forked from cloudfoundry-attic/garden-linux
/
fan_in.go
71 lines (54 loc) · 1.02 KB
/
fan_in.go
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package writer
import (
"errors"
"io"
"sync"
)
type FanIn interface {
Write(data []byte) (int, error)
Close() error
AddSink(sink io.WriteCloser)
AddSource(source io.Reader)
}
func NewFanIn() FanIn {
return &fanIn{hasSink: make(chan struct{})}
}
type fanIn struct {
w io.WriteCloser
closed bool
writeL sync.Mutex
hasSink chan struct{}
}
func (fw *fanIn) Write(data []byte) (int, error) {
<-fw.hasSink
fw.writeL.Lock()
defer fw.writeL.Unlock()
if fw.closed {
return 0, errors.New("write after close")
}
return fw.w.Write(data)
}
func (fw *fanIn) Close() error {
<-fw.hasSink
fw.writeL.Lock()
defer fw.writeL.Unlock()
if fw.closed {
return errors.New("already closed")
}
fw.closed = true
return fw.w.Close()
}
//AddSink can only be called once
func (fw *fanIn) AddSink(sink io.WriteCloser) {
fw.w = sink
// Allow Write and Close to proceed.
close(fw.hasSink)
}
func (fw *fanIn) AddSource(source io.Reader) {
go func() {
_, err := io.Copy(fw, source)
if err == nil {
fw.Close()
}
}()
}