some nullability

src/SharpCompress/Common/Rar/CryptKey3.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Security.Cryptography;
 using System.Text;
 using SharpCompress.Common.Rar.Headers;
@@ -12,7 +10,7 @@ internal class CryptKey3 : ICryptKey
 
     private string _password;
 
-    public CryptKey3(string password) => _password = password ?? "";
+    public CryptKey3(string? password) => _password = password ?? "";
 
     public ICryptoTransform Transformer(byte[] salt)
     {

src/SharpCompress/Common/Rar/Headers/ArchiveCryptHeader.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Threading;
 using System.Threading.Tasks;
 using SharpCompress.Common.Rar;

src/SharpCompress/Common/Rar/Headers/ArchiveCryptHeader.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using SharpCompress.Common.Rar;
 using SharpCompress.IO;
 

src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.Async.cs

@@ -65,7 +65,7 @@ public partial class RarHeaderFactory
             if (_isRar5 && _cryptInfo != null)
             {
                 await _cryptInfo.ReadInitVAsync(new AsyncMarkingBinaryReader(stream));
-                var _headerKey = new CryptKey5(Options.Password!, _cryptInfo);
+                var _headerKey = new CryptKey5(Options.Password.NotNull(), _cryptInfo);
 
                 reader = await AsyncRarCryptoBinaryReader.Create(
                     stream,
@@ -189,7 +189,7 @@ public partial class RarHeaderFactory
                                             Options.Password,
                                             fh.Rar5CryptoInfo.NotNull()
                                         )
-                                        : new CryptKey3(Options.Password)
+                                        : new CryptKey3(Options.Password.NotNull())
                                 );
                             }
                         }

src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs

@@ -62,7 +62,7 @@ public partial class RarHeaderFactory
             if (_isRar5 && _cryptInfo != null)
             {
                 _cryptInfo.ReadInitV(new MarkingBinaryReader(stream));
-                var _headerKey = new CryptKey5(Options.Password!, _cryptInfo);
+                var _headerKey = new CryptKey5(Options.Password.NotNull(), _cryptInfo);
 
                 reader = RarCryptoBinaryReader.Create(stream, _headerKey, _cryptInfo.Salt);
             }

src/SharpCompress/Common/SevenZip/ArchiveDatabase.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;

src/SharpCompress/Common/SevenZip/ArchiveDatabase.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -18,7 +16,7 @@ internal partial class ArchiveDatabase
     internal List<long> _packSizes = new();
     internal List<uint?> _packCrCs = new();
     internal List<CFolder> _folders = new();
-    internal List<int> _numUnpackStreamsVector;
+    internal List<int>? _numUnpackStreamsVector;
     internal List<CFileItem> _files = new();
 
     internal List<long> _packStreamStartPositions = new();
@@ -47,7 +45,7 @@ internal partial class ArchiveDatabase
         _packSizes.Count == 0
         && _packCrCs.Count == 0
         && _folders.Count == 0
-        && _numUnpackStreamsVector.Count == 0
+        && (_numUnpackStreamsVector?.Count ?? 0) == 0
         && _files.Count == 0;
 
     private void FillStartPos()
@@ -94,7 +92,7 @@ internal partial class ArchiveDatabase
 
                     _folderStartFileIndex.Add(i); // check it
 
-                    if (_numUnpackStreamsVector![folderIndex] != 0)
+                    if (_numUnpackStreamsVector.NotNull()[folderIndex] != 0)
                     {
                         break;
                     }

src/SharpCompress/Common/SevenZip/CCoderInfo.cs

@@ -1,11 +1,9 @@
-#nullable disable
-
 namespace SharpCompress.Common.SevenZip;
 
 internal class CCoderInfo
 {
     internal CMethodId _methodId;
-    internal byte[] _props;
+    internal byte[]? _props;
     internal int _numInStreams;
     internal int _numOutStreams;
 }

src/SharpCompress/Common/SevenZip/CFileItem.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 
 namespace SharpCompress.Common.SevenZip;
@@ -10,7 +8,7 @@ internal class CFileItem
     public uint? Attrib { get; internal set; }
     public uint? ExtendedAttrib { get; internal set; }
     public uint? Crc { get; internal set; }
-    public string Name { get; internal set; }
+    public string? Name { get; internal set; }
 
     public bool HasStream { get; internal set; }
     public bool IsDir { get; internal set; }

src/SharpCompress/Common/SevenZip/SevenZipFilePart.cs

@@ -34,7 +34,7 @@ internal class SevenZipFilePart : FilePart
     internal CFileItem Header { get; }
     internal CFolder? Folder { get; }
 
-    internal override string FilePartName => Header.Name;
+    internal override string? FilePartName => Header.Name;
 
     internal override Stream? GetRawStream() => null;
 

src/SharpCompress/Compressors/ADC/ADCStream.Async.cs

@@ -24,8 +24,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
-#nullable disable
-
 using System;
 using System.IO;
 using System.Threading;
@@ -78,11 +76,12 @@ public sealed partial class ADCStream
         var toCopy = count;
         var copied = 0;
 
-        while (_outPosition + toCopy >= _outBuffer.Length)
+        var outBuf = _outBuffer.NotNull();
+        while (_outPosition + toCopy >= outBuf.Length)
         {
             cancellationToken.ThrowIfCancellationRequested();
-            var piece = _outBuffer.Length - _outPosition;
-            Array.Copy(_outBuffer, _outPosition, buffer, inPosition, piece);
+            var piece = outBuf.Length - _outPosition;
+            Array.Copy(outBuf, _outPosition, buffer, inPosition, piece);
             inPosition += piece;
             copied += piece;
             _position += piece;
@@ -97,9 +96,10 @@ public sealed partial class ADCStream
             {
                 return copied;
             }
+            outBuf = _outBuffer;
         }
 
-        Array.Copy(_outBuffer, _outPosition, buffer, inPosition, toCopy);
+        Array.Copy(outBuf, _outPosition, buffer, inPosition, toCopy);
         _outPosition += toCopy;
         _position += toCopy;
         copied += toCopy;

src/SharpCompress/Compressors/ADC/ADCStream.cs

@@ -24,8 +24,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
-#nullable disable
-
 using System;
 using System.IO;
 using System.Threading;
@@ -56,7 +54,7 @@ public sealed partial class ADCStream : Stream
     /// <summary>
     /// Buffer with currently used chunk of decompressed data
     /// </summary>
-    private byte[] _outBuffer;
+    private byte[]? _outBuffer;
 
