Removing Strong-Signing from Assemblies at File Level (byte patching)

/***
 * 
 *  ASMEX by RiskCare Ltd.
 * 
 * This source is copyright (C) 2002 RiskCare Ltd. All rights reserved.
 * 
 * Disclaimer:
 * This code is provided 'as is', with absolutely no warranty expressed or
 * implied.  Any use of this code is at your own risk.
 *   
 * You are hereby granted the right to redistribute this source unmodified
 * in its original archive. 
 * You are hereby granted the right to use this code, or code based on it,
 * provided that you acknowledge RiskCare Ltd somewhere in the documentation
 * of your application. 
 * You are hereby granted the right to distribute changes to this source, 
 * provided that:
 * 
 * 1 -- This copyright notice is retained unchanged 
 * 2 -- Your changes are clearly marked 
 * 
 * Enjoy!
 * 
 * --------------------------------------------------------------------
 * 
 * If you use this code or have comments on it, please mail me at 
 * support@jbrowse.com or ben.peterson@riskcare.com
 * 
 */

using System;
using System.IO;
using System.Collections;
using System.Text;

namespace Asmex.FileViewer
{
    /// <summary>
    /// 'Types' in .NET metadata may be simple types, coded token types, or tables.
    /// Thus this enum describes all tables and codedtoken types as well as describing all types.
    /// </summary>
    public enum Types
    {
        //Tables
        Module = 0,
        TypeRef = 1,
        TypeDef = 2,
        FieldPtr = 3,
        Field = 4,
        MethodPtr = 5,
        Method = 6,
        ParamPtr = 7,
        Param = 8,
        InterfaceImpl = 9,
        MemberRef = 10,
        Constant = 11,
        CustomAttribute = 12,
        FieldMarshal = 13,
        Permission = 14,
        ClassLayout = 15,
        FieldLayout = 16,
        StandAloneSig = 17,
        EventMap = 18,
        EventPtr = 19,
        Event = 20,
        PropertyMap = 21,
        PropertyPtr = 22,
        Property = 23,
        MethodSemantics = 24,
        MethodImpl = 25,
        ModuleRef = 26,
        TypeSpec = 27,
        ImplMap = 28, //lidin book is wrong again here?  It has enclog at 28
        FieldRVA = 29,
        ENCLog = 30,
        ENCMap = 31,
        Assembly = 32,
        AssemblyProcessor = 33,
        AssemblyOS = 34,
        AssemblyRef = 35,
        AssemblyRefProcessor = 36,
        AssemblyRefOS = 37,
        File = 38,
        ExportedType = 39,
        ManifestResource = 40,
        NestedClass = 41,
        TypeTyPar = 42,
        MethodTyPar = 43,

        //Coded Token Types
        TypeDefOrRef = 64,
        HasConstant = 65,
        CustomAttributeType = 66,
        HasSemantic = 67,
        ResolutionScope = 68,
        HasFieldMarshal = 69,
        HasDeclSecurity = 70,
        MemberRefParent = 71,
        MethodDefOrRef = 72,
        MemberForwarded = 73,
        Implementation = 74,
        HasCustomAttribute = 75,

        //Simple
        UInt16 = 97,
        UInt32 = 99,
        String = 101,
        Blob = 102,
        Guid = 103,
        UserString = 112
    }

    /// <summary>
    /// The information that specifies one MD Table column
    /// </summary>
    public class ColDesc
    {
        private Types _type;
        private string _name;

        public ColDesc(Types type, string name)
        {
            _type = type;
            _name = name;
        }

        public string Name
        {
            get
            {
                return _name;
            }
        }

        public Types Type
        {
            get
            {
                return _type;
            }
        }
    }

    /// <summary>
    /// An MD table.  Includes the schema (a coldesc array) and some rows that are 
    /// accessed via the indexer
    /// </summary>
    public class Table : IEnumerable
    {
        private Types _type;
        private ColDesc[] _colDescs;
        private MDTables _helper;
        private Row[] _rows;
        private int _rowSize;
        private Byte[] data;

        public Table(Types type, Types[] colTypes, String[] colNames, MDTables helper, BinaryReader reader)
        {
            _type = type;
            _helper = helper;

