/* NAME lex.go DESCRIPTION lex.go provides a lexer to extract separate JPEG images from a MJPEG stream. AUTHOR Dan Kortschak <dan@ausocean.org> LICENSE lex.go is Copyright (C) 2017 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 along with revid in gpl.txt. If not, see http://www.gnu.org/licenses. */ // lex.go provides a lexer to extract separate JPEG images from a MJPEG stream. package mjpeg import ( "bufio" "bytes" "fmt" "io" "time" ) var noDelay = make(chan time.Time) func init() { close(noDelay) } // Lex parses MJPEG frames read from src into separate writes to dst with // successive writes being performed not earlier than the specified delay. func Lex(dst io.Writer, src io.Reader, delay time.Duration) error { var tick <-chan time.Time if delay == 0 { tick = noDelay } else { ticker := time.NewTicker(delay) defer ticker.Stop() tick = ticker.C } r := bufio.NewReader(src) for { buf := make([]byte, 2, 4<<10) n, err := r.Read(buf) if n < 2 { return nil } if err != nil { if err == io.EOF { return nil } return err } if !bytes.Equal(buf, []byte{0xff, 0xd8}) { return fmt.Errorf("parser: not MJPEG frame start: %#v", buf) } var last byte for { b, err := r.ReadByte() if err != nil { if err == io.EOF { return nil } return err } buf = append(buf, b) if last == 0xff && b == 0xd9 { break } last = b } <-tick _, err = dst.Write(buf) if err != nil { return err } } }