Fix bug in the sync version of ChunkedStream when we read a partial b…

…lock

src/NexusMods.DataModel/ChunkedStreams/ChunkedStream.cs

@@ -1,4 +1,5 @@
 using System.Buffers;
+using System.Diagnostics;
 using Reloaded.Memory.Extensions;
 
 namespace NexusMods.DataModel.ChunkedStreams;
@@ -43,8 +44,11 @@ public override int Read(byte[] buffer, int offset, int count)
         var chunkOffset = _position % _source.ChunkSize.Value;
         var isLastChunk = chunkIdx == _source.ChunkCount - 1;
         var chunk = GetChunk(chunkIdx);
+        var readToEnd = Math.Clamp(_source.Size.Value - _position, 0, Int32.MaxValue);
 
-        var toRead = Math.Min(count, (int)(_source.ChunkSize.Value - chunkOffset));
+        var toRead = Math.Min(buffer.Length, (int)(_source.ChunkSize.Value - chunkOffset));
+        toRead = Math.Min(toRead, (int)readToEnd);
+
         if (isLastChunk)
         {
             var lastChunkExtraSize = _source.Size.Value % _source.ChunkSize.Value;
@@ -58,6 +62,8 @@ public override int Read(byte[] buffer, int offset, int count)
             .Span
             .CopyTo(buffer.AsSpan(offset, toRead));
         _position += (ulong)toRead;
+
+        Debug.Assert(_position <= _source.Size.Value, "Read more than the size of the stream");
         return toRead;
     }
 
@@ -92,6 +98,7 @@ public override async ValueTask<int> ReadAsync(Memory<byte> buffer,
             .Span
             .CopyTo(buffer.Span.SliceFast(0, toRead));
         _position += (ulong)toRead;
+        Debug.Assert(_position <= _source.Size.Value, "Read more than the size of the stream");
         return toRead;
     }