1 files changed, 46 insertions, 0 deletions
diff --git a/embeddable-dll-service/csharp/Ringlogger.cs b/embeddable-dll-service/csharp/Ringlogger.cs
new file mode 100644
index 00000000..711c22e7
--- /dev/null
+++ b/embeddable-dll-service/csharp/Ringlogger.cs
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+using System;
+using System.IO;
+using System.IO.MemoryMappedFiles;
+using System.Text;
+
+namespace Tunnel
+{
+    public class Ringlogger
+    {
+        private readonly MemoryMappedViewAccessor _viewAccessor;
+
+        public Ringlogger(string filename)
+        {
+            var file = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
+            var mmap = MemoryMappedFile.CreateFromFile(file, null, 0, MemoryMappedFileAccess.Read, HandleInheritability.None, false);
+            _viewAccessor = mmap.CreateViewAccessor(0, 8 + 2048 * (512 + 8), MemoryMappedFileAccess.Read);
+            if (_viewAccessor.ReadUInt32(0) != 0xbadbabe)
+                throw new InvalidDataException("The provided file is missing the magic number.");
+        }
+
+        public void WriteTo(TextWriter writer)
+        {
+            var start = _viewAccessor.ReadUInt32(4);
+            for (var i = 0; i < 2048; ++i)
+            {
+                var lineOffset = 8 + (8 + 512) * ((i + start) % 2048);
+                var timeNs = _viewAccessor.ReadInt64(lineOffset);
+                if (timeNs == 0)
+                    continue;
+                var textBytes = new byte[512];
+                _viewAccessor.ReadArray<byte>(lineOffset + 8, textBytes, 0, textBytes.Length);
+                var nullByte = Array.IndexOf<byte>(textBytes, 0);
+                if (nullByte <= 0)
+                    continue;
+                var text = Encoding.UTF8.GetString(textBytes, 0, nullByte);
+                var time = DateTimeOffset.FromUnixTimeMilliseconds(timeNs / 1000000).ToString("yyyy'-'MM'-'dd HH':'mm':'ss'.'ffffff");
+                writer.WriteLine(String.Format("{0}: {1}", time, text));
+            }
+        }
+    }
+}