app-accessibility/brltty/files/brltty

#!/bin/sh

# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# Define some script constants.
scriptName="${0##*/}"

BRLTTY_USER="brltty"
BRLTTY_GROUP="brltty"

BRLTTY_SUBDIR="brltty"
BRLTTY_VARDIR="/var/lib/${BRLTTY_SUBDIR}"
BRLTTY_RUNDIR="/run/${BRLTTY_SUBDIR}"

BRLTTY_CFGFILE="/etc/brltty.conf"
BRLTTY_DEVFILE="${BRLTTY_RUNDIR}/device"
BRLTTY_DRVFILE="${BRLTTY_RUNDIR}/driver"
BRLTTY_ENVFILE="${BRLTTY_RUNDIR}/env"
BRLTTY_LOGFILE="${BRLTTY_RUNDIR}/log"
BRLTTY_PIDFILE="${BRLTTY_RUNDIR}/pid"

BRLAPI_SUBDIR="BrlAPI"
BRLAPI_SOCDIR="${BRLTTY_RUNDIR}/${BRLAPI_SUBDIR}"
# The number (0) must be kept in sync with the Host api parameter in
# brltty.conf.
BRLAPI_SOCFILE="${BRLAPI_SOCDIR}/0"

showUsageSummary() {
cat <<END-OF-USAGE-SUMMARY
Usage: ${scriptName} [-option ...] [action [argument ...]]

These options may be specified:
  -h  show this usage summary and then exit
  -q  be quiet - don't show informative output
  -v  be verbose - show host commands, etc

These actions may be specified:
  device
  driver
  pid
  prepare
  run [brltty-argument ...]
  stop
  test
  wait
END-OF-USAGE-SUMMARY
}

putLine() {
  local line="${1}"

  "${quietRequested}" || echo "${line}"
}

putFile() {
  local file="${1}"

  [ -f "${file}" ] || return 8
  "${quietRequested}" && return 0
  cat "${file}"
}

writeMessage() {
  local message="${1}"

  echo >&2 "${scriptName}: ${message}"
}

syntaxError() {
  local message="${1}"

  writeMessage "${message}"
  exit 2
}

# Set the option defaults.
helpRequested=false
quietRequested=false
verboseRequested=false

# Process the options.
while getopts ":hqv" option
do
  case "${option}"
  in
    h) helpRequested=true;;
    q) quietRequested=true;;
    v) verboseRequested=true;;

    :) syntaxError "missing operand: -${OPTARG}";;
   \?) syntaxError "unknown option: -${OPTARG}";;
    *) syntaxError "unimplemented option: -${option}";;
  esac
done

# Remove the options from the command line.
shift $((OPTIND - 1))

# If help was requested then just show the usage summary.
"${helpRequested}" && {
  showUsageSummary
  exit 0
}

# Set the default action (and its arguments).
[ "${#}" -eq 0 ] && set -- run

log() {
  local message="${*}"

  [ -t 2 ] && writeMessage "${message}"
  logger -t brltty_udev "${Message}"
}

executeHostCommand() {
  "${verboseRequested}" && writeMessage "host command: ${*}"

  "${@}"
  local exitStatus="${?}"

  "${verboseRequested}" && {
    [ "${exitStatus}" -eq 0 ] || writeMessage "exit status: ${exitStatus}"
  }

  return "${exitStatus}"
}

# Ensure that the needed directories exist and have the right ownership and permissions.
prepareNeededDirectories() {
  # NOTE: Chrome is observing ${BRLAPI_SOCDIR} for changes.
  # It is important to only remove world-readability *after* setting the
  # group ownership so that the browser doesn't lose read access.
  # This is a race that would cause chrome to stop observing the directory
  # and therefore not get notified when a braille display is connected.

  set -- "${BRLTTY_VARDIR}" "${BRLTTY_RUNDIR}" "${BRLAPI_SOCDIR}"
  executeHostCommand mkdir -p -m 0755 "${@}"
  executeHostCommand chown -R "${BRLTTY_USER}:${BRLTTY_GROUP}" "${@}"
  executeHostCommand chmod 750 "${@}"
}

# Send a signal to the process that owns the BrlAPI server socket.
sendSignal() {
  local signal="${1}"

  # This must be the last command so that we return its exit status.
  [ -e "${BRLAPI_SOCFILE}" ] && {
    executeHostCommand fuser -s -k -"${signal}" "${BRLAPI_SOCFILE}"
  }
}

isProcessRunning() {
  # This must be the last command so that we return its exit status.
  sendSignal 0
}

