module Sync_m

def initialize(*args)
  super
  sync_initialize
end

def sync_exclusive?
  sync_mode == EX
end

def sync_extend
  unless (defined? locked? and
          defined? shared? and
          defined? exclusive? and
          defined? lock and
          defined? unlock and
          defined? try_lock and
          defined? synchronize)
    Sync_m.define_aliases(singleton_class)
  end
  sync_initialize
end

def sync_initialize
  @sync_mode = UN
  @sync_waiting = []
  @sync_upgrade_waiting = []
  @sync_sh_locker = Hash.new
  @sync_ex_locker = nil
  @sync_ex_count = 0
  @sync_mutex = Thread::Mutex.new
end

def sync_inspect
  sync_iv = instance_variables.select{|iv| /^@sync_/ =~ iv.id2name}.collect{|iv| iv.id2name + '=' + instance_eval(iv.id2name).inspect}.join(",")
  print "<#{self.class}.extend Sync_m: #{inspect}, <Sync_m: #{sync_iv}>"
end

def sync_lock(m = EX)
  return unlock if m == UN
  Thread.handle_interrupt(StandardError => :on_blocking) do
    while true
      @sync_mutex.synchronize do
        begin
          if sync_try_lock_sub(m)
            return self
          else
            if sync_sh_locker[Thread.current]
              sync_upgrade_waiting.push [Thread.current, sync_sh_locker[Thread.current]]
              sync_sh_locker.delete(Thread.current)
            else
              unless sync_waiting.include?(Thread.current) || sync_upgrade_waiting.reverse_each.any?{|w| w.first == Thread.current }
                sync_waiting.push Thread.current
              end
            end
            @sync_mutex.sleep
          end
        ensure
          sync_waiting.delete(Thread.current)
        end
      end
    end
  end
  self
end

def sync_locked?
  sync_mode != UN
end

def sync_shared?
  sync_mode == SH
end

def sync_synchronize(mode = EX)
  Thread.handle_interrupt(StandardError => :on_blocking) do
    sync_lock(mode)
    begin
      yield
    ensure
      sync_unlock
    end
  end
end

def sync_try_lock(mode = EX)
  return unlock if mode == UN
  @sync_mutex.synchronize do
    sync_try_lock_sub(mode)
  end
end

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

def sync_unlock(m = EX)
  wakeup_threads = []
  @sync_mutex.synchronize do
    if sync_mode == UN
      Err::UnknownLocker.Fail(Thread.current)
    end
    m = sync_mode if m == EX and sync_mode == SH
    runnable = false
    case m
    when UN
      Err::UnknownLocker.Fail(Thread.current)
    when EX
      if sync_ex_locker == Thread.current
        if (self.sync_ex_count = sync_ex_count - 1) == 0
          self.sync_ex_locker = nil
          if sync_sh_locker.include?(Thread.current)
            self.sync_mode = SH
          else
            self.sync_mode = UN
          end
          runnable = true
        end
      else
        Err::UnknownLocker.Fail(Thread.current)
      end
    when SH
      if (count = sync_sh_locker[Thread.current]).nil?
        Err::UnknownLocker.Fail(Thread.current)
      else
        if (sync_sh_locker[Thread.current] = count - 1) == 0
          sync_sh_locker.delete(Thread.current)
          if sync_sh_locker.empty? and sync_ex_count == 0
            self.sync_mode = UN
            runnable = true
          end
        end
      end
    end
    if runnable
      if sync_upgrade_waiting.size > 0
        th, count = sync_upgrade_waiting.shift
        sync_sh_locker[th] = count
        th.wakeup
        wakeup_threads.push th
      else
        wait = sync_waiting
        self.sync_waiting = []
        for th in wait
          th.wakeup
          wakeup_threads.push th
        end
      end
    end
  end
  for th in wakeup_threads
    th.run
  end
  self
end