     /// <summary>
     /// Position in buffer of decompressed data
@@ -139,10 +137,11 @@ public sealed partial class ADCStream : Stream
         var toCopy = count;
         var copied = 0;
 
-        while (_outPosition + toCopy >= _outBuffer.Length)
+        while (_outPosition + toCopy >= _outBuffer.NotNull().Length)
         {
-            var piece = _outBuffer.Length - _outPosition;
-            Array.Copy(_outBuffer, _outPosition, buffer, inPosition, piece);
+            var outBuf = _outBuffer.NotNull();
+            var piece = outBuf.Length - _outPosition;
+            Array.Copy(outBuf, _outPosition, buffer, inPosition, piece);
             inPosition += piece;
             copied += piece;
             _position += piece;
@@ -155,7 +154,7 @@ public sealed partial class ADCStream : Stream
             }
         }
 
-        Array.Copy(_outBuffer, _outPosition, buffer, inPosition, toCopy);
+        Array.Copy(_outBuffer.NotNull(), _outPosition, buffer, inPosition, toCopy);
         _outPosition += toCopy;
         _position += toCopy;
         copied += toCopy;

src/SharpCompress/Compressors/LZMA/DecoderStream.cs

@@ -1,3 +1,5 @@
+#nullable disable
+
 using System;
 using System.IO;
 using System.Threading;

src/SharpCompress/Compressors/LZMA/LZ/LzBinTree.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.IO;
 
@@ -11,8 +9,8 @@ internal sealed class BinTree : InWindow
     private uint _cyclicBufferSize;
     private uint _matchMaxLen;
 
-    private uint[] _son;
-    private uint[] _hash;
+    private uint[]? _son;
+    private uint[]? _hash;
 
     private uint _cutValue = 0xFF;
     private uint _hashMask;
@@ -56,9 +54,10 @@ internal sealed class BinTree : InWindow
     public new void Init()
     {
         base.Init();
+        var hash = _hash.NotNull();
         for (uint i = 0; i < _hashSizeSum; i++)
         {
-            _hash[i] = K_EMPTY_HASH_VALUE;
+            hash[i] = K_EMPTY_HASH_VALUE;
         }
         _cyclicBufferPos = 0;
         ReduceOffsets(-1);
@@ -141,6 +140,8 @@ internal sealed class BinTree : InWindow
 
     public uint GetMatches(uint[] distances)
     {
+        var son = _son.NotNull();
+        var hash = _hash.NotNull();
         uint lenLimit;
         if (_pos + _matchMaxLen <= _streamPos)
         {
@@ -164,26 +165,27 @@ internal sealed class BinTree : InWindow
             hash2Value = 0,
             hash3Value = 0;
 
+        var bufferBase = _bufferBase.NotNull();
         if (_hashArray)
         {
-            var temp = Crc.TABLE[_bufferBase[cur]] ^ _bufferBase[cur + 1];
+            var temp = Crc.TABLE[bufferBase[cur]] ^ bufferBase[cur + 1];
             hash2Value = temp & (K_HASH2_SIZE - 1);
-            temp ^= ((uint)(_bufferBase[cur + 2]) << 8);
+            temp ^= ((uint)(bufferBase[cur + 2]) << 8);
             hash3Value = temp & (K_HASH3_SIZE - 1);
-            hashValue = (temp ^ (Crc.TABLE[_bufferBase[cur + 3]] << 5)) & _hashMask;
+            hashValue = (temp ^ (Crc.TABLE[bufferBase[cur + 3]] << 5)) & _hashMask;
         }
         else
         {
-            hashValue = _bufferBase[cur] ^ ((uint)(_bufferBase[cur + 1]) << 8);
+            hashValue = bufferBase[cur] ^ ((uint)(bufferBase[cur + 1]) << 8);
         }
 
-        var curMatch = _hash[_kFixHashSize + hashValue];
+        var curMatch = hash[_kFixHashSize + hashValue];
         if (_hashArray)
         {
-            var curMatch2 = _hash[hash2Value];
-            var curMatch3 = _hash[K_HASH3_OFFSET + hash3Value];
-            _hash[hash2Value] = _pos;
-            _hash[K_HASH3_OFFSET + hash3Value] = _pos;
+            var curMatch2 = hash[hash2Value];
+            var curMatch3 = hash[K_HASH3_OFFSET + hash3Value];
+            hash[hash2Value] = _pos;
+            hash[K_HASH3_OFFSET + hash3Value] = _pos;
             if (curMatch2 > matchMinPos)
             {
                 if (_bufferBase[_bufferOffset + curMatch2] == _bufferBase[cur])
@@ -212,7 +214,7 @@ internal sealed class BinTree : InWindow
             }
         }
 
-        _hash[_kFixHashSize + hashValue] = _pos;
+        hash[_kFixHashSize + hashValue] = _pos;
 
         var ptr0 = (_cyclicBufferPos << 1) + 1;
         var ptr1 = (_cyclicBufferPos << 1);
@@ -242,7 +244,7 @@ internal sealed class BinTree : InWindow
         {
             if (curMatch <= matchMinPos || count-- == 0)
             {
-                _son[ptr0] = _son[ptr1] = K_EMPTY_HASH_VALUE;
+                son[ptr0] = son[ptr1] = K_EMPTY_HASH_VALUE;
                 break;
             }
             var delta = _pos - curMatch;
@@ -270,24 +272,24 @@ internal sealed class BinTree : InWindow
                     distances[offset++] = delta - 1;
                     if (len == lenLimit)
                     {
-                        _son[ptr1] = _son[cyclicPos];
-                        _son[ptr0] = _son[cyclicPos + 1];
+                        son[ptr1] = son[cyclicPos];
+                        son[ptr0] = son[cyclicPos + 1];
                         break;
                     }
                 }
             }
             if (_bufferBase[pby1 + len] < _bufferBase[cur + len])
             {
-                _son[ptr1] = curMatch;
+                son[ptr1] = curMatch;
                 ptr1 = cyclicPos + 1;
-                curMatch = _son[ptr1];
+                curMatch = son[ptr1];
                 len1 = len;
             }
             else
             {
-                _son[ptr0] = curMatch;
+                son[ptr0] = curMatch;
                 ptr0 = cyclicPos;
-                curMatch = _son[ptr0];
+                curMatch = son[ptr0];
                 len0 = len;
             }
         }
@@ -297,6 +299,8 @@ internal sealed class BinTree : InWindow
 