            _colDescs = new ColDesc[colTypes.Length];

            for (int i = 0; i < _colDescs.Length; i++)
            {
                _colDescs[i] = new ColDesc(colTypes[i], colNames[i]);
            }

            _rows = new Row[helper.GetTableRows(type)];

            _rowSize = 0;
            foreach (ColDesc cd in _colDescs)
            {
                _rowSize += _helper.SizeOfType(cd.Type);
            }

            data = reader.ReadBytes(_rowSize*Count);
        }

        public Types Type
        {
            get
            {
                return _type;
            }
        }

        public ColDesc[] ColDescs
        {
            get
            {
                return _colDescs;
            }
        }

        public int Count
        {
            get
            {
                return _rows.Length;
            }
        }

        public IEnumerator GetEnumerator()
        {
            return new Enumerator(this);
        }

        // Source code change by Andrea Bertolotto - 2006/08/22 - Start

        public Byte[] RawData
        {
            get
            {
                return this.data;
            }
        }

        public int RowSize
        {
            get
            {
                return this._rowSize;
            }
        }

        // Source code change by Andrea Bertolotto - 2006/08/22 - End

        public Row this[int index]
        {
            get
            {
                if (_rows[index] == null)
                {
                    _rows[index] = GetRow(index);
                }
                return _rows[index];
            }
        }

        private Row GetRow(int idx)
        {
            MemoryStream stream = new MemoryStream(data);
            BinaryReader reader = new BinaryReader(stream);
            reader.BaseStream.Position = _rowSize*idx;

            TableCell[] cells = new TableCell[_colDescs.Length];
            for (int i = 0; i < _colDescs.Length; i++)
            {
                //uint valu = ReadSingleValue(_colDescs[i].Type, reader);
                //cells[i] = new TableCell(valu, _helper);
                cells[i] = new TableCell(_colDescs[i].Type, reader, _helper);
            }

            stream.Close();

            return new Row(cells, this);
        }

        public override String ToString()
        {
            StringBuilder sb = new StringBuilder(100);
            sb.Append(_type.ToString());
            sb.Append(" (");
            sb.Append(_rows.Length);
            sb.Append(")    (");

            for (int i = 0; i < this._colDescs.Length; ++i)
            {
                sb.Append(_colDescs[i].Name);
                if (i < _colDescs.Length - 1)
                {
                    sb.Append("  --   ");
                }
            }

            sb.Append(")");

            return sb.ToString();
        }

        private class Enumerator : IEnumerator
        {
            private Table _table;
            private int _curr;

            public Enumerator(Table table)
            {
                _table = table;
                Reset();
            }

            public void Reset()
            {
                _curr = -1;
            }

            public Boolean MoveNext()
            {
                _curr++;
                return (_curr < _table.Count);
            }

            public Object Current
            {
                get
                {
                    return _table[_curr];
                }
            }
        }
    }

    /// <summary>
    /// An MD Table row
    /// </summary>
    public class Row
    {
        private Table _table;
        private TableCell[] _cells;

        public Row(TableCell[] cells, Table table)
        {
            _cells = cells;
            _table = table;
        }

        public Table Table
        {
            get
            {
                return _table;
            }
        }

        public TableCell this[int index]
        {
            get
            {
                return _cells[index];
            }
        }

        public string RawString()
        {
            StringBuilder sb = new StringBuilder(100);

            for (int i = 0; i < _cells.Length; ++i)
            {
                sb.Append(_cells[i].RawData.ToString("X8"));
                if (i < _cells.Length - 1)
                {
                    sb.Append("   --    ");
                }
            }

            return sb.ToString();
        }

        public string CookedString()
        {
            StringBuilder sb = new StringBuilder(100);

            for (int i = 0; i < this._cells.Length; ++i)
            {
                sb.Append(_cells[i].Data);
                if (i < _cells.Length - 1)
                {
                    sb.Append("   --    ");
                }
            }

            return sb.ToString();
        }

        public override String ToString()
        {
            return RawString();
        }
    }

