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-rw-r--r--crypto/bzip2/src/BZip2Constants.cs66
-rw-r--r--crypto/bzip2/src/CBZip2InputStream.cs1002
-rw-r--r--crypto/bzip2/src/CBZip2OutputStream.cs561
-rw-r--r--crypto/bzip2/src/CRC.cs182
4 files changed, 820 insertions, 991 deletions
diff --git a/crypto/bzip2/src/BZip2Constants.cs b/crypto/bzip2/src/BZip2Constants.cs
index 4a5442d8b..d238c5b76 100644
--- a/crypto/bzip2/src/BZip2Constants.cs
+++ b/crypto/bzip2/src/BZip2Constants.cs
@@ -32,72 +32,18 @@ namespace Org.BouncyCastle.Apache.Bzip2
     *
     * @author <a href="mailto:keiron@aftexsw.com">Keiron Liddle</a>
     */
-    public class BZip2Constants {
-
+    public class BZip2Constants
+    {
         public const int baseBlockSize = 100000;
         public const int MAX_ALPHA_SIZE = 258;
-        public const int MAX_CODE_LEN = 23;
+        public const int MAX_CODE_LEN = 20;
+        public const int MAX_CODE_LEN_GEN = 17;
         public const int RUNA = 0;
         public const int RUNB = 1;
         public const int N_GROUPS = 6;
         public const int G_SIZE = 50;
         public const int N_ITERS = 4;
-        public const int MAX_SELECTORS = (2 + (900000 / G_SIZE));
+        public const int MAX_SELECTORS = 2 + (900000 / G_SIZE);
         public const int NUM_OVERSHOOT_BYTES = 20;
-
-        public static readonly int[] rNums = {
-            619, 720, 127, 481, 931, 816, 813, 233, 566, 247,
-            985, 724, 205, 454, 863, 491, 741, 242, 949, 214,
-            733, 859, 335, 708, 621, 574, 73, 654, 730, 472,
-            419, 436, 278, 496, 867, 210, 399, 680, 480, 51,
-            878, 465, 811, 169, 869, 675, 611, 697, 867, 561,
-            862, 687, 507, 283, 482, 129, 807, 591, 733, 623,
-            150, 238, 59, 379, 684, 877, 625, 169, 643, 105,
-            170, 607, 520, 932, 727, 476, 693, 425, 174, 647,
-            73, 122, 335, 530, 442, 853, 695, 249, 445, 515,
-            909, 545, 703, 919, 874, 474, 882, 500, 594, 612,
-            641, 801, 220, 162, 819, 984, 589, 513, 495, 799,
-            161, 604, 958, 533, 221, 400, 386, 867, 600, 782,
-            382, 596, 414, 171, 516, 375, 682, 485, 911, 276,
-            98, 553, 163, 354, 666, 933, 424, 341, 533, 870,
-            227, 730, 475, 186, 263, 647, 537, 686, 600, 224,
-            469, 68, 770, 919, 190, 373, 294, 822, 808, 206,
-            184, 943, 795, 384, 383, 461, 404, 758, 839, 887,
-            715, 67, 618, 276, 204, 918, 873, 777, 604, 560,
-            951, 160, 578, 722, 79, 804, 96, 409, 713, 940,
-            652, 934, 970, 447, 318, 353, 859, 672, 112, 785,
-            645, 863, 803, 350, 139, 93, 354, 99, 820, 908,
-            609, 772, 154, 274, 580, 184, 79, 626, 630, 742,
-            653, 282, 762, 623, 680, 81, 927, 626, 789, 125,
-            411, 521, 938, 300, 821, 78, 343, 175, 128, 250,
-            170, 774, 972, 275, 999, 639, 495, 78, 352, 126,
-            857, 956, 358, 619, 580, 124, 737, 594, 701, 612,
-            669, 112, 134, 694, 363, 992, 809, 743, 168, 974,
-            944, 375, 748, 52, 600, 747, 642, 182, 862, 81,
-            344, 805, 988, 739, 511, 655, 814, 334, 249, 515,
-            897, 955, 664, 981, 649, 113, 974, 459, 893, 228,
-            433, 837, 553, 268, 926, 240, 102, 654, 459, 51,
-            686, 754, 806, 760, 493, 403, 415, 394, 687, 700,
-            946, 670, 656, 610, 738, 392, 760, 799, 887, 653,
-            978, 321, 576, 617, 626, 502, 894, 679, 243, 440,
-            680, 879, 194, 572, 640, 724, 926, 56, 204, 700,
-            707, 151, 457, 449, 797, 195, 791, 558, 945, 679,
-            297, 59, 87, 824, 713, 663, 412, 693, 342, 606,
-            134, 108, 571, 364, 631, 212, 174, 643, 304, 329,
-            343, 97, 430, 751, 497, 314, 983, 374, 822, 928,
-            140, 206, 73, 263, 980, 736, 876, 478, 430, 305,
-            170, 514, 364, 692, 829, 82, 855, 953, 676, 246,
-            369, 970, 294, 750, 807, 827, 150, 790, 288, 923,
-            804, 378, 215, 828, 592, 281, 565, 555, 710, 82,
-            896, 831, 547, 261, 524, 462, 293, 465, 502, 56,
-            661, 821, 976, 991, 658, 869, 905, 758, 745, 193,
-            768, 550, 608, 933, 378, 286, 215, 979, 792, 961,
-            61, 688, 793, 644, 986, 403, 106, 366, 905, 644,
-            372, 567, 466, 434, 645, 210, 389, 550, 919, 135,
-            780, 773, 635, 389, 707, 100, 626, 958, 165, 504,
-            920, 176, 193, 713, 857, 265, 203, 50, 668, 108,
-            645, 990, 626, 197, 510, 357, 358, 850, 858, 364,
-            936, 638
-        };
     }
-}
\ No newline at end of file
+}
diff --git a/crypto/bzip2/src/CBZip2InputStream.cs b/crypto/bzip2/src/CBZip2InputStream.cs
index 09d39d145..f1d31a0ab 100644
--- a/crypto/bzip2/src/CBZip2InputStream.cs
+++ b/crypto/bzip2/src/CBZip2InputStream.cs
@@ -23,6 +23,7 @@
  */
 
 using System;
+using System.Diagnostics;
 using System.IO;
 
 using Org.BouncyCastle.Utilities;
@@ -42,30 +43,6 @@ namespace Org.BouncyCastle.Apache.Bzip2
     public class CBZip2InputStream
         : BaseInputStream 
 	{
-        private static void Cadvise()
-        {
-            throw new InvalidOperationException();
-        }
-
-        private static void CompressedStreamEOF()
-        {
-            Cadvise();
-        }
-
-        private void MakeMaps()
-        {
-            nInUse = 0;
-            for (int i = 0; i < 256; i++)
-            {
-                if (inUse[i])
-                {
-                    seqToUnseq[nInUse] = (char)i;
-                    unseqToSeq[i] = (char)nInUse;
-                    nInUse++;
-                }
-            }
-        }
-
         /*
         index of the last char in the block, so
         the block size == last + 1.
@@ -83,23 +60,18 @@ namespace Org.BouncyCastle.Apache.Bzip2
         */
         private int blockSize100k;
 
-        private bool blockRandomised;
-
         private int bsBuff;
         private int bsLive;
-        private CRC mCrc = new CRC();
+        private readonly CRC m_blockCrc = new CRC();
 
-        private bool[] inUse = new bool[256];
         private int nInUse;
 
-        private char[] seqToUnseq = new char[256];
-        private char[] unseqToSeq = new char[256];
+        private byte[] seqToUnseq = new byte[256];
 
-        private char[] selector = new char[BZip2Constants.MAX_SELECTORS];
-        private char[] selectorMtf = new char[BZip2Constants.MAX_SELECTORS];
+        private byte[] m_selectors = new byte[BZip2Constants.MAX_SELECTORS];
 
         private int[] tt;
-        private char[] ll8;
+        private byte[] ll8;
 
         /*
         freq table collected to save a pass over the data
@@ -107,63 +79,60 @@ namespace Org.BouncyCastle.Apache.Bzip2
         */
         private int[] unzftab = new int[256];
 
-        private int[][] limit = InitIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
-        private int[][] basev = InitIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
-        private int[][] perm = InitIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
+        private int[][] limit = CreateIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_CODE_LEN + 1);
+        private int[][] basev = CreateIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_CODE_LEN + 1);
+        private int[][] perm = CreateIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
         private int[] minLens = new int[BZip2Constants.N_GROUPS];
 
         private Stream bsStream;
 
         private bool streamEnd = false;
 
-        private int currentChar = -1;
+        private int currentByte = -1;
 
-        private const int START_BLOCK_STATE = 1;
-        private const int RAND_PART_A_STATE = 2;
-        private const int RAND_PART_B_STATE = 3;
-        private const int RAND_PART_C_STATE = 4;
-        private const int NO_RAND_PART_A_STATE = 5;
-        private const int NO_RAND_PART_B_STATE = 6;
-        private const int NO_RAND_PART_C_STATE = 7;
+        private const int RAND_PART_B_STATE = 1;
+        private const int RAND_PART_C_STATE = 2;
+        private const int NO_RAND_PART_B_STATE = 3;
+        private const int NO_RAND_PART_C_STATE = 4;
 
-        private int currentState = START_BLOCK_STATE;
+        private int currentState = 0;
 
-        private int storedBlockCRC, storedCombinedCRC, computedCombinedCRC;
+        private int m_expectedBlockCrc, m_expectedStreamCrc, m_streamCrc;
 
         int i2, count, chPrev, ch2;
         int i, tPos;
         int rNToGo = 0;
         int rTPos  = 0;
         int j2;
-        char z;
+        int z;
 
-        public CBZip2InputStream(Stream zStream) {
+        public CBZip2InputStream(Stream zStream)
+        {
             ll8 = null;
             tt = null;
-            BsSetStream(zStream);
-            Initialize();
-            InitBlock();
-            SetupBlock();
-        }
+            bsStream = zStream;
+            bsLive = 0;
+            bsBuff = 0;
 
-        internal static int[][] InitIntArray(int n1, int n2)
-        {
-            int[][] a = new int[n1][];
-            for (int k = 0; k < n1; ++k)
-            {
-                a[k] = new int[n2];
-            }
-            return a;
-        }
+            int magic1 = bsStream.ReadByte();
+            int magic2 = bsStream.ReadByte();
+            int version = bsStream.ReadByte();
+            int level = bsStream.ReadByte();
+            if (level < 0)
+                throw new EndOfStreamException();
 
-        internal static byte[][] InitByteArray(int n1, int n2)
-        {
-            byte[][] a = new byte[n1][];
-            for (int k = 0; k < n1; ++k)
-            {
-                a[k] = new byte[n2];
-            }
-            return a;
+            if (magic1 != 'B' | magic2 != 'Z' | version != 'h' | level < '1' | level > '9')
+                throw new IOException("Invalid stream header");
+
+            blockSize100k = level - '0';
+
+            int n = BZip2Constants.baseBlockSize * blockSize100k;
+            ll8 = new byte[n];
+            tt = new int[n];
+
+            m_streamCrc = 0;
+
+            BeginBlock();
         }
 
         public override int Read(byte[] buffer, int offset, int count)
@@ -192,21 +161,15 @@ namespace Org.BouncyCastle.Apache.Bzip2
             if (streamEnd)
                 return -1;
 
