custom file stream implementation

MareSynchronosServer/MareSynchronosStaticFilesServer/Utils/BlockFileDataSubstream.cs

@@ -0,0 +1,73 @@
+using System.Globalization;
+using System.Text;
+
+namespace MareSynchronosStaticFilesServer.Utils;
+
+public sealed class BlockFileDataSubstream : IDisposable
+{
+    private readonly MemoryStream _headerStream;
+    private readonly FileStream _dataStream;
+    private int _headerPosition = 0;
+    private long _dataPosition = 0;
+    private bool _disposed = false;
+
+    private long RemainingHeaderLength => _headerStream.Length - _headerPosition;
+    private long RemainingDataLength => _dataStream.Length - _dataPosition;
+
+    public BlockFileDataSubstream(FileStream dataStream)
+    {
+        _headerStream = new MemoryStream();
+        var headerStreamWriter = new BinaryWriter(_headerStream);
+        headerStreamWriter.Write(Encoding.ASCII.GetBytes("#" + new FileInfo(dataStream.Name).Name + ":" + dataStream.Length.ToString(CultureInfo.InvariantCulture) + "#"));
+        headerStreamWriter.Flush();
+        _headerStream.Position = 0;
+        _dataStream = dataStream;
+    }
+
+    public int Read(byte[] inputBuffer, int offset, int count)
+    {
+        int currentOffset = offset;
+        int currentCount = count;
+        int readHeaderBytes = 0;
+
+        if (RemainingHeaderLength > 0)
+        {
+            bool readOnlyHeader = currentCount <= RemainingHeaderLength;
+            byte[] readHeaderBuffer = new byte[Math.Min(currentCount, RemainingHeaderLength)];
+
+            readHeaderBytes = _headerStream.Read(readHeaderBuffer, 0, readHeaderBuffer.Length);
+            _headerPosition += readHeaderBytes;
+
+            Buffer.BlockCopy(readHeaderBuffer, 0, inputBuffer, currentOffset, readHeaderBytes);
+
+            if (readOnlyHeader)
+            {
+                return readHeaderBytes;
+            }
+
+            currentOffset += readHeaderBytes;
+            currentCount -= readHeaderBytes;
+        }
+
+        if (RemainingDataLength > 0)
+        {
+            byte[] readDataBuffer = new byte[currentCount];
+            var readDataBytes = _dataStream.Read(readDataBuffer, 0, readDataBuffer.Length);
+            _dataPosition += readDataBytes;
+
+            Buffer.BlockCopy(readDataBuffer, 0, inputBuffer, currentOffset, readDataBytes);
+
+            return readDataBytes + readHeaderBytes;
+        }
+
+        return 0;
+    }
+
+    public void Dispose()
+    {
+        if (_disposed) return;
+        _headerStream.Dispose();
+        _dataStream.Dispose();
+        _disposed = true;
+    }
+}