    /// <summary>
    /// A cell in an MD table
    /// </summary>
    public class TableCell
    {
        private uint _rawData;
        private Types _type;
        private object _data;

        public TableCell(Types type, BinaryReader reader, MDTables helper)
        {
            _type = type;

            try
            {
                // Fixed
                if (type == Types.UInt16)
                {
                    _rawData = reader.ReadUInt16();
                }
                if (type == Types.UInt32)
                {
                    _rawData = reader.ReadUInt32();
                }

                // Heap
                if (type == Types.String)
                {
                    _rawData = ((helper.GetStringIndexSize() == 2) ? reader.ReadUInt16() : reader.ReadUInt32());
                }
                if (type == Types.Guid)
                {
                    _rawData = ((helper.GetGuidIndexSize() == 2) ? reader.ReadUInt16() : reader.ReadUInt32());
                }
                if (type == Types.Blob)
                {
                    _rawData = ((helper.GetBlobIndexSize() == 2) ? reader.ReadUInt16() : reader.ReadUInt32());
                }

                // Rid
                if ((int) type < 64)
                {
                    Table table = helper.GetTable(type);
                    _rawData = ((uint) type << 24) | ((table.Count < 65536) ? reader.ReadUInt16() : reader.ReadUInt32());
                }
		
                    // Coded token (may need to be uncompressed from 2-byte form)
                else if ((int) type < 97)
                {
                    int codedToken = (helper.SizeOfType(type) == 2) ? reader.ReadUInt16() : reader.ReadInt32();
                    Types[] referredTables = helper.CodedTokenTypes(type);

                    int tableIndex = (codedToken & ~(-1 << helper.CodedTokenBits(referredTables.Length)));
                    int index = (codedToken >> helper.CodedTokenBits(referredTables.Length));

                    int token = helper.ToToken(referredTables[tableIndex], index - 1);
                    _rawData = (uint) token;
                }

                _data = CreateData(helper);
            }
            catch (Exception)
            {
                _type = Types.String;
                _data = "Unreadable cell: " + type + " " + _rawData;
            }
        }

        public uint RawData
        {
            get
            {
                return _rawData;
            }
        }

        public object Data
        {
            get
            {
                return _data;
            }
        }

        private object CreateData(MDTables helper)
        {
            switch (_type)
            {
                case Types.UInt16:
                    return (ushort) _rawData;
                case Types.UInt32:
                    return _rawData;
                case Types.String:
                    return helper.GetString((int) _rawData);
                case Types.Guid:
                    return helper.GetGuid((int) _rawData);
                case Types.Blob:
                    return helper.GetBlob((int) _rawData);
                    //case Types.UserString:
                    //	return _helper.GetBlob((int)_rawData); 
            }

            if ((int) _type < 64)
            {
                return new RID(_type, _rawData);
            }

            return new CodedToken(_rawData);
        }
    }

    /// <summary>
    /// An RID. 'type' is not part of the RID's actual content but rather a note saying what
    /// sort of column the RID was found in and thus what table it must refer to
    /// </summary>
    public class RID
    {
        private uint _rawData;
        private Types _type;

        public RID(Types type, uint raw)
        {
            _rawData = raw;
            _type = type;
        }

        public uint Raw
        {
            get
            {
                return _rawData;
            }
        }

        public override string ToString()
        {
            return _type.ToString() + " " + _rawData.ToString("X8");
        }
    }

    /// <summary>
    /// A coded token.  As with the RID class, 'type' is not actually data held in the coded token but a note
    /// telling us what kind of column the ct was found in and thus what kind of ct it must be
    /// </summary>
    public class CodedToken
    {
        private uint _rawData;

        public CodedToken(uint raw)
        {
            _rawData = raw;
        }

        public uint Raw
        {
            get
            {
                return _rawData;
            }
        }

        public override string ToString()
        {
            Types t = (Types) ((_rawData & 0xff000000) >> 24);

            return t.ToString() + " " + (_rawData & 0x00ffffff).ToString("X8");
        }
    }