-            int retChar = currentChar;
+            int result = currentByte;
             switch (currentState)
             {
-            case START_BLOCK_STATE:
-                break;
-            case RAND_PART_A_STATE:
-                break;
             case RAND_PART_B_STATE:
                 SetupRandPartB();
                 break;
             case RAND_PART_C_STATE:
                 SetupRandPartC();
                 break;
-            case NO_RAND_PART_A_STATE:
-                break;
             case NO_RAND_PART_B_STATE:
                 SetupNoRandPartB();
                 break;
@@ -214,329 +177,307 @@ namespace Org.BouncyCastle.Apache.Bzip2
                 SetupNoRandPartC();
                 break;
             default:
-                break;
+                throw new InvalidOperationException();
             }
-            return retChar;
+            return result;
         }
 
-        private void Initialize() {
-            char magic3, magic4;
-            magic3 = BsGetUChar();
-            magic4 = BsGetUChar();
-            if (magic3 != 'B' && magic4 != 'Z')
+        private void BeginBlock()
+        {
+            long magic48 = BsGetLong48();
+            if (magic48 != 0x314159265359L)
             {
-                throw new IOException("Not a BZIP2 marked stream");
-            }
-            magic3 = BsGetUChar();
-            magic4 = BsGetUChar();
-            if (magic3 != 'h' || magic4 < '1' || magic4 > '9') {
-                BsFinishedWithStream();
-                streamEnd = true;
-                return;
-            }
+                if (magic48 != 0x177245385090L)
+                    throw new IOException("Block header error");
 
-            SetDecompressStructureSizes(magic4 - '0');
-            computedCombinedCRC = 0;
-        }
+                m_expectedStreamCrc = BsGetInt32();
+                if (m_expectedStreamCrc != m_streamCrc)
+                    throw new IOException("Stream CRC error");
 
-        private void InitBlock() {
-            char magic1, magic2, magic3, magic4;
-            char magic5, magic6;
-            magic1 = BsGetUChar();
-            magic2 = BsGetUChar();
-            magic3 = BsGetUChar();
-            magic4 = BsGetUChar();
-            magic5 = BsGetUChar();
-            magic6 = BsGetUChar();
-            if (magic1 == 0x17 && magic2 == 0x72 && magic3 == 0x45
-                && magic4 == 0x38 && magic5 == 0x50 && magic6 == 0x90) {
-                Complete();
-                return;
-            }
-
-            if (magic1 != 0x31 || magic2 != 0x41 || magic3 != 0x59
-                || magic4 != 0x26 || magic5 != 0x53 || magic6 != 0x59) {
-                BadBlockHeader();
+                BsFinishedWithStream();
                 streamEnd = true;
                 return;
             }
 
-            storedBlockCRC = BsGetInt32();
+            m_expectedBlockCrc = BsGetInt32();
 
-            blockRandomised = BsR(1) == 1;
+            bool blockRandomised = BsGetBit() == 1;
 
             GetAndMoveToFrontDecode();
 
-            mCrc.InitialiseCRC();
-            currentState = START_BLOCK_STATE;
-        }
+            m_blockCrc.Initialise();
 
-        private void EndBlock()
-        {
-            int computedBlockCRC = mCrc.GetFinalCRC();
-            /* A bad CRC is considered a fatal error. */
-            if (storedBlockCRC != computedBlockCRC)
+            int[] cftab = new int[257];
             {
-                CrcError();
+                int accum = 0;
+                cftab[0] = 0;
+                for (i = 0; i < 256; ++i)
+                {
+                    accum += unzftab[i];
+                    cftab[i + 1] = accum;
+                }
+                if (accum != (last + 1))
+                    throw new InvalidOperationException();
             }
 
-            computedCombinedCRC = Integers.RotateLeft(computedCombinedCRC, 1) ^ computedBlockCRC;
-        }
-
-        private void Complete() {
-            storedCombinedCRC = BsGetInt32();
-            if (storedCombinedCRC != computedCombinedCRC) {
-                CrcError();
+            for (i = 0; i <= last; i++)
+            {
+                byte ch = ll8[i];
+                tt[cftab[ch]++] = i;
             }
 
-            BsFinishedWithStream();
-            streamEnd = true;
-        }
+            tPos = tt[origPtr];
 
-        private static void BlockOverrun() {
-            Cadvise();
-        }
+            count = 0;
+            i2 = 0;
+            ch2 = 256;   /* not a char and not EOF */
 
-        private static void BadBlockHeader() {
-            Cadvise();
+            if (blockRandomised)
+            {
+                rNToGo = 0;
+                rTPos = 0;
+                SetupRandPartA();
+            }
+            else
+            {
+                SetupNoRandPartA();
+            }
         }
 
-        private static void CrcError() {
-            Cadvise();
+        private void EndBlock()
+        {
+            int blockFinalCrc = m_blockCrc.GetFinal();
+            if (m_expectedBlockCrc != blockFinalCrc)
+                throw new IOException("Block CRC error");
+
+            m_streamCrc = Integers.RotateLeft(m_streamCrc, 1) ^ blockFinalCrc;
         }
 
-        private void BsFinishedWithStream() {
-            try {
-                if (this.bsStream != null) {
+        private void BsFinishedWithStream()
+        {
+            try
+            {
+                if (this.bsStream != null)
+                {
                     Platform.Dispose(this.bsStream);
                     this.bsStream = null;
                 }
-            } catch {
+            }
+            catch
+            {
                 //ignore
             }
         }
 
-		private void BsSetStream(Stream f) {
-            bsStream = f;
-            bsLive = 0;
-            bsBuff = 0;
+        private int BsGetBit()
+        {
+            if (bsLive == 0)
+            {
+                bsBuff = RequireByte();
+                bsLive = 7;
+                return (int)((uint)bsBuff >> 7);
+            }
+
+            --bsLive;
+
+            return (bsBuff >> bsLive) & 1;
         }
 
-        private int BsR(int n) {
-            int v;
-            while (bsLive < n) {
-                int zzi;
-                char thech = '\0';
-                try {
-                    thech = (char)bsStream.ReadByte();
-                } catch (IOException) {
-                    CompressedStreamEOF();
-                }
-                if (thech == '\uffff') {
-                    CompressedStreamEOF();
-                }
-                zzi = thech;
-                bsBuff = (bsBuff << 8) | (zzi & 0xff);
+        private int BsGetBits(int n)
+        {
+            Debug.Assert(1 <= n && n <= 24);
+
+            while (bsLive < n)
+            {
+                bsBuff = (bsBuff << 8) | RequireByte();
                 bsLive += 8;
             }
 
-            v = (bsBuff >> (bsLive - n)) & ((1 << n) - 1);
             bsLive -= n;
-            return v;
-        }
 
-        private char BsGetUChar()
-        {
-            return (char)BsR(8);
+            return (bsBuff >> bsLive) & ((1 << n) - 1);
         }
 
-        private int BsGetint()
+        private int BsGetBitsSmall(int n)
         {
-            //int u = 0;
-            //u = (u << 8) | BsR(8);
-            //u = (u << 8) | BsR(8);
-            //u = (u << 8) | BsR(8);
-            //u = (u << 8) | BsR(8);
-            //return u;
-            int u = BsR(16) << 16;
-            return u | BsR(16);
+            Debug.Assert(1 <= n && n <= 8);
+
+            if (bsLive < n)
+            {
+                bsBuff = (bsBuff << 8) | RequireByte();
+                bsLive += 8;
+            }
+
+            bsLive -= n;
+
+            return (bsBuff >> bsLive) & ((1 << n) - 1);
         }
 
-        private int BsGetIntVS(int numBits)
+        private int BsGetInt32()
         {
-            return BsR(numBits);
+            int u = BsGetBits(16) << 16;
+            return u | BsGetBits(16);
         }
 
-        private int BsGetInt32()
+        private long BsGetLong48()
         {
-            return BsGetint();
+            long u = (long)BsGetBits(24) << 24;
+            return u | (long)BsGetBits(24);
         }
 
         private void HbCreateDecodeTables(int[] limit, int[] basev, int[] perm, byte[] length, int minLen, int maxLen,
             int alphaSize)
         {
-            int i, j, vec;
-
-            int pp = 0;
-            for (i = minLen; i <= maxLen; i++) {
-                for (j = 0; j < alphaSize; j++) {
-                    if (length[j] == i) {
-                        perm[pp] = j;
-                        pp++;
+            Array.Clear(basev, 0, basev.Length);
+            Array.Clear(limit, 0, limit.Length);
+
+            int pp = 0, baseVal = 0;
+            for (int i = minLen; i <= maxLen; i++)
+            {
+                basev[i] = baseVal;
+                for (int j = 0; j < alphaSize; j++)
+                {
+                    if (length[j] == i)
+                    {
+                        perm[pp++] = j;
                     }
                 }
-            }
-
-            for (i = 0; i < BZip2Constants.MAX_CODE_LEN; i++) {
-                basev[i] = 0;
-            }
-            for (i = 0; i < alphaSize; i++) {
-                basev[length[i] + 1]++;
-            }
-
-            for (i = 1; i < BZip2Constants.MAX_CODE_LEN; i++) {
-                basev[i] += basev[i - 1];
-            }
-
-            for (i = 0; i < BZip2Constants.MAX_CODE_LEN; i++) {
-                limit[i] = 0;
-            }
-            vec = 0;
-
-            for (i = minLen; i <= maxLen; i++) {
-                vec += (basev[i + 1] - basev[i]);
-                limit[i] = vec - 1;
-                vec <<= 1;
-            }
-            for (i = minLen + 1; i <= maxLen; i++) {
-                basev[i] = ((limit[i - 1] + 1) << 1) - basev[i];
+                limit[i] = baseVal + pp;
+                baseVal += limit[i];
             }
         }
 
-        private void RecvDecodingTables()
+        private int RecvDecodingTables()
         {
-            byte[][] len = InitByteArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
-            int i, j, t, nGroups, nSelectors, alphaSize;
-            int minLen, maxLen;
-            bool[] inUse16 = new bool[16];
+            int i, j;
+
+            nInUse = 0;
 
             /* Receive the mapping table */
-            for (i = 0; i < 16; i++)
-            {
-                inUse16[i] = BsR(1) == 1;
-            }
+            int inUse16 = BsGetBits(16);
 
-            for (i = 0; i < 16; i++)
+            for (i = 0; i < 16; ++i)
             {
-                int i16 = i * 16;
-                if (inUse16[i])
+                if ((inUse16 & (0x8000 >> i)) != 0)
                 {
-                    for (j = 0; j < 16; j++)
-                    {
-                        inUse[i16 + j] = BsR(1) == 1;
-                    }
-                }
-                else
-                {
-                    for (j = 0; j < 16; j++)
+                    int inUse = BsGetBits(16);
+
+                    int i16 = i * 16;
+                    for (j = 0; j < 16; ++j)
                     {
-                        inUse[i16 + j] = false;
+                        if ((inUse & (0x8000 >> j)) != 0)
+                        {
+                            seqToUnseq[nInUse++] = (byte)(i16 + j);
+                        }
                     }
                 }
             }
 
