/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  /*
   * This package is based on the work done by Keiron Liddle, Aftex Software
   * <keiron@aftexsw.com> to whom the Ant project is very grateful for his
   * great code.
   */
  package org.apache.commons.compress.compressors.bzip2;
  
  import java.io.IOException;
  import java.io.InputStream;
  
  import org.apache.commons.compress.compressors.CompressorInputStream;
  
  /**
   * An input stream that decompresses from the BZip2 format to be read as any other stream.
   * 
   * @NotThreadSafe
   */
  public class BZip2CompressorInputStream extends CompressorInputStream implements
                                                                            BZip2Constants {
  
      /**
       * Index of the last char in the block, so the block size == last + 1.
       */
      private int last;
  
      /**
       * Index in zptr[] of original string after sorting.
       */
      private int origPtr;
  
      /**
       * always: in the range 0 .. 9. The current block size is 100000 * this
       * number.
       */
      private int blockSize100k;
  
      private boolean blockRandomised;
  
      private int bsBuff;
      private int bsLive;
      private final CRC crc = new CRC();
  
      private int nInUse;
  
      private InputStream in;
      private final boolean decompressConcatenated;
  
      private int currentChar = -1;
  
      private static final int EOF = 0;
      private static final int START_BLOCK_STATE = 1;
      private static final int RAND_PART_A_STATE = 2;
      private static final int RAND_PART_B_STATE = 3;
      private static final int RAND_PART_C_STATE = 4;
      private static final int NO_RAND_PART_A_STATE = 5;
      private static final int NO_RAND_PART_B_STATE = 6;
      private static final int NO_RAND_PART_C_STATE = 7;
  
      private int currentState = START_BLOCK_STATE;
  
      private int storedBlockCRC, storedCombinedCRC;
      private int computedBlockCRC, computedCombinedCRC;
  
      // Variables used by setup* methods exclusively
  
      private int su_count;
      private int su_ch2;
      private int su_chPrev;
      private int su_i2;
      private int su_j2;
      private int su_rNToGo;
      private int su_rTPos;
      private int su_tPos;
      private char su_z;
  
      /**
       * All memory intensive stuff. This field is initialized by initBlock().
       */
      private BZip2CompressorInputStream.Data data;
  
     /**
      * Constructs a new BZip2CompressorInputStream which decompresses bytes
      * read from the specified stream. This doesn't suppprt decompressing
      * concatenated .bz2 files.
      * 
      * @throws IOException
      *             if the stream content is malformed or an I/O error occurs.
      * @throws NullPointerException
      *             if <tt>in == null</tt>
      */
     public BZip2CompressorInputStream(final InputStream in) throws IOException {
         this(in, false);
     }
 
     /**
      * Constructs a new BZip2CompressorInputStream which decompresses bytes
      * read from the specified stream.
      *
      * @param in the InputStream from which this object should be created
      * @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 point to the next
      *                     byte after the .bz2 stream
      *
      * @throws IOException
      *             if the stream content is malformed or an I/O error occurs.
      * @throws NullPointerException
      *             if <tt>in == null</tt>
      */
     public BZip2CompressorInputStream(final InputStream in,
                                       final boolean decompressConcatenated)
             throws IOException {
         super();
 
         this.in = in;
         this.decompressConcatenated = decompressConcatenated;
 
         init(true);
         initBlock();
         setupBlock();
     }
 
     /** {@inheritDoc} */
     @Override
     public int read() throws IOException {
         if (this.in != null) {
             int r = read0();
             count(r < 0 ? -1 : 1);
             return r;
         } else {
             throw new IOException("stream closed");
         }
     }
 
