BZip2Compressor.cs

// BZip2Compressor.cs
// ------------------------------------------------------------------
//
// Copyright (c) 2011 Dino Chiesa.
// All rights reserved.
//
// This code module is part of DotNetZip, a zipfile class library.
//
// ------------------------------------------------------------------
//
// This code is licensed under the Microsoft Public License.
// See the file License.txt for the license details.
// More info on: http://dotnetzip.codeplex.com
//
// ------------------------------------------------------------------
//
// Last Saved: <2011-July-28 06:17:22>
//
// ------------------------------------------------------------------
//
// This module defines the BZip2Compressor class, which is a
// BZIP2-compressing encoder.  It is used internally in the BZIP2
// library, by the BZip2OutputStream class and its parallel variant,
// ParallelBZip2OutputStream. This code was originally based on Apache
// commons source code, and significantly modified.  The license below
// applies to the original Apache code and to this modified variant.
//
// ------------------------------------------------------------------


/*
 * 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.
 */


//
// Design notes:
//
// This class performs BZip2 compression. It is derived from the
// BZip2OutputStream from the Apache commons source code, but is
// significantly modified from that code. While the Apache class is a
// stream that compresses, this particular class simply performs
// compression.  It follows a Manager pattern. It manages an internal
// buffer for uncompressed data; callers place data into the buffer
// using the Fill() method. This class then compresses the data and
// writes the compressed form out, via the CompressAndWrite() method.
// Because BZip2 uses byte-shredding, this class relies on a BitWriter,
// and not a .NET Stream, to emit its output.  (*Think of the BitWriter
// class as an Adapter that enables Bit-oriented output to a standard
// byte-oriented .NET stream.)
//
// This class exists to support the two distinct output streams that
// perform BZip2 compression: BZip2OutputStream and
// ParallelBZip2OutputStream. These streams rely on BZip2Compressor to
// provide the encoder/compression logic.  This code has been derived
// from the bzip2 output stream in the Apache commons library; it has
// been significantly modified from that form, in order to provide a
// single compressor that could support both types of streams.
//
// In a bz2 file or stream, there is never any bit padding except for 0..7
// bits in the final byte in the file. Successive compressed blocks in a
// .bz2 file are not byte-aligned.
//
//

using System;
using System.IO;

// flymake: csc.exe /t:module BZip2InputStream.cs BZip2OutputStream.cs Rand.cs BCRC32.cs @@FILE@@

namespace Ionic.BZip2
{
    internal class BZip2Compressor
    {
        private int blockSize100k;  // 0...9
        private int currentByte = -1;
        private int runLength = 0;
        private int last;  // index into the block of the last char processed
        private int outBlockFillThreshold;
        private CompressionState cstate;
        private readonly Ionic.Crc.CRC32 crc = new Ionic.Crc.CRC32(true);
        BitWriter bw;
        int runs;

        /*
         * The following three vars are used when sorting. If too many long
         * comparisons happen, we stop sorting, randomise the block slightly, and
         * try again. I think this wrinkle in the implementation was removed from
         * a later rev of the C-language bzip, not sure. -DPC 24 Jul 2011
         *
         */
        private int workDone;
        private int workLimit;
        private bool firstAttempt;
        private bool blockRandomised;
        private int origPtr;

        private int nInUse;
        private int nMTF;

        private static readonly int SETMASK = (1 << 21);
        private static readonly int CLEARMASK = (~SETMASK);
        private static readonly byte GREATER_ICOST = 15;
        private static readonly byte LESSER_ICOST = 0;
        private static readonly int SMALL_THRESH = 20;
        private static readonly int DEPTH_THRESH = 10;
        private static readonly int WORK_FACTOR = 30;

        /**
         * Knuth's increments seem to work better than Incerpi-Sedgewick here.
         * Possibly because the number of elems to sort is usually small, typically
         * &lt;= 20.
         */
        private static readonly int[] increments = { 1, 4, 13, 40, 121, 364, 1093, 3280,
                                                     9841, 29524, 88573, 265720, 797161,
                                                     2391484 };