-            MakeMaps();
-            alphaSize = nInUse + 2;
+            if (nInUse < 1)
+                throw new InvalidOperationException();
+
+            int alphaSize = nInUse + 2;
 
             /* Now the selectors */
-            nGroups = BsR(3);
-            nSelectors = BsR(15);
-            for (i = 0; i < nSelectors; i++) {
-                j = 0;
-                while (BsR(1) == 1) {
-                    j++;
-                }
-                selectorMtf[i] = (char)j;
-            }
+            int nGroups = BsGetBitsSmall(3);
+            if (nGroups < 2 || nGroups > BZip2Constants.N_GROUPS)
+                throw new InvalidOperationException();
 
-            /* Undo the MTF values for the selectors. */
+            int nSelectors = BsGetBits(15);
+            if (nSelectors < 1)
+                throw new InvalidOperationException();
+
+            uint mtfGroups = 0x00543210U;
+            for (i = 0; i < nSelectors; i++)
             {
-                char[] pos = new char[BZip2Constants.N_GROUPS];
-                char tmp, v;
-                for (v = '\0'; v < nGroups; v++) {
-                    pos[v] = v;
+                int mtfSelector = 0;
+                while (BsGetBit() == 1)
+                {
+                    if (++mtfSelector >= nGroups)
+                        throw new InvalidOperationException();
                 }
 
-                for (i = 0; i < nSelectors; i++) {
-                    v = selectorMtf[i];
-                    tmp = pos[v];
-                    while (v > 0) {
-                        pos[v] = pos[v - 1];
-                        v--;
-                    }
-                    pos[0] = tmp;
-                    selector[i] = tmp;
+                // Ignore declared selectors in excess of the maximum usable number
+                if (i >= BZip2Constants.MAX_SELECTORS)
+                    continue;
+
+                // Undo the MTF value for the selector.
+                switch (mtfSelector)
+                {
+                case 0:
+                    break;
+                case 1:
+                    mtfGroups = (mtfGroups >>  4) & 0x00000FU | (mtfGroups << 4) & 0x0000F0U | mtfGroups & 0xFFFF00U;
+                    break;
+                case 2:
+                    mtfGroups = (mtfGroups >>  8) & 0x00000FU | (mtfGroups << 4) & 0x000FF0U | mtfGroups & 0xFFF000U;
+                    break;
+                case 3:
+                    mtfGroups = (mtfGroups >> 12) & 0x00000FU | (mtfGroups << 4) & 0x00FFF0U | mtfGroups & 0xFF0000U;
+                    break;
+                case 4:
+                    mtfGroups = (mtfGroups >> 16) & 0x00000FU | (mtfGroups << 4) & 0x0FFFF0U | mtfGroups & 0xF00000U;
+                    break;
+                case 5:
+                    mtfGroups = (mtfGroups >> 20) & 0x00000FU | (mtfGroups << 4) & 0xFFFFF0U;
+                    break;
+                default:
+                    throw new InvalidOperationException();
                 }
+
+                m_selectors[i] = (byte)(mtfGroups & 0xF);
             }
 
+            byte[] len_t = new byte[alphaSize];
+
             /* Now the coding tables */
-            for (t = 0; t < nGroups; t++)
+            for (int t = 0; t < nGroups; t++)
             {
-                byte[] len_t = len[t];
-                int curr = BsR(5);
+                int maxLen = 0, minLen = 32;
+                int curr = BsGetBitsSmall(5);
+                if ((curr < 1) | (curr > BZip2Constants.MAX_CODE_LEN))
+                    throw new InvalidOperationException();
+
                 for (i = 0; i < alphaSize; i++)
                 {
-                    while (BsR(1) == 1)
+                    int markerBit = BsGetBit();
+                    while (markerBit != 0)
                     {
-                        if (BsR(1) == 0)
-                        {
-                            curr++;
-                        }
-                        else
-                        {
-                            curr--;
-                        }
+                        int nextTwoBits = BsGetBitsSmall(2);
+                        curr += 1 - (nextTwoBits & 2);
+                        if ((curr < 1) | (curr > BZip2Constants.MAX_CODE_LEN))
+                            throw new InvalidOperationException();
+                        markerBit = nextTwoBits & 1;
                     }
+
                     len_t[i] = (byte)curr;
+                    maxLen = System.Math.Max(maxLen, curr);
+                    minLen = System.Math.Min(minLen, curr);
                 }
-            }
 
-            /* Create the Huffman decoding tables */
-            for (t = 0; t < nGroups; t++)
-            {
-                minLen = 32;
-                maxLen = 0;
-                byte[] len_t = len[t];
-                for (i = 0; i < alphaSize; i++)
-                {
-                    int lti = len_t[i];
-                    if (lti > maxLen)
-                    {
-                        maxLen = lti;
-                    }
-                    if (lti < minLen)
-                    {
-                        minLen = lti;
-                    }
-                }
+                /* Create the Huffman decoding tables */
                 HbCreateDecodeTables(limit[t], basev[t], perm[t], len_t, minLen, maxLen, alphaSize);
                 minLens[t] = minLen;
             }
+
+            return nSelectors;
         }
 
         private void GetAndMoveToFrontDecode()
         {
-            char[] yy = new char[256];
-            int i, j, nextSym, limitLast;
-            int EOB, groupNo, groupPos;
+            byte[] yy = new byte[256];
+            int i, j, nextSym;
+
+            int limitLast = BZip2Constants.baseBlockSize * blockSize100k;
 
-            limitLast = BZip2Constants.baseBlockSize * blockSize100k;
-            origPtr = BsGetIntVS(24);
+            origPtr = BsGetBits(24);
+            if (origPtr > 10 + limitLast)
+                throw new InvalidOperationException();
 
-            RecvDecodingTables();
-            EOB = nInUse + 1;
-            groupNo = -1;
-            groupPos = 0;
+            int nSelectors = RecvDecodingTables();
+
+            int alphaSize = nInUse + 2;
+            int EOB = nInUse + 1;
 
             /*
             Setting up the unzftab entries here is not strictly
@@ -544,153 +485,107 @@ namespace Org.BouncyCastle.Apache.Bzip2
             in a separate pass, and so saves a block's worth of
             cache misses.
             */
-            for (i = 0; i <= 255; i++)
-            {
-                unzftab[i] = 0;
-            }
+            Array.Clear(unzftab, 0, unzftab.Length);
 
             for (i = 0; i <= 255; i++)
             {
-                yy[i] = (char)i;
+                yy[i] = (byte)i;
             }
 
             last = -1;
 
+            int groupNo = 0;
+            int groupPos = BZip2Constants.G_SIZE - 1;
+            int groupSel = m_selectors[groupNo];
+            int groupMinLen = minLens[groupSel];
+            int[] groupLimits = limit[groupSel];
+            int[] groupPerm = perm[groupSel];
+            int[] groupBase = basev[groupSel];
+
             {
-                int zt, zn, zvec, zj;
-                if (groupPos == 0)
-                {
-                    groupNo++;
-                    groupPos = BZip2Constants.G_SIZE;
-                }
-                groupPos--;
-                zt = selector[groupNo];
-                zn = minLens[zt];
-                zvec = BsR(zn);
-                while (zvec > limit[zt][zn])
+                int zn = groupMinLen;
+                int zvec = BsGetBits(groupMinLen);
+                while (zvec >= groupLimits[zn])
                 {
-                    zn++;
-                    {
-                        {
-                            while (bsLive < 1)
-                            {
-                                int zzi;
-                                char thech = '\0';
-                                try
-                                {
-                                    thech = (char)bsStream.ReadByte();
-                                }
-                                catch (IOException)
-                                {
-                                    CompressedStreamEOF();
-                                }
-                                if (thech == '\uffff')
-                                {
-                                    CompressedStreamEOF();
-                                }
-                                zzi = thech;
-                                bsBuff = (bsBuff << 8) | (zzi & 0xff);
-                                bsLive += 8;
-                            }
-                        }
-                        zj = (bsBuff >> (bsLive - 1)) & 1;
-                        bsLive--;
-                    }
-                    zvec = (zvec << 1) | zj;
+                    if (++zn > BZip2Constants.MAX_CODE_LEN)
+                        throw new InvalidOperationException();
+
+                    zvec = (zvec << 1) | BsGetBit();
                 }
-                nextSym = perm[zt][zvec - basev[zt][zn]];
+                int permIndex = zvec - groupBase[zn];
+                if (permIndex >= alphaSize)
+                    throw new InvalidOperationException();
+
+                nextSym = groupPerm[permIndex];
             }
 
             while (nextSym != EOB)
             {
-                if (nextSym == BZip2Constants.RUNA || nextSym == BZip2Constants.RUNB)
+                //if (nextSym == BZip2Constants.RUNA || nextSym == BZip2Constants.RUNB)
+                if (nextSym <= BZip2Constants.RUNB)
                 {
-                    char ch;
-                    int s = -1;
-                    int N = 1;
+                    int n = 1, s = 0;
                     do
                     {
-                        if (nextSym == BZip2Constants.RUNA)
-                        {
-                            s += (0 + 1) * N;
-                        }
-                        else if (nextSym == BZip2Constants.RUNB)
-                        {
-                            s += (1 + 1) * N;
-                        }
-                        N = N * 2;
+                        if (n > 1024 * 1024)
+                            throw new InvalidOperationException();
+
+                        s += n << nextSym;
+                        n <<= 1;
+
                         {
-                            int zt, zn, zvec, zj;
                             if (groupPos == 0)
                             {
-                                groupNo++;
+                                if (++groupNo >= nSelectors)
+                                    throw new InvalidOperationException();
+
                                 groupPos = BZip2Constants.G_SIZE;
+                                groupSel = m_selectors[groupNo];
+                                groupMinLen = minLens[groupSel];
+                                groupLimits = limit[groupSel];
+                                groupPerm = perm[groupSel];
+                                groupBase = basev[groupSel];
                             }
                             groupPos--;
-                            zt = selector[groupNo];
-                            zn = minLens[zt];
-                            zvec = BsR(zn);
-                            while (zvec > limit[zt][zn])
+
+                            int zn = groupMinLen;
+                            int zvec = BsGetBits(groupMinLen);
+                            while (zvec >= groupLimits[zn])
                             {
-                                zn++;
-                                {
-                                    {
-                                        while (bsLive < 1)
-                                        {
-                                            int zzi;
-                                            char thech = '\0';
-                                            try
-                                            {
-                                                thech = (char)bsStream.ReadByte();
-                                            }
-                                            catch (IOException)
-                                            {
-                                                CompressedStreamEOF();
-                                            }
-                                            if (thech == '\uffff')
-                                            {
-                                                CompressedStreamEOF();
-                                            }
-                                            zzi = thech;
-                                            bsBuff = (bsBuff << 8) | (zzi & 0xff);
-                                            bsLive += 8;
-                                        }
-                                    }
-                                    zj = (bsBuff >> (bsLive - 1)) & 1;
-                                    bsLive--;
-                                }
-                                zvec = (zvec << 1) | zj;
+                                if (++zn > BZip2Constants.MAX_CODE_LEN)
+                                    throw new InvalidOperationException();
+
+                                zvec = (zvec << 1) | BsGetBit();
                             }
-                            nextSym = perm[zt][zvec - basev[zt][zn]];
+                            int permIndex = zvec - groupBase[zn];
+                            if (permIndex >= alphaSize)
+                                throw new InvalidOperationException();
+
+                            nextSym = groupPerm[permIndex];
                         }
                     }
-                    while (nextSym == BZip2Constants.RUNA || nextSym == BZip2Constants.RUNB);
+                    //while (nextSym == BZip2Constants.RUNA || nextSym == BZip2Constants.RUNB);
+                    while (nextSym <= BZip2Constants.RUNB);
 
