X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/244159419c42341baeb388236ad29cc546b7eca1..1b16fe46cccf4af94349ddad730b5c7f3bc03718:/sdk/go/streamer/streamer.go

diff --git a/sdk/go/streamer/streamer.go b/sdk/go/streamer/streamer.go
index 2217dd3352..c8d012f765 100644
--- a/sdk/go/streamer/streamer.go
+++ b/sdk/go/streamer/streamer.go
@@ -36,15 +36,20 @@ Alternately, if you already have a filled buffer and just want to read out from
 package streamer
 
 import (
+	"errors"
+	"fmt"
 	"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 +60,13 @@ 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 +75,13 @@ 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 +132,50 @@ 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
+}
+
+func (this *StreamReader) Seek(offset int64, whence int) (int64, error) {
+	var want int64
+	switch whence {
+	case io.SeekStart:
+		want = offset
+	case io.SeekCurrent:
+		want = int64(this.offset) + offset
+	case io.SeekEnd:
+		want = int64(this.Len()) + offset
+	default:
+		return int64(this.offset), fmt.Errorf("invalid whence %d", whence)
+	}
+	if want < 0 {
+		return int64(this.offset), fmt.Errorf("attempted seek to %d", want)
+	}
+	if want > int64(this.Len()) {
+		want = int64(this.Len())
+	}
+	this.offset = int(want)
+	return want, nil
+}
+
+func (this *StreamReader) Len() uint64 {
+	return uint64(len(this.stream.buffer))
 }