1/*
2Copyright 2018 The Kubernetes Authors.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17package remotecommand
18
19import (
20	"io"
21)
22
23// readerWrapper delegates to an io.Reader so that only the io.Reader interface is implemented,
24// to keep io.Copy from doing things we don't want when copying from the reader to the data stream.
25//
26// If the Stdin io.Reader provided to remotecommand implements a WriteTo function (like bytes.Buffer does[1]),
27// io.Copy calls that method[2] to attempt to write the entire buffer to the stream in one call.
28// That results in an oversized call to spdystream.Stream#Write [3],
29// which results in a single oversized data frame[4] that is too large.
30//
31// [1] https://golang.org/pkg/bytes/#Buffer.WriteTo
32// [2] https://golang.org/pkg/io/#Copy
33// [3] https://github.com/kubernetes/kubernetes/blob/90295640ef87db9daa0144c5617afe889e7992b2/vendor/github.com/docker/spdystream/stream.go#L66-L73
34// [4] https://github.com/kubernetes/kubernetes/blob/90295640ef87db9daa0144c5617afe889e7992b2/vendor/github.com/docker/spdystream/spdy/write.go#L302-L304
35type readerWrapper struct {
36	reader io.Reader
37}
38
39func (r readerWrapper) Read(p []byte) (int, error) {
40	return r.reader.Read(p)
41}
42