-                    s++;
-                    ch = seqToUnseq[yy[0]];
+                    byte ch = seqToUnseq[yy[0]];
                     unzftab[ch] += s;
 
-                    while (s > 0)
-                    {
-                        last++;
-                        ll8[last] = ch;
-                        s--;
-                    }
+                    if (last >= limitLast - s)
+                        throw new InvalidOperationException("Block overrun");
 
-                    if (last >= limitLast)
+                    while (--s >= 0)
                     {
-                        BlockOverrun();
+                        ll8[++last] = ch;
                     }
+
                     continue;
                 }
                 else
                 {
                     if (++last >= limitLast)
-                    {
-                        BlockOverrun();
-                    }
+                        throw new InvalidOperationException("Block overrun");
 
-                    char tmp = yy[nextSym - 1];
+                    byte tmp = yy[nextSym - 1];
                     unzftab[seqToUnseq[tmp]]++;
                     ll8[last] = seqToUnseq[tmp];
 
@@ -714,217 +609,202 @@ namespace Org.BouncyCastle.Apache.Bzip2
                     yy[0] = tmp;
 
                     {
-                        int zt, zn, zvec, zj;
                         if (groupPos == 0)
                         {
-                            groupNo++;
+                            if (++groupNo >= nSelectors)
+                                throw new InvalidOperationException();
+
                             groupPos = BZip2Constants.G_SIZE;
+                            groupSel = m_selectors[groupNo];
+                            groupMinLen = minLens[groupSel];
+                            groupLimits = limit[groupSel];
+                            groupPerm = perm[groupSel];
+                            groupBase = basev[groupSel];
                         }
                         groupPos--;
-                        zt = selector[groupNo];
-                        zn = minLens[zt];
-                        zvec = BsR(zn);
-                        while (zvec > limit[zt][zn])
+
+                        int zn = groupMinLen;
+                        int zvec = BsGetBits(groupMinLen);
+                        while (zvec >= groupLimits[zn])
                         {
-                            zn++;
-                            {
-                                {
-                                    while (bsLive < 1)
-                                    {
-                                        int zzi;
-                                        char thech = '\0';
-                                        try
-                                        {
-                                            thech = (char)bsStream.ReadByte();
-                                        }
-                                        catch (IOException)
-                                        {
-                                            CompressedStreamEOF();
-                                        }
-                                        zzi = thech;
-                                        bsBuff = (bsBuff << 8) | (zzi & 0xff);
-                                        bsLive += 8;
-                                    }
-                                }
-                                zj = (bsBuff >> (bsLive - 1)) & 1;
-                                bsLive--;
-                            }
-                            zvec = (zvec << 1) | zj;
+                            if (++zn > BZip2Constants.MAX_CODE_LEN)
+                                throw new InvalidOperationException();
+
+                            zvec = (zvec << 1) | BsGetBit();
                         }
-                        nextSym = perm[zt][zvec - basev[zt][zn]];
+                        int permIndex = zvec - groupBase[zn];
+                        if (permIndex >= alphaSize)
+                            throw new InvalidOperationException();
+
+                        nextSym = groupPerm[permIndex];
                     }
                     continue;
                 }
             }
-        }
 
-        private void SetupBlock() {
-            int[] cftab = new int[257];
-            char ch;
+            if (origPtr > last)
+                throw new InvalidOperationException();
 
-            cftab[0] = 0;
-            for (i = 1; i <= 256; i++) {
-                cftab[i] = unzftab[i - 1];
-            }
-            for (i = 1; i <= 256; i++) {
-                cftab[i] += cftab[i - 1];
-            }
+            // Check unzftab entries are in range.
+            {
+                int nblock = last + 1;
+                int check = 0;
 
-            for (i = 0; i <= last; i++) {
-                ch = ll8[i];
-                tt[cftab[ch]] = i;
-                cftab[ch]++;
+                for (i = 0; i <= 255; i++)
+                {
+                    int t = unzftab[i];
+                    check |= t;
+                    check |= nblock - t;
+                }
+                if (check < 0)
+                    throw new InvalidOperationException();
             }
-            cftab = null;
-
-            tPos = tt[origPtr];
-
-            count = 0;
-            i2 = 0;
-            ch2 = 256;   /* not a char and not EOF */
+        }
 
-            if (blockRandomised) {
-                rNToGo = 0;
-                rTPos = 0;
-                SetupRandPartA();
-            } else {
-                SetupNoRandPartA();
-            }
+        private int RequireByte()
+        {
+            int b = bsStream.ReadByte();
+            if (b < 0)
+                throw new EndOfStreamException();
+            return b & 0xFF;
         }
 
-        private void SetupRandPartA() {
-            if (i2 <= last) {
+        private void SetupRandPartA()
+        {
+            if (i2 <= last)
+            {
                 chPrev = ch2;
                 ch2 = ll8[tPos];
                 tPos = tt[tPos];
-                if (rNToGo == 0) {
-                    rNToGo = BZip2Constants.rNums[rTPos];
-                    rTPos++;
-                    if (rTPos == 512) {
-                        rTPos = 0;
-                    }
+                if (rNToGo == 0)
+                {
+                    rNToGo = CBZip2OutputStream.RNums[rTPos++];
+                    rTPos &= 0x1FF;
                 }
                 rNToGo--;
-                ch2 ^= (rNToGo == 1) ? 1 : 0;
+                ch2 ^= rNToGo == 1 ? 1 : 0;
                 i2++;
 
-                currentChar = ch2;
+                currentByte = ch2;
                 currentState = RAND_PART_B_STATE;
-                mCrc.UpdateCRC((byte)ch2);
-            } else {
+                m_blockCrc.Update((byte)ch2);
+            }
+            else
+            {
                 EndBlock();
-                InitBlock();
-                SetupBlock();
+                BeginBlock();
             }
         }
 
-        private void SetupNoRandPartA() {
-            if (i2 <= last) {
+        private void SetupNoRandPartA()
+        {
+            if (i2 <= last)
+            {
                 chPrev = ch2;
                 ch2 = ll8[tPos];
                 tPos = tt[tPos];
                 i2++;
 
-                currentChar = ch2;
+                currentByte = ch2;
                 currentState = NO_RAND_PART_B_STATE;
-                mCrc.UpdateCRC((byte)ch2);
-            } else {
+                m_blockCrc.Update((byte)ch2);
+            }
+            else
+            {
                 EndBlock();
-                InitBlock();
-                SetupBlock();
+                BeginBlock();
             }
         }
 
-        private void SetupRandPartB() {
-            if (ch2 != chPrev) {
-                currentState = RAND_PART_A_STATE;
+        private void SetupRandPartB()
+        {
+            if (ch2 != chPrev)
+            {
                 count = 1;
                 SetupRandPartA();
-            } else {
-                count++;
-                if (count >= 4) {
-                    z = ll8[tPos];
-                    tPos = tt[tPos];
-                    if (rNToGo == 0) {
-                        rNToGo = BZip2Constants.rNums[rTPos];
-                        rTPos++;
-                        if (rTPos == 512) {
-                            rTPos = 0;
-                        }
-                    }
-                    rNToGo--;
-                    z ^= (char)((rNToGo == 1) ? 1 : 0);
-                    j2 = 0;
-                    currentState = RAND_PART_C_STATE;
-                    SetupRandPartC();
-                } else {
-                    currentState = RAND_PART_A_STATE;
-                    SetupRandPartA();
-                }
             }
-        }
-
-        private void SetupRandPartC() {
-            if (j2 < z) {
-                currentChar = ch2;
-                mCrc.UpdateCRC((byte)ch2);
-                j2++;
-            } else {
-                currentState = RAND_PART_A_STATE;
-                i2++;
-                count = 0;
+            else if (++count < 4)
+            {
                 SetupRandPartA();
             }
+            else
+            {
+                z = ll8[tPos];
+                tPos = tt[tPos];
+                if (rNToGo == 0)
+                {
+                    rNToGo = CBZip2OutputStream.RNums[rTPos++];
+                    rTPos &= 0x1FF;
+                }
+                rNToGo--;
+                z ^= rNToGo == 1 ? 1 : 0;
+                j2 = 0;
+                currentState = RAND_PART_C_STATE;
+                SetupRandPartC();
+            }
         }
 
-        private void SetupNoRandPartB() {
-            if (ch2 != chPrev) {
-                currentState = NO_RAND_PART_A_STATE;
+        private void SetupNoRandPartB()
+        {
+            if (ch2 != chPrev)
+            {
                 count = 1;
                 SetupNoRandPartA();
-            } else {
-                count++;
-                if (count >= 4) {
-                    z = ll8[tPos];
-                    tPos = tt[tPos];
-                    currentState = NO_RAND_PART_C_STATE;
-                    j2 = 0;
-                    SetupNoRandPartC();
-                } else {
-                    currentState = NO_RAND_PART_A_STATE;
-                    SetupNoRandPartA();
-                }
+            }
+            else if (++count < 4)
+            {
+                SetupNoRandPartA();
+            }
+            else
+            {
+                z = ll8[tPos];
+                tPos = tt[tPos];
+                currentState = NO_RAND_PART_C_STATE;
+                j2 = 0;
+                SetupNoRandPartC();
             }
         }
 
-        private void SetupNoRandPartC() {
-            if (j2 < z) {
-                currentChar = ch2;
-                mCrc.UpdateCRC((byte)ch2);
+        private void SetupRandPartC()
+        {
+            if (j2 < z)
+            {
+                currentByte = ch2;
+                m_blockCrc.Update((byte)ch2);
                 j2++;
-            } else {
-                currentState = NO_RAND_PART_A_STATE;
+            }
+            else
+            {
                 i2++;
                 count = 0;
-                SetupNoRandPartA();
+                SetupRandPartA();
             }
         }
 
-        private void SetDecompressStructureSizes(int newSize100k) {
-            if (!(0 <= newSize100k && newSize100k <= 9 && 0 <= blockSize100k
-                && blockSize100k <= 9)) {
-                // throw new IOException("Invalid block size");
+        private void SetupNoRandPartC()
+        {
+            if (j2 < z)
+            {
+                currentByte = ch2;
+                m_blockCrc.Update((byte)ch2);
+                j2++;
             }
-
-            blockSize100k = newSize100k;
-
-            if (newSize100k == 0) {
-                return;
+            else
+            {
+                i2++;
+                count = 0;
+                SetupNoRandPartA();
             }
+        }
 
