X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/f4ca9ad94a6bb006d1f3c7ba207837f1736d1247..cad7d333436703d48c2811de8a26caef9fc130ad:/sdk/go/streamer/streamer.go

diff --git a/sdk/go/streamer/streamer.go b/sdk/go/streamer/streamer.go
index 2217dd3352..396e311038 100644
--- a/sdk/go/streamer/streamer.go
+++ b/sdk/go/streamer/streamer.go
@@ -1,3 +1,7 @@
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 /* AsyncStream pulls data in from a io.Reader source (such as a file or network
 socket) and fans out to any number of StreamReader sinks.
 
@@ -36,15 +40,19 @@ Alternately, if you already have a filled buffer and just want to read out from
 package streamer
 
 import (
+	"errors"
 	"io"
 )
 
+var ErrAlreadyClosed = errors.New("cannot close a stream twice")
+
 type AsyncStream struct {
 	buffer            []byte
 	requests          chan sliceRequest
 	add_reader        chan bool
 	subtract_reader   chan bool
 	wait_zero_readers chan bool
+	closed            bool
 }
 
 // Reads from the buffer managed by the Transfer()
@@ -55,7 +63,13 @@ type StreamReader struct {
 }
 
 func AsyncStreamFromReader(buffersize int, source io.Reader) *AsyncStream {
-	t := &AsyncStream{make([]byte, buffersize), make(chan sliceRequest), make(chan bool), make(chan bool), make(chan bool)}
+	t := &AsyncStream{
+		buffer:            make([]byte, buffersize),
+		requests:          make(chan sliceRequest),
+		add_reader:        make(chan bool),
+		subtract_reader:   make(chan bool),
+		wait_zero_readers: make(chan bool),
+	}
 
 	go t.transfer(source)
 	go t.readersMonitor()
@@ -64,7 +78,13 @@ func AsyncStreamFromReader(buffersize int, source io.Reader) *AsyncStream {
 }
 
 func AsyncStreamFromSlice(buf []byte) *AsyncStream {
-	t := &AsyncStream{buf, make(chan sliceRequest), make(chan bool), make(chan bool), make(chan bool)}
+	t := &AsyncStream{
+		buffer:            buf,
+		requests:          make(chan sliceRequest),
+		add_reader:        make(chan bool),
+		subtract_reader:   make(chan bool),
+		wait_zero_readers: make(chan bool),
+	}
 
 	go t.transfer(nil)
 	go t.readersMonitor()
@@ -115,16 +135,24 @@ func (this *StreamReader) WriteTo(dest io.Writer) (written int64, err error) {
 
 // Close the responses channel
 func (this *StreamReader) Close() error {
+	if this.stream == nil {
+		return ErrAlreadyClosed
+	}
 	this.stream.subtract_reader <- true
 	close(this.responses)
 	this.stream = nil
 	return nil
 }
 
-func (this *AsyncStream) Close() {
+func (this *AsyncStream) Close() error {
+	if this.closed {
+		return ErrAlreadyClosed
+	}
+	this.closed = true
 	this.wait_zero_readers <- true
 	close(this.requests)
 	close(this.add_reader)
 	close(this.subtract_reader)
 	close(this.wait_zero_readers)
+	return nil
 }