module IO::Event::Support

def self.buffer?

@returns [Boolean] Whether the IO::Buffer class is available.

Some features are only availble if the IO::Buffer class is available. 
def self.buffer?
	IO.const_defined?(:Buffer)
end

def self.fiber_scheduler_v1?

To be removed on 31 Mar 2025.

@returns [Boolean] Whether the IO::Buffer class is available.

The basic fiber scheduler was introduced along side the IO::Buffer class. 
def self.fiber_scheduler_v1?
	IO.const_defined?(:Buffer)
end

def self.fiber_scheduler_v2?

To be removed on 31 Mar 2026.

More advanced read/write methods and blocking controls were introduced in Ruby 3.2. 
def self.fiber_scheduler_v2?
	# Some interface changes were back-ported incorrectly:
	# https://github.com/ruby/ruby/pull/10778
	# Specifically "Improvements to IO::Buffer read/write/pread/pwrite."
	# Missing correct size calculation.
	return false if RUBY_VERSION >= "3.2.5"
	
	IO.const_defined?(:Buffer) and Fiber.respond_to?(:blocking) and IO::Buffer.instance_method(:read).arity == -1
end

def self.fiber_scheduler_v3?

To become the default 31 Mar 2026.

Updated inferfaces for read/write and IO::Buffer were introduced in Ruby 3.3, including pread/pwrite. 
def self.fiber_scheduler_v3?
	if fiber_scheduler_v2?
		return true if RUBY_VERSION >= "3.3"
		
		# Feature detection if required:
		begin
			IO::Buffer.new.slice(0, 0).write(STDOUT)
			return true
		rescue
			return false
		end
	end
end