module Sync_m

def sync_try_lock_sub(m)
  case m
  when SH
    case sync_mode
    when UN
      self.sync_mode = m
      sync_sh_locker[Thread.current] = 1
      ret = true
    when SH
      count = 0 unless count = sync_sh_locker[Thread.current]
      sync_sh_locker[Thread.current] = count + 1
      ret = true
    when EX
      # in EX mode, lock will upgrade to EX lock
      if sync_ex_locker == Thread.current
        self.sync_ex_count = sync_ex_count + 1
        ret = true
      else
        ret = false
      end
    end
  when EX
    if sync_mode == UN or
        sync_mode == SH && sync_sh_locker.size == 1 && sync_sh_locker.include?(Thread.current)
      self.sync_mode = m
      self.sync_ex_locker = Thread.current
      self.sync_ex_count = 1
      ret = true
    elsif sync_mode == EX && sync_ex_locker == Thread.current
      self.sync_ex_count = sync_ex_count + 1
      ret = true
    else
      ret = false
    end
  else
    Err::LockModeFailer.Fail m
  end
  return ret
end