blob: c9cdaf27a7b9f4215f1c615253e54fca160f226e [file] [log] [blame]
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fakenet
import (
// NewConn returns a net.Conn built on top of the supplied reader and writer.
// It decouples the read and write on the conn from the underlying stream
// to enable Close to abort ones that are in progress.
// It's primary use is to fake a network connection from stdin and stdout.
func NewConn(name string, in io.ReadCloser, out io.WriteCloser) net.Conn {
c := &fakeConn{
name: name,
reader: newFeeder(in.Read),
writer: newFeeder(out.Write),
in: in,
out: out,
return c
type fakeConn struct {
name string
reader *connFeeder
writer *connFeeder
in io.ReadCloser
out io.WriteCloser
type fakeAddr string
// connFeeder serializes calls to the source function (io.Reader.Read or
// io.Writer.Write) by delegating them to a channel. This also allows calls to
// be intercepted when the connection is closed, and cancelled early if the
// connection is closed while the calls are still outstanding.
type connFeeder struct {
source func([]byte) (int, error)
input chan []byte
result chan feedResult
mu sync.Mutex
closed bool
done chan struct{}
type feedResult struct {
n int
err error
func (c *fakeConn) Close() error {
return nil
func (c *fakeConn) Read(b []byte) (n int, err error) { return }
func (c *fakeConn) Write(b []byte) (n int, err error) { return }
func (c *fakeConn) LocalAddr() net.Addr { return fakeAddr( }
func (c *fakeConn) RemoteAddr() net.Addr { return fakeAddr( }
func (c *fakeConn) SetDeadline(t time.Time) error { return nil }
func (c *fakeConn) SetReadDeadline(t time.Time) error { return nil }
func (c *fakeConn) SetWriteDeadline(t time.Time) error { return nil }
func (a fakeAddr) Network() string { return "fake" }
func (a fakeAddr) String() string { return string(a) }
func newFeeder(source func([]byte) (int, error)) *connFeeder {
return &connFeeder{
source: source,
input: make(chan []byte),
result: make(chan feedResult),
done: make(chan struct{}),
func (f *connFeeder) close() {
if !f.closed {
f.closed = true
func (f *connFeeder) do(b []byte) (n int, err error) {
// send the request to the worker
select {
case f.input <- b:
case <-f.done:
return 0, io.EOF
// get the result from the worker
select {
case r := <-f.result:
return r.n, r.err
case <-f.done:
return 0, io.EOF
func (f *connFeeder) run() {
var b []byte
for {
// wait for an input request
select {
case b = <-f.input:
case <-f.done:
// invoke the underlying method
n, err := f.source(b)
// send the result back to the requester
select {
case f.result <- feedResult{n: n, err: err}:
case <-f.done: