revid/file.go: wrote AVDevice implementation for file containing audio or video media

revid/file.go

@@ -0,0 +1,54 @@
+/*
+DESCRIPTION
+  file.go provides an implementation of the AVDevice interface for media files.
+
+AUTHORS
+  Saxon A. Nelson-Milton <saxon@ausocean.org>
+
+LICENSE
+  Copyright (C) 2019 the Australian Ocean Lab (AusOcean)
+
+  It is free software: you can redistribute it and/or modify them
+  under the terms of the GNU General Public License as published by the
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+  for more details.
+
+  You should have received a copy of the GNU General Public License
+  in gpl.txt.  If not, see http://www.gnu.org/licenses.
+*/
+
+package revid
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+type AVFile struct {
+	f   io.ReadCloser
+	cfg Config
+}
+
+func NewAVFile() *AVFile                     { return &AVFile{} }
+func (m *AVFile) Stop() error                { return m.f.Close() }
+func (m *AVFile) Read(p []byte) (int, error) { return m.f.Read(p) }
+
+func (m *AVFile) Set(c Config) error {
+	m.cfg = c
+	return nil
+}
+
+func (m *AVFile) Start() error {
+	var err error
+	m.f, err = os.Open(m.cfg.InputPath)
+	if err != nil {
+		return fmt.Errorf("could not open media file: %w", err)
+	}
+	return nil
+}