importer: refactor

- Use lease API (previoisly, GC was not supported)
- Refactored interfaces for ease of future Docker v1 importer support

For usage, please refer to `ctr images import --help`.

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

import.go

@@ -1,120 +0,0 @@
-package containerd
-
-import (
-	"archive/tar"
-	"context"
-	"encoding/json"
-	"io"
-	"io/ioutil"
-	"strings"
-
-	"github.com/containerd/containerd/content"
-	"github.com/containerd/containerd/errdefs"
-	"github.com/containerd/containerd/images"
-	"github.com/containerd/containerd/reference"
-	digest "github.com/opencontainers/go-digest"
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-	"github.com/pkg/errors"
-)
-
-func resolveOCIIndex(idx ocispec.Index, refObject string) (*ocispec.Descriptor, error) {
-	tag, dgst := reference.SplitObject(refObject)
-	if tag == "" && dgst == "" {
-		return nil, errors.Errorf("unexpected object: %q", refObject)
-	}
-	for _, m := range idx.Manifests {
-		if m.Digest == dgst {
-			return &m, nil
-		}
-		annot, ok := m.Annotations[ocispec.AnnotationRefName]
-		if ok && annot == tag && tag != "" {
-			return &m, nil
-		}
-	}
-	return nil, errors.Errorf("not found: %q", refObject)
-}
-
-func (c *Client) importFromOCITar(ctx context.Context, ref string, reader io.Reader, iopts importOpts) (Image, error) {
-	tr := tar.NewReader(reader)
-	store := c.ContentStore()
-	var desc *ocispec.Descriptor
-	for {
-		hdr, err := tr.Next()
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			return nil, err
-		}
-		if hdr.Typeflag != tar.TypeReg && hdr.Typeflag != tar.TypeRegA {
-			continue
-		}
-		if hdr.Name == "index.json" {
-			desc, err = onUntarIndexJSON(tr, iopts.refObject)
-			if err != nil {
-				return nil, err
-			}
-			continue
-		}
-		if strings.HasPrefix(hdr.Name, "blobs/") {
-			if err := onUntarBlob(ctx, tr, store, hdr.Name, hdr.Size); err != nil {
-				return nil, err
-			}
-		}
-	}
-	if desc == nil {
-		return nil, errors.Errorf("no descriptor found for reference object %q", iopts.refObject)
-	}
-	imgrec := images.Image{
-		Name:   ref,
-		Target: *desc,
-		Labels: iopts.labels,
-	}
-	is := c.ImageService()
-	if updated, err := is.Update(ctx, imgrec, "target"); err != nil {
-		if !errdefs.IsNotFound(err) {
-			return nil, err
-		}
-
-		created, err := is.Create(ctx, imgrec)
-		if err != nil {
-			return nil, err
-		}
-
-		imgrec = created
-	} else {
-		imgrec = updated
-	}
-
-	img := &image{
-		client: c,
-		i:      imgrec,
-	}
-	return img, nil
-}
-
-func onUntarIndexJSON(r io.Reader, refObject string) (*ocispec.Descriptor, error) {
-	b, err := ioutil.ReadAll(r)
-	if err != nil {
-		return nil, err
-	}
-	var idx ocispec.Index
-	if err := json.Unmarshal(b, &idx); err != nil {
-		return nil, err
-	}
-	return resolveOCIIndex(idx, refObject)
-}
-
-func onUntarBlob(ctx context.Context, r io.Reader, store content.Store, name string, size int64) error {
-	// name is like "blobs/sha256/deadbeef"
-	split := strings.Split(name, "/")
-	if len(split) != 3 {
-		return errors.Errorf("unexpected name: %q", name)
-	}
-	algo := digest.Algorithm(split[1])
-	if !algo.Available() {
-		return errors.Errorf("unsupported algorithm: %s", algo)
-	}
-	dgst := digest.NewDigestFromHex(algo.String(), split[2])
-	return content.WriteBlob(ctx, store, "unknown-"+dgst.String(), r, size, dgst)
-}