    /// <summary>
    /// The collection of all md tables in the file
    /// </summary>
    public class MDTables
    {
        private Hashtable _ctok;
        private Table[] _td;
        private int[] _codedTokenBits;
        private MModule _mod;

        public MDTables(BinaryReader reader, MModule mod)
        {
            _mod = mod;

            SetupSchema(reader);

            //reader may now be accessed randomly to fill in actual strings etc.
        }

        public Table[] Tables
        {
            get
            {
                return _td;
            }
        }

        public Types[] CodedTokenTypes(Types t)
        {
            return (Types[]) _ctok[t];
        }

        public int CodedTokenBits(Types t)
        {
            return _codedTokenBits[(int) t];
        }

        public int CodedTokenBits(int i)
        {
            return _codedTokenBits[i];
        }

        public Table GetTable(int token)
        {
            int idx = token >> 24;
            if (idx >= _td.Length)
            {
                throw new ModException("MDTables: No such table");
            }
            return _td[idx];
        }

        public Table GetTable(Types type)
        {
            int idx = (int) type;
            if (idx >= _td.Length)
            {
                throw new ModException("MDTables: No such table");
            }
            return _td[idx];
        }

        public uint GetTableRows(Types t)
        {
            int idx = (int) t;
            if (idx < 0 || idx > _mod.ModHeaders.MetaDataTableHeader.TableLengths.Length)
            {
                throw new ModException("MDHelper: Tried to get length of nonexistant table");
            }
            return _mod.ModHeaders.MetaDataTableHeader.TableLengths[(int) t];
        }

        public int ToToken(Types tableType, int index)
        {
            int type = (int) tableType;
            index++;
            if (index < 0)
            {
                return -1;
            }
            return ((type << 24) | index);
        }

        public string GetString(int offset)
        {
            if (offset < 0 || offset > _mod.StringHeap.Length)
            {
                throw new ModException("MDTables: string offs out of range.");
            }
            string s = (string) _mod.StringHeap.GetByOffset(offset);
            return s;
        }

        public MDBlob GetBlob(int offset)
        {
            if (offset < 0 || offset > _mod.BlobHeap.Length)
            {
                throw new ModException("MDTables: blob offs out of range.");
            }
            return (MDBlob) _mod.BlobHeap.GetByOffset(offset);
        }

        //hmm.  'offsets' in the guid heap actually seem to be 1-based indexes?  And an index of 0 means empty?  
        //ITS NOT LIKE THIS IS ACTUALLY ***DOCUMENTED*** ANYWHERE AFTER ALL.
        public MDGUID GetGuid(int offset)
        {
            if (offset == 0)
            {
                return MDGUID.Empty;
            }
            if (offset < 1 || offset > _mod.GUIDHeap.Length/16)
            {
                throw new ModException("MDTables: GUID offs out of range.");
            }
            return (MDGUID) _mod.GUIDHeap[offset - 1];
        }

        public int GetStringIndexSize()
        {
            return ((_mod.ModHeaders.MetaDataTableHeader.HeapOffsetSizes & 0x01) != 0) ? 4 : 2;
        }

        public int GetGuidIndexSize()
        {
            return ((_mod.ModHeaders.MetaDataTableHeader.HeapOffsetSizes & 0x02) != 0) ? 4 : 2;
        }

        public int GetBlobIndexSize()
        {
            return ((_mod.ModHeaders.MetaDataTableHeader.HeapOffsetSizes & 0x04) != 0) ? 4 : 2;
        }

        //Note that the size of a type cannot be known until at least table sizes are loaded from file
        public int SizeOfType(Types type)
        {
            // Fixed
            if (type == Types.UInt16)
            {
                return 2;
            }
            if (type == Types.UInt32)
            {
                return 4;
            }

            // Heap
            if (type == Types.String)
            {
                return GetStringIndexSize();
            }
            if (type == Types.Blob)
            {
                return GetBlobIndexSize();
            }
            if (type == Types.Guid)
            {
                return GetGuidIndexSize();
            }

            // RID
            if ((int) type < 64)
            {
                uint rows = GetTableRows(type);
                return (rows < 65536) ? 2 : 4;
            }