     /*
      * (non-Javadoc)
      * 
      * @see java.io.InputStream#read(byte[], int, int)
      */
     @Override
     public int read(final byte[] dest, final int offs, final int len)
         throws IOException {
         if (offs < 0) {
             throw new IndexOutOfBoundsException("offs(" + offs + ") < 0.");
         }
         if (len < 0) {
             throw new IndexOutOfBoundsException("len(" + len + ") < 0.");
         }
         if (offs + len > dest.length) {
             throw new IndexOutOfBoundsException("offs(" + offs + ") + len("
                                                 + len + ") > dest.length(" + dest.length + ").");
         }
         if (this.in == null) {
             throw new IOException("stream closed");
         }
 
         final int hi = offs + len;
         int destOffs = offs;
         for (int b; (destOffs < hi) && ((b = read0()) >= 0);) {
             dest[destOffs++] = (byte) b;
         }
 
         int c = (destOffs == offs) ? -1 : (destOffs - offs);
         count(c);
         return c;
     }
 
     private void makeMaps() {
         final boolean[] inUse = this.data.inUse;
         final byte[] seqToUnseq = this.data.seqToUnseq;
 
         int nInUseShadow = 0;
 
         for (int i = 0; i < 256; i++) {
             if (inUse[i]) {
                 seqToUnseq[nInUseShadow++] = (byte) i;
             }
         }
 
         this.nInUse = nInUseShadow;
     }
 
     private int read0() throws IOException {
         final int retChar = this.currentChar;
 
         switch (this.currentState) {
         case EOF:
             return -1;
 
         case START_BLOCK_STATE:
             throw new IllegalStateException();
 
         case RAND_PART_A_STATE:
             throw new IllegalStateException();
 
         case RAND_PART_B_STATE:
             setupRandPartB();
             break;
 
         case RAND_PART_C_STATE:
             setupRandPartC();
             break;
 
         case NO_RAND_PART_A_STATE:
             throw new IllegalStateException();
 
         case NO_RAND_PART_B_STATE:
             setupNoRandPartB();
             break;
 
         case NO_RAND_PART_C_STATE:
             setupNoRandPartC();
             break;
 
         default:
             throw new IllegalStateException();
         }
 
         return retChar;
     }
 
     private boolean init(boolean isFirstStream) throws IOException {
         if (null == in) {
             throw new IOException("No InputStream");
         }
 
         int magic0 = this.in.read();
         if (magic0 == -1 && !isFirstStream) {
             return false;
         }
         int magic1 = this.in.read();
         int magic2 = this.in.read();
 
         if (magic0 != 'B' || magic1 != 'Z' || magic2 != 'h') {
             throw new IOException(isFirstStream
                     ? "Stream is not in the BZip2 format"
                     : "Garbage after a valid BZip2 stream");
         }
 
         int blockSize = this.in.read();
         if ((blockSize < '1') || (blockSize > '9')) {
             throw new IOException("BZip2 block size is invalid");
         }
 
         this.blockSize100k = blockSize - '0';
 
         this.bsLive = 0;
         this.computedCombinedCRC = 0;
 
         return true;
     }
 
     private void initBlock() throws IOException {
         char magic0;
         char magic1;
         char magic2;
         char magic3;
         char magic4;
         char magic5;
 
         while (true) {
             // Get the block magic bytes.
             magic0 = bsGetUByte();
             magic1 = bsGetUByte();
             magic2 = bsGetUByte();
             magic3 = bsGetUByte();
             magic4 = bsGetUByte();
             magic5 = bsGetUByte();
 
             // If isn't end of stream magic, break out of the loop.
             if (magic0 != 0x17 || magic1 != 0x72 || magic2 != 0x45
                     || magic3 != 0x38 || magic4 != 0x50 || magic5 != 0x90) {
                 break;
             }
 
             // End of stream was reached. Check the combined CRC and
             // advance to the next .bz2 stream if decoding concatenated
             // streams.
             if (complete()) {
                 return;
             }
         }
 
         if (magic0 != 0x31 || // '1'
             magic1 != 0x41 || // ')'
             magic2 != 0x59 || // 'Y'
             magic3 != 0x26 || // '&'
             magic4 != 0x53 || // 'S'
             magic5 != 0x59 // 'Y'
             ) {
             this.currentState = EOF;
             throw new IOException("bad block header");
         } else {
             this.storedBlockCRC = bsGetInt();
             this.blockRandomised = bsR(1) == 1;
 
