Class: FiberScheduler::Selector

Inherits:
Object
  • Object
show all
Defined in:
lib/fiber_scheduler/selector.rb

Defined Under Namespace

Classes: Waiter

Constant Summary collapse

EAGAIN = 
Errno::EAGAIN::Errno

Instance Method Summary collapse

Constructor Details

#initialize(fiber) ⇒ Selector

Returns a new instance of Selector.



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# File 'lib/fiber_scheduler/selector.rb', line 62

def initialize(fiber)
  @fiber = fiber

  @waiting = {}.compare_by_identity
  @ready = []
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 69

def close
  @fiber = nil
  @waiting = nil
  @ready = nil
end

#io_read(fiber, io, buffer, length) ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 91

def io_read(fiber, io, buffer, length)
  offset = 0

  loop do
    maximum_size = buffer.size - offset

    result = Fiber.new(blocking: true) {
      io.read_nonblock(maximum_size, exception: false)
    }.resume

    case result
    when :wait_readable
      if length > 0
        io_wait(fiber, io, IO::READABLE)
      else
        return -EAGAIN
      end
    when :wait_writable
      if length > 0
        io_wait(fiber, io, IO::WRITABLE)
      else
        return -EAGAIN
      end
    when nil
      break
    else
      buffer.set_string(result, offset)

      size = result.bytesize
      offset += size
      break if size >= length
      length -= size
    end
  end

  offset
end

#io_wait(fiber, io, events) ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 83

def io_wait(fiber, io, events)
  waiter = @waiting[io] = Waiter.new(fiber, events, @waiting[io])

  @fiber.transfer
ensure
  waiter&.invalidate
end

#io_write(fiber, io, buffer, length) ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 129

def io_write(fiber, io, buffer, length)
  offset = 0

  loop do
    maximum_size = buffer.size - offset

    chunk = buffer.get_string(offset, maximum_size)
    result = Fiber.new(blocking: true) {
      io.write_nonblock(chunk, exception: false)
    }.resume

    case result
    when :wait_readable
      if length > 0
        io_wait(fiber, io, IO::READABLE)
      else
        return -EAGAIN
      end
    when :wait_writable
      if length > 0
        io_wait(fiber, io, IO::WRITABLE)
      else
        return -EAGAIN
      end
    else
      offset += result
      break if result >= length
      length -= result
    end
  end

  offset
end

#process_wait(fiber, pid, flags) ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 163

def process_wait(fiber, pid, flags)
  reader, writer = IO.pipe

  thread = Thread.new do
    Process::Status.wait(pid, flags)
  ensure
    writer.close
  end

  io_wait(fiber, reader, IO::READABLE)

  thread.value
ensure
  reader.close
  writer.close
  thread&.kill
end

#push(fiber) ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 79

def push(fiber)
  @ready.push(fiber)
end

#select(duration = nil) ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 181

def select(duration = nil)
  if @ready.any?
    # If we have popped items from the ready list, they may influence the
    # duration calculation, so we don't delay the event loop:
    duration = 0

    count = @ready.size
    count.times do
      fiber = @ready.shift
      fiber.transfer if fiber.alive?
    end
  end

  readable = []
  writable = []

  @waiting.each do |io, waiter|
    waiter.each do |fiber, events|
      if (events & IO::READABLE) > 0
        readable << io
      end

      if (events & IO::WRITABLE) > 0
        writable << io
      end
    end
  end

  duration = 0 if @ready.any?
  readable, writable, _ = IO.select(readable, writable, nil, duration)

  ready = Hash.new(0)

  readable&.each do |io|
    ready[io] |= IO::READABLE
  end

  writable&.each do |io|
    ready[io] |= IO::WRITABLE
  end

  ready.each do |io, events|
    waiter = @waiting.delete(io)
    waiter.transfer(events)
  end

  ready.size
end

#transfer ⇒ Object 



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# File 'lib/fiber_scheduler/selector.rb', line 75

def transfer
  @fiber.transfer
end