Add support for duplex streams.

Author: ioquatix

lib/io/stream.rb

@@ -1,15 +1,19 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2023-2025, by Samuel Williams.
+# Copyright, 2023-2026, by Samuel Williams.
 
 require_relative "stream/version"
 require_relative "stream/buffered"
+require_relative "stream/duplex"
 
 # @namespace
 class IO
 	# @namespace
 	module Stream
+		def self.Duplex(input, output = input, **options)
+			Buffered.wrap(Duplex.new(input, output), **options)
+		end
 	end
 
 	# Convert any IO-like object into a buffered stream.

lib/io/stream/buffered.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2024-2025, by Samuel Williams.
+# Copyright, 2024-2026, by Samuel Williams.
 
 require_relative "generic"
 require_relative "connection_reset_error"

lib/io/stream/duplex.rb

@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2026, by Samuel Williams.
+
+module IO::Stream
+	# A low-level duplex IO adapter that composes distinct readable and writable endpoints.
+	class Duplex
+		def initialize(input, output = input)
+			@input = input
+			@output = output
+		end
+		
+		attr :input
+		attr :output
+		
+		def to_io
+			@input || @output
+		end
+		
+		def timeout
+			[@input.timeout, @output.timeout].compact.max
+		end
+		
+		def timeout=(duration)
+			@input.timeout = duration
+			@output.timeout = duration
+		end
+		
+		def closed?
+			@input.closed? && @output.closed?
+		end
+		
+		def close_read
+			return if @input.closed?
+			
+			if @input.respond_to?(:close_read)
+				@input.close_read
+			else
+				@input.close
+			end
+		end
+		
+		def close_write
+			return if @output.closed?
+			
+			if @output.respond_to?(:close_write)
+				@output.close_write
+			else
+				@output.close
+			end
+		end
+		
+		def readable?
+			@input.readable?
+		end
+		
+		def close
+			@output.close unless @output.closed?
+			@input.close unless @input.closed?
+		end
+		
+		def write(buffer)
+			@output.write(buffer)
+		end
+		
+		def read_nonblock(size, buffer, exception: false)
+			@input.read_nonblock(size, buffer, exception: exception)
+		end
+		
+		def wait_readable(duration = @timeout)
+			@input.wait_readable(duration)
+		end
+		
+		def wait_writable(duration = @timeout)
+			@output.wait_writable(duration)
+		end
+	end
+end

lib/io/stream/generic.rb

@@ -1,14 +1,15 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2023-2025, by Samuel Williams.
+# Copyright, 2023-2026, by Samuel Williams.
 
 require_relative "string_buffer"
 require_relative "readable"
 require_relative "writable"
 
 require_relative "shim/buffered"
 require_relative "shim/readable"
+require_relative "shim/timeout"
 
 require_relative "openssl"
 

lib/io/stream/openssl.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2024-2025, by Samuel Williams.
+# Copyright, 2024-2026, by Samuel Williams.
 
 require "openssl"
 

lib/io/stream/readable.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2025, by Samuel Williams.
+# Copyright, 2025-2026, by Samuel Williams.
 
 require_relative "string_buffer"
 

lib/io/stream/shim/timeout.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2024-2026, by Samuel Williams.
+
+require "stringio"
+
+class StringIO
+	unless method_defined?(:timeout)
+		def timeout
+			@timeout
+		end
+	end
+	
+	unless method_defined?(:timeout=)
+		def timeout=(duration)
+			@timeout = duration
+		end
+	end
+end

license.md

@@ -1,6 +1,6 @@
 # MIT License
 
-Copyright, 2023-2025, by Samuel Williams.  
+Copyright, 2023-2026, by Samuel Williams.  
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

releases.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+  - Introduce `IO::Stream::Duplex` as a low-level duplex transport for composing separate input and output endpoints.
+  - Add `IO::Stream::Duplex(input, output)` as a convenient constructor that returns a buffered stream wrapping a duplex transport.
+  - Add a timeout compatibility shim for `StringIO` so duplex streams composed from in-memory endpoints can participate in the timeout interface consistently.
   - Remove old OpenSSL method shims.
 
 ## v0.11.0

test/io/stream.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2024, by Samuel Williams.
+# Copyright, 2024-2026, by Samuel Williams.
 
 require "io/stream"
 
@@ -22,4 +22,23 @@
 
 		expect(stream2).to be_equal(stream)
 	end
+	
+	it "can wrap an existing duplex stream" do
+		input = StringIO.new
+		output = StringIO.new
+		
+		duplex = IO::Stream::Duplex.new(input, output)
+		stream = IO::Stream(duplex)
+		
+		expect(stream).to be_a(IO::Stream::Buffered)
+		expect(stream.io).to be_equal(duplex)
+	end
+	
+	it "provides timeout shims for StringIO-backed duplex streams" do
+		duplex = IO::Stream::Duplex.new(StringIO.new, StringIO.new)
+		
+		expect(duplex.timeout).to be_nil
+		expect(duplex.timeout = 0.5).to be == 0.5
+		expect(duplex.timeout).to be == 0.5
+	end
 end