        /// <summary>
        ///   BZip2Compressor writes its compressed data out via a BitWriter. This
        ///   is necessary because BZip2 does byte shredding.
        /// </summary>
        public BZip2Compressor(BitWriter writer)
            : this(writer, BZip2.MaxBlockSize)
        {
        }

        public BZip2Compressor(BitWriter writer, int blockSize)
        {
            this.blockSize100k = blockSize;
            this.bw = writer;

            // 20 provides a margin of slop (not to say "Safety"). The maximum
            // size of an encoded run in the output block is 5 bytes, so really, 5
            // bytes ought to do, but this is a margin of slop found in the
            // original bzip code. Not sure if important for decoding
            // (decompressing).  So we'll leave the slop.
            this.outBlockFillThreshold = (blockSize * BZip2.BlockSizeMultiple) - 20;
            this.cstate = new CompressionState(blockSize);
            Reset();
        }


        void Reset()
        {
            // initBlock();
            this.crc.Reset();
            this.currentByte = -1;
            this.runLength = 0;
            this.last = -1;
            for (int i = 256; --i >= 0;)
                this.cstate.inUse[i] = false;
            //bw.Reset();  xxx? want this?  no no no
        }


        public int BlockSize
        {
            get { return this.blockSize100k; }
        }

        public uint Crc32
        {
            get; private set;
        }

        public int AvailableBytesOut
        {
            get; private set;
        }

        /// <summary>
        ///   The number of uncompressed bytes being held in the buffer.
        /// </summary>
        /// <remarks>
        ///   <para>
        ///     I am thinking this may be useful in a Stream that uses this
        ///     compressor class. In the Close() method on the stream it could
        ///     check this value to see if anything has been written at all.  You
        ///     may think the stream could easily track the number of bytes it
        ///     wrote, which would eliminate the need for this. But, there is the
        ///     case where the stream writes a complete block, and it is full, and
        ///     then writes no more. In that case the stream may want to check.
        ///   </para>
        /// </remarks>
        public int UncompressedBytes
        {
            get { return this.last + 1; }
        }


        /// <summary>
        ///   Accept new bytes into the compressor data buffer
        /// </summary>
        /// <remarks>
        ///   <para>
        ///     This method does the first-level (cheap) run-length encoding, and
        ///     stores the encoded data into the rle block.
        ///   </para>
        /// </remarks>
        public int Fill(byte[] buffer, int offset, int count)
        {
            if (this.last >= this.outBlockFillThreshold)
                return 0; // We're full, I tell you!

            int bytesWritten = 0;
            int limit = offset + count;
            int rc;

            // do run-length-encoding until block is full
            do
            {
                rc = write0(buffer[offset++]);
                if (rc > 0) bytesWritten++;
            } while (offset < limit && rc == 1);

            return bytesWritten;
        }



        /// <summary>
        ///   Process one input byte into the block.
        /// </summary>
        ///
        /// <remarks>
        ///   <para>
        ///     To "process" the byte means to do the run-length encoding.
        ///     There are 3 possible return values:
        ///
        ///        0 - the byte was not written, in other words, not
        ///            encoded into the block. This happens when the
        ///            byte b would require the start of a new run, and
        ///            the block has no more room for new runs.
        ///
        ///        1 - the byte was written, and the block is not full.
        ///
        ///        2 - the byte was written, and the block is full.
        ///
        ///   </para>
        /// </remarks>
        /// <returns>0 if the byte was not written, non-zero if written.</returns>
        private int write0(byte b)
        {
            bool rc;
            // there is no current run in progress
            if (this.currentByte == -1)
            {
                this.currentByte = b;
                this.runLength++;
                return 1;
            }

            // this byte is the same as the current run in progress
            if (this.currentByte == b)
            {
                if (++this.runLength > 254)
                {
                    rc = AddRunToOutputBlock(false);
                    this.currentByte = -1;
                    this.runLength = 0;
                    return (rc) ? 2 : 1;
                }
                return 1; // not full
            }

            // This byte requires a new run.
            // Put the prior run into the Run-length-encoded block,
            // and try to start a new run.
            rc = AddRunToOutputBlock(false);

            if (rc)
            {
                this.currentByte = -1;
                this.runLength = 0;
                // returning 0 implies the block is full, and the byte was not written.
                return 0;
            }

            // start a new run
            this.runLength = 1;
            this.currentByte = b;
            return 1;
        }

