blah.go

func (ns *NetworkSimulator) NewConnPair(local, remote peer.ID) (*Conn, *Conn, error) {
	r1, w1 := io.Pipe()
	r2, w2 := io.Pipe()

	laddr := ns.listeners[local].Multiaddr()
	raddr := ns.listeners[remote].Multiaddr()

	ltok := make(chan struct{}, 1)
	rtok := make(chan struct{}, 1)

	ltok <- struct{}{}
	rtok <- struct{}{}

	return &Conn{
			read:       r1,
			write:      w2,
			local:      local,
			remote:     remote,
			laddr:      laddr,
			raddr:      raddr,
			writeToken: ltok,
		},
		&Conn{
			read:       r2,
			write:      w1,
			local:      remote,
			remote:     local,
			laddr:      raddr,
			raddr:      laddr,
			writeToken: rtok,
		}, nil
}

type Conn struct {
	read       io.ReadCloser
	write      io.WriteCloser
	local      peer.ID
	remote     peer.ID
	laddr      ma.Multiaddr
	raddr      ma.Multiaddr
	writeToken chan struct{}
}

func (c *Conn) Read(b []byte) (int, error) {
	return c.read.Read(b)
}

func (c *Conn) Write(b []byte) (int, error) {
	t, ok := <-c.writeToken
	if !ok {
		return 0, errors.New("attempted to write on a closed connection")
	}
	go func() {
		c.write.Write(b)
		c.writeToken <- t
	}()
	return len(b), nil
}