             /**
              * Allocate data here instead in constructor, so we do not allocate
              * it if the input file is empty.
              */
             if (this.data == null) {
                 this.data = new Data(this.blockSize100k);
             }
 
             // currBlockNo++;
             getAndMoveToFrontDecode();
 
             this.crc.initialiseCRC();
             this.currentState = START_BLOCK_STATE;
         }
     }
 
     private void endBlock() throws IOException {
         this.computedBlockCRC = this.crc.getFinalCRC();
 
         // A bad CRC is considered a fatal error.
         if (this.storedBlockCRC != this.computedBlockCRC) {
             // make next blocks readable without error
             // (repair feature, not yet documented, not tested)
             this.computedCombinedCRC = (this.storedCombinedCRC << 1)
                 | (this.storedCombinedCRC >>> 31);
             this.computedCombinedCRC ^= this.storedBlockCRC;
 
             throw new IOException("BZip2 CRC error");
         }
 
         this.computedCombinedCRC = (this.computedCombinedCRC << 1)
             | (this.computedCombinedCRC >>> 31);
         this.computedCombinedCRC ^= this.computedBlockCRC;
     }
 
     private boolean complete() throws IOException {
         this.storedCombinedCRC = bsGetInt();
         this.currentState = EOF;
         this.data = null;
 
         if (this.storedCombinedCRC != this.computedCombinedCRC) {
             throw new IOException("BZip2 CRC error");
         }
 
         // Look for the next .bz2 stream if decompressing
         // concatenated files.
         return !decompressConcatenated || !init(false);
     }
 
     @Override
     public void close() throws IOException {
         InputStream inShadow = this.in;
         if (inShadow != null) {
             try {
                 if (inShadow != System.in) {
                     inShadow.close();
                 }
             } finally {
                 this.data = null;
                 this.in = null;
             }
         }
     }
 
     private int bsR(final int n) throws IOException {
         int bsLiveShadow = this.bsLive;
         int bsBuffShadow = this.bsBuff;
 
         if (bsLiveShadow < n) {
             final InputStream inShadow = this.in;
             do {
                 int thech = inShadow.read();
 
                 if (thech < 0) {
                     throw new IOException("unexpected end of stream");
                 }
 
                 bsBuffShadow = (bsBuffShadow << 8) | thech;
                 bsLiveShadow += 8;
             } while (bsLiveShadow < n);
 
             this.bsBuff = bsBuffShadow;
         }
 
         this.bsLive = bsLiveShadow - n;
         return (bsBuffShadow >> (bsLiveShadow - n)) & ((1 << n) - 1);
     }
 
     private boolean bsGetBit() throws IOException {
         int bsLiveShadow = this.bsLive;
         int bsBuffShadow = this.bsBuff;
 
         if (bsLiveShadow < 1) {
             int thech = this.in.read();
 
             if (thech < 0) {
                 throw new IOException("unexpected end of stream");
             }
 
             bsBuffShadow = (bsBuffShadow << 8) | thech;
             bsLiveShadow += 8;
             this.bsBuff = bsBuffShadow;
         }
 
         this.bsLive = bsLiveShadow - 1;
         return ((bsBuffShadow >> (bsLiveShadow - 1)) & 1) != 0;
     }
 
     private char bsGetUByte() throws IOException {
         return (char) bsR(8);
     }
 
     private int bsGetInt() throws IOException {
         return (((((bsR(8) << 8) | bsR(8)) << 8) | bsR(8)) << 8) | bsR(8);
     }
 
