Constants, InputStreamStatistics {
    043
    044    private static final class Data {
    045
    046        // (with blockSize 900k)
    047        final boolean[] inUse = new boolean[256]; // 256 byte
    048
    049        final byte[] seqToUnseq = new byte[256]; // 256 byte
    050        final byte[] selector = new byte[MAX_SELECTORS]; // 18002 byte
    051        final byte[] selectorMtf = new byte[MAX_SELECTORS]; // 18002 byte
    052
    053        /**
    054         * Freq table collected to save a pass over the data during decompression.
    055         */
    056        final int[] unzftab = new int[256]; // 1024 byte
    057
    058        final int[][] limit = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
    059        final int[][] base = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
    060        final int[][] perm = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
    061        final int[] minLens = new int[N_GROUPS]; // 24 byte
    062
    063        final int[] cftab = new int[257]; // 1028 byte
    064        final char[] getAndMoveToFrontDecode_yy = new char[256]; // 512 byte
    065        final char[][] temp_charArray2d = new char[N_GROUPS][MAX_ALPHA_SIZE]; // 3096
    066        // byte
    067        final byte[] recvDecodingTables_pos = new byte[N_GROUPS]; // 6 byte
    068        // ---------------
    069        // 60798 byte
    070
    071        int[] tt; // 3600000 byte
    072        final byte[] ll8; // 900000 byte
    073
    074        // ---------------
    075        // 4560782 byte
    076        // ===============
    077
    078        Data(final int blockSize100k) {
    079            this.ll8 = new byte[blockSize100k * BASEBLOCKSIZE];
    080        }
    081
    082        /**
    083         * Initializes the {@link #tt} array.
    084         *
    085         * This method is called when the required length of the array is known. I don't initialize it at construction time to avoid unnecessary memory
    086         * allocation when compressing small files.
    087         */
    088        int[] initTT(final int length) {
    089            int[] ttShadow = this.tt;
    090
    091            // tt.length should always be >= length, but theoretically
    092            // it can happen, if the compressor mixed small and large
    093            // blocks. Normally only the last block will be smaller
    094            // than others.
    095            if (ttShadow == null || ttShadow.length < length) {
    096                this.tt = ttShadow = new int[length];
    097            }
    098
    099            return ttShadow;
    100        }
    101
    102    }
    103
    104    private static final int EOF = 0;
    105
    106    private static final int START_BLOCK_STATE = 1;
    107
    108    private static final int RAND_PART_A_STATE = 2;
    109
    110    private static final int RAND_PART_B_STATE = 3;
    111
    112    private static final int RAND_PART_C_STATE = 4;
    113
    114    private static final int NO_RAND_PART_A_STATE = 5;
    115    private static final int NO_RAND_PART_B_STATE = 6;
    116
    117    private static final int NO_RAND_PART_C_STATE = 7;
    118
    119    private static boolean bsGetBit(final BitInputStream bin) throws IOException {
    120        return bsR(bin, 1) != 0;
    121    }
    122
    123    private static int bsGetInt(final BitInputStream bin) throws IOException {
    124        return bsR(bin, 32);
    125    }
    126
    127    private static char bsGetUByte(final BitInputStream bin) throws IOException {
    128        return (char) bsR(bin, 8);
    129    }
    130
    131    /**
    132     * read bits from the input stream
    133     *
    134     * @param n the number of bits to read, must not exceed 32?
    135     * @return the requested bits combined into an int
    136     * @throws IOException if an I/O error occurs.
    137     */
    138    private static int bsR(final BitInputStream bin, final int n) throws IOException {
    139        final long thech = bin.readBits(n);
    140        if (thech < 0) {
    141            throw new IOException("Unexpected end of stream");
    142        }
    143        return (int) thech;
    144    }
    145
    146    private static void checkBounds(final int checkVal, final int limitExclusive, final String name) throws IOException {
    147        if (checkVal < 0) {
    148            throw new IOException("Corrupted input, " + name + " value negative");
    149        }
    150        if (checkVal >= limitExclusive) {
    151            throw new IOException("Corrupted input, " + name + " value too big");
    152        }
    153    }
    154
    155    /**
    156     * Called by createHuffmanDecodingTables() exclusively.
