av/device/raspistill/imp_release.go

// +build !test

/*
DESCRIPTION
  release.go provides implementations for the Raspistill struct for release
  conditions, i.e. we're running on a raspberry pi with access to the actual
  raspistill utility with a pi camera connected. The code here runs a raspistill
  background process and reads captured images from the camera.

AUTHORS
  Saxon 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 raspistill

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"os/exec"
	"strings"

	"bitbucket.org/ausocean/av/revid/config"
	"bitbucket.org/ausocean/utils/logging"
)

type raspistill struct {
	cfg       config.Config
	cmd       *exec.Cmd
	out       io.ReadCloser
	log       logging.Logger
	done      chan struct{}
	isRunning bool
}

func new(l logging.Logger) raspistill {
	return raspistill{
		log:  l,
		done: make(chan struct{}),
	}
}

func (r *Raspistill) stop() error {
	if r.isRunning == false {
		return nil
	}
	close(r.done)
	if r.cmd == nil || r.cmd.Process == nil {
		return errors.New("raspistill process was never started")
	}
	err := r.cmd.Process.Kill()
	if err != nil {
		return fmt.Errorf("could not kill raspistill process: %w", err)
	}
	r.isRunning = false
	return r.out.Close()
}

func (r *Raspistill) start() error {
	args := []string{
		"--output", "-",
		"--nopreview",
		"--width", fmt.Sprint(r.cfg.Width),
		"--height", fmt.Sprint(r.cfg.Height),
		"--rotation", fmt.Sprint(r.cfg.Rotation),
		"--timeout", fmt.Sprint(r.cfg.TimelapseDuration),
		"--timelapse", fmt.Sprint(r.cfg.TimelapseInterval),
		"--quality", fmt.Sprint(r.cfg.JPEGQuality),
	}

	r.log.Info(pkg+"raspistill args", "args", strings.Join(args, " "))
	r.cmd = exec.Command("raspistill", args...)

	var err error
	r.out, err = r.cmd.StdoutPipe()
	if err != nil {
		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() {
		errScnr := bufio.NewScanner(stderr)
		for {
			select {
			case <-r.done:
				r.log.Info("raspistill.Stop() called, finished checking stderr")
				return
			default:
			}

			if errScnr.Scan() {
				r.log.Error("error line from raspistill stderr", "error", errScnr.Text())
				continue
			}

			err := errScnr.Err()
			if err != nil {
				r.log.Error("error from stderr scan", "error", err)
			}
		}
	}()

	err = r.cmd.Start()
	if err != nil {
		return fmt.Errorf("could not start raspistill process: %w", err)
	}
	r.isRunning = true

	return nil
}

func (r *Raspistill) read(p []byte) (int, error) {
	if r.out != nil {
		return r.out.Read(p)
	}
	return 0, errNotStarted
}