# Stop any brltty processes that might be holding on to the
# BrlAPI server socket.  We try hard, because failure to free up the socket
# will lock the braille user out from the machine!
stopProcess() {
  sendSignal TERM || return 0

  log "waiting for brltty to terminate"
  local delay=0.1 # in seconds
  local limit=5
  local try=0

  while [ $((try += 1)) -le "${limit}" ]
  do
    executeHostCommand sleep "${delay}"
    sendSignal TERM || return 0
  done

  log "forcing brltty to terminate"
  sendSignal KILL
}

noMoreParameters() {
  [ "${#}" -eq 0 ] || syntaxError "too many parameters"
}

action_device() {
  noMoreParameters "${@}"

  putFile "${BRLTTY_DEVFILE}"
  exit "${?}"
}

action_driver() {
  noMoreParameters "${@}"

  putFile "${BRLTTY_DRVFILE}"
  exit "${?}"
}

action_pid() {
  noMoreParameters "${@}"

  putFile "${BRLTTY_PIDFILE}"
  exit "${?}"
}

action_prepare() {
  noMoreParameters "${@}"

  prepareNeededDirectories
  exit "${?}"
}

# Run brltty within a minijail.
action_run() {
  stopProcess
  prepareNeededDirectories

  # Files created by the daemon shouldn't be accessible by users not in the
  # brltty group.
  executeHostCommand umask 0007

  # If the Bluetooth address is defined then use that device.
  [ -n "${ADDRESS}" ] && {
    executeHostCommand export BRLTTY_BRAILLE_DEVICE="bluetooth:${ADDRESS}"
  }

  echo "${BRLTTY_BRAILLE_DEVICE}" >"${BRLTTY_DEVFILE}"
  echo "${BRLTTY_BRAILLE_DRIVER}" >"${BRLTTY_DRVFILE}"

  log "starting brltty -" \
      "device:${BRLTTY_BRAILLE_DEVICE:-unknown}" \
      "driver:${BRLTTY_BRAILLE_DRIVER:-unknown}"

  executeHostCommand export BRLTTY_CONFIGURATION_FILE="${BRLTTY_CFGFILE}"
  executeHostCommand export BRLTTY_UPDATABLE_DIRECTORY="${BRLTTY_VARDIR}"
  executeHostCommand export BRLTTY_WRITABLE_DIRECTORY="${BRLTTY_RUNDIR}"
  executeHostCommand export BRLTTY_PID_FILE="${BRLTTY_PIDFILE}"
  executeHostCommand export BRLTTY_LOG_FILE="${BRLTTY_LOGFILE}"

  # The provided arguments for brltty are in ${@}.
  # Add ours before them in case they contain syntax errors.
  set -- -E "${@}" # Allow options to be specified via environment variables.
  set -- -n "${@}" # Keep brltty in the foreground.
  set -- -q "${@}" # Suppress the start message.

  # Run brltty within a restricted environment.
  env >"${BRLTTY_ENVFILE}"
  executeHostCommand exec \
    /sbin/minijail0 -u "${BRLTTY_USER}" -g "${BRLTTY_GROUP}" -G -- \
    /bin/brltty "${@}"

  # We shouldn't get here - but we might because exec can fail.
  exit "${?}"
}

action_stop() {
  noMoreParameters "${@}"

  stopProcess
  exit "${?}"
}

action_test() {
  noMoreParameters "${@}"

  isProcessRunning
  local exitStatus="${?}"

  [ "${exitStatus}" -eq 0 ] && putLine "running" || putLine "stopped"
  exit "${exitStatus}"
}

action_wait() {
  noMoreParameters "${@}"

  local delay=0.5
  local limit=10
  local try=0

  while isProcessRunning
  do
    [ $((try += 1)) -gt "${limit}" ] && {
      log "brltty has not terminated"
      exit 9
    }

    executeHostCommand sleep "${delay}"
  done

  exit 0
}

[ "${#}" -eq 0 ] && syntaxError "missing action"
action="${1}"
shift

case "${action}"
in
  device | driver | pid | prepare | run | stop | test | wait)
    "action_${action}" "${@}"
    ;;

  *) syntaxError "unknown action: ${action}";;
esac

# Just in case we get here.
exit 0