    157     */
    158    private static void hbCreateDecodeTables(final int[] limit, final int[] base, final int[] perm, final char[] length, final int minLen, final int maxLen,
    159            final int alphaSize) throws IOException {
    160        for (int i = minLen, pp = 0; i <= maxLen; i++) {
    161            for (int j = 0; j < alphaSize; j++) {
    162                if (length[j] == i) {
    163                    perm[pp++] = j;
    164                }
    165            }
    166        }
    167
    168        for (int i = MAX_CODE_LEN; --i > 0;) {
    169            base[i] = 0;
    170            limit[i] = 0;
    171        }
    172
    173        for (int i = 0; i < alphaSize; i++) {
    174            final int l = length[i];
    175            checkBounds(l, MAX_ALPHA_SIZE, "length");
    176            base[l + 1]++;
    177        }
    178
    179        for (int i = 1, b = base[0]; i < MAX_CODE_LEN; i++) {
    180            b += base[i];
    181            base[i] = b;
    182        }
    183
    184        for (int i = minLen, vec = 0, b = base[i]; i <= maxLen; i++) {
    185            final int nb = base[i + 1];
    186            vec += nb - b;
    187            b = nb;
    188            limit[i] = vec - 1;
    189            vec <<= 1;
    190        }
    191
    192        for (int i = minLen + 1; i <= maxLen; i++) {
    193            base[i] = (limit[i - 1] + 1 << 1) - base[i];
    194        }
    195    }
    196
    197    /**
    198     * Checks if the signature matches what is expected for a bzip2 file.
    199     *
    200     * @param signature the bytes to check
    201     * @param length    the number of bytes to check
    202     * @return true, if this stream is a bzip2 compressed stream, false otherwise
    203     * @since 1.1
    204     */
    205    public static boolean matches(final byte[] signature, final int length) {
    206        return length >= 3 && signature[0] == 'B' && signature[1] == 'Z' && signature[2] == 'h';
    207    }
    208
    209    /**
    210     * Index of the last char in the block, so the block size == last + 1.
    211     */
    212    private int last;
    213
    214    /**
    215     * Index in zptr[] of original string after sorting.
    216     */
    217    private int origPtr;
    218    /**
    219     * always: in the range 0 .. 9. The current block size is 100000 * this number.
    220     */
    221    private int blockSize100k;
    222
    223    // Variables used by setup* methods exclusively
    224
    225    private boolean blockRandomised;
    226    private final CRC crc = new CRC();
    227    private int nInUse;
    228    private BitInputStream bin;
    229    private final boolean decompressConcatenated;
    230    private int currentState = START_BLOCK_STATE;
    231    private int storedBlockCRC;
    232    private int storedCombinedCRC;
    233    private int computedCombinedCRC;
    234    private int su_count;
    235    private int su_ch2;
    236    private int su_chPrev;
    237    private int su_i2;
    238    private int su_j2;
    239    private int su_rNToGo;
    240    private int su_rTPos;
    241    private int su_tPos;
    242    private char su_z;
    243
    244    /**
    245     * All memory intensive stuff. This field is initialized by initBlock().
    246     */
    247    private BZip2CompressorInputStream.Data data;
    248
    249    /**
    250     * Constructs a new BZip2CompressorInputStream which decompresses bytes read from the specified stream. This doesn't support decompressing concatenated .bz2
    251     * files.
    252     *
    253     * @param in the InputStream from which this object should be created
    254     * @throws IOException          if the stream content is malformed or an I/O error occurs.
    255     * @throws NullPointerException if {@code in == null}
    256     */
    257    public BZip2CompressorInputStream(final InputStream in) throws IOException {
    258        this(in, false);
    259    }
    260
    261    /**
    262     * Constructs a new BZip2CompressorInputStream which decompresses bytes read from the specified stream.
    263     *
    264     * @param in                     the InputStream from which this object should be created
    265     * @param decompressConcatenated if true, decompress until the end of the input; if false, stop after the first .bz2 stream and leave the input position to
    266     *                               point to the next byte after the .bz2 stream
    267     *
    268     * @throws IOException if {@code in == null}, the stream content is malformed, or an I/O error occurs.