            // CodedToken
            Types[] referredTypes = CodedTokenTypes(type);
            if (referredTypes != null)
            {
                uint maxRows = 0;
                foreach (Types referredType in referredTypes)
                {
                    if (referredType != Types.UserString) //but what if there is a large user string table?
                    {
                        uint rows = GetTableRows(referredType);
                        if (maxRows < rows)
                        {
                            maxRows = rows;
                        }
                    }
                }

                maxRows = maxRows << CodedTokenBits(referredTypes.Length);
                return (maxRows < 65536) ? 2 : 4;
            }

            throw new ModException("Table: Sizeof invalid token type.");
        }

        /// <summary>
        /// .NET expects the consumer of the metadata to know the schema of the metadata database.
        /// that schema is represented here as an array of 'table' objs which will be filled with actual
        /// rows elsewhere.
        /// </summary>
        /// <param name="reader"></param>
        private void SetupSchema(BinaryReader reader)
        {
            //number of bits in coded token tag for a coded token that refers to n tables.
            //values 5-17 are not used :I
            _codedTokenBits = new[] {0, 1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5};

            //Hash telling us what tables a given coded token type can refer to
            _ctok = new Hashtable();
            _ctok[Types.TypeDefOrRef] = new[] {Types.TypeDef, Types.TypeRef, Types.TypeSpec};
            _ctok[Types.HasConstant] = new[] {Types.Field, Types.Param, Types.Property};
            _ctok[Types.CustomAttributeType] = new[] {Types.TypeRef, Types.TypeDef, Types.Method, Types.MemberRef, Types.UserString};
            _ctok[Types.HasSemantic] = new[] {Types.Event, Types.Property};
            _ctok[Types.ResolutionScope] = new[] {Types.Module, Types.ModuleRef, Types.AssemblyRef, Types.TypeRef};
            _ctok[Types.HasFieldMarshal] = new[] {Types.Field, Types.Param};
            _ctok[Types.HasDeclSecurity] = new[] {Types.TypeDef, Types.Method, Types.Assembly};
            _ctok[Types.MemberRefParent] = new[] {Types.TypeDef, Types.TypeRef, Types.ModuleRef, Types.Method, Types.TypeSpec};
            _ctok[Types.MethodDefOrRef] = new[] {Types.Method, Types.MemberRef};
            _ctok[Types.MemberForwarded] = new[] {Types.Field, Types.Method};
            _ctok[Types.Implementation] = new[] {Types.File, Types.AssemblyRef, Types.ExportedType};
            _ctok[Types.HasCustomAttribute] = new[]
                                              {
                                                  Types.Method, Types.Field, Types.TypeRef, Types.TypeDef, Types.Param, Types.InterfaceImpl,
                                                  Types.MemberRef, Types.Module, Types.Permission, Types.Property, Types.Event, Types.StandAloneSig,
                                                  Types.ModuleRef, Types.TypeSpec, Types.Assembly, Types.AssemblyRef, Types.File, Types.ExportedType,
                                                  Types.ManifestResource
                                              };