-            int n = BZip2Constants.baseBlockSize * newSize100k;
-            ll8 = new char[n];
-            tt = new int[n];
+        internal static int[][] CreateIntArray(int n1, int n2)
+        {
+            int[][] a = new int[n1][];
+            for (int k = 0; k < n1; ++k)
+            {
+                a[k] = new int[n2];
+            }
+            return a;
         }
     }
 }
diff --git a/crypto/bzip2/src/CBZip2OutputStream.cs b/crypto/bzip2/src/CBZip2OutputStream.cs
index 307f59cd0..156c32e3e 100644
--- a/crypto/bzip2/src/CBZip2OutputStream.cs
+++ b/crypto/bzip2/src/CBZip2OutputStream.cs
@@ -24,6 +24,7 @@
 
 using System;
 using System.Collections;
+using System.Diagnostics;
 using System.IO;
 
 using Org.BouncyCastle.Utilities;
@@ -51,27 +52,33 @@ namespace Org.BouncyCastle.Apache.Bzip2
         protected const int SMALL_THRESH = 20;
         protected const int DEPTH_THRESH = 10;
 
-        private bool finished;
-
-        private static void Panic()
-        {
-            throw new InvalidOperationException();
-        }
+        internal static readonly ushort[] RNums = {
+            619, 720, 127, 481, 931, 816, 813, 233, 566, 247, 985, 724, 205, 454, 863, 491, 741, 242, 949, 214, 733,
+            859, 335, 708, 621, 574, 73, 654, 730, 472, 419, 436, 278, 496, 867, 210, 399, 680, 480, 51, 878, 465, 811,
+            169, 869, 675, 611, 697, 867, 561, 862, 687, 507, 283, 482, 129, 807, 591, 733, 623, 150, 238, 59, 379, 684,
+            877, 625, 169, 643, 105, 170, 607, 520, 932, 727, 476, 693, 425, 174, 647, 73, 122, 335, 530, 442, 853, 695,
+            249, 445, 515, 909, 545, 703, 919, 874, 474, 882, 500, 594, 612, 641, 801, 220, 162, 819, 984, 589, 513,
+            495, 799, 161, 604, 958, 533, 221, 400, 386, 867, 600, 782, 382, 596, 414, 171, 516, 375, 682, 485, 911,
+            276, 98, 553, 163, 354, 666, 933, 424, 341, 533, 870, 227, 730, 475, 186, 263, 647, 537, 686, 600, 224, 469,
+            68, 770, 919, 190, 373, 294, 822, 808, 206, 184, 943, 795, 384, 383, 461, 404, 758, 839, 887, 715, 67, 618,
+            276, 204, 918, 873, 777, 604, 560, 951, 160, 578, 722, 79, 804, 96, 409, 713, 940, 652, 934, 970, 447, 318,
+            353, 859, 672, 112, 785, 645, 863, 803, 350, 139, 93, 354, 99, 820, 908, 609, 772, 154, 274, 580, 184, 79,
+            626, 630, 742, 653, 282, 762, 623, 680, 81, 927, 626, 789, 125, 411, 521, 938, 300, 821, 78, 343, 175, 128,
+            250, 170, 774, 972, 275, 999, 639, 495, 78, 352, 126, 857, 956, 358, 619, 580, 124, 737, 594, 701, 612, 669,
+            112, 134, 694, 363, 992, 809, 743, 168, 974, 944, 375, 748, 52, 600, 747, 642, 182, 862, 81, 344, 805, 988,
+            739, 511, 655, 814, 334, 249, 515, 897, 955, 664, 981, 649, 113, 974, 459, 893, 228, 433, 837, 553, 268,
+            926, 240, 102, 654, 459, 51, 686, 754, 806, 760, 493, 403, 415, 394, 687, 700, 946, 670, 656, 610, 738, 392,
+            760, 799, 887, 653, 978, 321, 576, 617, 626, 502, 894, 679, 243, 440, 680, 879, 194, 572, 640, 724, 926, 56,
+            204, 700, 707, 151, 457, 449, 797, 195, 791, 558, 945, 679, 297, 59, 87, 824, 713, 663, 412, 693, 342, 606,
+            134, 108, 571, 364, 631, 212, 174, 643, 304, 329, 343, 97, 430, 751, 497, 314, 983, 374, 822, 928, 140, 206,
+            73, 263, 980, 736, 876, 478, 430, 305, 170, 514, 364, 692, 829, 82, 855, 953, 676, 246, 369, 970, 294, 750,
+            807, 827, 150, 790, 288, 923, 804, 378, 215, 828, 592, 281, 565, 555, 710, 82, 896, 831, 547, 261, 524, 462,
+            293, 465, 502, 56, 661, 821, 976, 991, 658, 869, 905, 758, 745, 193, 768, 550, 608, 933, 378, 286, 215, 979,
+            792, 961, 61, 688, 793, 644, 986, 403, 106, 366, 905, 644, 372, 567, 466, 434, 645, 210, 389, 550, 919, 135,
+            780, 773, 635, 389, 707, 100, 626, 958, 165, 504, 920, 176, 193, 713, 857, 265, 203, 50, 668, 108, 645, 990,
+            626, 197, 510, 357, 358, 850, 858, 364, 936, 638 };
 
-        private void MakeMaps()
-        {
-            int i;
-            nInUse = 0;
-            for (i = 0; i < 256; i++)
-            {
-                if (inUse[i])
-                {
-                    seqToUnseq[nInUse] = (byte)i;
-                    unseqToSeq[i] = (byte)nInUse;
-                    nInUse++;
-                }
-            }
-        }
+        private bool finished;
 
         protected static void HbMakeCodeLengths(byte[] len, int[] freq, int alphaSize, int maxLen)
         {
@@ -113,9 +120,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
                     }
                 }
                 if (!(nHeap < (BZip2Constants.MAX_ALPHA_SIZE + 2)))
-                {
-                    Panic();
-                }
+                    throw new InvalidOperationException();
 
                 while (nHeap > 1)
                 {
@@ -124,7 +129,8 @@ namespace Org.BouncyCastle.Apache.Bzip2
                     {
                         int zz = 1;
                         int tmp = heap[zz];
-                        while (true) {
+                        while (true) 
+                        {
                             int yy = zz << 1;
                             if (yy > nHeap)
                                 break;
@@ -192,11 +198,10 @@ namespace Org.BouncyCastle.Apache.Bzip2
                     }
                 }
                 if (!(nNodes < (BZip2Constants.MAX_ALPHA_SIZE * 2)))
-                {
-                    Panic();
-                }
+                    throw new InvalidOperationException();
 
-                bool tooLong = false;
+                //bool tooLong = false;
+                int tooLongBits = 0;
                 for (int i = 1; i <= alphaSize; i++)
                 {
                     int j = 0;
@@ -207,16 +212,15 @@ namespace Org.BouncyCastle.Apache.Bzip2
                         j++;
                     }
                     len[i - 1] = (byte)j;
-                    if (j > maxLen)
-                    {
-                        tooLong = true;
-                    }
+                    //tooLong |= j > maxLen;
+                    tooLongBits |= maxLen - j;
                 }
 
-                if (!tooLong)
+                //if (!tooLong)
+                if (tooLongBits >= 0)
                     break;
 
-                for (int i = 1; i < alphaSize; i++)
+                for (int i = 1; i <= alphaSize; i++)
                 {
                     int j = weight[i] >> 8;
                     j = 1 + (j / 2);
@@ -239,24 +243,22 @@ namespace Org.BouncyCastle.Apache.Bzip2
         always: in the range 0 .. 9.
         The current block size is 100000 * this number.
         */
-        readonly int blockSize100k;
-
-        private int allowableBlockSize;
+        private readonly int blockSize100k;
+        private readonly int allowableBlockSize;
 
         bool blockRandomised;
+        IList blocksortStack = Platform.CreateArrayList();
 
         int bsBuff;
-        int bsLive;
-        readonly CRC mCrc = new CRC();
+        int bsLivePos;
+        private readonly CRC m_blockCrc = new CRC();
 
         private bool[] inUse = new bool[256];
         private int nInUse;
 
-        private byte[] seqToUnseq = new byte[256];
         private byte[] unseqToSeq = new byte[256];
 
-        private char[] selector = new char[BZip2Constants.MAX_SELECTORS];
-        private char[] selectorMtf = new char[BZip2Constants.MAX_SELECTORS];
+        private byte[] m_selectors = new byte[BZip2Constants.MAX_SELECTORS];
 
         private byte[] blockBytes;
         private ushort[] quadrantShorts;
@@ -280,6 +282,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
 
         private int currentByte = -1;
         private int runLength = 0;
+        private int m_streamCrc;
 
         public CBZip2OutputStream(Stream outStream)
             : this(outStream, 9)
@@ -296,18 +299,49 @@ namespace Org.BouncyCastle.Apache.Bzip2
             outStream.WriteByte((byte)'B');
             outStream.WriteByte((byte)'Z');
 
-            BsSetStream(outStream);
+            bsStream = outStream;
+            bsBuff = 0;
+            bsLivePos = 32;
 
             workFactor = 50;
-            if (blockSize > 9) {
+            if (blockSize > 9)
+            {
                 blockSize = 9;
             }
-            if (blockSize < 1) {
+            else if (blockSize < 1)
+            {
                 blockSize = 1;
             }
             blockSize100k = blockSize;
-            AllocateCompressStructures();
-            Initialize();
+
+            /* 20 is just a paranoia constant */
+            allowableBlockSize = BZip2Constants.baseBlockSize * blockSize100k - 20;
+
+            int n = BZip2Constants.baseBlockSize * blockSize100k;
+            blockBytes = new byte[(n + 1 + BZip2Constants.NUM_OVERSHOOT_BYTES)];
+            quadrantShorts = new ushort[(n + 1 + BZip2Constants.NUM_OVERSHOOT_BYTES)];
+            zptr = new int[n];
+            ftab = new int[65537];
+
+            /*
+            The back end needs a place to store the MTF values
+            whilst it calculates the coding tables.  We could
+            put them in the zptr array.  However, these values
+            will fit in a short, so we overlay szptr at the
+            start of zptr, in the hope of reducing the number
+            of cache misses induced by the multiple traversals
+            of the MTF values when calculating coding tables.
+            Seems to improve compression speed by about 1%.
+            */
+            // NOTE: We can't "overlay" in C#, so we just share zptr
+            szptr = zptr;
+
+            // Write `magic' bytes h indicating file-format == huffmanised, followed by a digit indicating blockSize100k
+            outStream.WriteByte((byte)'h');
+            outStream.WriteByte((byte)('0' + blockSize100k));
+
+            m_streamCrc = 0;
+
             InitBlock();
         }
 