    269     */
    270    public BZip2CompressorInputStream(final InputStream in, final boolean decompressConcatenated) throws IOException {
    271        this.bin = new BitInputStream(in == System.in ? CloseShieldInputStream.wrap(in) : in, ByteOrder.BIG_ENDIAN);
    272        this.decompressConcatenated = decompressConcatenated;
    273        init(true);
    274        initBlock();
    275    }
    276
    277    @Override
    278    public void close() throws IOException {
    279        final BitInputStream inShadow = this.bin;
    280        if (inShadow != null) {
    281            try {
    282                inShadow.close();
    283            } finally {
    284                this.data = null;
    285                this.bin = null;
    286            }
    287        }
    288    }
    289
    290    private boolean complete() throws IOException {
    291        this.storedCombinedCRC = bsGetInt(bin);
    292        this.currentState = EOF;
    293        this.data = null;
    294        if (this.storedCombinedCRC != this.computedCombinedCRC) {
    295            throw new IOException("BZip2 CRC error");
    296        }
    297        // Look for the next .bz2 stream if decompressing
    298        // concatenated files.
    299        return !decompressConcatenated || !init(false);
    300    }
    301
    302    /**
    303     * Called by recvDecodingTables() exclusively.
    304     */
    305    private void createHuffmanDecodingTables(final int alphaSize, final int nGroups) throws IOException {
    306        final Data dataShadow = this.data;
    307        final char[][] len = dataShadow.temp_charArray2d;
    308        final int[] minLens = dataShadow.minLens;
    309        final int[][] limit = dataShadow.limit;
    310        final int[][] base = dataShadow.base;
    311        final int[][] perm = dataShadow.perm;
    312
    313        for (int t = 0; t < nGroups; t++) {
    314            int minLen = 32;
    315            int maxLen = 0;
    316            final char[] len_t = len[t];
    317            for (int i = alphaSize; --i >= 0;) {
    318                final char lent = len_t[i];
    319                if (lent > maxLen) {
    320                    maxLen = lent;
    321                }
    322                if (lent < minLen) {
    323                    minLen = lent;
    324                }
    325            }
    326            hbCreateDecodeTables(limit[t], base[t], perm[t], len[t], minLen, maxLen, alphaSize);
    327            minLens[t] = minLen;
    328        }
    329    }
    330
    331    private void endBlock() throws IOException {
    332        final int computedBlockCRC = this.crc.getValue();
    333        // A bad CRC is considered a fatal error.
    334        if (this.storedBlockCRC != computedBlockCRC) {
    335            // make next blocks readable without error
    336            // (repair feature, not yet documented, not tested)
    337            this.computedCombinedCRC = this.storedCombinedCRC << 1 | this.storedCombinedCRC >>> 31;
    338            this.computedCombinedCRC ^= this.storedBlockCRC;
    339            throw new IOException("BZip2 CRC error");
    340        }
    341        this.computedCombinedCRC = this.computedCombinedCRC << 1 | this.computedCombinedCRC >>> 31;
    342        this.computedCombinedCRC ^= computedBlockCRC;
    343    }
    344
    345    private void getAndMoveToFrontDecode() throws IOException {
    346        final BitInputStream bin = this.bin;
    347        this.origPtr = bsR(bin, 24);
    348        recvDecodingTables();
    349        final Data dataShadow = this.data;
    350        final byte[] ll8 = dataShadow.ll8;
    351        final int[] unzftab = dataShadow.unzftab;
    352        final byte[] selector = dataShadow.selector;
    353        final byte[] seqToUnseq = dataShadow.seqToUnseq;
    354        final char[] yy = dataShadow.getAndMoveToFrontDecode_yy;
    355        final int[] minLens = dataShadow.minLens;
    356        final int[][] limit = dataShadow.limit;
    357        final int[][] base = dataShadow.base;
    358        final int[][] perm = dataShadow.perm;
    359        final int limitLast = this.blockSize100k * 100000;
    360
    361        /*
    362         * Setting up the unzftab entries here is not strictly necessary, but it does save having to do it later in a separate pass, and so saves a block's
    363         * worth of cache misses.
