From 0bc0c28fbabfc842fb2768d2d7196b28b380d842 Mon Sep 17 00:00:00 2001
From: Morten Nielsen <mn@iter.dk>
Date: Wed, 29 Jul 2020 17:09:25 -0700
Subject: [PATCH] Adds EndOfStreamReached event for buffered streams and better
 handle streams that can't auto-rewind

Fixes #73
---
 src/NmeaParser/BufferedStreamDevice.cs | 31 +++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/NmeaParser/BufferedStreamDevice.cs b/src/NmeaParser/BufferedStreamDevice.cs
index da55a95..8980a7f 100644
--- a/src/NmeaParser/BufferedStreamDevice.cs
+++ b/src/NmeaParser/BufferedStreamDevice.cs
@@ -61,9 +61,20 @@ namespace NmeaParser
             var stream = await GetStreamAsync().ConfigureAwait(false);
             StreamReader sr = new StreamReader(stream);
             m_stream = new BufferedStream(sr, emulationSettings);
+            m_stream.EndOfStreamReached += OnEndOfStreamReached;
             return m_stream;
         }
 
+        private void OnEndOfStreamReached(object sender, EventArgs e)
+        {
+            EndOfStreamReached?.Invoke(this, e);
+            if (m_stream is BufferedStream stream && !stream.CanRewind && IsOpen)
+            {
+                // If we can't rewind the stream, stop
+                _ = CloseAsync();
+            }
+        }
+
         /// <summary>
         /// Gets or sets the emulated baud rate. Defaults to 115200
         /// </summary>
@@ -107,7 +118,11 @@ namespace NmeaParser
         /// <inheritdoc />
         protected override Task CloseStreamAsync(System.IO.Stream stream)
         {
-            m_stream?.Dispose();
+            if (m_stream != null)
+            {
+                m_stream.EndOfStreamReached -= OnEndOfStreamReached;
+                m_stream?.Dispose();
+            }
             return Task.FromResult(true);
         }
 
@@ -134,6 +149,11 @@ namespace NmeaParser
             EmptyLine
         }
 
+        /// <summary>
+        /// Raised when the stream has reached the end. If the stream can be revound, it'll start over, unless you stop the device in this thread.
+        /// </summary>
+        public event EventHandler? EndOfStreamReached;
+
         // stream that slowly populates a buffer from a StreamReader to simulate nmea messages coming
         // in lastLineRead by lastLineRead at a steady stream
         private class BufferedStream : Stream
@@ -159,6 +179,8 @@ namespace NmeaParser
                 m_readTask = StartReadLoop(m_tcs.Token);
             }
 
+            internal bool CanRewind => m_sr.BaseStream.CanSeek;
+
             private async Task StartReadLoop(CancellationToken cancellationToken)
             {
                 await Task.Yield();
@@ -230,7 +252,12 @@ namespace NmeaParser
                 if (m_tcs.IsCancellationRequested)
                     return null;
                 if (m_sr.EndOfStream)
+                {
+                    EndOfStreamReached?.Invoke(this, EventArgs.Empty);
+                    if (m_tcs.IsCancellationRequested)
+                        return null;
                     m_sr.BaseStream.Seek(0, SeekOrigin.Begin); //start over
+                }
                 return m_sr.ReadLine() + '\n';
             }
 
@@ -295,6 +322,8 @@ namespace NmeaParser
                 m_sr.Dispose();
                 base.Dispose(disposing);
             }
+
+            internal event EventHandler? EndOfStreamReached;
         }
     }
 }