        /// <summary>
        ///   Append one run to the output block.
        /// </summary>
        ///
        /// <remarks>
        ///   <para>
        ///     This compressor does run-length-encoding before BWT and etc. This
        ///     method simply appends a run to the output block. The append always
        ///     succeeds. The return value indicates whether the block is full:
        ///     false (not full) implies that at least one additional run could be
        ///     processed.
        ///   </para>
        /// </remarks>
        /// <returns>true if the block is now full; otherwise false.</returns>
        private bool AddRunToOutputBlock(bool final)
        {
            runs++;
            /* add_pair_to_block ( EState* s ) */
            int previousLast = this.last;

            // sanity check only - because of the check done at the
            // bottom of this method, and the logic in write0(), this
            // should never ever happen.
            if (previousLast >= this.outBlockFillThreshold && !final)
            {
                var msg = String.Format("block overrun(final={2}): {0} >= threshold ({1})",
                                        previousLast, this.outBlockFillThreshold, final);
                throw new Exception(msg);
            }

            // NB: the index used here into block is always (last+2).  This is
            // because last is -1 based - the initial value is -1, a flag value
            // used to indicate that nothing has yet been written into the
            // block. The endBlock() fn tests for -1 to detect empty blocks. Also,
            // the first byte of block is used, during sorting, to hold block[last
            // +1], which is the final byte value that had been written into the
            // rle block. For those two reasons, the base offset from last is
            // always +2.

            byte b = (byte) this.currentByte;
            byte[] block = this.cstate.block;
            this.cstate.inUse[b] = true;
            int rl = this.runLength;
            this.crc.UpdateCRC(b, rl);

            switch (rl)
            {
                case 1:
                    block[previousLast + 2] = b;
                    this.last = previousLast + 1;
                    break;

                case 2:
                    block[previousLast + 2] = b;
                    block[previousLast + 3] = b;
                    this.last = previousLast + 2;
                    break;

                case 3:
                    block[previousLast + 2] = b;
                    block[previousLast + 3] = b;
                    block[previousLast + 4] = b;
                    this.last = previousLast + 3;
                    break;

                default:
                    rl -= 4;
                    this.cstate.inUse[rl] = true;
                    block[previousLast + 2] = b;
                    block[previousLast + 3] = b;
                    block[previousLast + 4] = b;
                    block[previousLast + 5] = b;
                    block[previousLast + 6] = (byte) rl;
                    this.last = previousLast + 5;
                    break;
            }

            // is full?
            return (this.last >= this.outBlockFillThreshold);
        }


        /// <summary>
        ///   Compress the data that has been placed (Run-length-encoded) into the
        ///   block. The compressed data goes into the CompressedBytes array.
        /// </summary>
        /// <remarks>
        ///   <para>
        ///     Side effects: 1.  fills the CompressedBytes array.  2. sets the
        ///     AvailableBytesOut property.
        ///   </para>
        /// </remarks>
        public void CompressAndWrite() // endBlock
        {
            if (this.runLength > 0)
                AddRunToOutputBlock(true);

            this.currentByte = -1;

            // Console.WriteLine("  BZip2Compressor:CompressAndWrite (r={0} bcrc={1:X8})",
            //                   runs, this.crc.Crc32Result);

            // has any data been written?
            if (this.last == -1)
                return; // no data; nothing to compress

            /* sort the block and establish posn of original string */
            blockSort();

            /*
             * A 6-byte block header, the value chosen arbitrarily as 0x314159265359
             * :-). A 32 bit value does not really give a strong enough guarantee
             * that the value will not appear by chance in the compressed
             * datastream. Worst-case probability of this event, for a 900k block,
             * is about 2.0e-3 for 32 bits, 1.0e-5 for 40 bits and 4.0e-8 for 48
             * bits. For a compressed file of size 100Gb -- about 100000 blocks --
             * only a 48-bit marker will do. NB: normal compression/ decompression
             * donot rely on these statistical properties. They are only important
             * when trying to recover blocks from damaged files.
             */
            this.bw.WriteByte(0x31);
            this.bw.WriteByte(0x41);
            this.bw.WriteByte(0x59);
            this.bw.WriteByte(0x26);
            this.bw.WriteByte(0x53);
            this.bw.WriteByte(0x59);

            this.Crc32 = (uint) this.crc.Crc32Result;
            this.bw.WriteInt(this.Crc32);