    364         */
    365        for (int i = 256; --i >= 0;) {
    366            yy[i] = (char) i;
    367            unzftab[i] = 0;
    368        }
    369
    370        int groupNo = 0;
    371        int groupPos = G_SIZE - 1;
    372        final int eob = this.nInUse + 1;
    373        int nextSym = getAndMoveToFrontDecode0();
    374        int lastShadow = -1;
    375        int zt = selector[groupNo] & 0xff;
    376        checkBounds(zt, N_GROUPS, "zt");
    377        int[] base_zt = base[zt];
    378        int[] limit_zt = limit[zt];
    379        int[] perm_zt = perm[zt];
    380        int minLens_zt = minLens[zt];
    381
    382        while (nextSym != eob) {
    383            if (nextSym == RUNA || nextSym == RUNB) {
    384                int s = -1;
    385
    386                for (int n = 1; true; n <<= 1) {
    387                    if (nextSym == RUNA) {
    388                        s += n;
    389                    } else if (nextSym == RUNB) {
    390                        s += n << 1;
    391                    } else {
    392                        break;
    393                    }
    394
    395                    if (groupPos == 0) {
    396                        groupPos = G_SIZE - 1;
    397                        checkBounds(++groupNo, MAX_SELECTORS, "groupNo");
    398                        zt = selector[groupNo] & 0xff;
    399                        checkBounds(zt, N_GROUPS, "zt");
    400                        base_zt = base[zt];
    401                        limit_zt = limit[zt];
    402                        perm_zt = perm[zt];
    403                        minLens_zt = minLens[zt];
    404                    } else {
    405                        groupPos--;
    406                    }
    407
    408                    int zn = minLens_zt;
    409                    checkBounds(zn, MAX_ALPHA_SIZE, "zn");
    410                    int zvec = bsR(bin, zn);
    411                    while (zvec > limit_zt[zn]) {
    412                        checkBounds(++zn, MAX_ALPHA_SIZE, "zn");
    413                        zvec = zvec << 1 | bsR(bin, 1);
    414                    }
    415                    final int tmp = zvec - base_zt[zn];
    416                    checkBounds(tmp, MAX_ALPHA_SIZE, "zvec");
    417                    nextSym = perm_zt[tmp];
    418                }
    419                checkBounds(s, this.data.ll8.length, "s");
    420
    421                final int yy0 = yy[0];
    422                checkBounds(yy0, 256, "yy");
    423                final byte ch = seqToUnseq[yy0];
    424                unzftab[ch & 0xff] += s + 1;
    425
    426                final int from = ++lastShadow;
    427                lastShadow += s;
    428                checkBounds(lastShadow, this.data.ll8.length, "lastShadow");
    429                Arrays.fill(ll8, from, lastShadow + 1, ch);
    430
    431                if (lastShadow >= limitLast) {
    432                    throw new IOException("Block overrun while expanding RLE in MTF, " + lastShadow + " exceeds " + limitLast);
    433                }
    434            } else {
    435                if (++lastShadow >= limitLast) {
    436                    throw new IOException("Block overrun in MTF, " + lastShadow + " exceeds " + limitLast);
    437                }
    438                checkBounds(nextSym, 256 + 1, "nextSym");
    439
    440                final char tmp = yy[nextSym - 1];
    441                checkBounds(tmp, 256, "yy");
    442                unzftab[seqToUnseq[tmp] & 0xff]++;
    443                ll8[lastShadow] = seqToUnseq[tmp];
    444
    445                /*
    446                 * This loop is hammered during decompression, hence avoid native method call overhead of System.arraycopy for very small ranges to copy.