     public void Skip(uint num)
     {
+        var son = _son.NotNull();
+        var hash = _hash.NotNull();
         do
         {
             uint lenLimit;
@@ -323,10 +327,10 @@ internal sealed class BinTree : InWindow
             {
                 var temp = Crc.TABLE[_bufferBase[cur]] ^ _bufferBase[cur + 1];
                 var hash2Value = temp & (K_HASH2_SIZE - 1);
-                _hash[hash2Value] = _pos;
+                hash[hash2Value] = _pos;
                 temp ^= ((uint)(_bufferBase[cur + 2]) << 8);
                 var hash3Value = temp & (K_HASH3_SIZE - 1);
-                _hash[K_HASH3_OFFSET + hash3Value] = _pos;
+                hash[K_HASH3_OFFSET + hash3Value] = _pos;
                 hashValue = (temp ^ (Crc.TABLE[_bufferBase[cur + 3]] << 5)) & _hashMask;
             }
             else
@@ -334,8 +338,8 @@ internal sealed class BinTree : InWindow
                 hashValue = _bufferBase[cur] ^ ((uint)(_bufferBase[cur + 1]) << 8);
             }
 
-            var curMatch = _hash[_kFixHashSize + hashValue];
-            _hash[_kFixHashSize + hashValue] = _pos;
+            var curMatch = hash[_kFixHashSize + hashValue];
+            hash[_kFixHashSize + hashValue] = _pos;
 
             var ptr0 = (_cyclicBufferPos << 1) + 1;
             var ptr1 = (_cyclicBufferPos << 1);
@@ -349,7 +353,7 @@ internal sealed class BinTree : InWindow
             {
                 if (curMatch <= matchMinPos || count-- == 0)
                 {
-                    _son[ptr0] = _son[ptr1] = K_EMPTY_HASH_VALUE;
+                    son[ptr0] = son[ptr1] = K_EMPTY_HASH_VALUE;
                     break;
                 }
 
@@ -374,23 +378,23 @@ internal sealed class BinTree : InWindow
                     }
                     if (len == lenLimit)
                     {
-                        _son[ptr1] = _son[cyclicPos];
-                        _son[ptr0] = _son[cyclicPos + 1];
+                        son[ptr1] = son[cyclicPos];
+                        son[ptr0] = son[cyclicPos + 1];
                         break;
                     }
                 }
                 if (_bufferBase[pby1 + len] < _bufferBase[cur + len])
                 {
-                    _son[ptr1] = curMatch;
+                    son[ptr1] = curMatch;
                     ptr1 = cyclicPos + 1;
-                    curMatch = _son[ptr1];
+                    curMatch = son[ptr1];
                     len1 = len;
                 }
                 else
                 {
-                    _son[ptr0] = curMatch;
+                    son[ptr0] = curMatch;
                     ptr0 = cyclicPos;
-                    curMatch = _son[ptr0];
+                    curMatch = son[ptr0];
                     len0 = len;
                 }
             }
@@ -418,8 +422,8 @@ internal sealed class BinTree : InWindow
     private void Normalize()
     {
         var subValue = _pos - _cyclicBufferSize;
-        NormalizeLinks(_son, _cyclicBufferSize * 2, subValue);
-        NormalizeLinks(_hash, _hashSizeSum, subValue);
+        NormalizeLinks(_son.NotNull(), _cyclicBufferSize * 2, subValue);
+        NormalizeLinks(_hash.NotNull(), _hashSizeSum, subValue);
         ReduceOffsets((int)subValue);
     }
 

src/SharpCompress/Compressors/LZMA/LzmaDecoder.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.IO;
 using System.Threading;
@@ -25,6 +23,7 @@ public partial class Decoder : ICoder, ISetDecoderProperties
             )
             {
                 return await _lowCoder[posState]
+                    .NotNull()
                     .DecodeAsync(rangeDecoder, cancellationToken)
                     .ConfigureAwait(false);
             }
@@ -35,6 +34,7 @@ public partial class Decoder : ICoder, ISetDecoderProperties
             )
             {
                 symbol += await _midCoder[posState]
+                    .NotNull()
                     .DecodeAsync(rangeDecoder, cancellationToken)
                     .ConfigureAwait(false);
             }
@@ -108,7 +108,8 @@ public partial class Decoder : ICoder, ISetDecoderProperties
             byte prevByte,
             CancellationToken cancellationToken = default
         ) =>
-            await _coders[GetState(pos, prevByte)]
+            await _coders
+                .NotNull()[GetState(pos, prevByte)]
                 .DecodeNormalAsync(rangeDecoder, cancellationToken)
                 .ConfigureAwait(false);
 
@@ -119,7 +120,8 @@ public partial class Decoder : ICoder, ISetDecoderProperties
             byte matchByte,
             CancellationToken cancellationToken = default
         ) =>
-            await _coders[GetState(pos, prevByte)]
+            await _coders
+                .NotNull()[GetState(pos, prevByte)]
                 .DecodeWithMatchByteAsync(rangeDecoder, matchByte, cancellationToken)
                 .ConfigureAwait(false);
     }
@@ -137,26 +139,26 @@ public partial class Decoder : ICoder, ISetDecoderProperties
         {
             CreateDictionary();
         }
-        await _outWindow.InitAsync(outStream);
+        await _outWindow.NotNull().InitAsync(outStream);
         if (outSize > 0)
         {
-            _outWindow.SetLimit(outSize);
+            _outWindow.NotNull().SetLimit(outSize);
         }
         else
         {
-            _outWindow.SetLimit(long.MaxValue - _outWindow.Total);
+            _outWindow.NotNull().SetLimit(long.MaxValue - _outWindow.NotNull().Total);
         }
 
         var rangeDecoder = new RangeCoder.Decoder();
         await rangeDecoder.InitAsync(inStream, cancellationToken).ConfigureAwait(false);
 