     /**
      * Called by createHuffmanDecodingTables() exclusively.
      */
     private static void hbCreateDecodeTables(final int[] limit,
                                              final int[] base, final int[] perm, final char[] length,
                                              final int minLen, final int maxLen, final int alphaSize) {
         for (int i = minLen, pp = 0; i <= maxLen; i++) {
             for (int j = 0; j < alphaSize; j++) {
                 if (length[j] == i) {
                     perm[pp++] = j;
                 }
             }
         }
 
         for (int i = MAX_CODE_LEN; --i > 0;) {
             base[i] = 0;
             limit[i] = 0;
         }
 
         for (int i = 0; i < alphaSize; i++) {
             base[length[i] + 1]++;
         }
 
         for (int i = 1, b = base[0]; i < MAX_CODE_LEN; i++) {
             b += base[i];
             base[i] = b;
         }
 
         for (int i = minLen, vec = 0, b = base[i]; i <= maxLen; i++) {
             final int nb = base[i + 1];
             vec += nb - b;
             b = nb;
             limit[i] = vec - 1;
             vec <<= 1;
         }
 
         for (int i = minLen + 1; i <= maxLen; i++) {
             base[i] = ((limit[i - 1] + 1) << 1) - base[i];
         }
     }
 
     private void recvDecodingTables() throws IOException {
         final Data dataShadow = this.data;
         final boolean[] inUse = dataShadow.inUse;
         final byte[] pos = dataShadow.recvDecodingTables_pos;
         final byte[] selector = dataShadow.selector;
         final byte[] selectorMtf = dataShadow.selectorMtf;
 
         int inUse16 = 0;
 
         /* Receive the mapping table */
         for (int i = 0; i < 16; i++) {
             if (bsGetBit()) {
                 inUse16 |= 1 << i;
             }
         }
 
         for (int i = 256; --i >= 0;) {
             inUse[i] = false;
         }
 
         for (int i = 0; i < 16; i++) {
             if ((inUse16 & (1 << i)) != 0) {
                 final int i16 = i << 4;
                 for (int j = 0; j < 16; j++) {
                     if (bsGetBit()) {
                         inUse[i16 + j] = true;
                     }
                 }
             }
         }
 
         makeMaps();
         final int alphaSize = this.nInUse + 2;
 
         /* Now the selectors */
         final int nGroups = bsR(3);
         final int nSelectors = bsR(15);
 
         for (int i = 0; i < nSelectors; i++) {
             int j = 0;
             while (bsGetBit()) {
                 j++;
             }
             selectorMtf[i] = (byte) j;
         }
 
         /* Undo the MTF values for the selectors. */
         for (int v = nGroups; --v >= 0;) {
             pos[v] = (byte) v;
         }
 
         for (int i = 0; i < nSelectors; i++) {
             int v = selectorMtf[i] & 0xff;
             final byte tmp = pos[v];
             while (v > 0) {
                 // nearly all times v is zero, 4 in most other cases
                 pos[v] = pos[v - 1];
                 v--;
             }
             pos[0] = tmp;
             selector[i] = tmp;
         }
 
         final char[][] len = dataShadow.temp_charArray2d;
 
         /* Now the coding tables */
         for (int t = 0; t < nGroups; t++) {
             int curr = bsR(5);
             final char[] len_t = len[t];
             for (int i = 0; i < alphaSize; i++) {
                 while (bsGetBit()) {
                     curr += bsGetBit() ? -1 : 1;
                 }
                 len_t[i] = (char) curr;
             }
         }
 
         // finally create the Huffman tables
         createHuffmanDecodingTables(alphaSize, nGroups);
     }
 
