10990: Use AsyncStream to minimize store-and-forward latency

[arvados.git] / sdk / go / streamer / streamer.go

diff --git a/sdk/go/streamer/streamer.go b/sdk/go/streamer/streamer.go
index a46ca4cc55aa5c3faa8ccdbe5b73339aacfa50ef..c8d012f76591470551e51dcb8faea87eea2aecea 100644 (file)
--- a/sdk/go/streamer/streamer.go
+++ b/sdk/go/streamer/streamer.go
@@ -37,6 +37,7 @@ package streamer
 
 import (
        "errors"
+       "fmt"
        "io"
 )
 
@@ -152,3 +153,29 @@ func (this *AsyncStream) Close() error {
        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))
+}