-        await CodeAsync(_dictionarySize, _outWindow, rangeDecoder, cancellationToken)
+        await CodeAsync(_dictionarySize, _outWindow.NotNull(), rangeDecoder, cancellationToken)
             .ConfigureAwait(false);
 
-        await _outWindow.ReleaseStreamAsync(cancellationToken).ConfigureAwait(false);
+        await _outWindow.NotNull().ReleaseStreamAsync(cancellationToken).ConfigureAwait(false);
         rangeDecoder.ReleaseStream();
 
-        await _outWindow.DisposeAsync().ConfigureAwait(false);
+        await _outWindow.NotNull().DisposeAsync().ConfigureAwait(false);
         _outWindow = null;
     }
 
@@ -339,6 +341,6 @@ public partial class Decoder : ICoder, ISetDecoderProperties
         {
             CreateDictionary();
         }
-        await _outWindow.TrainAsync(stream);
+        await _outWindow.NotNull().TrainAsync(stream);
     }
 }

src/SharpCompress/Compressors/LZMA/LzmaDecoder.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
@@ -15,8 +13,12 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
     {
         private BitDecoder _choice = new();
         private BitDecoder _choice2 = new();
-        private readonly BitTreeDecoder[] _lowCoder = new BitTreeDecoder[Base.K_NUM_POS_STATES_MAX];
-        private readonly BitTreeDecoder[] _midCoder = new BitTreeDecoder[Base.K_NUM_POS_STATES_MAX];
+        private readonly BitTreeDecoder?[] _lowCoder = new BitTreeDecoder?[
+            Base.K_NUM_POS_STATES_MAX
+        ];
+        private readonly BitTreeDecoder?[] _midCoder = new BitTreeDecoder?[
+            Base.K_NUM_POS_STATES_MAX
+        ];
         private BitTreeDecoder _highCoder = new(Base.K_NUM_HIGH_LEN_BITS);
         private uint _numPosStates;
 
@@ -35,8 +37,8 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
             _choice.Init();
             for (uint posState = 0; posState < _numPosStates; posState++)
             {
-                _lowCoder[posState].Init();
-                _midCoder[posState].Init();
+                _lowCoder[posState].NotNull().Init();
+                _midCoder[posState].NotNull().Init();
             }
             _choice2.Init();
             _highCoder.Init();
@@ -46,12 +48,12 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
         {
             if (_choice.Decode(rangeDecoder) == 0)
             {
-                return _lowCoder[posState].Decode(rangeDecoder);
+                return _lowCoder[posState].NotNull().Decode(rangeDecoder);
             }
             var symbol = Base.K_NUM_LOW_LEN_SYMBOLS;
             if (_choice2.Decode(rangeDecoder) == 0)
             {
-                symbol += _midCoder[posState].Decode(rangeDecoder);
+                symbol += _midCoder[posState].NotNull().Decode(rangeDecoder);
             }
             else
             {
@@ -110,7 +112,7 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
             }
         }
 
-        private Decoder2[] _coders;
+        private Decoder2[]? _coders;
         private int _numPrevBits;
         private int _numPosBits;
         private uint _posMask;
@@ -134,10 +136,11 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
 
         public void Init()
         {
+            var coders = _coders.NotNull();
             var numStates = (uint)1 << (_numPrevBits + _numPosBits);
             for (uint i = 0; i < numStates; i++)
             {
-                _coders[i].Init();
+                coders[i].Init();
             }
         }
 
@@ -145,17 +148,18 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
             ((pos & _posMask) << _numPrevBits) + (uint)(prevByte >> (8 - _numPrevBits));
 
         public byte DecodeNormal(RangeCoder.Decoder rangeDecoder, uint pos, byte prevByte) =>
-            _coders[GetState(pos, prevByte)].DecodeNormal(rangeDecoder);
+            _coders.NotNull()[GetState(pos, prevByte)].DecodeNormal(rangeDecoder);
 
         public byte DecodeWithMatchByte(
             RangeCoder.Decoder rangeDecoder,
             uint pos,
             byte prevByte,
             byte matchByte
-        ) => _coders[GetState(pos, prevByte)].DecodeWithMatchByte(rangeDecoder, matchByte);
+        ) =>
+            _coders.NotNull()[GetState(pos, prevByte)].DecodeWithMatchByte(rangeDecoder, matchByte);
     }
 
-    private OutWindow _outWindow;
+    private OutWindow? _outWindow;
 
     private readonly BitDecoder[] _isMatchDecoders = new BitDecoder[
         Base.K_NUM_STATES << Base.K_NUM_POS_STATES_BITS_MAX
@@ -285,32 +289,32 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
         Stream outStream,
         long inSize,
         long outSize,
-        ICodeProgress progress
+        ICodeProgress? progress
     )
     {
         if (_outWindow is null)
         {
             CreateDictionary();
         }
-        _outWindow.Init(outStream);
+        _outWindow.NotNull().Init(outStream);
         if (outSize > 0)
         {
-            _outWindow.SetLimit(outSize);
+            _outWindow.NotNull().SetLimit(outSize);
         }
         else
         {
-            _outWindow.SetLimit(long.MaxValue - _outWindow.Total);
+            _outWindow.NotNull().SetLimit(long.MaxValue - _outWindow.NotNull().Total);
         }
 
         var rangeDecoder = new RangeCoder.Decoder();
         rangeDecoder.Init(inStream);
 
-        Code(_dictionarySize, _outWindow, rangeDecoder);
+        Code(_dictionarySize, _outWindow.NotNull(), rangeDecoder);
 
-        _outWindow.ReleaseStream();
+        _outWindow.NotNull().ReleaseStream();
         rangeDecoder.ReleaseStream();
 
-        _outWindow.Dispose();
+        _outWindow.NotNull().Dispose();
         _outWindow = null;
     }
 
@@ -473,6 +477,6 @@ public partial class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Strea
         {
             CreateDictionary();
         }
-        _outWindow.Train(stream);
+        _outWindow.NotNull().Train(stream);
     }
 }

src/SharpCompress/Compressors/LZMA/LzmaStream.Async.cs

@@ -147,7 +147,7 @@ public partial class LzmaStream
                 _decoder.SetDecoderProperties(Properties);
             }
 