    447                 */
    448                if (nextSym <= 16) {
    449                    for (int j = nextSym - 1; j > 0;) {
    450                        yy[j] = yy[--j];
    451                    }
    452                } else {
    453                    System.arraycopy(yy, 0, yy, 1, nextSym - 1);
    454                }
    455
    456                yy[0] = tmp;
    457
    458                if (groupPos == 0) {
    459                    groupPos = G_SIZE - 1;
    460                    checkBounds(++groupNo, MAX_SELECTORS, "groupNo");
    461                    zt = selector[groupNo] & 0xff;
    462                    checkBounds(zt, N_GROUPS, "zt");
    463                    base_zt = base[zt];
    464                    limit_zt = limit[zt];
    465                    perm_zt = perm[zt];
    466                    minLens_zt = minLens[zt];
    467                } else {
    468                    groupPos--;
    469                }
    470
    471                int zn = minLens_zt;
    472                checkBounds(zn, MAX_ALPHA_SIZE, "zn");
    473                int zvec = bsR(bin, zn);
    474                while (zvec > limit_zt[zn]) {
    475                    checkBounds(++zn, MAX_ALPHA_SIZE, "zn");
    476                    zvec = zvec << 1 | bsR(bin, 1);
    477                }
    478                final int idx = zvec - base_zt[zn];
    479                checkBounds(idx, MAX_ALPHA_SIZE, "zvec");
    480                nextSym = perm_zt[idx];
    481            }
    482        }
    483
    484        this.last = lastShadow;
    485    }
    486
    487    private int getAndMoveToFrontDecode0() throws IOException {
    488        final Data dataShadow = this.data;
    489        final int zt = dataShadow.selector[0] & 0xff;
    490        checkBounds(zt, N_GROUPS, "zt");
    491        final int[] limit_zt = dataShadow.limit[zt];
    492        int zn = dataShadow.minLens[zt];
    493        checkBounds(zn, MAX_ALPHA_SIZE, "zn");
    494        int zvec = bsR(bin, zn);
    495        while (zvec > limit_zt[zn]) {
    496            checkBounds(++zn, MAX_ALPHA_SIZE, "zn");
    497            zvec = zvec << 1 | bsR(bin, 1);
    498        }
    499        final int tmp = zvec - dataShadow.base[zt][zn];
    500        checkBounds(tmp, MAX_ALPHA_SIZE, "zvec");
    501
    502        return dataShadow.perm[zt][tmp];
    503    }
    504
    505    /**
    506     * @since 1.17
    507     */
    508    @Override
    509    public long getCompressedCount() {
    510        return bin.getBytesRead();
    511    }
    512
    513    private boolean init(final boolean isFirstStream) throws IOException {
    514        if (null == bin) {
    515            throw new IOException("No InputStream");
    516        }
    517
    518        if (!isFirstStream) {
    519            bin.clearBitCache();
    520        }
    521
    522        final int magic0 = readNextByte(this.bin);
    523        if (magic0 == -1 && !isFirstStream) {
    524            return false;
    525        }
    526        final int magic1 = readNextByte(this.bin);
    527        final int magic2 = readNextByte(this.bin);
    528
    529        if (magic0 != 'B' || magic1 != 'Z' || magic2 != 'h') {
    530            throw new IOException(isFirstStream ? "Stream is not in the BZip2 format" : "Unexpected data after a valid BZip2 stream");
    531        }
    532
    533        final int blockSize = readNextByte(this.bin);
    534        if (blockSize < '1' || blockSize > '9') {
    535            throw new IOException("BZip2 block size is invalid");
    536        }
    537
    538        this.blockSize100k = blockSize - '0';
    539
    540        this.computedCombinedCRC = 0;
    541
    542        return true;
    543    }
    544
    545    private void initBlock() throws IOException {
    546        final BitInputStream bin = this.bin;
    547        char magic0;
    548        char magic1;
    549        char magic2;
    550        char magic3;
    551        char magic4;
    552        char magic5;
    553
    554        while (true) {
    555            // Get the block magic bytes.
    556            magic0 = bsGetUByte(bin);
    557            magic1 = bsGetUByte(bin);
    558            magic2 = bsGetUByte(bin);
    559            magic3 = bsGetUByte(bin);
    560            magic4 = bsGetUByte(bin);
    561            magic5 = bsGetUByte(bin);
    562
    563            // If isn't end of stream magic, break out of the loop.
    564            if (magic0 != 0x17 || magic1 != 0x72 || magic2 != 0x45 || magic3 != 0x38 || magic4 != 0x50 || magic5 != 0x90) {
    565                break;
    566            }
    567
    568            // End of stream was reached. Check the combined CRC and
    569            // advance to the next .bz2 stream if decoding concatenated
    570            // streams.
    571            if (complete()) {
    572                return;
    573            }
    574        }
    575
    576        if (magic0 != 0x31 || // '1'
    577                magic1 != 0x41 || // ')'
    578                magic2 != 0x59 || // 'Y'
    579                magic3 != 0x26 || // '&'
    580                magic4 != 0x53 || // 'S'
    581                magic5 != 0x59 // 'Y'
    582        ) {
    583            this.currentState = EOF;
    584            throw new IOException("Bad block header");
    585        }
    586        this.storedBlockCRC = bsGetInt(bin);
    587        this.blockRandomised = bsR(bin, 1) == 1;
    588
    589        /*
    590         * Allocate data here instead in constructor, so we do not allocate it if the input file is empty.