     /**
      * Called by recvDecodingTables() exclusively.
      */
     private void createHuffmanDecodingTables(final int alphaSize,
                                              final int nGroups) {
         final Data dataShadow = this.data;
         final char[][] len = dataShadow.temp_charArray2d;
         final int[] minLens = dataShadow.minLens;
         final int[][] limit = dataShadow.limit;
         final int[][] base = dataShadow.base;
         final int[][] perm = dataShadow.perm;
 
         for (int t = 0; t < nGroups; t++) {
             int minLen = 32;
             int maxLen = 0;
             final char[] len_t = len[t];
             for (int i = alphaSize; --i >= 0;) {
                 final char lent = len_t[i];
                 if (lent > maxLen) {
                     maxLen = lent;
                 }
                 if (lent < minLen) {
                     minLen = lent;
                 }
             }
             hbCreateDecodeTables(limit[t], base[t], perm[t], len[t], minLen,
                                  maxLen, alphaSize);
             minLens[t] = minLen;
         }
     }
 
     private void getAndMoveToFrontDecode() throws IOException {
         this.origPtr = bsR(24);
         recvDecodingTables();
 
         final InputStream inShadow = this.in;
         final Data dataShadow = this.data;
         final byte[] ll8 = dataShadow.ll8;
         final int[] unzftab = dataShadow.unzftab;
         final byte[] selector = dataShadow.selector;
         final byte[] seqToUnseq = dataShadow.seqToUnseq;
         final char[] yy = dataShadow.getAndMoveToFrontDecode_yy;
         final int[] minLens = dataShadow.minLens;
         final int[][] limit = dataShadow.limit;
         final int[][] base = dataShadow.base;
         final int[][] perm = dataShadow.perm;
         final int limitLast = this.blockSize100k * 100000;
 
         /*
          * 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 worth of cache misses.
          */
         for (int i = 256; --i >= 0;) {
             yy[i] = (char) i;
             unzftab[i] = 0;
         }
 
         int groupNo = 0;
         int groupPos = G_SIZE - 1;
         final int eob = this.nInUse + 1;
         int nextSym = getAndMoveToFrontDecode0(0);
         int bsBuffShadow = this.bsBuff;
         int bsLiveShadow = this.bsLive;
         int lastShadow = -1;
         int zt = selector[groupNo] & 0xff;
         int[] base_zt = base[zt];
         int[] limit_zt = limit[zt];
         int[] perm_zt = perm[zt];
         int minLens_zt = minLens[zt];
 
         while (nextSym != eob) {
             if ((nextSym == RUNA) || (nextSym == RUNB)) {
                 int s = -1;
 
                 for (int n = 1; true; n <<= 1) {
                     if (nextSym == RUNA) {
                         s += n;
                     } else if (nextSym == RUNB) {
                         s += n << 1;
                     } else {
                         break;
                     }
 
                     if (groupPos == 0) {
                         groupPos = G_SIZE - 1;
                         zt = selector[++groupNo] & 0xff;
                         base_zt = base[zt];
                         limit_zt = limit[zt];
                         perm_zt = perm[zt];
                         minLens_zt = minLens[zt];
                     } else {
                         groupPos--;
                     }
 
                     int zn = minLens_zt;
 
                     // Inlined:
                     // int zvec = bsR(zn);
                     while (bsLiveShadow < zn) {
                         final int thech = inShadow.read();
                         if (thech >= 0) {
                             bsBuffShadow = (bsBuffShadow << 8) | thech;
                             bsLiveShadow += 8;
                             continue;
                         } else {
                             throw new IOException("unexpected end of stream");
                         }
                     }
                     int zvec = (bsBuffShadow >> (bsLiveShadow - zn))
                         & ((1 << zn) - 1);
                     bsLiveShadow -= zn;
 
                     while (zvec > limit_zt[zn]) {
                         zn++;
                         while (bsLiveShadow < 1) {
                             final int thech = inShadow.read();
                             if (thech >= 0) {
                                 bsBuffShadow = (bsBuffShadow << 8) | thech;
                                 bsLiveShadow += 8;
                                 continue;
                             } else {
                                 throw new IOException(
                                                       "unexpected end of stream");
                             }
                         }
                         bsLiveShadow--;
                         zvec = (zvec << 1)
                             | ((bsBuffShadow >> bsLiveShadow) & 1);
                     }
                     nextSym = perm_zt[zvec - base_zt[zn]];
                 }
 
                 final byte ch = seqToUnseq[yy[0]];
                 unzftab[ch & 0xff] += s + 1;
 
                 while (s-- >= 0) {
                     ll8[++lastShadow] = ch;
                 }
 
                 if (lastShadow >= limitLast) {
                     throw new IOException("block overrun");
                 }
             } else {
                 if (++lastShadow >= limitLast) {
                     throw new IOException("block overrun");
                 }
 
                 final char tmp = yy[nextSym - 1];
                 unzftab[seqToUnseq[tmp] & 0xff]++;
                 ll8[lastShadow] = seqToUnseq[tmp];
 