            //md db schema is represented in the arguments to table constructors...
            _td = new Table[0x2C];
            _td[0x00] = new Table(Types.Module, new[] {Types.UInt16, Types.String, Types.Guid, Types.Guid, Types.Guid},
                                  new[] {"Generation", "Name", "Mvid", "EncId", "EncBaseId"}, this, reader);
            _td[0x01] = new Table(Types.TypeRef, new[] {Types.ResolutionScope, Types.String, Types.String},
                                  new[] {"ResolutionScope", "Name", "Namespace"}, this, reader);
            _td[0x02] = new Table(Types.TypeDef, new[] {Types.UInt32, Types.String, Types.String, Types.TypeDefOrRef, Types.Field, Types.Method},
                                  new[] {"Flags", "Name", "Namespace", "Extends", "FieldList", "MethodList"}, this, reader);
            _td[0x03] = new Table(Types.FieldPtr, new[] {Types.Field}, new[] {"Field"}, this, reader);
            _td[0x04] = new Table(Types.Field, new[] {Types.UInt16, Types.String, Types.Blob}, new[] {"Flags", "Name", "Signature"}, this, reader);
            _td[0x05] = new Table(Types.MethodPtr, new[] {Types.Method}, new[] {"Method"}, this, reader);
            _td[0x06] = new Table(Types.Method, new[] {Types.UInt32, Types.UInt16, Types.UInt16, Types.String, Types.Blob, Types.Param},
                                  new[] {"RVA", "ImplFlags", "Flags", "Name", "Signature", "ParamList"}, this, reader);
            _td[0x07] = new Table(Types.ParamPtr, new[] {Types.Param}, new[] {"Param"}, this, reader);
            _td[0x08] = new Table(Types.Param, new[] {Types.UInt16, Types.UInt16, Types.String}, new[] {"Flags", "Sequence", "Name"}, this, reader);
            _td[0x09] = new Table(Types.InterfaceImpl, new[] {Types.TypeDef, Types.TypeDefOrRef}, new[] {"Class", "Interface"}, this, reader);
            _td[0x0A] = new Table(Types.MemberRef, new[] {Types.MemberRefParent, Types.String, Types.Blob}, new[] {"Class", "Name", "Signature"}, this,
                                  reader);
            _td[0x0B] = new Table(Types.Constant, new[] {Types.UInt16, Types.HasConstant, Types.Blob}, new[] {"Type", "Parent", "Value"}, this, reader);
            _td[0x0C] = new Table(Types.CustomAttribute, new[] {Types.HasCustomAttribute, Types.CustomAttributeType, Types.Blob},
                                  new[] {"Type", "Parent", "Value"}, this, reader);
            _td[0x0D] = new Table(Types.FieldMarshal, new[] {Types.HasFieldMarshal, Types.Blob}, new[] {"Parent", "Native"}, this, reader);
            _td[0x0E] = new Table(Types.Permission, new[] {Types.UInt16, Types.HasDeclSecurity, Types.Blob},
                                  new[] {"Action", "Parent", "PermissionSet"}, this, reader);
            _td[0x0F] = new Table(Types.ClassLayout, new[] {Types.UInt16, Types.UInt32, Types.TypeDef}, new[] {"PackingSize", "ClassSize", "Parent"},
                                  this, reader);
            _td[0x10] = new Table(Types.FieldLayout, new[] {Types.UInt32, Types.Field}, new[] {"Offset", "Field"}, this, reader);
            _td[0x11] = new Table(Types.StandAloneSig, new[] {Types.Blob}, new[] {"Signature"}, this, reader);
            _td[0x12] = new Table(Types.EventMap, new[] {Types.TypeDef, Types.Event}, new[] {"Parent", "EventList"}, this, reader);
            _td[0x13] = new Table(Types.EventPtr, new[] {Types.Event}, new[] {"Event"}, this, reader);
            _td[0x14] = new Table(Types.Event, new[] {Types.UInt16, Types.String, Types.TypeDefOrRef}, new[] {"EventFlags", "Name", "EventType"}, this,
                                  reader);
            _td[0x15] = new Table(Types.PropertyMap, new[] {Types.TypeDef, Types.Property}, new[] {"Parent", "PropertyList"}, this, reader);
            _td[0x16] = new Table(Types.PropertyPtr, new[] {Types.Property}, new[] {"Property"}, this, reader);
            _td[0x17] = new Table(Types.Property, new[] {Types.UInt16, Types.String, Types.Blob}, new[] {"PropFlags", "Name", "Type"}, this, reader);
            _td[0x18] = new Table(Types.MethodSemantics, new[] {Types.UInt16, Types.Method, Types.HasSemantic},
                                  new[] {"Semantic", "Method", "Association"}, this, reader);
            _td[0x19] = new Table(Types.MethodImpl, new[] {Types.TypeDef, Types.MethodDefOrRef, Types.MethodDefOrRef},
