From 6506a3021fee732935515800b80419c2f966da00 Mon Sep 17 00:00:00 2001
From: Saxon Nelson-Milton <saxon@ausocean.org>
Date: Sat, 19 Dec 2020 12:52:49 +1030
Subject: [PATCH] device/file & revid/pipeline.go: add looping functionality to
 file device and removing from processFrom

---
 device/file/file.go | 21 +++++++++++++++-
 revid/pipeline.go   | 59 +++++++++++++++++++--------------------------
 2 files changed, 45 insertions(+), 35 deletions(-)

diff --git a/device/file/file.go b/device/file/file.go
index 0ec2d928..c78f56e5 100644
--- a/device/file/file.go
+++ b/device/file/file.go
@@ -82,7 +82,26 @@ func (m *AVFile) Stop() error {
 // called and Stop has since been called, an error is returned.
 func (m *AVFile) Read(p []byte) (int, error) {
 	if m.f != nil {
-		return m.f.Read(p)
+		n, err := m.f.Read()
+		if err != nil {
+			// In the case that we reach end of file but loop is true, we want to
+			// seek to start and keep reading from there.
+			if err == io.EOF && m.cfg.Loop {
+				_, err = m.f.Seek(0,io.SeekStart)
+				if err != nil {
+					return 0, fmt.Errorf("could not seek to start of file for input loop: %w",err)
+				}
+
+				// Now that we've seeked to start, let's try reading again.
+				n, err = m.f.Read()
+				if err != nil {
+					return n, fmt.Errorf("could not read after start seek: %w",err)
+				}
+				return n, nil
+			}
+			return n, err
+		}
+		return n, nil  
 	}
 	return 0, errors.New("AV file is closed")
 }
diff --git a/revid/pipeline.go b/revid/pipeline.go
index 7d770a42..7cda947d 100644
--- a/revid/pipeline.go
+++ b/revid/pipeline.go
@@ -332,41 +332,32 @@ func (r *Revid) setLexer(c uint8, isRTSP bool) error {
 func (r *Revid) processFrom(in device.AVDevice, delay time.Duration) {
 	defer r.wg.Done()
 
-	for l := true; l; l = r.cfg.Loop {
-		err := in.Start()
-		if err != nil {
-			r.err <- fmt.Errorf("could not start input device: %w", err)
-			return
-		}
+	err := in.Start()
+	if err != nil {
+		r.err <- fmt.Errorf("could not start input device: %w", err)
+		return
+	}
 
-		// Lex data from input device, in, until finished or an error is encountered.
-		// For a continuous source e.g. a camera or microphone, we should remain
-		// in this call indefinitely unless in.Stop() is called and an io.EOF is forced.
-		r.cfg.Logger.Log(logger.Debug, "lexing")
-		err = r.lexTo(r.filters[0], in, delay)
-		switch err {
-		case nil, io.EOF:
-			r.cfg.Logger.Log(logger.Info, "end of file")
-		case io.ErrUnexpectedEOF:
-			r.cfg.Logger.Log(logger.Info, "unexpected EOF from input")
-		default:
-			r.err <- err
-		}
-		r.cfg.Logger.Log(logger.Info, "finished reading input")
+	// Lex data from input device, in, until finished or an error is encountered.
+	// For a continuous source e.g. a camera or microphone, we should remain
+	// in this call indefinitely unless in.Stop() is called and an io.EOF is forced.
+	r.cfg.Logger.Log(logger.Debug, "lexing")
+	err = r.lexTo(r.filters[0], in, delay)
+	switch err {
+	case nil, io.EOF:
+		r.cfg.Logger.Log(logger.Info, "end of file")
+	case io.ErrUnexpectedEOF:
+		r.cfg.Logger.Log(logger.Info, "unexpected EOF from input")
+	default:
+		r.err <- err
+	}
+	r.cfg.Logger.Log(logger.Info, "finished reading input")
 
-		r.cfg.Logger.Log(logger.Debug, "stopping input")
-		err = in.Stop()
-		if err != nil {
-			r.err <- fmt.Errorf("could not stop input source: %w", err)
-		} else {
-			r.cfg.Logger.Log(logger.Info, "input stopped")
-		}
-
-		// If we're looping and we get a stop signal we return.
-		select {
-		case <-r.stop:
-			return
-		default:
-		}
+	r.cfg.Logger.Log(logger.Debug, "stopping input")
+	err = in.Stop()
+	if err != nil {
+		r.err <- fmt.Errorf("could not stop input source: %w", err)
+	} else {
+		r.cfg.Logger.Log(logger.Info, "input stopped")
 	}
 }