class Eventbox

Retrieves the Eventbox options of this class.

@return [Hash] The options for instantiation of this class. @see with_options

# File lib/eventbox.rb, line 47
def self.eventbox_options
  {
    threadpool: Thread,
    guard_time: 0.5,
    gc_actions: false,
  }
end

@private

Create a new {Eventbox} instance.

All arguments are passed to the init() method when defined.

# File lib/eventbox.rb, line 94
def initialize(*args, **kwargs, &block)
  options = self.class.eventbox_options

  # This instance variable is set to self here, but replaced by Boxable#action to a WeakRef
  @__eventbox__ = self

  # Verify that all public methods are properly wrapped and no unsafe methods exist
  # This check is done at the first instanciation only and doesn't slow down subsequently.
  # Since test and set operations aren't atomic, it can happen that the check is executed several times.
  # This is considered less harmful than slowing all instanciations down by a mutex.
  unless self.class.instance_variable_defined?(:@eventbox_methods_checked)
    self.class.instance_variable_set(:@eventbox_methods_checked, true)

    obj = Object.new
    meths = methods - obj.methods - [:__getobj__, :shutdown!, :shared_object, :€]
    prmeths = private_methods - obj.private_methods
    prohib = meths.find do |name|
      !prmeths.include?(:"__#{name}__")
    end
    if prohib
      meth = method(prohib)
      raise InvalidAccess, "method `#{prohib}' at #{meth.source_location.join(":")} is not properly defined -> it must be created per async_call, sync_call, yield_call or private prefix"
    end
  end

  # Run the processing of calls (the event loop) in a separate class.
  # Otherwise it would block GC'ing of self.
  @__event_loop__ = EventLoop.new(options[:threadpool], options[:guard_time])
  ObjectSpace.define_finalizer(self, @__event_loop__.method(:send_shutdown))

  init(*args, **kwargs, &block)
end

Create a new derived class with the given options.

The options are merged with the options of the base class. The following options are available:

@param threadpool [Object] A threadpool.

Can be either +Thread+ (default) or a {Eventbox::Threadpool} instance.

@param guard_time Event scope methods should not do blocking operations.

Eventbox measures the time of each call to event scope methods and warns, when it is exceeded.
There are several ways to configure guard_time:
* Set to +nil+: Disable measuring of time to process event scope methods.
* Set to a +Numeric+ value: Maximum number of seconds allowed for event scope methods.
* Set to a +Proc+ object: Called after each call to an event scope method.
  The +Proc+ object is called with the number of seconds the call took as first and the name as second argument.

@param gc_actions [Boolean] Enable or disable (default) garbage collection of running actions.

Setting this to true permits the garbage collector to shutdown running action threads and subsequently delete the corresponding Eventbox object.

# File lib/eventbox.rb, line 71
def self.with_options(**options)
  Class.new(self) do
    define_singleton_method(:eventbox_options) do
      super().merge(options)
    end

    def self.inspect
      klazz = self
      until name=klazz.name
        klazz = klazz.superclass
      end
      "#{name}#{eventbox_options}"
    end
  end
end

Mark an object as to be shared instead of copied.

A marked object is never passed as copy, but passed as reference. The object is therefore wrapped as {WrappedObject} or {ExternalObject} when used in an unsafe scope. Objects marked within the event scope are wrapped as {WrappedObject}, which denies access from external/action scope or the event scope of a different Eventbox instance. Objects marked in external/action scope are wrapped as {ExternalObject} which allows {External.send asynchronous calls} from event scope. In all cases the object can be passed as reference and is automatically unwrapped when passed back to the original scope. It can therefore be used to modify the original object even after traversing the boundaries.

The mark is stored for the lifetime of the object, so that it's enough to mark only once at object creation.

Due to {Eventbox::Sanitizer Sanitizer dissection} of non-marshalable objects, wrapping and unwrapping works even if the shared object is stored within another object as instance variable or within a collection class. This is in contrast to €-variables which can only wrap the argument object as a whole when entering the event scope. See the difference here:

A = Struct.new(:a)
class Bo < Eventbox
  sync_call def go(struct, €struct)
    p struct            # prints #<struct A a=#<Eventbox::ExternalObject @object="abc" @name=:a>>
    p €struct           # prints #<Eventbox::ExternalObject @object=#<struct A a="abc"> @name=:€struct>
    [struct, €struct]
  end
end
e = Bo.new
o = A.new(e.shared_object("abc"))
e.go(o, o)              # => [#<struct A a="abc">, #<struct A a="abc">]

# File lib/eventbox.rb, line 267
       def shared_object(object)
  @__event_loop__.shared_object(object)
end

Force stop of all action threads spawned by this {Eventbox} instance.

It is possible to enable automatic cleanup of action threads by the garbage collector through {Eventbox.with_options}. However in some cases automatic garbage collection doesn't remove all instances due to running action threads. Calling shutdown! when the work of the instance is done, ensures that it is GC'ed in all cases.

If {shutdown!} is called externally, it blocks until all actions threads have terminated.