            /* Now a single bit indicating randomisation. */
            this.bw.WriteBits(1, (this.blockRandomised)?1U:0U);

            /* Finally, block's contents proper. */
            moveToFrontCodeAndSend();

            Reset();
        }


        private void randomiseBlock()
        {
            bool[] inUse = this.cstate.inUse;
            byte[] block = this.cstate.block;
            int lastShadow = this.last;

            for (int i = 256; --i >= 0;)
                inUse[i] = false;

            int rNToGo = 0;
            int rTPos = 0;
            for (int i = 0, j = 1; i <= lastShadow; i = j, j++)
            {
                if (rNToGo == 0)
                {
                    rNToGo = (char) Rand.Rnums(rTPos);
                    if (++rTPos == 512)
                    {
                        rTPos = 0;
                    }
                }

                rNToGo--;
                block[j] ^= (byte) ((rNToGo == 1) ? 1 : 0);

                // handle 16 bit signed numbers
                inUse[block[j] & 0xff] = true;
            }

            this.blockRandomised = true;
        }

        private void mainSort()
        {
            CompressionState dataShadow = this.cstate;
            int[] runningOrder = dataShadow.mainSort_runningOrder;
            int[] copy = dataShadow.mainSort_copy;
            bool[] bigDone = dataShadow.mainSort_bigDone;
            int[] ftab = dataShadow.ftab;
            byte[] block = dataShadow.block;
            int[] fmap = dataShadow.fmap;
            char[] quadrant = dataShadow.quadrant;
            int lastShadow = this.last;
            int workLimitShadow = this.workLimit;
            bool firstAttemptShadow = this.firstAttempt;

            // Set up the 2-byte frequency table
            for (int i = 65537; --i >= 0;)
            {
                ftab[i] = 0;
            }

            /*
             * In the various block-sized structures, live data runs from 0 to
             * last+NUM_OVERSHOOT_BYTES inclusive. First, set up the overshoot area
             * for block.
             */
            for (int i = 0; i < BZip2.NUM_OVERSHOOT_BYTES; i++)
            {
                block[lastShadow + i + 2] = block[(i % (lastShadow + 1)) + 1];
            }
            for (int i = lastShadow + BZip2.NUM_OVERSHOOT_BYTES +1; --i >= 0;)
            {
                quadrant[i] = '\0';
            }
            block[0] = block[lastShadow + 1];

            // Complete the initial radix sort:

            int c1 = block[0] & 0xff;
            for (int i = 0; i <= lastShadow; i++)
            {
                int c2 = block[i + 1] & 0xff;
                ftab[(c1 << 8) + c2]++;
                c1 = c2;
            }

            for (int i = 1; i <= 65536; i++)
                ftab[i] += ftab[i - 1];

            c1 = block[1] & 0xff;
            for (int i = 0; i < lastShadow; i++)
            {
                int c2 = block[i + 2] & 0xff;
                fmap[--ftab[(c1 << 8) + c2]] = i;
                c1 = c2;
            }

            fmap[--ftab[((block[lastShadow + 1] & 0xff) << 8) + (block[1] & 0xff)]] = lastShadow;

            /*
             * Now ftab contains the first loc of every small bucket. Calculate the
             * running order, from smallest to largest big bucket.
             */
            for (int i = 256; --i >= 0;)
            {
                bigDone[i] = false;
                runningOrder[i] = i;
            }

            for (int h = 364; h != 1;)
            {
                h /= 3;
                for (int i = h; i <= 255; i++)
                {
                    int vv = runningOrder[i];
                    int a = ftab[(vv + 1) << 8] - ftab[vv << 8];
                    int b = h - 1;
                    int j = i;
                    for (int ro = runningOrder[j - h]; (ftab[(ro + 1) << 8] - ftab[ro << 8]) > a; ro = runningOrder[j
                                                                                                                    - h])
                    {
                        runningOrder[j] = ro;
                        j -= h;
                        if (j <= b)
                        {
                            break;
                        }
                    }
                    runningOrder[j] = vv;
                }
            }