-            await _rangeDecoder.InitAsync(_inputStream, cancellationToken);
+            await _rangeDecoder.InitAsync(_inputStream.NotNull(), cancellationToken);
         }
         else if (control > 0x02)
         {

src/SharpCompress/Compressors/LZMA/RangeCoder/RangeCoder.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -17,7 +15,7 @@ internal partial class Encoder
             {
                 var b = (byte)(temp + (_low >> 32));
                 var buffer = new[] { b };
-                await _stream.WriteAsync(buffer, 0, 1, cancellationToken).ConfigureAwait(false);
+                await Stream.WriteAsync(buffer, 0, 1, cancellationToken).ConfigureAwait(false);
                 temp = 0xFF;
             } while (--_cacheSize != 0);
             _cache = (byte)(((uint)_low) >> 24);
@@ -72,7 +70,7 @@ internal partial class Encoder
     }
 
     public async ValueTask FlushStreamAsync(CancellationToken cancellationToken = default) =>
-        await _stream.FlushAsync(cancellationToken).ConfigureAwait(false);
+        await Stream.FlushAsync(cancellationToken).ConfigureAwait(false);
 }
 
 internal partial class Decoder
@@ -103,7 +101,7 @@ internal partial class Decoder
         while (_range < K_TOP_VALUE)
         {
             var buffer = new byte[1];
-            var read = await _stream
+            var read = await Stream
                 .ReadAsync(buffer, 0, 1, cancellationToken)
                 .ConfigureAwait(false);
             if (read == 0)
@@ -121,7 +119,7 @@ internal partial class Decoder
         if (_range < K_TOP_VALUE)
         {
             var buffer = new byte[1];
-            var read = await _stream
+            var read = await Stream
                 .ReadAsync(buffer, 0, 1, cancellationToken)
                 .ConfigureAwait(false);
             if (read == 0)
@@ -152,7 +150,7 @@ internal partial class Decoder
 
             if (range < K_TOP_VALUE)
             {
-                var read = await _stream
+                var read = await Stream
                     .ReadAsync(buffer, 0, 1, cancellationToken)
                     .ConfigureAwait(false);
                 if (read == 0)

src/SharpCompress/Compressors/LZMA/RangeCoder/RangeCoder.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.IO;
 using System.Runtime.CompilerServices;
 
@@ -9,7 +7,7 @@ internal partial class Encoder
 {
     public const uint K_TOP_VALUE = (1 << 24);
 
-    private Stream _stream;
+    private Stream? _stream;
 
     public ulong _low;
     public uint _range;
@@ -22,6 +20,8 @@ internal partial class Encoder
 
     public void ReleaseStream() => _stream = null;
 
+    private Stream Stream => _stream.NotNull();
+
     public void Init()
     {
         //StartPosition = Stream.Position;
@@ -40,9 +40,9 @@ internal partial class Encoder
         }
     }
 
-    public void FlushStream() => _stream.Flush();
+    public void FlushStream() => Stream.Flush();
 
-    public void CloseStream() => _stream.Dispose();
+    public void CloseStream() => Stream.Dispose();
 
     public void ShiftLow()
     {
@@ -51,7 +51,7 @@ internal partial class Encoder
             var temp = _cache;
             do
             {
-                _stream.WriteByte((byte)(temp + (_low >> 32)));
+                Stream.WriteByte((byte)(temp + (_low >> 32)));
                 temp = 0xFF;
             } while (--_cacheSize != 0);
             _cache = (byte)(((uint)_low) >> 24);
@@ -86,7 +86,7 @@ internal partial class Decoder
     public uint _range;
     public uint _code;
 
-    public Stream _stream;
+    public Stream? _stream;
     public long _total;
 
     public void Init(Stream stream)
@@ -97,7 +97,7 @@ internal partial class Decoder
         _range = 0xFFFFFFFF;
         for (var i = 0; i < 5; i++)
         {
-            _code = (_code << 8) | (byte)_stream.ReadByte();
+            _code = (_code << 8) | (byte)stream.ReadByte();
         }
         _total = 5;
     }
@@ -106,11 +106,13 @@ internal partial class Decoder
         // Stream.ReleaseStream();
         _stream = null;
 
+    private Stream Stream => _stream.NotNull();
+
     public void Normalize()
     {
         while (_range < K_TOP_VALUE)
         {
-            _code = (_code << 8) | (byte)_stream.ReadByte();
+            _code = (_code << 8) | (byte)Stream.ReadByte();
             _range <<= 8;
             _total++;
         }
@@ -121,7 +123,7 @@ internal partial class Decoder
     {
         if (_range < K_TOP_VALUE)
         {
-            _code = (_code << 8) | (byte)_stream.ReadByte();
+            _code = (_code << 8) | (byte)Stream.ReadByte();
             _range <<= 8;
             _total++;
         }
@@ -150,7 +152,7 @@ internal partial class Decoder
 
             if (range < K_TOP_VALUE)
             {
-                code = (code << 8) | (byte)_stream.ReadByte();
+                code = (code << 8) | (byte)Stream.ReadByte();
                 range <<= 8;
                 _total++;
             }

src/SharpCompress/Compressors/LZMA/RangeCoder/RangeCoderBit.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Threading;
 using System.Threading.Tasks;
 

src/SharpCompress/Compressors/LZMA/RangeCoder/RangeCoderBitTree.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Threading;
 using System.Threading.Tasks;
 

src/SharpCompress/Compressors/PPMd/PpmdStream.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.IO;
 using System.Threading;
@@ -15,9 +13,9 @@ public class PpmdStream : Stream
     private readonly PpmdProperties _properties;
     private readonly Stream _stream;
     private readonly bool _compress;
-    private Model _model;
-    private ModelPpm _modelH;
-    private Decoder _decoder;
+    private Model? _model;
+    private ModelPpm? _modelH;
+    private Decoder? _decoder;
     private long _position;
     private bool _isDisposed;
 
