`module Support`

Helper methods for detecting support for various features.

Definitions

`def self.buffer?`

Some features are only availble if the IO::Buffer class is available.

Signature

returns　Boolean: Whether the IO::Buffer class is available.

Implementation

def self.buffer?
	IO.const_defined?(:Buffer)
end

`def self.fiber_scheduler_v1?`

The basic fiber scheduler was introduced along side the IO::Buffer class.

To be removed on 31 Mar 2025.

Signature

returns　Boolean: Whether the IO::Buffer class is available.

Implementation

def self.fiber_scheduler_v1?
	IO.const_defined?(:Buffer)
end

`def self.fiber_scheduler_v2?`

More advanced read/write methods and blocking controls were introduced in Ruby 3.2.

To be removed on 31 Mar 2026.

Implementation

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?`

Updated inferfaces for read/write and IO::Buffer were introduced in Ruby 3.3, including pread/pwrite.

To become the default 31 Mar 2026.

Implementation

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