// forwardDataFrames moves data from one gRPC transport `Stream` to another in async fashion.
// It returns an error channel. `nil` on it signifies everything was fine, anything else is a serious problem.
func forwardDataFrames(srcStream *transport.Stream, dstStream *transport.Stream, dstTransport transportWriter) chan error {
ret := make(chan error, 1)
go func() {
data := make([]byte, 4096)
opt := &transport.Options{}
for {
n, err := srcStream.Read(data)
if err != nil { // including io.EOF
// Send nil to terminate the stream.
opt.Last = true
dstTransport.Write(dstStream, nil, opt)
ret <- err
break
}
if err := dstTransport.Write(dstStream, data[:n], opt); err != nil {
ret <- err
break
}
}
close(ret)
}()
return ret
}