@@ -178,7 +176,7 @@ public class PpmdStream : Stream
         {
             if (_compress)
             {
-                _model.EncodeBlock(_stream, new MemoryStream(), true);
+                _model.NotNull().EncodeBlock(_stream, new MemoryStream(), true);
             }
         }
         base.Dispose(isDisposing);
@@ -201,12 +199,12 @@ public class PpmdStream : Stream
         var size = 0;
         if (_properties.Version == PpmdVersion.I1)
         {
-            size = _model.DecodeBlock(_stream, buffer, offset, count);
+            size = _model.NotNull().DecodeBlock(_stream, buffer, offset, count);
         }
         if (_properties.Version == PpmdVersion.H)
         {
             int c;
-            while (size < count && (c = _modelH.DecodeChar()) >= 0)
+            while (size < count && (c = _modelH.NotNull().DecodeChar()) >= 0)
             {
                 buffer[offset++] = (byte)c;
                 size++;
@@ -215,7 +213,7 @@ public class PpmdStream : Stream
         if (_properties.Version == PpmdVersion.H7Z)
         {
             int c;
-            while (size < count && (c = _modelH.DecodeChar(_decoder)) >= 0)
+            while (size < count && (c = _modelH.NotNull().DecodeChar(_decoder.NotNull())) >= 0)
             {
                 buffer[offset++] = (byte)c;
                 size++;
@@ -247,6 +245,7 @@ public class PpmdStream : Stream
         if (_properties.Version == PpmdVersion.I1)
         {
             size = await _model
+                .NotNull()
                 .DecodeBlockAsync(_stream, buffer, offset, count, cancellationToken)
                 .ConfigureAwait(false);
         }
@@ -255,7 +254,12 @@ public class PpmdStream : Stream
             int c;
             while (
                 size < count
-                && (c = await _modelH.DecodeCharAsync(cancellationToken).ConfigureAwait(false)) >= 0
+                && (
+                    c = await _modelH
+                        .NotNull()
+                        .DecodeCharAsync(cancellationToken)
+                        .ConfigureAwait(false)
+                ) >= 0
             )
             {
                 buffer[offset++] = (byte)c;
@@ -269,7 +273,8 @@ public class PpmdStream : Stream
                 size < count
                 && (
                     c = await _modelH
-                        .DecodeCharAsync(_decoder, cancellationToken)
+                        .NotNull()
+                        .DecodeCharAsync(_decoder.NotNull(), cancellationToken)
                         .ConfigureAwait(false)
                 ) >= 0
             )
@@ -304,6 +309,7 @@ public class PpmdStream : Stream
             // Need to use a temporary buffer since DecodeBlockAsync works with byte[]
             var tempBuffer = new byte[count];
             size = await _model
+                .NotNull()
                 .DecodeBlockAsync(_stream, tempBuffer, 0, count, cancellationToken)
                 .ConfigureAwait(false);
             tempBuffer.AsMemory(0, size).CopyTo(buffer);
@@ -313,7 +319,12 @@ public class PpmdStream : Stream
             int c;
             while (
                 size < count
-                && (c = await _modelH.DecodeCharAsync(cancellationToken).ConfigureAwait(false)) >= 0
+                && (
+                    c = await _modelH
+                        .NotNull()
+                        .DecodeCharAsync(cancellationToken)
+                        .ConfigureAwait(false)
+                ) >= 0
             )
             {
                 buffer.Span[offset++] = (byte)c;
@@ -327,7 +338,8 @@ public class PpmdStream : Stream
                 size < count
                 && (
                     c = await _modelH
-                        .DecodeCharAsync(_decoder, cancellationToken)
+                        .NotNull()
+                        .DecodeCharAsync(_decoder.NotNull(), cancellationToken)
                         .ConfigureAwait(false)
                 ) >= 0
             )
@@ -345,7 +357,7 @@ public class PpmdStream : Stream
     {
         if (_compress)
         {
-            _model.EncodeBlock(_stream, new MemoryStream(buffer, offset, count), false);
+            _model.NotNull().EncodeBlock(_stream, new MemoryStream(buffer, offset, count), false);
         }
     }
 }

src/SharpCompress/Compressors/Rar/RarStream.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Buffers;
 using System.IO;
@@ -47,7 +45,7 @@ internal partial class RarStream
         if (tmpCount > 0)
         {
             var toCopy = tmpCount < count ? tmpCount : count;
-            Buffer.BlockCopy(tmpBuffer, tmpOffset, buffer, offset, toCopy);
+            Buffer.BlockCopy(tmpBuffer.NotNull(), tmpOffset, buffer, offset, toCopy);
             tmpOffset += toCopy;
             tmpCount -= toCopy;
             offset += toCopy;

src/SharpCompress/Compressors/Rar/RarStream.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Buffers;
 using System.IO;
@@ -15,11 +13,11 @@ internal partial class RarStream : Stream
 
     private bool fetch;
 
-    private byte[] tmpBuffer = ArrayPool<byte>.Shared.Rent(65536);
+    private byte[]? tmpBuffer = ArrayPool<byte>.Shared.Rent(65536);
     private int tmpOffset;
     private int tmpCount;
 
-    private byte[] outBuffer;
+    private byte[]? outBuffer;
     private int outOffset;
     private int outCount;
     private int outTotal;
@@ -47,8 +45,11 @@ internal partial class RarStream : Stream
         {
             if (disposing)
             {
-                ArrayPool<byte>.Shared.Return(this.tmpBuffer);
-                this.tmpBuffer = null;
+                if (this.tmpBuffer is not null)
+                {
+                    ArrayPool<byte>.Shared.Return(this.tmpBuffer);
+                    this.tmpBuffer = null;
+                }
                 readStream.Dispose();
             }
             isDisposed = true;
@@ -79,7 +80,7 @@ internal partial class RarStream : Stream
         if (tmpCount > 0)
         {
             var toCopy = tmpCount < count ? tmpCount : count;
-            Buffer.BlockCopy(tmpBuffer, tmpOffset, buffer, offset, toCopy);
+            Buffer.BlockCopy(tmpBuffer.NotNull(), tmpOffset, buffer, offset, toCopy);
             tmpOffset += toCopy;
             tmpCount -= toCopy;
             offset += toCopy;
@@ -119,7 +120,7 @@ internal partial class RarStream : Stream
         if (outCount > 0)
         {
             var toCopy = outCount < count ? outCount : count;
-            Buffer.BlockCopy(buffer, offset, outBuffer, outOffset, toCopy);
+            Buffer.BlockCopy(buffer, offset, outBuffer.NotNull(), outOffset, toCopy);
             outOffset += toCopy;
             outCount -= toCopy;
             offset += toCopy;
@@ -129,7 +130,7 @@ internal partial class RarStream : Stream
         if (count > 0)
         {
             EnsureBufferCapacity(count);
-            Buffer.BlockCopy(buffer, offset, tmpBuffer, tmpCount, count);
+            Buffer.BlockCopy(buffer, offset, tmpBuffer.NotNull(), tmpCount, count);
             tmpCount += count;
             tmpOffset = 0;
             unpack.Suspended = true;
@@ -142,15 +143,16 @@ internal partial class RarStream : Stream
 