    591         */
    592        if (this.data == null) {
    593            this.data = new Data(this.blockSize100k);
    594        }
    595
    596        // currBlockNo++;
    597        getAndMoveToFrontDecode();
    598
    599        this.crc.reset();
    600        this.currentState = START_BLOCK_STATE;
    601    }
    602
    603    private void makeMaps() {
    604        final boolean[] inUse = this.data.inUse;
    605        final byte[] seqToUnseq = this.data.seqToUnseq;
    606
    607        int nInUseShadow = 0;
    608
    609        for (int i = 0; i < 256; i++) {
    610            if (inUse[i]) {
    611                seqToUnseq[nInUseShadow++] = (byte) i;
    612            }
    613        }
    614
    615        this.nInUse = nInUseShadow;
    616    }
    617
    618    @Override
    619    public int read() throws IOException {
    620        if (this.bin != null) {
    621            final int r = read0();
    622            count(r < 0 ? -1 : 1);
    623            return r;
    624        }
    625        throw new IOException("Stream closed");
    626    }
    627
    628    /*
    629     * (non-Javadoc)
    630     *
    631     * @see java.io.InputStream#read(byte[], int, int)
    632     */
    633    @Override
    634    public int read(final byte[] dest, final int offs, final int len) throws IOException {
    635        if (offs < 0) {
    636            throw new IndexOutOfBoundsException("offs(" + offs + ") < 0.");
    637        }
    638        if (len < 0) {
    639            throw new IndexOutOfBoundsException("len(" + len + ") < 0.");
    640        }
    641        if (offs + len > dest.length) {
    642            throw new IndexOutOfBoundsException("offs(" + offs + ") + len(" + len + ") > dest.length(" + dest.length + ").");
    643        }
    644        if (this.bin == null) {
    645            throw new IOException("Stream closed");
    646        }
    647        if (len == 0) {
    648            return 0;
    649        }
    650
    651        final int hi = offs + len;
    652        int destOffs = offs;
    653        int b;
    654        while (destOffs < hi && (b = read0()) >= 0) {
    655            dest[destOffs++] = (byte) b;
    656            count(1);
    657        }
    658
    659        return destOffs == offs ? -1 : destOffs - offs;
    660    }
    661
    662    private int read0() throws IOException {
    663        switch (currentState) {
    664        case EOF:
    665            return -1;
    666
    667        case START_BLOCK_STATE:
    668            return setupBlock();
    669
    670        case RAND_PART_A_STATE:
    671            throw new IllegalStateException();
    672
    673        case RAND_PART_B_STATE:
    674            return setupRandPartB();
    675
    676        case RAND_PART_C_STATE:
    677            return setupRandPartC();
    678
    679        case NO_RAND_PART_A_STATE:
    680            throw new IllegalStateException();
    681
    682        case NO_RAND_PART_B_STATE:
    683            return setupNoRandPartB();
    684
    685        case NO_RAND_PART_C_STATE:
    686            return setupNoRandPartC();
    687
    688        default:
    689            throw new IllegalStateException();
    690        }
    691    }
    692
    693    private int readNextByte(final BitInputStream in) throws IOException {
    694        final long b = in.readBits(8);
    695        return (int) b;
    696    }
    697
    698    private void recvDecodingTables() throws IOException {
    699        final BitInputStream bin = this.bin;
    700        final Data dataShadow = this.data;
    701        final boolean[] inUse = dataShadow.inUse;
    702        final byte[] pos = dataShadow.recvDecodingTables_pos;
    703        final byte[] selector = dataShadow.selector;
    704        final byte[] selectorMtf = dataShadow.selectorMtf;
    705
    706        int inUse16 = 0;
    707
    708        /* Receive the mapping table */
    709        for (int i = 0; i < 16; i++) {
    710            if (bsGetBit(bin)) {
    711                inUse16 |= 1 << i;
    712            }
    713        }
    714
    715        Arrays.fill(inUse, false);
    716        for (int i = 0; i < 16; i++) {
    717            if ((inUse16 & 1 << i) != 0) {
    718                final int i16 = i << 4;
    719                for (int j = 0; j < 16; j++) {
