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utils.go
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/
utils.go
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/*
* Copyright (c) 2022. Nydus Developers. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*/
package converter
import (
"archive/tar"
"bytes"
"compress/gzip"
"context"
"encoding/json"
"fmt"
"io"
"path/filepath"
"github.com/containerd/containerd/content"
"github.com/opencontainers/go-digest"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
)
type File struct {
Name string
Reader io.Reader
Size int64
}
type writeCloser struct {
closed bool
io.WriteCloser
action func() error
}
func (c *writeCloser) Close() error {
if c.closed {
return nil
}
if err := c.WriteCloser.Close(); err != nil {
return err
}
c.closed = true
if err := c.action(); err != nil {
return err
}
return nil
}
func newWriteCloser(wc io.WriteCloser, action func() error) *writeCloser {
return &writeCloser{
WriteCloser: wc,
action: action,
}
}
type seekReader struct {
io.ReaderAt
pos int64
}
func (ra *seekReader) Read(p []byte) (int, error) {
n, err := ra.ReaderAt.ReadAt(p, ra.pos)
ra.pos += int64(n)
return n, err
}
func (ra *seekReader) Seek(offset int64, whence int) (int64, error) {
switch {
case whence == io.SeekCurrent:
ra.pos += offset
case whence == io.SeekStart:
ra.pos = offset
default:
return 0, fmt.Errorf("unsupported whence %d", whence)
}
return ra.pos, nil
}
func newSeekReader(ra io.ReaderAt) *seekReader {
return &seekReader{
ReaderAt: ra,
pos: 0,
}
}
// packToTar packs files to .tar(.gz) stream then return reader.
func packToTar(files []File, compress bool) io.ReadCloser {
dirHdr := &tar.Header{
Name: "image",
Mode: 0755,
Typeflag: tar.TypeDir,
}
pr, pw := io.Pipe()
go func() {
// Prepare targz writer
var tw *tar.Writer
var gw *gzip.Writer
var err error
if compress {
gw = gzip.NewWriter(pw)
tw = tar.NewWriter(gw)
} else {
tw = tar.NewWriter(pw)
}
defer func() {
err1 := tw.Close()
var err2 error
if gw != nil {
err2 = gw.Close()
}
var finalErr error
// Return the first error encountered to the other end and ignore others.
switch {
case err != nil:
finalErr = err
case err1 != nil:
finalErr = err1
case err2 != nil:
finalErr = err2
}
pw.CloseWithError(finalErr)
}()
// Write targz stream
if err = tw.WriteHeader(dirHdr); err != nil {
return
}
for _, file := range files {
hdr := tar.Header{
Name: filepath.Join("image", file.Name),
Mode: 0444,
Size: file.Size,
}
if err = tw.WriteHeader(&hdr); err != nil {
return
}
if _, err = io.Copy(tw, file.Reader); err != nil {
return
}
}
}()
return pr
}
// Copied from containerd/containerd project, copyright The containerd Authors.
// https://github.com/containerd/containerd/blob/4902059cb554f4f06a8d06a12134c17117809f4e/images/converter/default.go#L385
func readJSON(ctx context.Context, cs content.Store, x interface{}, desc ocispec.Descriptor) (map[string]string, error) {
info, err := cs.Info(ctx, desc.Digest)
if err != nil {
return nil, err
}
labels := info.Labels
if labels == nil {
labels = map[string]string{}
}
b, err := content.ReadBlob(ctx, cs, desc)
if err != nil {
return nil, err
}
if err := json.Unmarshal(b, x); err != nil {
return nil, err
}
return labels, nil
}
// Copied from containerd/containerd project, copyright The containerd Authors.
// https://github.com/containerd/containerd/blob/4902059cb554f4f06a8d06a12134c17117809f4e/images/converter/default.go#L401
func writeJSON(ctx context.Context, cs content.Store, x interface{}, oldDesc ocispec.Descriptor, labels map[string]string) (*ocispec.Descriptor, error) {
b, err := json.Marshal(x)
if err != nil {
return nil, err
}
dgst := digest.SHA256.FromBytes(b)
ref := fmt.Sprintf("converter-write-json-%s", dgst.String())
w, err := content.OpenWriter(ctx, cs, content.WithRef(ref))
if err != nil {
return nil, err
}
if err := content.Copy(ctx, w, bytes.NewReader(b), int64(len(b)), dgst, content.WithLabels(labels)); err != nil {
return nil, err
}
if err := w.Close(); err != nil {
return nil, err
}
newDesc := oldDesc
newDesc.Size = int64(len(b))
newDesc.Digest = dgst
return &newDesc, nil
}