                 /*
                  * This loop is hammered during decompression, hence avoid
                  * native method call overhead of System.arraycopy for very
                  * small ranges to copy.
                  */
                 if (nextSym <= 16) {
                     for (int j = nextSym - 1; j > 0;) {
                         yy[j] = yy[--j];
                     }
                 } else {
                     System.arraycopy(yy, 0, yy, 1, nextSym - 1);
                 }
 
                 yy[0] = tmp;
 
                 if (groupPos == 0) {
                     groupPos = G_SIZE - 1;
                     zt = selector[++groupNo] & 0xff;
                     base_zt = base[zt];
                     limit_zt = limit[zt];
                     perm_zt = perm[zt];
                     minLens_zt = minLens[zt];
                 } else {
                     groupPos--;
                 }
 
                 int zn = minLens_zt;
 
                 // Inlined:
                 // int zvec = bsR(zn);
                 while (bsLiveShadow < zn) {
                     final int thech = inShadow.read();
                     if (thech >= 0) {
                         bsBuffShadow = (bsBuffShadow << 8) | thech;
                         bsLiveShadow += 8;
                         continue;
                     } else {
                         throw new IOException("unexpected end of stream");
                     }
                 }
                 int zvec = (bsBuffShadow >> (bsLiveShadow - zn))
                     & ((1 << zn) - 1);
                 bsLiveShadow -= zn;
 
                 while (zvec > limit_zt[zn]) {
                     zn++;
                     while (bsLiveShadow < 1) {
                         final int thech = inShadow.read();
                         if (thech >= 0) {
                             bsBuffShadow = (bsBuffShadow << 8) | thech;
                             bsLiveShadow += 8;
                             continue;
                         } else {
                             throw new IOException("unexpected end of stream");
                         }
                     }
                     bsLiveShadow--;
                     zvec = (zvec << 1) | ((bsBuffShadow >> bsLiveShadow) & 1);
                 }
                 nextSym = perm_zt[zvec - base_zt[zn]];
             }
         }
 
         this.last = lastShadow;
         this.bsLive = bsLiveShadow;
         this.bsBuff = bsBuffShadow;
     }
 
     private int getAndMoveToFrontDecode0(final int groupNo) throws IOException {
         final InputStream inShadow = this.in;
         final Data dataShadow = this.data;
         final int zt = dataShadow.selector[groupNo] & 0xff;
         final int[] limit_zt = dataShadow.limit[zt];
         int zn = dataShadow.minLens[zt];
         int zvec = bsR(zn);
         int bsLiveShadow = this.bsLive;
         int bsBuffShadow = this.bsBuff;
 
         while (zvec > limit_zt[zn]) {
             zn++;
             while (bsLiveShadow < 1) {
                 final int thech = inShadow.read();
 
                 if (thech >= 0) {
                     bsBuffShadow = (bsBuffShadow << 8) | thech;
                     bsLiveShadow += 8;
                     continue;
                 } else {
                     throw new IOException("unexpected end of stream");
                 }
             }
             bsLiveShadow--;
             zvec = (zvec << 1) | ((bsBuffShadow >> bsLiveShadow) & 1);
         }
 
         this.bsLive = bsLiveShadow;
         this.bsBuff = bsBuffShadow;
 
         return dataShadow.perm[zt][zvec - dataShadow.base[zt][zn]];
     }
 
     private void setupBlock() throws IOException {
         if (this.data == null) {
             return;
         }
 
