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pipes.go
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pipes.go
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package xfer
import (
"io"
"sync"
"github.com/gorilla/websocket"
)
// Pipe is a bi-directional channel from someone thing in the probe
// to the UI.
type Pipe interface {
Ends() (io.ReadWriter, io.ReadWriter)
CopyToWebsocket(io.ReadWriter, *websocket.Conn) error
Close() error
Closed() bool
OnClose(func())
}
type pipe struct {
mtx sync.Mutex
wg sync.WaitGroup
port, starboard io.ReadWriter
quit chan struct{}
closed bool
onClose func()
}
// NewPipe makes a new... pipe.
func NewPipe() Pipe {
r1, w1 := io.Pipe()
r2, w2 := io.Pipe()
return &pipe{
port: struct {
io.Reader
io.Writer
}{
r1, w2,
},
starboard: struct {
io.Reader
io.Writer
}{
r2, w1,
},
quit: make(chan struct{}),
}
}
func (p *pipe) Ends() (io.ReadWriter, io.ReadWriter) {
return p.port, p.starboard
}
func (p *pipe) Close() error {
p.mtx.Lock()
var onClose func()
if !p.closed {
p.closed = true
close(p.quit)
onClose = p.onClose
}
p.mtx.Unlock()
p.wg.Wait()
// Don't run onClose under lock.
if onClose != nil {
onClose()
}
return nil
}
func (p *pipe) Closed() bool {
p.mtx.Lock()
defer p.mtx.Unlock()
return p.closed
}
func (p *pipe) OnClose(f func()) {
p.mtx.Lock()
defer p.mtx.Unlock()
p.onClose = f
}
// CopyToWebsocket copies pipe data to/from a websocket. It blocks.
func (p *pipe) CopyToWebsocket(end io.ReadWriter, conn *websocket.Conn) error {
p.mtx.Lock()
if p.closed {
p.mtx.Unlock()
return nil
}
p.wg.Add(1)
p.mtx.Unlock()
defer p.wg.Done()
errors := make(chan error, 1)
// Read-from-UI loop
go func() {
for {
_, buf, err := conn.ReadMessage() // TODO type should be binary message
if err != nil {
errors <- err
return
}
if _, err := end.Write(buf); err != nil {
errors <- err
return
}
}
}()
// Write-to-UI loop
go func() {
buf := make([]byte, 1024)
for {
n, err := end.Read(buf)
if err != nil {
errors <- err
return
}
if err := conn.WriteMessage(websocket.BinaryMessage, buf[:n]); err != nil {
errors <- err
return
}
}
}()
// block until one of the goroutines exits
// this convoluted mechanism is to ensure we only close the websocket once.
select {
case err := <-errors:
return err
case <-p.quit:
return nil
}
}