    720                    if (bsGetBit(bin)) {
    721                        inUse[i16 + j] = true;
    722                    }
    723                }
    724            }
    725        }
    726
    727        makeMaps();
    728        final int alphaSize = this.nInUse + 2;
    729        /* Now the selectors */
    730        final int nGroups = bsR(bin, 3);
    731        final int selectors = bsR(bin, 15);
    732        if (selectors < 0) {
    733            throw new IOException("Corrupted input, nSelectors value negative");
    734        }
    735        checkBounds(alphaSize, MAX_ALPHA_SIZE + 1, "alphaSize");
    736        checkBounds(nGroups, N_GROUPS + 1, "nGroups");
    737
    738        // Don't fail on nSelectors overflowing boundaries but discard the values in overflow
    739        // See https://gnu.wildebeest.org/blog/mjw/2019/08/02/bzip2-and-the-cve-that-wasnt/
    740        // and https://sourceware.org/ml/bzip2-devel/2019-q3/msg00007.html
    741
    742        for (int i = 0; i < selectors; i++) {
    743            int j = 0;
    744            while (bsGetBit(bin)) {
    745                j++;
    746            }
    747            if (i < MAX_SELECTORS) {
    748                selectorMtf[i] = (byte) j;
    749            }
    750        }
    751        final int nSelectors = Math.min(selectors, MAX_SELECTORS);
    752
    753        /* Undo the MTF values for the selectors. */
    754        for (int v = nGroups; --v >= 0;) {
    755            pos[v] = (byte) v;
    756        }
    757
    758        for (int i = 0; i < nSelectors; i++) {
    759            int v = selectorMtf[i] & 0xff;
    760            checkBounds(v, N_GROUPS, "selectorMtf");
    761            final byte tmp = pos[v];
    762            while (v > 0) {
    763                // nearly all times v is zero, 4 in most other cases
    764                pos[v] = pos[v - 1];
    765                v--;
    766            }
    767            pos[0] = tmp;
    768            selector[i] = tmp;
    769        }
    770
    771        final char[][] len = dataShadow.temp_charArray2d;
    772
    773        /* Now the coding tables */
    774        for (int t = 0; t < nGroups; t++) {
    775            int curr = bsR(bin, 5);
    776            final char[] len_t = len[t];
    777            for (int i = 0; i < alphaSize; i++) {
    778                while (bsGetBit(bin)) {
    779                    curr += bsGetBit(bin) ? -1 : 1;
    780                }
    781                len_t[i] = (char) curr;
    782            }
    783        }
    784
    785        // finally create the Huffman tables
    786        createHuffmanDecodingTables(alphaSize, nGroups);
    787    }
    788
    789    private int setupBlock() throws IOException {
    790        if (currentState == EOF || this.data == null) {
    791            return -1;
    792        }
    793
    794        final int[] cftab = this.data.cftab;
    795        final int ttLen = this.last + 1;
    796        final int[] tt = this.data.initTT(ttLen);
    797        final byte[] ll8 = this.data.ll8;
    798        cftab[0] = 0;
    799        System.arraycopy(this.data.unzftab, 0, cftab, 1, 256);
    800
    801        for (int i = 1, c = cftab[0]; i <= 256; i++) {
    802            c += cftab[i];
    803            cftab[i] = c;
    804        }
    805
    806        for (int i = 0, lastShadow = this.last; i <= lastShadow; i++) {
    807            final int tmp = cftab[ll8[i] & 0xff]++;
    808            checkBounds(tmp, ttLen, "tt index");
    809            tt[tmp] = i;
    810        }
    811
    812        if (this.origPtr < 0 || this.origPtr >= tt.length) {
    813            throw new IOException("Stream corrupted");
    814        }
    815
    816        this.su_tPos = tt[this.origPtr];
    817        this.su_count = 0;
    818        this.su_i2 = 0;
    819        this.su_ch2 = 256; /* not a char and not EOF */
    820
    821        if (this.blockRandomised) {
    822            this.su_rNToGo = 0;
    823            this.su_rTPos = 0;
    824            return setupRandPartA();
    825        }
    826        return setupNoRandPartA();
    827    }
    828
    829    private int setupNoRandPartA() throws IOException {
    830        if (this.su_i2 <= this.last) {
    831            this.su_chPrev = this.su_ch2;