         final int[] cftab = this.data.cftab;
         final int[] tt = this.data.initTT(this.last + 1);
         final byte[] ll8 = this.data.ll8;
         cftab[0] = 0;
         System.arraycopy(this.data.unzftab, 0, cftab, 1, 256);
 
         for (int i = 1, c = cftab[0]; i <= 256; i++) {
             c += cftab[i];
             cftab[i] = c;
         }
 
         for (int i = 0, lastShadow = this.last; i <= lastShadow; i++) {
             tt[cftab[ll8[i] & 0xff]++] = i;
         }
 
         if ((this.origPtr < 0) || (this.origPtr >= tt.length)) {
             throw new IOException("stream corrupted");
         }
 
         this.su_tPos = tt[this.origPtr];
         this.su_count = 0;
         this.su_i2 = 0;
         this.su_ch2 = 256; /* not a char and not EOF */
 
         if (this.blockRandomised) {
             this.su_rNToGo = 0;
             this.su_rTPos = 0;
             setupRandPartA();
         } else {
             setupNoRandPartA();
         }
     }
 
     private void setupRandPartA() throws IOException {
         if (this.su_i2 <= this.last) {
             this.su_chPrev = this.su_ch2;
             int su_ch2Shadow = this.data.ll8[this.su_tPos] & 0xff;
             this.su_tPos = this.data.tt[this.su_tPos];
             if (this.su_rNToGo == 0) {
                 this.su_rNToGo = Rand.rNums(this.su_rTPos) - 1;
                 if (++this.su_rTPos == 512) {
                     this.su_rTPos = 0;
                 }
             } else {
                 this.su_rNToGo--;
             }
             this.su_ch2 = su_ch2Shadow ^= (this.su_rNToGo == 1) ? 1 : 0;
             this.su_i2++;
             this.currentChar = su_ch2Shadow;
             this.currentState = RAND_PART_B_STATE;
             this.crc.updateCRC(su_ch2Shadow);
         } else {
             endBlock();
             initBlock();
             setupBlock();
         }
     }
 
     private void setupNoRandPartA() throws IOException {
         if (this.su_i2 <= this.last) {
             this.su_chPrev = this.su_ch2;
             int su_ch2Shadow = this.data.ll8[this.su_tPos] & 0xff;
             this.su_ch2 = su_ch2Shadow;
             this.su_tPos = this.data.tt[this.su_tPos];
             this.su_i2++;
             this.currentChar = su_ch2Shadow;
             this.currentState = NO_RAND_PART_B_STATE;
             this.crc.updateCRC(su_ch2Shadow);
         } else {
             this.currentState = NO_RAND_PART_A_STATE;
             endBlock();
             initBlock();
             setupBlock();
         }
     }
 
     private void setupRandPartB() throws IOException {
         if (this.su_ch2 != this.su_chPrev) {
             this.currentState = RAND_PART_A_STATE;
             this.su_count = 1;
             setupRandPartA();
         } else if (++this.su_count >= 4) {
             this.su_z = (char) (this.data.ll8[this.su_tPos] & 0xff);
             this.su_tPos = this.data.tt[this.su_tPos];
             if (this.su_rNToGo == 0) {
                 this.su_rNToGo = Rand.rNums(this.su_rTPos) - 1;
                 if (++this.su_rTPos == 512) {
                     this.su_rTPos = 0;
                 }
             } else {
                 this.su_rNToGo--;
             }
             this.su_j2 = 0;
             this.currentState = RAND_PART_C_STATE;
             if (this.su_rNToGo == 1) {
                 this.su_z ^= 1;
             }
             setupRandPartC();
         } else {
             this.currentState = RAND_PART_A_STATE;
             setupRandPartA();
         }
     }
 