            /*
             * The main sorting loop.
             */
            for (int i = 0; i <= 255; i++)
            {
                /*
                 * Process big buckets, starting with the least full.
                 */
                int ss = runningOrder[i];

                // Step 1:
                /*
                 * Complete the big bucket [ss] by quicksorting any unsorted small
                 * buckets [ss, j]. Hopefully previous pointer-scanning phases have
                 * already completed many of the small buckets [ss, j], so we don't
                 * have to sort them at all.
                 */
                for (int j = 0; j <= 255; j++)
                {
                    int sb = (ss << 8) + j;
                    int ftab_sb = ftab[sb];
                    if ((ftab_sb & SETMASK) != SETMASK)
                    {
                        int lo = ftab_sb & CLEARMASK;
                        int hi = (ftab[sb + 1] & CLEARMASK) - 1;
                        if (hi > lo)
                        {
                            mainQSort3(dataShadow, lo, hi, 2);
                            if (firstAttemptShadow
                                && (this.workDone > workLimitShadow))
                            {
                                return;
                            }
                        }
                        ftab[sb] = ftab_sb | SETMASK;
                    }
                }

                // Step 2:
                // Now scan this big bucket so as to synthesise the
                // sorted order for small buckets [t, ss] for all t != ss.

                for (int j = 0; j <= 255; j++)
                {
                    copy[j] = ftab[(j << 8) + ss] & CLEARMASK;
                }

                for (int j = ftab[ss << 8] & CLEARMASK, hj = (ftab[(ss + 1) << 8] & CLEARMASK); j < hj; j++)
                {
                    int fmap_j = fmap[j];
                    c1 = block[fmap_j] & 0xff;
                    if (!bigDone[c1])
                    {
                        fmap[copy[c1]] = (fmap_j == 0) ? lastShadow : (fmap_j - 1);
                        copy[c1]++;
                    }
                }

                for (int j = 256; --j >= 0;)
                    ftab[(j << 8) + ss] |= SETMASK;

                // Step 3:
                /*
                 * The ss big bucket is now done. Record this fact, and update the
                 * quadrant descriptors. Remember to update quadrants in the
                 * overshoot area too, if necessary. The "if (i < 255)" test merely
                 * skips this updating for the last bucket processed, since updating
                 * for the last bucket is pointless.
                 */
                bigDone[ss] = true;

                if (i < 255)
                {
                    int bbStart = ftab[ss << 8] & CLEARMASK;
                    int bbSize = (ftab[(ss + 1) << 8] & CLEARMASK) - bbStart;
                    int shifts = 0;

                    while ((bbSize >> shifts) > 65534)
                    {
                        shifts++;
                    }

                    for (int j = 0; j < bbSize; j++)
                    {
                        int a2update = fmap[bbStart + j];
                        char qVal = (char) (j >> shifts);
                        quadrant[a2update] = qVal;
                        if (a2update < BZip2.NUM_OVERSHOOT_BYTES)
                        {
                            quadrant[a2update + lastShadow + 1] = qVal;
                        }
                    }
                }

            }
        }


        private void blockSort()
        {
            this.workLimit = WORK_FACTOR * this.last;
            this.workDone = 0;
            this.blockRandomised = false;
            this.firstAttempt = true;
            mainSort();

            if (this.firstAttempt && (this.workDone > this.workLimit))
            {
                randomiseBlock();
                this.workLimit = this.workDone = 0;
                this.firstAttempt = false;
                mainSort();
            }

            int[] fmap = this.cstate.fmap;
            this.origPtr = -1;
            for (int i = 0, lastShadow = this.last; i <= lastShadow; i++)
            {
                if (fmap[i] == 0)
                {
                    this.origPtr = i;
                    break;
                }
            }

            // assert (this.origPtr != -1) : this.origPtr;
        }


        /**
         * This is the most hammered method of this class.
         *
         * <p>
         * This is the version using unrolled loops.
         * </p>
         */
        private bool mainSimpleSort(CompressionState dataShadow, int lo,
                                    int hi, int d)
        {
            int bigN = hi - lo + 1;
            if (bigN < 2)
            {
                return this.firstAttempt && (this.workDone > this.workLimit);
            }

            int hp = 0;
            while (increments[hp] < bigN)
                hp++;

            int[] fmap = dataShadow.fmap;
            char[] quadrant = dataShadow.quadrant;
            byte[] block = dataShadow.block;
            int lastShadow = this.last;
            int lastPlus1 = lastShadow + 1;
            bool firstAttemptShadow = this.firstAttempt;
            int workLimitShadow = this.workLimit;
            int workDoneShadow = this.workDone;

            // Following block contains unrolled code which could be shortened by
            // coding it in additional loops.

