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layers.go
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layers.go
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// Copyright 2022 Upbound Inc
//
// 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 xpkg
import (
"archive/tar"
"bytes"
"fmt"
"io"
"os"
"github.com/crossplane/crossplane-runtime/pkg/errors"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/tarball"
)
// Layer creates a v1.Layer that represetns the layer contents for the xpkg and
// adds a corresponding label to the image Config for the layer.
func Layer(r io.Reader, fileName, annotation string, fileSize int64, mode os.FileMode, cfg *v1.Config) (v1.Layer, error) {
tarBuf := new(bytes.Buffer)
tw := tar.NewWriter(tarBuf)
exHdr := &tar.Header{
Name: fileName,
Mode: int64(mode),
Size: fileSize,
}
if err := writeLayer(tw, exHdr, r); err != nil {
return nil, err
}
// TODO(hasheddan): we currently return a new reader every time here in
// order to calculate digest, then subsequently write contents to disk. We
// can greatly improve performance during package build by avoiding reading
// every layer into memory.
layer, err := tarball.LayerFromOpener(func() (io.ReadCloser, error) {
return io.NopCloser(bytes.NewReader(tarBuf.Bytes())), nil
})
if err != nil {
return nil, errors.Wrap(err, errLayerFromTar)
}
d, err := layer.Digest()
if err != nil {
return nil, errors.Wrap(err, errDigestInvalid)
}
// add annotation label to config if a non-empty label is specified
if annotation != "" {
cfg.Labels[Label(d.String())] = annotation
}
return layer, nil
}
func writeLayer(tw *tar.Writer, hdr *tar.Header, buf io.Reader) error {
if err := tw.WriteHeader(hdr); err != nil {
return errors.Wrap(err, errTarFromStream)
}
if _, err := io.Copy(tw, buf); err != nil {
return errors.Wrap(err, errTarFromStream)
}
if err := tw.Close(); err != nil {
return errors.Wrap(err, errTarFromStream)
}
return nil
}
// Label constructs a specially formated label using the annotationKey.
func Label(annotation string) string {
return fmt.Sprintf("%s:%s", AnnotationKey, annotation)
}