    832            final int su_ch2Shadow = this.data.ll8[this.su_tPos] & 0xff;
    833            this.su_ch2 = su_ch2Shadow;
    834            checkBounds(this.su_tPos, this.data.tt.length, "su_tPos");
    835            this.su_tPos = this.data.tt[this.su_tPos];
    836            this.su_i2++;
    837            this.currentState = NO_RAND_PART_B_STATE;
    838            this.crc.update(su_ch2Shadow);
    839            return su_ch2Shadow;
    840        }
    841        this.currentState = NO_RAND_PART_A_STATE;
    842        endBlock();
    843        initBlock();
    844        return setupBlock();
    845    }
    846
    847    private int setupNoRandPartB() throws IOException {
    848        if (this.su_ch2 != this.su_chPrev) {
    849            this.su_count = 1;
    850            return setupNoRandPartA();
    851        }
    852        if (++this.su_count >= 4) {
    853            checkBounds(this.su_tPos, this.data.ll8.length, "su_tPos");
    854            this.su_z = (char) (this.data.ll8[this.su_tPos] & 0xff);
    855            this.su_tPos = this.data.tt[this.su_tPos];
    856            this.su_j2 = 0;
    857            return setupNoRandPartC();
    858        }
    859        return setupNoRandPartA();
    860    }
    861
    862    private int setupNoRandPartC() throws IOException {
    863        if (this.su_j2 < this.su_z) {
    864            final int su_ch2Shadow = this.su_ch2;
    865            this.crc.update(su_ch2Shadow);
    866            this.su_j2++;
    867            this.currentState = NO_RAND_PART_C_STATE;
    868            return su_ch2Shadow;
    869        }
    870        this.su_i2++;
    871        this.su_count = 0;
    872        return setupNoRandPartA();
    873    }
    874
    875    private int setupRandPartA() throws IOException {
    876        if (this.su_i2 <= this.last) {
    877            this.su_chPrev = this.su_ch2;
    878            int su_ch2Shadow = this.data.ll8[this.su_tPos] & 0xff;
    879            checkBounds(this.su_tPos, this.data.tt.length, "su_tPos");
    880            this.su_tPos = this.data.tt[this.su_tPos];
    881            if (this.su_rNToGo == 0) {
    882                this.su_rNToGo = Rand.rNums(this.su_rTPos) - 1;
    883                if (++this.su_rTPos == 512) {
    884                    this.su_rTPos = 0;
    885                }
    886            } else {
    887                this.su_rNToGo--;
    888            }
    889            this.su_ch2 = su_ch2Shadow ^= this.su_rNToGo == 1 ? 1 : 0;
    890            this.su_i2++;
    891            this.currentState = RAND_PART_B_STATE;
    892            this.crc.update(su_ch2Shadow);
    893            return su_ch2Shadow;
    894        }
    895        endBlock();
    896        initBlock();
    897        return setupBlock();
    898    }
    899
    900    private int setupRandPartB() throws IOException {
    901        if (this.su_ch2 != this.su_chPrev) {
    902            this.currentState = RAND_PART_A_STATE;
    903            this.su_count = 1;
    904            return setupRandPartA();
    905        }
    906        if (++this.su_count < 4) {
    907            this.currentState = RAND_PART_A_STATE;
    908            return setupRandPartA();
    909        }
    910        this.su_z = (char) (this.data.ll8[this.su_tPos] & 0xff);
    911        checkBounds(this.su_tPos, this.data.tt.length, "su_tPos");
    912        this.su_tPos = this.data.tt[this.su_tPos];
    913        if (this.su_rNToGo == 0) {
    914            this.su_rNToGo = Rand.rNums(this.su_rTPos) - 1;
    915            if (++this.su_rTPos == 512) {
    916                this.su_rTPos = 0;
    917            }
    918        } else {
    919            this.su_rNToGo--;
    920        }
    921        this.su_j2 = 0;
    922        this.currentState = RAND_PART_C_STATE;
    923        if (this.su_rNToGo == 1) {
    924            this.su_z ^= 1;
    925        }
    926        return setupRandPartC();
    927    }
    928
    929    private int setupRandPartC() throws IOException {
    930        if (this.su_j2 < this.su_z) {
    931            this.crc.update(this.su_ch2);
    932            this.su_j2++;
    933            return this.su_ch2;
    934        }
    935        this.currentState = RAND_PART_A_STATE;
    936        this.su_i2++;
    937        this.su_count = 0;
    938        return setupRandPartA();
    939    }
    940}