@@ -320,25 +354,22 @@ namespace Org.BouncyCastle.Apache.Bzip2
         {
             if (currentByte == value)
             {
-                runLength++;
-                if (runLength > 254)
+                if (++runLength > 254)
                 {
                     WriteRun();
                     currentByte = -1;
                     runLength = 0;
                 }
+                return;
             }
-            else if (currentByte == -1)
-            {
-                currentByte = value;
-                runLength++;
-            }
-            else
+
+            if (currentByte >= 0)
             {
                 WriteRun();
-                runLength = 1;
-                currentByte = value;
             }
+
+            currentByte = value;
+            runLength = 1;
         }
 
         private void WriteRun()
@@ -351,39 +382,42 @@ namespace Org.BouncyCastle.Apache.Bzip2
 
             inUse[currentByte] = true;
 
-            for (int i = 0; i < runLength; i++)
-            {
-                mCrc.UpdateCRC((byte)currentByte);
-            }
-
             switch (runLength)
             {
             case 1:
                 blockBytes[++count] = (byte)currentByte;
+                m_blockCrc.Update((byte)currentByte);
                 break;
             case 2:
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)currentByte;
+                m_blockCrc.Update((byte)currentByte);
+                m_blockCrc.Update((byte)currentByte);
                 break;
             case 3:
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)currentByte;
+                m_blockCrc.Update((byte)currentByte);
+                m_blockCrc.Update((byte)currentByte);
+                m_blockCrc.Update((byte)currentByte);
                 break;
             default:
-                inUse[runLength - 4] = true;
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)currentByte;
                 blockBytes[++count] = (byte)(runLength - 4);
+                inUse[runLength - 4] = true;
+                m_blockCrc.UpdateRun((byte)currentByte, runLength);
                 break;
             }
         }
 
         bool closed = false;
 
-//        protected void Finalize() {
+//        protected void Finalize()
+//        {
 //            Close();
 //        }
 
@@ -440,37 +474,21 @@ namespace Org.BouncyCastle.Apache.Bzip2
             bsStream.Flush();
         }
 
-        private int combinedCRC;
-
-        private void Initialize()
-        {
-            /* Write `magic' bytes h indicating file-format == huffmanised,
-            followed by a digit indicating blockSize100k.
-            */
-            BsPutUChar('h');
-            BsPutUChar('0' + blockSize100k);
-
-            combinedCRC = 0;
-        }
-
         private void InitBlock()
         {
-            mCrc.InitialiseCRC();
+            m_blockCrc.Initialise();
             count = 0;
 
             for (int i = 0; i < 256; i++)
             {
                 inUse[i] = false;
             }
-
-            /* 20 is just a paranoia constant */
-            allowableBlockSize = BZip2Constants.baseBlockSize * blockSize100k - 20;
         }
 
         private void EndBlock()
         {
-            int blockCRC = mCrc.GetFinalCRC();
-            combinedCRC = Integers.RotateLeft(combinedCRC, 1) ^ blockCRC;
+            int blockFinalCrc = m_blockCrc.GetFinal();
+            m_streamCrc = Integers.RotateLeft(m_streamCrc, 1) ^ blockFinalCrc;
 
             /* sort the block and establish posn of original string */
             DoReversibleTransformation();
@@ -488,24 +506,20 @@ namespace Org.BouncyCastle.Apache.Bzip2
             They are only important when trying to recover blocks from
             damaged files.
             */
-            BsPutUChar(0x31);
-            BsPutUChar(0x41);
-            BsPutUChar(0x59);
-            BsPutUChar(0x26);
-            BsPutUChar(0x53);
-            BsPutUChar(0x59);
+            BsPutLong48(0x314159265359L);
 
             /* Now the block's CRC, so it is in a known place. */
-            BsPutint(blockCRC);
+            BsPutInt32(blockFinalCrc);
 
             /* Now a single bit indicating randomisation. */
-            BsW(1, blockRandomised ? 1 : 0);
+            BsPutBit(blockRandomised ? 1 : 0);
 
             /* Finally, block's contents proper. */
             MoveToFrontCodeAndSend();
         }
 
-        private void EndCompression() {
+        private void EndCompression()
+        {
             /*
             Now another magic 48-bit number, 0x177245385090, to
             indicate the end of the last block.  (Sqrt(pi), if
@@ -513,14 +527,9 @@ namespace Org.BouncyCastle.Apache.Bzip2
             too much repetition -- 27 18 28 18 28 46 -- for me
             to feel statistically comfortable.  Call me paranoid.)
             */
-            BsPutUChar(0x17);
-            BsPutUChar(0x72);
-            BsPutUChar(0x45);
-            BsPutUChar(0x38);
-            BsPutUChar(0x50);
-            BsPutUChar(0x90);
+            BsPutLong48(0x177245385090L);
 
-            BsPutint(combinedCRC);
+            BsPutInt32(m_streamCrc);
 
             BsFinishedWithStream();
         }
@@ -534,72 +543,85 @@ namespace Org.BouncyCastle.Apache.Bzip2
                 {
                     if (length[i] == n)
                     {
-                        code[i] = vec;
-                        vec++;
+                        code[i] = vec++;
                     }
                 }
                 vec <<= 1;
             }
         }
 
-        private void BsSetStream(Stream f)
+        private void BsFinishedWithStream()
         {
-            bsStream = f;
-            bsLive = 0;
-            bsBuff = 0;
+            if (bsLivePos < 32)
+            {
+                bsStream.WriteByte((byte)(bsBuff >> 24));
+                bsBuff = 0;
+                bsLivePos = 32;
+            }
         }
 
-        private void BsFinishedWithStream()
+        private void BsPutBit(int v)
         {
-            while (bsLive > 0)
+            --bsLivePos;
+            bsBuff |= v << bsLivePos;
+
+            if (bsLivePos <= 24)
             {
-                bsStream.WriteByte((byte)(bsBuff >> 24)); // write 8-bit
+                bsStream.WriteByte((byte)(bsBuff >> 24));
                 bsBuff <<= 8;
-                bsLive -= 8;
+                bsLivePos += 8;
             }
         }
 
-        private void BsW(int n, int v)
+        private void BsPutBits(int n, int v)
         {
-            while (bsLive >= 8)
+            Debug.Assert(1 <= n && n <= 24);
+
+            bsLivePos -= n;
+            bsBuff |= v << bsLivePos;
+
+            while (bsLivePos <= 24)
             {
-                bsStream.WriteByte((byte)(bsBuff >> 24)); // write 8-bit
+                bsStream.WriteByte((byte)(bsBuff >> 24));
                 bsBuff <<= 8;
-                bsLive -= 8;
+                bsLivePos += 8;
             }
-            bsBuff |= v << (32 - bsLive - n);
-            bsLive += n;
         }
 
-        private void BsPutUChar(int c)
+        private void BsPutBitsSmall(int n, int v)
         {
-            BsW(8, c);
+            Debug.Assert(1 <= n && n <= 8);
+
+            bsLivePos -= n;
+            bsBuff |= v << bsLivePos;
+
+            if (bsLivePos <= 24)
+            {
+                bsStream.WriteByte((byte)(bsBuff >> 24));
+                bsBuff <<= 8;
+                bsLivePos += 8;
+            }
         }
 
-        private void BsPutint(int u)
+        private void BsPutInt32(int u)
         {
-            //BsW(8, (u >> 24) & 0xff);
-            //BsW(8, (u >> 16) & 0xff);
-            //BsW(8, (u >>  8) & 0xff);
-            //BsW(8,  u        & 0xff);
-            BsW(16, (u >> 16) & 0xFFFF);
-            BsW(16, u & 0xFFFF);
+            BsPutBits(16, (u >> 16) & 0xFFFF);
+            BsPutBits(16, u & 0xFFFF);
         }
 
-        private void BsPutIntVS(int numBits, int c)
+        private void BsPutLong48(long u)
         {
-            BsW(numBits, c);
+            BsPutBits(24, (int)(u >> 24) & 0xFFFFFF);
+            BsPutBits(24, (int)u & 0xFFFFFF);
         }
 
-        private void SendMTFValues()
+        private void SendMtfValues()
         {
-            byte[][] len = CBZip2InputStream.InitByteArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
+            byte[][] len = InitByteArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
 
-            int v, t, i, j, gs, ge, bt, bc, iter;
-            int nSelectors = 0, alphaSize, minLen, maxLen, selCtr;
-            int nGroups;
+            int v, t, i, j, bt, bc, iter;
 
-            alphaSize = nInUse + 2;
+            int alphaSize = nInUse + 2;
             for (t = 0; t < BZip2Constants.N_GROUPS; t++)
             {
                 byte[] len_t = len[t];
@@ -611,10 +633,9 @@ namespace Org.BouncyCastle.Apache.Bzip2
 
             /* Decide how many coding tables to use */
             if (nMTF <= 0)
-            {
-                Panic();
-            }
+                throw new InvalidOperationException();
 
+            int nGroups;
             if (nMTF < 200)
             {
                 nGroups = 2;
@@ -638,16 +659,13 @@ namespace Org.BouncyCastle.Apache.Bzip2
 
             /* Generate an initial set of coding tables */
             {
-                int tFreq, aFreq;
-
                 int nPart = nGroups;
-                int remF  = nMTF;
-                gs = 0;
+                int remF = nMTF;
+                int ge = -1;
                 while (nPart > 0)
                 {
-                    tFreq = remF / nPart;
-                    ge = gs - 1;
-                    aFreq = 0;
+                    int gs = ge + 1;
+                    int aFreq = 0, tFreq = remF / nPart;
                     while (aFreq < tFreq && ge < alphaSize - 1)
                     {
                         aFreq += mtfFreq[++ge];
@@ -673,12 +691,11 @@ namespace Org.BouncyCastle.Apache.Bzip2
                     }
 
                     nPart--;
-                    gs = ge + 1;
                     remF -= aFreq;
                 }
             }
 
-            int[][] rfreq = CBZip2InputStream.InitIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
+            int[][] rfreq = CBZip2InputStream.CreateIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
             int[] fave = new int[BZip2Constants.N_GROUPS];
             short[] cost = new short[BZip2Constants.N_GROUPS];
             byte[] len_0 = len[0];
@@ -688,9 +705,8 @@ namespace Org.BouncyCastle.Apache.Bzip2
             byte[] len_4 = len[4];
             byte[] len_5 = len[5];
 
-            /*
-            Iterate up to N_ITERS times to improve the tables.
-            */
+            // Iterate up to N_ITERS times to improve the tables.
+            int nSelectors = 0;
             for (iter = 0; iter < BZip2Constants.N_ITERS; iter++)
             {
                 for (t = 0; t < nGroups; t++)
@@ -705,7 +721,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
                 }
 
                 nSelectors = 0;
-                gs = 0;
+                int gs = 0;
                 while (gs < nMTF)
                 {
                     /* Set group start & end marks. */
@@ -714,7 +730,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
                      * Calculate the cost of this group as coded by each of the coding tables.
                      */
 
