8be340e37b
After some analysis, it was found that Content.Reader was generally redudant to an io.ReaderAt. This change removes `Content.Reader` in favor of a `Content.ReaderAt`. In general, `ReaderAt` can perform better over interfaces with indeterminant latency because it avoids remote state for reads. Where a reader is required, a helper is provided to convert it into an `io.SectionReader`. Signed-off-by: Stephen J Day <stephen.day@docker.com>
68 lines
1.8 KiB
Go
68 lines
1.8 KiB
Go
package containerd
|
|
|
|
import (
|
|
"archive/tar"
|
|
"context"
|
|
"io"
|
|
|
|
"github.com/containerd/containerd/content"
|
|
"github.com/containerd/containerd/images"
|
|
"github.com/containerd/containerd/oci"
|
|
ocispecs "github.com/opencontainers/image-spec/specs-go"
|
|
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
|
|
)
|
|
|
|
func (c *Client) exportToOCITar(ctx context.Context, desc ocispec.Descriptor, writer io.Writer, eopts exportOpts) error {
|
|
tw := tar.NewWriter(writer)
|
|
img := oci.Tar(tw)
|
|
|
|
// For tar, we defer creating index until end of the function.
|
|
if err := oci.Init(img, oci.InitOpts{SkipCreateIndex: true}); err != nil {
|
|
return err
|
|
}
|
|
cs := c.ContentStore()
|
|
handlers := images.Handlers(
|
|
images.ChildrenHandler(cs),
|
|
exportHandler(cs, img),
|
|
)
|
|
// For tar, we need to use Walk instead of Dispatch for ensuring sequential write
|
|
if err := images.Walk(ctx, handlers, desc); err != nil {
|
|
return err
|
|
}
|
|
// For tar, we don't use oci.PutManifestDescriptorToIndex() which allows appending desc to existing index.json
|
|
// but requires img to support random read access so as to read index.json.
|
|
return oci.WriteIndex(img,
|
|
ocispec.Index{
|
|
Versioned: ocispecs.Versioned{
|
|
SchemaVersion: 2,
|
|
},
|
|
Manifests: []ocispec.Descriptor{desc},
|
|
},
|
|
)
|
|
}
|
|
|
|
func exportHandler(cs content.Store, img oci.ImageDriver) images.HandlerFunc {
|
|
return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
|
|
r, err := cs.ReaderAt(ctx, desc.Digest)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
defer r.Close()
|
|
|
|
w, err := oci.NewBlobWriter(img, desc.Digest.Algorithm())
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
if _, err = io.Copy(w, content.NewReader(r)); err != nil {
|
|
return nil, err
|
|
}
|
|
if err = w.Commit(desc.Size, desc.Digest); err != nil {
|
|
return nil, err
|
|
}
|
|
if err = w.Close(); err != nil {
|
|
return nil, err
|
|
}
|
|
return nil, nil
|
|
}
|
|
}
|