     private void EnsureBufferCapacity(int count)
     {
-        if (this.tmpBuffer.Length < this.tmpCount + count)
+        var buffer = this.tmpBuffer.NotNull();
+        if (buffer.Length < this.tmpCount + count)
         {
             var newLength =
-                this.tmpBuffer.Length * 2 > this.tmpCount + count
-                    ? this.tmpBuffer.Length * 2
+                buffer.Length * 2 > this.tmpCount + count
+                    ? buffer.Length * 2
                     : this.tmpCount + count;
             var newBuffer = ArrayPool<byte>.Shared.Rent(newLength);
-            Buffer.BlockCopy(this.tmpBuffer, 0, newBuffer, 0, this.tmpCount);
-            var oldBuffer = this.tmpBuffer;
+            Buffer.BlockCopy(buffer, 0, newBuffer, 0, this.tmpCount);
+            var oldBuffer = buffer;
             this.tmpBuffer = newBuffer;
             ArrayPool<byte>.Shared.Return(oldBuffer);
         }

src/SharpCompress/Compressors/Xz/Crc32.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 
 namespace SharpCompress.Compressors.Xz;
@@ -10,7 +8,7 @@ public static class Crc32
     public const uint DefaultPolynomial = 0xedb88320u;
     public const uint DefaultSeed = 0xffffffffu;
 
-    private static uint[] defaultTable;
+    private static uint[]? defaultTable;
 
     public static uint Compute(byte[] buffer) => Compute(DefaultSeed, buffer);
 

src/SharpCompress/Compressors/Xz/Crc64.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 
 namespace SharpCompress.Compressors.Xz;
@@ -9,7 +7,7 @@ public static class Crc64
 {
     public const ulong DefaultSeed = 0x0;
 
-    internal static ulong[] Table;
+    internal static ulong[]? Table;
 
     public const ulong Iso3309Polynomial = 0xD800000000000000;
 

src/SharpCompress/Compressors/Xz/XZStream.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.IO;
 using System.Threading;
@@ -36,7 +34,7 @@ public sealed partial class XZStream : XZReadOnlyStream
 
     private void AssertBlockCheckTypeIsSupported()
     {
-        switch (Header.BlockCheckType)
+        switch (Header.NotNull().BlockCheckType)
         {
             case CheckType.NONE:
             case CheckType.CRC32:
@@ -49,11 +47,11 @@ public sealed partial class XZStream : XZReadOnlyStream
     }
 
     private readonly Stream _baseStream;
-    public XZHeader Header { get; private set; }
-    public XZIndex Index { get; private set; }
-    public XZFooter Footer { get; private set; }
+    public XZHeader? Header { get; private set; }
+    public XZIndex? Index { get; private set; }
+    public XZFooter? Footer { get; private set; }
     public bool HeaderIsRead { get; private set; }
-    private XZBlock _currentBlock;
+    private XZBlock? _currentBlock;
 
     private bool _endOfStream;
 
@@ -113,7 +111,7 @@ public sealed partial class XZStream : XZReadOnlyStream
 
                 var remaining = count - bytesRead;
                 var newOffset = offset + bytesRead;
-                var justRead = _currentBlock.Read(buffer, newOffset, remaining);
+                var justRead = _currentBlock.NotNull().Read(buffer, newOffset, remaining);
                 if (justRead < remaining)
                 {
                     NextBlock();
@@ -130,5 +128,9 @@ public sealed partial class XZStream : XZReadOnlyStream
     }
 
     private void NextBlock() =>
-        _currentBlock = new XZBlock(BaseStream, Header.BlockCheckType, Header.BlockCheckSize);
+        _currentBlock = new XZBlock(
+            BaseStream,
+            Header.NotNull().BlockCheckType,
+            Header.NotNull().BlockCheckSize
+        );
 }

src/SharpCompress/Crypto/BlockTransformer.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Security.Cryptography;
 

src/SharpCompress/Crypto/Crc32Stream.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.IO;
 
@@ -15,7 +13,7 @@ public sealed class Crc32Stream : Stream
     public const uint DEFAULT_POLYNOMIAL = 0xedb88320u;
     public const uint DEFAULT_SEED = 0xffffffffu;
 
-    private static uint[] _defaultTable;
+    private static uint[]? _defaultTable;
 
     public Crc32Stream(Stream stream)
         : this(stream, DEFAULT_POLYNOMIAL, DEFAULT_SEED) { }

src/SharpCompress/LazyAsyncReadOnlyCollection.cs

@@ -1,4 +1,3 @@
-#nullable disable
 using System;
 using System.Collections;
 using System.Collections.Generic;

src/SharpCompress/LazyReadOnlyCollection.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -43,7 +41,7 @@ internal sealed class LazyReadOnlyCollection<T> : ICollection<T>
 
         #region IEnumerator Members
 
-        object IEnumerator.Current => Current;
+        object? IEnumerator.Current => Current;
 
         public bool MoveNext()
         {

src/SharpCompress/Readers/Ace/MultiVolumeAceReader.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -15,7 +13,7 @@ namespace SharpCompress.Readers.Ace;
 internal class MultiVolumeAceReader : AceReader
 {
     private readonly IEnumerator<Stream> streams;
-    private Stream tempStream;
+    private Stream? tempStream;
 
     internal MultiVolumeAceReader(IEnumerable<Stream> streams, ReaderOptions options)
         : base(options) => this.streams = streams.GetEnumerator();
@@ -54,13 +52,13 @@ internal class MultiVolumeAceReader : AceReader
     {
         private readonly MultiVolumeAceReader reader;
         private readonly IEnumerator<Stream> nextReadableStreams;
-        private Stream tempStream;
+        private Stream? tempStream;
         private bool isFirst = true;
 
         internal MultiVolumeStreamEnumerator(
             MultiVolumeAceReader r,
             IEnumerator<Stream> nextReadableStreams,
-            Stream tempStream
+            Stream? tempStream
         )
         {
             reader = r;
@@ -72,7 +70,12 @@ internal class MultiVolumeAceReader : AceReader
 