-                    ge = System.Math.Min(gs + BZip2Constants.G_SIZE - 1, nMTF - 1);
+                    int ge = System.Math.Min(gs + BZip2Constants.G_SIZE - 1, nMTF - 1);
 
                     if (nGroups == 6)
                     {
@@ -759,18 +775,19 @@ namespace Org.BouncyCastle.Apache.Bzip2
                     Find the coding table which is best for this group,
                     and record its identity in the selector table.
                     */
-                    bc = 999999999;
-                    bt = -1;
-                    for (t = 0; t < nGroups; t++)
+                    bc = cost[0];
+                    bt = 0;
+                    for (t = 1; t < nGroups; t++)
                     {
-                        if (cost[t] < bc)
+                        short cost_t = cost[t];
+                        if (cost_t < bc)
                         {
-                            bc = cost[t];
+                            bc = cost_t;
                             bt = t;
                         }
                     }
                     fave[bt]++;
-                    selector[nSelectors] = (char) bt;
+                    m_selectors[nSelectors] = (byte)bt;
                     nSelectors++;
 
                     /*
@@ -790,77 +807,32 @@ namespace Org.BouncyCastle.Apache.Bzip2
                 */
                 for (t = 0; t < nGroups; t++)
                 {
-                    HbMakeCodeLengths(len[t], rfreq[t], alphaSize, 20);
+                    HbMakeCodeLengths(len[t], rfreq[t], alphaSize, BZip2Constants.MAX_CODE_LEN_GEN);
                 }
             }
 
-            rfreq = null;
-            fave = null;
-            cost = null;
+            if (nGroups >= 8 || nGroups > BZip2Constants.N_GROUPS)
+                throw new InvalidOperationException();
+            if (nSelectors >= 32768 || nSelectors > BZip2Constants.MAX_SELECTORS)
+                throw new InvalidOperationException();
 
-            if (!(nGroups < 8))
-            {
-                Panic();
-            }
-            if (!(nSelectors < 32768 && nSelectors <= (2 + (900000 / BZip2Constants.G_SIZE))))
-            {
-                Panic();
-            }
-
-            /* Compute MTF values for the selectors. */
-            {
-                char[] pos = new char[BZip2Constants.N_GROUPS];
-                char ll_i, tmp2, tmp;
-                for (i = 0; i < nGroups; i++)
-                {
-                    pos[i] = (char)i;
-                }
-                for (i = 0; i < nSelectors; i++)
-                {
-                    ll_i = selector[i];
-                    j = 0;
-                    tmp = pos[j];
-                    while (ll_i != tmp)
-                    {
-                        j++;
-                        tmp2 = tmp;
-                        tmp = pos[j];
-                        pos[j] = tmp2;
-                    }
-                    pos[0] = tmp;
-                    selectorMtf[i] = (char)j;
-                }
-            }
-
-            int[][] code = CBZip2InputStream.InitIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
+            int[][] code = CBZip2InputStream.CreateIntArray(BZip2Constants.N_GROUPS, BZip2Constants.MAX_ALPHA_SIZE);
 
             /* Assign actual codes for the tables. */
             for (t = 0; t < nGroups; t++)
             {
-                minLen = 32;
-                maxLen = 0;
+                int maxLen = 0, minLen = 32;
                 byte[] len_t = len[t];
                 for (i = 0; i < alphaSize; i++)
                 {
                     int lti = len_t[i];
-                    if (lti > maxLen)
-                    {
-                        maxLen = lti;
-                    }
-                    if (lti < minLen)
-                    {
-                        minLen = lti;
-                    }
-                }
-                if (maxLen > 20)
-                {
-                    Panic();
+                    maxLen = System.Math.Max(maxLen, lti);
+                    minLen = System.Math.Min(minLen, lti);
                 }
-                if (minLen < 1)
-                {
-                    Panic();
-                }
-                HbAssignCodes(code[t], len[t], minLen, maxLen, alphaSize);
+                if (minLen < 1 | maxLen > BZip2Constants.MAX_CODE_LEN_GEN)
+                    throw new InvalidOperationException();
+
+                HbAssignCodes(code[t], len_t, minLen, maxLen, alphaSize);
             }
 
             /* Transmit the mapping table. */
@@ -882,7 +854,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
 
 				for (i = 0; i < 16; i++)
                 {
-                    BsW(1, inUse16[i] ? 1 : 0);
+                    BsPutBit(inUse16[i] ? 1 : 0);
                 }
 
                 for (i = 0; i < 16; i++)
@@ -892,29 +864,38 @@ namespace Org.BouncyCastle.Apache.Bzip2
                         int i16 = i * 16;
                         for (j = 0; j < 16; j++)
                         {
-                            BsW(1, inUse[i16 + j] ? 1 : 0);
+                            BsPutBit(inUse[i16 + j] ? 1 : 0);
                         }
                     }
                 }
             }
 
             /* Now the selectors. */
-            BsW(3, nGroups);
-            BsW(15, nSelectors);
-            for (i = 0; i < nSelectors; i++)
+            BsPutBitsSmall(3, nGroups);
+            BsPutBits(15, nSelectors);
             {
-                int count = selectorMtf[i];
-                //for (j = 0; j < count; j++)
-                //{
-                //    BsW(1, 1);
-                //}
-                //BsW(1, 0);
-                while (count >= 24)
+                byte[] pos = new byte[BZip2Constants.N_GROUPS];
+                for (i = 0; i < nGroups; i++)
                 {
-                    BsW(24, 0xFFFFFF);
-                    count -= 24;
+                    pos[i] = (byte)i;
+                }
+
+                for (i = 0; i < nSelectors; i++)
+                {
+                    // Compute MTF values for the selector.
+                    byte ll_i = m_selectors[i];
+                    int mtfSelector = 1;
+                    byte tmp = pos[0];
+                    while (ll_i != tmp)
+                    {
+                        byte tmp2 = tmp;
+                        tmp = pos[mtfSelector];
+                        pos[mtfSelector++] = tmp2;
+                    }
+                    pos[0] = tmp;
+
+                    BsPutBitsSmall(mtfSelector, (1 << mtfSelector) - 2);
                 }
-                BsW(count + 1, (1 << (count + 1)) - 2);
             }
 
             /* Now the coding tables. */
@@ -922,55 +903,55 @@ namespace Org.BouncyCastle.Apache.Bzip2
             {
                 byte[] len_t = len[t];
                 int curr = len_t[0];
-                BsW(5, curr);
-                for (i = 0; i < alphaSize; i++)
+                BsPutBitsSmall(6, curr << 1);
+                for (i = 1; i < alphaSize; i++)
                 {
                     int lti = len_t[i];
                     while (curr < lti)
                     {
-                        BsW(2, 2);
+                        BsPutBitsSmall(2, 2);
                         curr++; /* 10 */
                     }
                     while (curr > lti)
                     {
-                        BsW(2, 3);
+                        BsPutBitsSmall(2, 3);
                         curr--; /* 11 */
                     }
-                    BsW(1, 0);
+                    BsPutBit(0);
                 }
             }
 
             /* And finally, the block data proper */
-            selCtr = 0;
-            gs = 0;
-            while (gs < nMTF)
             {
-                ge = System.Math.Min(gs + BZip2Constants.G_SIZE - 1, nMTF - 1);
+                int selCtr = 0;
+                int gs = 0;
+                while (gs < nMTF)
+                {
+                    int ge = System.Math.Min(gs + BZip2Constants.G_SIZE - 1, nMTF - 1);
 
-                int selector_selCtr = selector[selCtr];
-                byte[] len_selCtr = len[selector_selCtr];
-                int[] code_selCtr = code[selector_selCtr];
+                    int selector_selCtr = m_selectors[selCtr];
+                    byte[] len_selCtr = len[selector_selCtr];
+                    int[] code_selCtr = code[selector_selCtr];
 
-                for (i = gs; i <= ge; i++)
-                {
-                    int sfmap_i = szptr[i];
-                    BsW(len_selCtr[sfmap_i], code_selCtr[sfmap_i]);
-                }
+                    for (i = gs; i <= ge; i++)
+                    {
+                        int sfmap_i = szptr[i];
+                        BsPutBits(len_selCtr[sfmap_i], code_selCtr[sfmap_i]);
+                    }
 
-                gs = ge + 1;
-                selCtr++;
-            }
-            if (!(selCtr == nSelectors))
-            {
-                Panic();
+                    gs = ge + 1;
+                    selCtr++;
+                }
+                if (selCtr != nSelectors)
+                    throw new InvalidOperationException();
             }
         }
 
         private void MoveToFrontCodeAndSend()
         {
-            BsPutIntVS(24, origPtr);
-            GenerateMTFValues();
-            SendMTFValues();
+            BsPutBits(24, origPtr);
+            GenerateMtfValues();
+            SendMtfValues();
         }
 
         private Stream bsStream;
@@ -1092,7 +1073,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
         {
             int unLo, unHi, ltLo, gtHi, n, m;
 
-            IList stack = Platform.CreateArrayList();
+            IList stack = blocksortStack;
             int stackCount = 0;
             StackElem stackElem;
 
@@ -1367,9 +1348,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
                         }
 
                         if (!(((bbSize - 1) >> shifts) <= 65535))
-                        {
-                            Panic();
-                        }
+                            throw new InvalidOperationException();
                     }
 
                     /*
@@ -1408,24 +1387,19 @@ namespace Org.BouncyCastle.Apache.Bzip2
                 inUse[i] = false;
             }
 
-            int rNToGo = 0;
-            int rTPos = 0;
+            int rNToGo = 0, rTPos = 0;
 
-            for (int i = 0; i < count; i++)
+            for (int i = 1; i <= count; i++)
             {
                 if (rNToGo == 0)
                 {
-                    rNToGo = BZip2Constants.rNums[rTPos];
-
-                    if (++rTPos == 512)
-                    {
-                        rTPos = 0;
-                    }
+                    rNToGo = RNums[rTPos++];
+                    rTPos &= 0x1FF;
                 }
                 rNToGo--;
-                blockBytes[i + 1] ^= (byte)((rNToGo == 1) ? 1 : 0);
+                blockBytes[i] ^= (byte)(rNToGo == 1 ? 1 : 0);
 
-                inUse[blockBytes[i + 1]] = true;
+                inUse[blockBytes[i]] = true;
             }
         }
 
@@ -1458,9 +1432,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
             }
 
             if (origPtr == -1)
-            {
-                Panic();
-            }
+                throw new InvalidOperationException();
         }
 
         private bool FullGtU(int i1, int i2)
@@ -1568,29 +1540,7 @@ namespace Org.BouncyCastle.Apache.Bzip2
         private static readonly int[] incs = { 1, 4, 13, 40, 121, 364, 1093, 3280, 9841, 29524, 88573, 265720, 797161,
             2391484 };
 
-        private void AllocateCompressStructures()
-        {
-            int n = BZip2Constants.baseBlockSize * blockSize100k;
-            blockBytes = new byte[(n + 1 + BZip2Constants.NUM_OVERSHOOT_BYTES)];
-            quadrantShorts = new ushort[(n + 1 + BZip2Constants.NUM_OVERSHOOT_BYTES)];
-            zptr = new int[n];
-            ftab = new int[65537];
-
-            /*
-            The back end needs a place to store the MTF values
-            whilst it calculates the coding tables.  We could
-            put them in the zptr array.  However, these values
-            will fit in a short, so we overlay szptr at the
-            start of zptr, in the hope of reducing the number
-            of cache misses induced by the multiple traversals
-            of the MTF values when calculating coding tables.
-            Seems to improve compression speed by about 1%.
-            */
-            // NOTE: We can't "overlay" in C#, so we just share zptr
-            szptr = zptr;
-        }
-
-        private void GenerateMTFValues()
+        private void GenerateMtfValues()
         {
             byte[] yy = new byte[256];
             int i, j;
@@ -1598,7 +1548,16 @@ namespace Org.BouncyCastle.Apache.Bzip2
             int wr;
             int EOB;
 