                                  new[] {"Class", "MethodBody", "MethodDeclaration"}, this, reader);
            _td[0x1A] = new Table(Types.ModuleRef, new[] {Types.String}, new[] {"Name"}, this, reader);
            _td[0x1B] = new Table(Types.TypeSpec, new[] {Types.Blob}, new[] {"Signature"}, this, reader);
            _td[0x1C] = new Table(Types.ImplMap, new[] {Types.UInt16, Types.MemberForwarded, Types.String, Types.ModuleRef},
                                  new[] {"MappingFlags", "MemberForwarded", "ImportName", "ImportScope"}, this, reader);
            _td[0x1D] = new Table(Types.FieldRVA, new[] {Types.UInt32, Types.Field}, new[] {"RVA", "Field"}, this, reader);
            _td[0x1E] = new Table(Types.ENCLog, new[] {Types.UInt32, Types.UInt32}, new[] {"Token", "FuncCode"}, this, reader);
            _td[0x1F] = new Table(Types.ENCMap, new[] {Types.UInt32}, new[] {"Token"}, this, reader);
            _td[0x20] = new Table(Types.Assembly,
                                  new[]
                                  {
                                      Types.UInt32, Types.UInt16, Types.UInt16, Types.UInt16, Types.UInt16, Types.UInt32, Types.Blob, Types.String,
                                      Types.String
                                  },
                                  new[]
                                  {
                                      "HashAlgId", "MajorVersion", "MinorVersion", "BuildNumber", "RevisionNumber", "Flags", "PublicKey", "Name",
                                      "Locale"
                                  }, this, reader);
            _td[0x21] = new Table(Types.AssemblyProcessor, new[] {Types.UInt32}, new[] {"Processor"}, this, reader);
            _td[0x22] = new Table(Types.AssemblyOS, new[] {Types.UInt32, Types.UInt32, Types.UInt32},
                                  new[] {"OSPlatformId", "OSMajorVersion", "OSMinorVersion"}, this, reader);
            _td[0x23] = new Table(Types.AssemblyRef,
                                  new[]
                                  {
                                      Types.UInt16, Types.UInt16, Types.UInt16, Types.UInt16, Types.UInt32, Types.Blob, Types.String, Types.String,
                                      Types.Blob
                                  },
                                  new[]
                                  {
                                      "MajorVersion", "MinorVersion", "BuildNumber", "RevisionNumber", "Flags", "PublicKeyOrToken", "Name", "Locale",
                                      "HashValue"
                                  }, this, reader);
            _td[0x24] = new Table(Types.AssemblyRefProcessor, new[] {Types.UInt32, Types.AssemblyRef}, new[] {"Processor", "AssemblyRef"}, this,
                                  reader);
            _td[0x25] = new Table(Types.AssemblyRefOS, new[] {Types.UInt32, Types.UInt32, Types.UInt32, Types.AssemblyRef},
                                  new[] {"OSPlatformId", "OSMajorVersion", "OSMinorVersion", "AssemblyRef"}, this, reader);
            _td[0x26] = new Table(Types.File, new[] {Types.UInt32, Types.String, Types.Blob}, new[] {"Flags", "Name", "HashValue"}, this, reader);
            _td[0x27] = new Table(Types.ExportedType, new[] {Types.UInt32, Types.UInt32, Types.String, Types.String, Types.Implementation},
                                  new[] {"Flags", "TypeDefId", "TypeName", "TypeNamespace", "TypeImplementation"}, this, reader);
            _td[0x28] = new Table(Types.ManifestResource, new[] {Types.UInt32, Types.UInt32, Types.String, Types.Implementation},
                                  new[] {"Offset", "Flags", "Name", "Implementation"}, this, reader);
            _td[0x29] = new Table(Types.NestedClass, new[] {Types.TypeDef, Types.TypeDef}, new[] {"NestedClass", "EnclosingClass"}, this, reader);
            //unused TyPar tables taken from Roeder's reflector... are these documented anywhere?  Since they are always empty, does it matter
            _td[0x2A] = new Table(Types.TypeTyPar, new[] {Types.UInt16, Types.TypeDef, Types.TypeDefOrRef, Types.String},
                                  new[] {"Number", "Class", "Bound", "Name"}, this, reader);
            _td[0x2B] = new Table(Types.MethodTyPar, new[] {Types.UInt16, Types.Method, Types.TypeDefOrRef, Types.String},
                                  new[] {"Number", "Method", "Bound", "Name"}, this, reader);
        }
    }
}