Got at least one data fetching method working; turns out, we can't use a patched LogicStack to get the data

Vendor/EmbedIO-3.5.2/Internal/CompressionStream.cs

@@ -0,0 +1,121 @@
+using System;
+using System.IO;
+using System.IO.Compression;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace EmbedIO.Internal
+{
+    internal class CompressionStream : Stream
+    {
+        private readonly Stream _target;
+        private readonly bool _leaveOpen;
+
+        public CompressionStream(Stream target, CompressionMethod compressionMethod)
+        {
+            switch (compressionMethod)
+            {
+                case CompressionMethod.Deflate:
+                    _target = new DeflateStream(target, CompressionMode.Compress, true);
+                    _leaveOpen = false;
+                    break;
+                case CompressionMethod.Gzip:
+                    _target = new GZipStream(target, CompressionMode.Compress, true);
+                    _leaveOpen = false;
+                    break;
+                default:
+                    _target = target;
+                    _leaveOpen = true;
+                    break;
+            }
+
+            UncompressedLength = 0;
+        }
+
+        public long UncompressedLength { get; private set; }
+
+        public override bool CanRead => false;
+
+        public override bool CanSeek => false;
+
+        public override bool CanWrite => true;
+
+        public override long Length => throw SeekingNotSupported();
+        
+        public override long Position
+        {
+            get => throw SeekingNotSupported();
+            set => throw SeekingNotSupported();
+        }
+
+        public override void Flush() => _target.Flush();
+
+        public override Task FlushAsync(CancellationToken cancellationToken) => _target.FlushAsync(cancellationToken);
+
+        public override int Read(byte[] buffer, int offset, int count) => throw ReadingNotSupported();
+
+        public override int ReadByte() => throw ReadingNotSupported();
+
+        public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
+            => throw ReadingNotSupported();
+
+        public override int EndRead(IAsyncResult asyncResult) => throw ReadingNotSupported();
+
+        public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) => throw ReadingNotSupported();
+
+        public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
+            => throw ReadingNotSupported();
+
+        public override long Seek(long offset, SeekOrigin origin) => throw SeekingNotSupported();
+
+        public override void SetLength(long value) => throw SeekingNotSupported();
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            _target.Write(buffer, offset, count);
+            UncompressedLength += count;
+        }
+
+        public override void WriteByte(byte value)
+        {
+            _target.WriteByte(value);
+            UncompressedLength++;
+        }
+
+        public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
+            => _target.BeginWrite(
+                buffer,
+                offset,
+                count,
+                ar => {
+                    UncompressedLength += count;
+                    callback(ar);
+                },
+                state);
+
+        public override void EndWrite(IAsyncResult asyncResult)
+        {
+            _target.EndWrite(asyncResult);
+        }
+
+        public override async Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            await _target.WriteAsync(buffer, offset, count, cancellationToken).ConfigureAwait(false);
+            UncompressedLength += count;
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing && !_leaveOpen)
+            {
+                _target.Dispose();
+            }
+
+            base.Dispose(disposing);
+        }
+
+        private static Exception ReadingNotSupported() => new NotSupportedException("This stream does not support reading.");
+
+        private static Exception SeekingNotSupported() => new NotSupportedException("This stream does not support seeking.");
+    }
+}