-            MakeMaps();
+            nInUse = 0;
+
+            for (i = 0; i < 256; i++)
+            {
+                if (inUse[i])
+                {
+                    unseqToSeq[i] = (byte)nInUse++;
+                }
+            }
+
             EOB = nInUse + 1;
 
             for (i = 0; i <= EOB; i++)
@@ -1679,5 +1638,15 @@ namespace Org.BouncyCastle.Apache.Bzip2
 
             nMTF = wr;
         }
+
+        internal static byte[][] InitByteArray(int n1, int n2)
+        {
+            byte[][] a = new byte[n1][];
+            for (int k = 0; k < n1; ++k)
+            {
+                a[k] = new byte[n2];
+            }
+            return a;
+        }
     }
 }
diff --git a/crypto/bzip2/src/CRC.cs b/crypto/bzip2/src/CRC.cs
index ac2db776a..a66340e22 100644
--- a/crypto/bzip2/src/CRC.cs
+++ b/crypto/bzip2/src/CRC.cs
@@ -23,6 +23,9 @@
  */
 
 using System;
+using System.Diagnostics;
+
+using Org.BouncyCastle.Utilities;
 
 namespace Org.BouncyCastle.Apache.Bzip2
 {
@@ -34,94 +37,125 @@ namespace Org.BouncyCastle.Apache.Bzip2
     */
     internal class CRC
     {
+        // Values are byte-reversed
         private static readonly uint[] Crc32Table = {
-            0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9,
-            0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
-            0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
-            0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
-            0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9,
-            0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
-            0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011,
-            0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd,
-            0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
-            0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5,
-            0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81,
-            0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
-            0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49,
-            0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
-            0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
-            0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d,
-            0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae,
-            0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
-            0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
-            0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca,
-            0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
-            0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
-            0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066,
-            0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
-            0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e,
-            0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692,
-            0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
-            0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a,
-            0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
-            0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
-            0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686,
-            0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
-            0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
-            0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
-            0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f,
-            0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
-            0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47,
-            0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b,
-            0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
-            0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623,
-            0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7,
-            0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
-            0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f,
-            0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
-            0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
-            0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b,
-            0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f,
-            0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
-            0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
-            0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c,
-            0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
-            0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
-            0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30,
-            0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
-            0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088,
-            0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654,
-            0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
-            0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c,
-            0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
-            0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
-            0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0,
-            0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
-            0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
-            0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
+            0x00000000, 0xB71DC104, 0x6E3B8209, 0xD926430D,
+            0xDC760413, 0x6B6BC517, 0xB24D861A, 0x0550471E,
+            0xB8ED0826, 0x0FF0C922, 0xD6D68A2F, 0x61CB4B2B,
+            0x649B0C35, 0xD386CD31, 0x0AA08E3C, 0xBDBD4F38,
+            0x70DB114C, 0xC7C6D048, 0x1EE09345, 0xA9FD5241,
+            0xACAD155F, 0x1BB0D45B, 0xC2969756, 0x758B5652,
+            0xC836196A, 0x7F2BD86E, 0xA60D9B63, 0x11105A67,
+            0x14401D79, 0xA35DDC7D, 0x7A7B9F70, 0xCD665E74,
+            0xE0B62398, 0x57ABE29C, 0x8E8DA191, 0x39906095,
+            0x3CC0278B, 0x8BDDE68F, 0x52FBA582, 0xE5E66486,
+            0x585B2BBE, 0xEF46EABA, 0x3660A9B7, 0x817D68B3,
+            0x842D2FAD, 0x3330EEA9, 0xEA16ADA4, 0x5D0B6CA0,
+            0x906D32D4, 0x2770F3D0, 0xFE56B0DD, 0x494B71D9,
+            0x4C1B36C7, 0xFB06F7C3, 0x2220B4CE, 0x953D75CA,
+            0x28803AF2, 0x9F9DFBF6, 0x46BBB8FB, 0xF1A679FF,
+            0xF4F63EE1, 0x43EBFFE5, 0x9ACDBCE8, 0x2DD07DEC,
+            0x77708634, 0xC06D4730, 0x194B043D, 0xAE56C539,
+            0xAB068227, 0x1C1B4323, 0xC53D002E, 0x7220C12A,
+            0xCF9D8E12, 0x78804F16, 0xA1A60C1B, 0x16BBCD1F,
+            0x13EB8A01, 0xA4F64B05, 0x7DD00808, 0xCACDC90C,
+            0x07AB9778, 0xB0B6567C, 0x69901571, 0xDE8DD475,
+            0xDBDD936B, 0x6CC0526F, 0xB5E61162, 0x02FBD066,
+            0xBF469F5E, 0x085B5E5A, 0xD17D1D57, 0x6660DC53,
+            0x63309B4D, 0xD42D5A49, 0x0D0B1944, 0xBA16D840,
+            0x97C6A5AC, 0x20DB64A8, 0xF9FD27A5, 0x4EE0E6A1,
+            0x4BB0A1BF, 0xFCAD60BB, 0x258B23B6, 0x9296E2B2,
+            0x2F2BAD8A, 0x98366C8E, 0x41102F83, 0xF60DEE87,
+            0xF35DA999, 0x4440689D, 0x9D662B90, 0x2A7BEA94,
+            0xE71DB4E0, 0x500075E4, 0x892636E9, 0x3E3BF7ED,
+            0x3B6BB0F3, 0x8C7671F7, 0x555032FA, 0xE24DF3FE,
+            0x5FF0BCC6, 0xE8ED7DC2, 0x31CB3ECF, 0x86D6FFCB,
+            0x8386B8D5, 0x349B79D1, 0xEDBD3ADC, 0x5AA0FBD8,
+            0xEEE00C69, 0x59FDCD6D, 0x80DB8E60, 0x37C64F64,
+            0x3296087A, 0x858BC97E, 0x5CAD8A73, 0xEBB04B77,
+            0x560D044F, 0xE110C54B, 0x38368646, 0x8F2B4742,
+            0x8A7B005C, 0x3D66C158, 0xE4408255, 0x535D4351,
+            0x9E3B1D25, 0x2926DC21, 0xF0009F2C, 0x471D5E28,
+            0x424D1936, 0xF550D832, 0x2C769B3F, 0x9B6B5A3B,
+            0x26D61503, 0x91CBD407, 0x48ED970A, 0xFFF0560E,
+            0xFAA01110, 0x4DBDD014, 0x949B9319, 0x2386521D,
+            0x0E562FF1, 0xB94BEEF5, 0x606DADF8, 0xD7706CFC,
+            0xD2202BE2, 0x653DEAE6, 0xBC1BA9EB, 0x0B0668EF,
+            0xB6BB27D7, 0x01A6E6D3, 0xD880A5DE, 0x6F9D64DA,
+            0x6ACD23C4, 0xDDD0E2C0, 0x04F6A1CD, 0xB3EB60C9,
+            0x7E8D3EBD, 0xC990FFB9, 0x10B6BCB4, 0xA7AB7DB0,
+            0xA2FB3AAE, 0x15E6FBAA, 0xCCC0B8A7, 0x7BDD79A3,
+            0xC660369B, 0x717DF79F, 0xA85BB492, 0x1F467596,
+            0x1A163288, 0xAD0BF38C, 0x742DB081, 0xC3307185,
+            0x99908A5D, 0x2E8D4B59, 0xF7AB0854, 0x40B6C950,
+            0x45E68E4E, 0xF2FB4F4A, 0x2BDD0C47, 0x9CC0CD43,
+            0x217D827B, 0x9660437F, 0x4F460072, 0xF85BC176,
+            0xFD0B8668, 0x4A16476C, 0x93300461, 0x242DC565,
+            0xE94B9B11, 0x5E565A15, 0x87701918, 0x306DD81C,
+            0x353D9F02, 0x82205E06, 0x5B061D0B, 0xEC1BDC0F,
+            0x51A69337, 0xE6BB5233, 0x3F9D113E, 0x8880D03A,
+            0x8DD09724, 0x3ACD5620, 0xE3EB152D, 0x54F6D429,
+            0x7926A9C5, 0xCE3B68C1, 0x171D2BCC, 0xA000EAC8,
+            0xA550ADD6, 0x124D6CD2, 0xCB6B2FDF, 0x7C76EEDB,
+            0xC1CBA1E3, 0x76D660E7, 0xAFF023EA, 0x18EDE2EE,
+            0x1DBDA5F0, 0xAAA064F4, 0x738627F9, 0xC49BE6FD,
+            0x09FDB889, 0xBEE0798D, 0x67C63A80, 0xD0DBFB84,
+            0xD58BBC9A, 0x62967D9E, 0xBBB03E93, 0x0CADFF97,
+            0xB110B0AF, 0x060D71AB, 0xDF2B32A6, 0x6836F3A2,
+            0x6D66B4BC, 0xDA7B75B8, 0x035D36B5, 0xB440F7B1,
         };
 
-        private uint m_globalCrc;
+        private uint m_value = 0U;
 
-        internal CRC()
+        internal void Initialise()
         {
-            InitialiseCRC();
+            m_value = 0xFFFFFFFF;
         }
 
-        internal void InitialiseCRC()
+        internal int GetFinal()
         {
-            m_globalCrc = 0xffffffff;
+            return (int)~Integers.ReverseBytes(m_value);
         }
 
-        internal int GetFinalCRC()
+        internal void Update(byte inCh)
         {
-            return (int)~m_globalCrc;
+            m_value = (m_value >> 8) ^ Crc32Table[(byte)(m_value ^ inCh)];
         }
 
-        internal void UpdateCRC(byte inCh)
+        internal void UpdateRun(byte inCh, int runLength)
         {
-            uint index = (m_globalCrc >> 24) ^ inCh;
-            m_globalCrc = (m_globalCrc << 8) ^ Crc32Table[index];
+            Debug.Assert(runLength >= 4);
+
+            uint inCh2 = (uint)inCh << 8 | inCh;
+            uint inCh4 = inCh2 << 16 | inCh2;
+
+            do
+            {
+                m_value ^= inCh4;
+                m_value = (m_value >> 8) ^ Crc32Table[(byte)m_value];
+                m_value = (m_value >> 8) ^ Crc32Table[(byte)m_value];
+                m_value = (m_value >> 8) ^ Crc32Table[(byte)m_value];
+                m_value = (m_value >> 8) ^ Crc32Table[(byte)m_value];
+            }
+            while ((runLength -= 4) >= 4);
+
+            switch (runLength & 3)
+            {
+            case 0:
+                break;
+            case 1:
+                Update(inCh);
+                break;
+            case 2:
+                Update(inCh);
+                Update(inCh);
+                break;
+            case 3:
+                Update(inCh);
+                Update(inCh);
+                Update(inCh);
+                break;
+            }
         }
     }
 }