If {shutdown!} is called in the event scope, it just triggers the termination of all action threads and returns afterwards. Optionally {shutdown!} can be called with a block. It is called when all actions threads terminated.

# File lib/eventbox.rb, line 319
       def shutdown!(&completion_block)
  @__event_loop__.shutdown(&completion_block)
end

@private

# File lib/eventbox.rb, line 145
          def __getobj__
  self
end

Create a proc object for asynchronous (fire-and-forget) calls similar to {async_call}.

It can be passed to external scope and called from there like so:

class MyBox < Eventbox
  sync_call def print(p1)
    async_proc do |p2|
      puts "#{p1} #{p2}"
    end
  end
end
MyBox.new.print("Hello").call("world")   # Prints "Hello world"

The created object can be safely called from any thread. All block arguments are passed through the {Sanitizer}. The block itself might not do any blocking calls or expensive computations - this would impair responsiveness of the {Eventbox} instance. Instead use {Eventbox.action} in these cases.

The block always returns self to the caller.

# File lib/eventbox.rb, line 182
def async_proc(name=nil, &block)
  @__event_loop__.new_async_proc(name=nil, &block)
end

Get the context of the waiting external call within a yield or sync method or closure.

Callable within the event scope only.

@returns [BlockingExternalCallContext] The current call context.

Returns +nil+ in async_call or async_proc context.

Usable as first parameter to {ExternalProc.call} and {ExternalObject.send}.

# File lib/eventbox.rb, line 292
        def call_context
  if @__event_loop__.event_scope?
    @__event_loop__._latest_call_context
  else
    raise InvalidAccess, "not in event scope"
  end
end

@private

Provide access to the eventbox instance as either

• self within the eventbox instance itself or

• WeakRef.new(self).__getobj__ within actions.

This allows actions to be GC'ed, when the related Eventbox instance is no longer in use.

# File lib/eventbox.rb, line 140
def eventbox
  @__eventbox__.__getobj__
end

Initialize a new {Eventbox} instance.

This method is executed for initialization of a Eventbox instance. This method receives all arguments given to Eventbox.new after they have passed the {Sanitizer}. It can be used like initialize in ordinary ruby classes including super to initialize included modules or base classes.

{init} can be defined as either {sync_call} or {async_call} with no difference. {init} can also be defined as {yield_call}, so that the new call is blocked until the result is yielded. {init} can even be defined as {action}, so that each instance of the class immediately starts a new thread.

# File lib/eventbox.rb, line 160
def init(*args)
end

Starts a new action dedicated to call external objects.

It returns a {CallContext} which can be used with {Eventbox::ExternalObject#send} and {Eventbox::ExternalProc#call}.

@returns [ActionCallContext] A new call context provided by a newly started action.

# File lib/eventbox.rb, line 280
        def new_action_call_context
  ActionCallContext.new(@__event_loop__)
end

Create a Proc object for synchronous calls similar to {sync_call}.

It can be passed to external scope and called from there like so:

class MyBox < Eventbox
  sync_call def print(p1)
    sync_proc do |p2|
      "#{p1} #{p2}"
    end
  end
end
puts MyBox.new.print("Hello").call("world")   # Prints "Hello world"

The created object can be safely called from any thread. All block arguments as well as the result value are passed through the {Sanitizer}. The block itself might not do any blocking calls or expensive computations - this would impair responsiveness of the {Eventbox} instance. Instead use {Eventbox.action} in these cases.

This Proc is simular to {async_proc}, but when the block is invoked, it is executed and it's return value is returned to the caller. Since all processing within the event scope of an {Eventbox} instance must not execute blocking operations, sync procs can only return immediate values. For deferred results use {yield_proc} instead.

# File lib/eventbox.rb, line 207
def sync_proc(name=nil, &block)
  @__event_loop__.new_sync_proc(name=nil, &block)
end

Create a Proc object for calls with deferred result similar to {yield_call}.

It can be passed to external scope and called from there like so:

class MyBox < Eventbox
  sync_call def print(p1)
    yield_proc do |p2, result|
      result.yield "#{p1} #{p2}"
    end
  end
end
puts MyBox.new.print("Hello").call("world")   # Prints "Hello world"

This proc type is simular to {sync_proc}, however it's not the result of the block that is returned. Instead the block is called with one additional argument in the event scope, which is used to yield a result value. The result value can be yielded within the called block, but it can also be called by any other event scope or external method, leading to a deferred proc return. The external thread calling this proc is suspended until a result is yielded. However the Eventbox object keeps responsive to calls from other threads.

The created object can be safely called from any thread. If yield procs are called in the event scope, they must get a Proc object as the last argument. It is called when a result was yielded.

All block arguments as well as the result value are passed through the {Sanitizer}. The block itself might not do any blocking calls or expensive computations - this would impair responsiveness of the {Eventbox} instance. Instead use {Eventbox.action} in these cases.

# File lib/eventbox.rb, line 237
def yield_proc(name=nil, &block)
  @__event_loop__.new_yield_proc(name=nil, &block)
end