     private void setupRandPartC() throws IOException {
         if (this.su_j2 < this.su_z) {
             this.currentChar = this.su_ch2;
             this.crc.updateCRC(this.su_ch2);
             this.su_j2++;
         } else {
             this.currentState = RAND_PART_A_STATE;
             this.su_i2++;
             this.su_count = 0;
             setupRandPartA();
         }
     }
 
     private void setupNoRandPartB() throws IOException {
         if (this.su_ch2 != this.su_chPrev) {
             this.su_count = 1;
             setupNoRandPartA();
         } else if (++this.su_count >= 4) {
             this.su_z = (char) (this.data.ll8[this.su_tPos] & 0xff);
             this.su_tPos = this.data.tt[this.su_tPos];
             this.su_j2 = 0;
             setupNoRandPartC();
         } else {
             setupNoRandPartA();
         }
     }
 
     private void setupNoRandPartC() throws IOException {
         if (this.su_j2 < this.su_z) {
             int su_ch2Shadow = this.su_ch2;
             this.currentChar = su_ch2Shadow;
             this.crc.updateCRC(su_ch2Shadow);
             this.su_j2++;
             this.currentState = NO_RAND_PART_C_STATE;
         } else {
             this.su_i2++;
             this.su_count = 0;
             setupNoRandPartA();
         }
     }
 
     private static final class Data extends Object {
 
         // (with blockSize 900k)
         final boolean[] inUse = new boolean[256]; // 256 byte
 
         final byte[] seqToUnseq = new byte[256]; // 256 byte
         final byte[] selector = new byte[MAX_SELECTORS]; // 18002 byte
         final byte[] selectorMtf = new byte[MAX_SELECTORS]; // 18002 byte
 
         /**
          * Freq table collected to save a pass over the data during
          * decompression.
          */
         final int[] unzftab = new int[256]; // 1024 byte
 
         final int[][] limit = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
         final int[][] base = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
         final int[][] perm = new int[N_GROUPS][MAX_ALPHA_SIZE]; // 6192 byte
         final int[] minLens = new int[N_GROUPS]; // 24 byte
 
         final int[] cftab = new int[257]; // 1028 byte
         final char[] getAndMoveToFrontDecode_yy = new char[256]; // 512 byte
         final char[][] temp_charArray2d = new char[N_GROUPS][MAX_ALPHA_SIZE]; // 3096
         // byte
         final byte[] recvDecodingTables_pos = new byte[N_GROUPS]; // 6 byte
         // ---------------
         // 60798 byte
 
         int[] tt; // 3600000 byte
         byte[] ll8; // 900000 byte
 
         // ---------------
         // 4560782 byte
         // ===============
 
         Data(int blockSize100k) {
             super();
 
             this.ll8 = new byte[blockSize100k * BZip2Constants.BASEBLOCKSIZE];
         }
 
         /**
          * Initializes the {@link #tt} array.
          * 
          * This method is called when the required length of the array is known.
          * I don't initialize it at construction time to avoid unneccessary
          * memory allocation when compressing small files.
          */
         int[] initTT(int length) {
             int[] ttShadow = this.tt;
 
             // tt.length should always be >= length, but theoretically
             // it can happen, if the compressor mixed small and large
             // blocks. Normally only the last block will be smaller
             // than others.
             if ((ttShadow == null) || (ttShadow.length < length)) {
                 this.tt = ttShadow = new int[length];
             }
 
             return ttShadow;
         }
 
     }
 
     /**
      * Checks if the signature matches what is expected for a bzip2 file.
      * 
      * @param signature
      *            the bytes to check
      * @param length
      *            the number of bytes to check
      * @return true, if this stream is a bzip2 compressed stream, false otherwise
      * 
      * @since 1.1
      */
     public static boolean matches(byte[] signature, int length) {
 
         if (length < 3) {
             return false;
         }
 
         if (signature[0] != 'B') {
             return false;
         }
 
         if (signature[1] != 'Z') {
             return false;
         }
 
         if (signature[2] != 'h') {
             return false;
         }
 
         return true;
     }
 }