            // HP:
            while (--hp >= 0)
            {
                int h = increments[hp];
                int mj = lo + h - 1;

                for (int i = lo + h; i <= hi;)
                {
                    // copy
                    for (int k = 3; (i <= hi) && (--k >= 0); i++)
                    {
                        int v = fmap[i];
                        int vd = v + d;
                        int j = i;

                        // for (int a;
                        // (j > mj) && mainGtU((a = fmap[j - h]) + d, vd,
                        // block, quadrant, lastShadow);
                        // j -= h) {
                        // fmap[j] = a;
                        // }
                        //
                        // unrolled version:

                        // start inline mainGTU
                        bool onceRunned = false;
                        int a = 0;

                        HAMMER: while (true)
                        {
                            if (onceRunned)
                            {
                                fmap[j] = a;
                                if ((j -= h) <= mj)
                                {
                                    goto END_HAMMER;
                                }
                            }
                            else {
                                onceRunned = true;
                            }

                            a = fmap[j - h];
                            int i1 = a + d;
                            int i2 = vd;

                            // following could be done in a loop, but
                            // unrolled it for performance:
                            if (block[i1 + 1] == block[i2 + 1])
                            {
                                if (block[i1 + 2] == block[i2 + 2])
                                {
                                    if (block[i1 + 3] == block[i2 + 3])
                                    {
                                        if (block[i1 + 4] == block[i2 + 4])
                                        {
                                            if (block[i1 + 5] == block[i2 + 5])
                                            {
                                                if (block[(i1 += 6)] == block[(i2 += 6)])
                                                {
                                                    int x = lastShadow;
                                                    X: while (x > 0)
                                                    {
                                                        x -= 4;

                                                        if (block[i1 + 1] == block[i2 + 1])
                                                        {
                                                            if (quadrant[i1] == quadrant[i2])
                                                            {
                                                                if (block[i1 + 2] == block[i2 + 2])
                                                                {
                                                                    if (quadrant[i1 + 1] == quadrant[i2 + 1])
                                                                    {
                                                                        if (block[i1 + 3] == block[i2 + 3])
                                                                        {
                                                                            if (quadrant[i1 + 2] == quadrant[i2 + 2])
                                                                            {
                                                                                if (block[i1 + 4] == block[i2 + 4])
                                                                                {
                                                                                    if (quadrant[i1 + 3] == quadrant[i2 + 3])
                                                                                    {
                                                                                        if ((i1 += 4) >= lastPlus1)
                                                                                        {
                                                                                            i1 -= lastPlus1;
                                                                                        }
                                                                                        if ((i2 += 4) >= lastPlus1)
                                                                                        {
                                                                                            i2 -= lastPlus1;
                                                                                        }
                                                                                        workDoneShadow++;
                                                                                        goto X;
                                                                                    }
                                                                                    else if ((quadrant[i1 + 3] > quadrant[i2 + 3]))
                                                                                    {
                                                                                        goto HAMMER;
                                                                                    }
                                                                                    else {
                                                                                        goto END_HAMMER;
                                                                                    }
                                                                                }
                                                                                else if ((block[i1 + 4] & 0xff) > (block[i2 + 4] & 0xff))
                                                                                {
                                                                                    goto HAMMER;
                                                                                }
                                                                                else {
                                                                                    goto END_HAMMER;
                                                                                }
                                                                            }
                                                                            else if ((quadrant[i1 + 2] > quadrant[i2 + 2]))
                                                                            {
                                                                                goto HAMMER;
                                                                            }
                                                                            else {
                                                                                goto END_HAMMER;
                                                                            }
                                                                        }
                                                                        else if ((block[i1 + 3] & 0xff) > (block[i2 + 3] & 0xff))
                                                                        {
                                                                            goto HAMMER;
                                                                        }
                                                                        else {
                                                                            goto END_HAMMER;
                                                                        }
                                                                    }
                                                                    else if ((quadrant[i1 + 1] > quadrant[i2 + 1]))
                                                                    {
                                                                        goto HAMMER;
                                                                    }
                                                                    else {
                                                                        goto END_HAMMER;
                                                                    }
                                                                }
                                                                else if ((block[i1 + 2] & 0xff) > (block[i2 + 2] & 0xff))
                                                                {
                                                                    goto HAMMER;
                                                                }
                                                                else {
                                                                    goto END_HAMMER;
                                                                }
                                                            }
                                                            else if ((quadrant[i1] > quadrant[i2]))
                                                            {
                                                                goto HAMMER;
                                                            }
                                                            else {
                                                                goto END_HAMMER;
                                                            }
                                                        }
                                                        else if ((block[i1 + 1] & 0xff) > (block[i2 + 1] & 0xff))
                                                        {
                                                            goto HAMMER;
                                                        }
                                                        else {
                                                            goto END_HAMMER;
                                                        }

