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stream.go
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stream.go
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package jsonstream
import (
"bytes"
"io"
"sync"
"github.com/alibaba/pouch/pkg/log"
)
// JSONStream represents a stream transfer, the data be encoded with json.
type JSONStream struct {
w io.Writer
cache chan interface{}
wg sync.WaitGroup
f Formater
closingCh chan struct{}
}
// New creates a 'JSONStream' instance and use a goroutine to recv/send data.
func New(out io.Writer, f Formater) *JSONStream {
format := f
if format == nil {
format = newDefaultFormat()
}
stream := &JSONStream{
w: out,
cache: make(chan interface{}, 16),
f: format,
closingCh: make(chan struct{}),
}
stream.wg.Add(1)
go func() {
defer func() {
stream.wg.Done()
close(stream.closingCh)
}()
f := stream.f
// begin to write.
if err := stream.writeDelim(f.BeginWrite); err != nil {
log.With(nil).Errorf("failed to write begin delim: %v", err)
return
}
for {
o, ok := <-stream.cache
if !ok && o == nil {
break
}
if err := stream.writeObj(o, f.Write); err != nil {
log.With(nil).Errorf("failed to write object: %v", err)
return
}
}
// end to write.
if err := stream.writeDelim(f.EndWrite); err != nil {
log.With(nil).Errorf("failed to write end delim: %v", err)
}
}()
return stream
}
// Wait waits the stream to finish.
func (s *JSONStream) Wait() {
s.wg.Wait()
}
// WriteObject writes a object to client via stream tranfer.
func (s *JSONStream) WriteObject(obj interface{}) error {
select {
case s.cache <- obj:
case <-s.closingCh:
}
return nil
}
// Close closes the stream transfer.
func (s *JSONStream) Close() error {
close(s.cache)
return nil
}
func (s *JSONStream) writeDelim(f func() ([]byte, error)) error {
b, err := f()
if err != nil {
return err
}
return s.write(bytes.NewBuffer(b))
}
func (s *JSONStream) writeObj(o interface{}, f func(interface{}) ([]byte, error)) error {
b, err := f(o)
if err != nil {
return err
}
return s.write(bytes.NewBuffer(b))
}
func (s *JSONStream) write(buf *bytes.Buffer) error {
for {
if _, err := buf.WriteTo(s.w); err != nil {
if err == io.ErrShortWrite {
continue
}
return err
}
break
}
return nil
}