Merged in raspivid-stderr (pull request #299)

device/raspivid/raspivid.go: piping stderr and checking for errors

Approved-by: Saxon Milton <saxon.milton@gmail.com>

device/raspivid/raspivid.go

@@ -28,6 +28,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os/exec"
 	"strings"
 
@@ -106,14 +107,20 @@ var AutoWhiteBalanceModes = [...]string{
 // Raspivid is an implementation of AVDevice that provides control over the
 // raspivid command to allow reading of data from a Raspberry Pi camera.
 type Raspivid struct {
-	cfg config.Config
-	cmd *exec.Cmd
-	out io.ReadCloser
-	log config.Logger
+	cfg  config.Config
+	cmd  *exec.Cmd
+	out  io.ReadCloser
+	log  config.Logger
+	done chan struct{}
 }
 
 // New returns a new Raspivid.
-func New(l config.Logger) *Raspivid { return &Raspivid{log: l} }
+func New(l config.Logger) *Raspivid {
+	return &Raspivid{
+		log:  l,
+		done: make(chan struct{}),
+	}
+}
 
 // Name returns the name of the device.
 func (r *Raspivid) Name() string {
@@ -250,6 +257,32 @@ func (r *Raspivid) Start() error {
 		return fmt.Errorf("could not pipe command output: %w", err)
 	}
 
+	stderr, err := r.cmd.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("could not pipe command error: %w", err)
+	}
+
+	go func() {
+		for {
+			select {
+			case <-r.done:
+				r.cfg.Logger.Log(logger.Info, "raspivid.Stop() called, finished checking stderr")
+				return
+			default:
+				buf, err := ioutil.ReadAll(stderr)
+				if err != nil {
+					r.cfg.Logger.Log(logger.Error, "could not read stderr", "error", err)
+					return
+				}
+
+				if len(buf) != 0 {
+					r.cfg.Logger.Log(logger.Error, "error from raspivid stderr", "error", string(buf))
+					return
+				}
+			}
+		}
+	}()
+
 	err = r.cmd.Start()
 	if err != nil {
 		return fmt.Errorf("could not start raspivid command: %w", err)
@@ -269,6 +302,7 @@ func (r *Raspivid) Read(p []byte) (int, error) {
 
 // Stop will terminate the raspivid process and close the output pipe.
 func (r *Raspivid) Stop() error {
+	close(r.done)
 	if r.cmd == nil || r.cmd.Process == nil {
 		return errors.New("raspivid process was never started")
 	}