vendor: add buildkit

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/moby/buildkit/session/content/attachable.go

@@ -0,0 +1,132 @@
+package content
+
+import (
+	"context"
+
+	api "github.com/containerd/containerd/api/services/content/v1"
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/services/content/contentserver"
+	"github.com/moby/buildkit/session"
+	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+)
+
+// GRPCHeaderID is a gRPC header for store ID
+const GRPCHeaderID = "buildkit-attachable-store-id"
+
+type attachableContentStore struct {
+	stores map[string]content.Store
+}
+
+func (cs *attachableContentStore) choose(ctx context.Context) (content.Store, error) {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, errors.Wrap(errdefs.ErrInvalidArgument, "request lacks metadata")
+	}
+
+	values := md[GRPCHeaderID]
+	if len(values) == 0 {
+		return nil, errors.Wrapf(errdefs.ErrInvalidArgument, "request lacks metadata %q", GRPCHeaderID)
+	}
+	id := values[0]
+	store, ok := cs.stores[id]
+	if !ok {
+		return nil, errors.Wrapf(errdefs.ErrNotFound, "unknown store %s", id)
+	}
+	return store, nil
+}
+
+func (cs *attachableContentStore) Info(ctx context.Context, dgst digest.Digest) (content.Info, error) {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return content.Info{}, err
+	}
+	return store.Info(ctx, dgst)
+}
+
+func (cs *attachableContentStore) Update(ctx context.Context, info content.Info, fieldpaths ...string) (content.Info, error) {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return content.Info{}, err
+	}
+	return store.Update(ctx, info, fieldpaths...)
+}
+
+func (cs *attachableContentStore) Walk(ctx context.Context, fn content.WalkFunc, fs ...string) error {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return err
+	}
+	return store.Walk(ctx, fn, fs...)
+}
+
+func (cs *attachableContentStore) Delete(ctx context.Context, dgst digest.Digest) error {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return err
+	}
+	return store.Delete(ctx, dgst)
+}
+
+func (cs *attachableContentStore) ListStatuses(ctx context.Context, fs ...string) ([]content.Status, error) {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return store.ListStatuses(ctx, fs...)
+}
+
+func (cs *attachableContentStore) Status(ctx context.Context, ref string) (content.Status, error) {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return content.Status{}, err
+	}
+	return store.Status(ctx, ref)
+}
+
+func (cs *attachableContentStore) Abort(ctx context.Context, ref string) error {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return err
+	}
+	return store.Abort(ctx, ref)
+}
+
+func (cs *attachableContentStore) Writer(ctx context.Context, opts ...content.WriterOpt) (content.Writer, error) {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return store.Writer(ctx, opts...)
+}
+
+func (cs *attachableContentStore) ReaderAt(ctx context.Context, desc ocispec.Descriptor) (content.ReaderAt, error) {
+	store, err := cs.choose(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return store.ReaderAt(ctx, desc)
+}
+
+type attachable struct {
+	service api.ContentServer
+}
+
+// NewAttachable creates session.Attachable from aggregated stores.
+// A key of the store map is an ID string that is used for choosing underlying store.
+func NewAttachable(stores map[string]content.Store) session.Attachable {
+	store := &attachableContentStore{stores: stores}
+	service := contentserver.New(store)
+	a := attachable{
+		service: service,
+	}
+	return &a
+}
+
+func (a *attachable) Register(server *grpc.Server) {
+	api.RegisterContentServer(server, a.service)
+}