Update vendor

vendor/github.com/google/go-containerregistry/pkg/v1/v1util/zip.go

@@ -0,0 +1,92 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package v1util
+
+import (
+	"bytes"
+	"compress/gzip"
+	"io"
+)
+
+var gzipMagicHeader = []byte{'\x1f', '\x8b'}
+
+// GzipReadCloser reads uncompressed input data from the io.ReadCloser and
+// returns an io.ReadCloser from which compressed data may be read.
+// This uses gzip.BestSpeed for the compression level.
+func GzipReadCloser(r io.ReadCloser) io.ReadCloser {
+	return GzipReadCloserLevel(r, gzip.BestSpeed)
+}
+
+// GzipReadCloserLevel reads uncompressed input data from the io.ReadCloser and
+// returns an io.ReadCloser from which compressed data may be read.
+// Refer to compress/gzip for the level:
+// https://golang.org/pkg/compress/gzip/#pkg-constants
+func GzipReadCloserLevel(r io.ReadCloser, level int) io.ReadCloser {
+	pr, pw := io.Pipe()
+
+	// Returns err so we can pw.CloseWithError(err)
+	go func() error {
+		// TODO(go1.14): Just defer {pw,gw,r}.Close like you'd expect.
+		// Context: https://golang.org/issue/24283
+		gw, err := gzip.NewWriterLevel(pw, level)
+		if err != nil {
+			return pw.CloseWithError(err)
+		}
+
+		if _, err := io.Copy(gw, r); err != nil {
+			defer r.Close()
+			defer gw.Close()
+			return pw.CloseWithError(err)
+		}
+		defer pw.Close()
+		defer r.Close()
+		defer gw.Close()
+
+		return nil
+	}()
+
+	return pr
+}
+
+// GunzipReadCloser reads compressed input data from the io.ReadCloser and
+// returns an io.ReadCloser from which uncompessed data may be read.
+func GunzipReadCloser(r io.ReadCloser) (io.ReadCloser, error) {
+	gr, err := gzip.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	return &readAndCloser{
+		Reader: gr,
+		CloseFunc: func() error {
+			if err := gr.Close(); err != nil {
+				return err
+			}
+			return r.Close()
+		},
+	}, nil
+}
+
+// IsGzipped detects whether the input stream is compressed.
+func IsGzipped(r io.Reader) (bool, error) {
+	magicHeader := make([]byte, 2)
+	n, err := r.Read(magicHeader)
+	if n == 0 && err == io.EOF {
+		return false, nil
+	}
+	if err != nil {
+		return false, err
+	}
+	return bytes.Equal(magicHeader, gzipMagicHeader), nil
+}