                                                    }
                                                    goto END_HAMMER;
                                                } // while x > 0
                                                else {
                                                    if ((block[i1] & 0xff) > (block[i2] & 0xff))
                                                    {
                                                        goto HAMMER;
                                                    }
                                                    else {
                                                        goto END_HAMMER;
                                                    }
                                                }
                                            }
                                            else if ((block[i1 + 5] & 0xff) > (block[i2 + 5] & 0xff))
                                            {
                                                goto HAMMER;
                                            }
                                            else {
                                                goto END_HAMMER;
                                            }
                                        }
                                        else if ((block[i1 + 4] & 0xff) > (block[i2 + 4] & 0xff))
                                        {
                                            goto HAMMER;
                                        }
                                        else {
                                            goto END_HAMMER;
                                        }
                                    }
                                    else if ((block[i1 + 3] & 0xff) > (block[i2 + 3] & 0xff))
                                    {
                                        goto HAMMER;
                                    }
                                    else {
                                        goto END_HAMMER;
                                    }
                                }
                                else if ((block[i1 + 2] & 0xff) > (block[i2 + 2] & 0xff))
                                {
                                    goto HAMMER;
                                }
                                else {
                                    goto END_HAMMER;
                                }
                            }
                            else if ((block[i1 + 1] & 0xff) > (block[i2 + 1] & 0xff))
                            {
                                goto HAMMER;
                            }
                            else {
                                goto END_HAMMER;
                            }

                        } // HAMMER

                        END_HAMMER:
                        // end inline mainGTU

                        fmap[j] = v;
                    }

                    if (firstAttemptShadow && (i <= hi)
                        && (workDoneShadow > workLimitShadow))
                    {
                        goto END_HP;
                    }
                }
            }
            END_HP:

            this.workDone = workDoneShadow;
            return firstAttemptShadow && (workDoneShadow > workLimitShadow);
        }



        private static void vswap(int[] fmap, int p1, int p2, int n)
        {
            n += p1;
            while (p1 < n)
            {
                int t = fmap[p1];
                fmap[p1++] = fmap[p2];
                fmap[p2++] = t;
            }
        }

        private static byte med3(byte a, byte b, byte c)
        {
            return (a < b) ? (b < c ? b : a < c ? c : a) : (b > c ? b : a > c ? c
                                                            : a);
        }


        /**
         * Method "mainQSort3", file "blocksort.c", BZip2 1.0.2
         */
        private void mainQSort3(CompressionState dataShadow, int loSt,
                                int hiSt, int dSt)
        {
            int[] stack_ll = dataShadow.stack_ll;
            int[] stack_hh = dataShadow.stack_hh;
            int[] stack_dd = dataShadow.stack_dd;
            int[] fmap = dataShadow.fmap;
            byte[] block = dataShadow.block;

            stack_ll[0] = loSt;
            stack_hh[0] = hiSt;
            stack_dd[0] = dSt;

            for (int sp = 1; --sp >= 0;)
            {
                int lo = stack_ll[sp];
                int hi = stack_hh[sp];
                int d = stack_dd[sp];