         IEnumerator IEnumerable.GetEnumerator() => this;
 
-        public FilePart Current { get; private set; }
+        private FilePart? _current;
+        public FilePart Current
+        {
+            get => _current.NotNull();
+            private set => _current = value;
+        }
 
         public void Dispose() { }
 
@@ -82,7 +85,7 @@ internal class MultiVolumeAceReader : AceReader
         {
             if (isFirst)
             {
-                Current = reader.Entry.Parts.First();
+                _current = reader.Entry.Parts.First();
                 isFirst = false; //first stream already to go
                 return true;
             }
@@ -93,7 +96,7 @@ internal class MultiVolumeAceReader : AceReader
             }
             if (tempStream != null)
             {
-                reader.LoadStreamForReading(tempStream);
+                reader.LoadStreamForReading(tempStream.NotNull());
                 tempStream = null;
             }
             else if (!nextReadableStreams.MoveNext())
@@ -107,7 +110,7 @@ internal class MultiVolumeAceReader : AceReader
                 reader.LoadStreamForReading(nextReadableStreams.Current);
             }
 
-            Current = reader.Entry.Parts.First();
+            _current = reader.Entry.Parts.First();
             return true;
         }
 

src/SharpCompress/Readers/Arj/MultiVolumeArjReader.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -16,7 +14,7 @@ namespace SharpCompress.Readers.Arj;
 internal class MultiVolumeArjReader : ArjReader
 {
     private readonly IEnumerator<Stream> streams;
-    private Stream tempStream;
+    private Stream? tempStream;
 
     internal MultiVolumeArjReader(IEnumerable<Stream> streams, ReaderOptions options)
         : base(options) => this.streams = streams.GetEnumerator();
@@ -55,13 +53,13 @@ internal class MultiVolumeArjReader : ArjReader
     {
         private readonly MultiVolumeArjReader reader;
         private readonly IEnumerator<Stream> nextReadableStreams;
-        private Stream tempStream;
+        private Stream? tempStream;
         private bool isFirst = true;
 
         internal MultiVolumeStreamEnumerator(
             MultiVolumeArjReader r,
             IEnumerator<Stream> nextReadableStreams,
-            Stream tempStream
+            Stream? tempStream
         )
         {
             reader = r;
@@ -73,7 +71,12 @@ internal class MultiVolumeArjReader : ArjReader
 
         IEnumerator IEnumerable.GetEnumerator() => this;
 
-        public FilePart Current { get; private set; }
+        private FilePart? _current;
+        public FilePart Current
+        {
+            get => _current.NotNull();
+            private set => _current = value;
+        }
 
         public void Dispose() { }
 
@@ -94,7 +97,7 @@ internal class MultiVolumeArjReader : ArjReader
             }
             if (tempStream != null)
             {
-                reader.LoadStreamForReading(tempStream);
+                reader.LoadStreamForReading(tempStream.NotNull());
                 tempStream = null;
             }
             else if (!nextReadableStreams.MoveNext())

src/SharpCompress/Readers/Rar/MultiVolumeRarReader.Async.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
@@ -26,13 +24,13 @@ internal partial class MultiVolumeRarReader : RarReader
     {
         private readonly MultiVolumeRarReader reader;
         private readonly IEnumerator<Stream> nextReadableStreams;
-        private Stream tempStream;
+        private Stream? tempStream;
         private bool isFirst = true;
 
         internal MultiVolumeStreamAsyncEnumerator(
             MultiVolumeRarReader r,
             IEnumerator<Stream> nextReadableStreams,
-            Stream tempStream
+            Stream? tempStream
         )
         {
             reader = r;
@@ -40,7 +38,12 @@ internal partial class MultiVolumeRarReader : RarReader
             this.tempStream = tempStream;
         }
 
-        public FilePart Current { get; private set; }
+        private FilePart? _current;
+        public FilePart Current
+        {
+            get => _current.NotNull();
+            private set => _current = value;
+        }
 
         public async ValueTask<bool> MoveNextAsync()
         {
@@ -57,7 +60,7 @@ internal partial class MultiVolumeRarReader : RarReader
             }
             if (tempStream != null)
             {
-                await reader.LoadStreamForReadingAsync(tempStream);
+                await reader.LoadStreamForReadingAsync(tempStream.NotNull());
                 tempStream = null;
             }
             else if (!nextReadableStreams.MoveNext())

src/SharpCompress/Readers/Rar/MultiVolumeRarReader.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
@@ -14,7 +12,7 @@ namespace SharpCompress.Readers.Rar;
 internal partial class MultiVolumeRarReader : RarReader
 {
     private readonly IEnumerator<Stream> streams;
-    private Stream tempStream;
+    private Stream? tempStream;
 
     internal MultiVolumeRarReader(IEnumerable<Stream> streams, ReaderOptions options)
         : base(options) => this.streams = streams.GetEnumerator();
@@ -55,13 +53,13 @@ internal partial class MultiVolumeRarReader : RarReader
     {
         private readonly MultiVolumeRarReader reader;
         private readonly IEnumerator<Stream> nextReadableStreams;
-        private Stream tempStream;
+        private Stream? tempStream;
         private bool isFirst = true;
 
         internal MultiVolumeStreamEnumerator(
             MultiVolumeRarReader r,
             IEnumerator<Stream> nextReadableStreams,
-            Stream tempStream
+            Stream? tempStream
         )
         {
             reader = r;
@@ -73,7 +71,12 @@ internal partial class MultiVolumeRarReader : RarReader
 
         IEnumerator IEnumerable.GetEnumerator() => this;
 
-        public FilePart Current { get; private set; }
+        private FilePart? _current;
+        public FilePart Current
+        {
+            get => _current.NotNull();
+            private set => _current = value;
+        }
 
         public void Dispose() { }
 
@@ -94,7 +97,7 @@ internal partial class MultiVolumeRarReader : RarReader
             }
             if (tempStream != null)
             {
-                reader.LoadStreamForReading(tempStream);
+                reader.LoadStreamForReading(tempStream.NotNull());
                 tempStream = null;
             }
             else if (!nextReadableStreams.MoveNext())