OCI: Add From/ToProto helpers for Descriptor

Helpers to convert from the OCI image specs [Descriptor] to its protobuf
structure for Descriptor and vice-versa appear three times. It seems sane
to just expose this facility in /oci.

Signed-off-by: Danny Canter <danny@dcantah.dev>

contrib/diffservice/service.go

@@ -20,12 +20,11 @@ import (
 	"context"
 
 	diffapi "github.com/containerd/containerd/api/services/diff/v1"
-	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
+	"github.com/containerd/containerd/oci"
 	"github.com/containerd/typeurl/v2"
-	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -49,7 +48,7 @@ func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi
 	var (
 		ocidesc ocispec.Descriptor
 		err     error
-		desc    = toDescriptor(er.Diff)
+		desc    = oci.DescriptorFromProto(er.Diff)
 		mounts  = mount.FromProto(er.Mounts)
 	)
 
@@ -68,7 +67,7 @@ func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi
 	}
 
 	return &diffapi.ApplyResponse{
-		Applied: fromDescriptor(ocidesc),
+		Applied: oci.DescriptorToProto(ocidesc),
 	}, nil
 }
 
@@ -104,24 +103,6 @@ func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.D
 	}
 
 	return &diffapi.DiffResponse{
-		Diff: fromDescriptor(ocidesc),
+		Diff: oci.DescriptorToProto(ocidesc),
 	}, nil
 }
-
-func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
-	return ocispec.Descriptor{
-		MediaType:   d.MediaType,
-		Digest:      digest.Digest(d.Digest),
-		Size:        d.Size,
-		Annotations: d.Annotations,
-	}
-}
-
-func fromDescriptor(d ocispec.Descriptor) *types.Descriptor {
-	return &types.Descriptor{
-		MediaType:   d.MediaType,
-		Digest:      d.Digest.String(),
-		Size:        d.Size,
-		Annotations: d.Annotations,
-	}
-}

diff/proxy/differ.go

@@ -20,14 +20,13 @@ import (
 	"context"
 
 	diffapi "github.com/containerd/containerd/api/services/diff/v1"
-	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
+	"github.com/containerd/containerd/oci"
 	"github.com/containerd/containerd/pkg/epoch"
 	"github.com/containerd/containerd/protobuf"
 	ptypes "github.com/containerd/containerd/protobuf/types"
-	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 
 	"google.golang.org/protobuf/types/known/timestamppb"
@@ -59,7 +58,7 @@ func (r *diffRemote) Apply(ctx context.Context, desc ocispec.Descriptor, mounts
 	}
 
 	req := &diffapi.ApplyRequest{
-		Diff:     fromDescriptor(desc),
+		Diff:     oci.DescriptorToProto(desc),
 		Mounts:   mount.ToProto(mounts),
 		Payloads: payloads,
 	}
@@ -67,7 +66,7 @@ func (r *diffRemote) Apply(ctx context.Context, desc ocispec.Descriptor, mounts
 	if err != nil {
 		return ocispec.Descriptor{}, errdefs.FromGRPC(err)
 	}
-	return toDescriptor(resp.Applied), nil
+	return oci.DescriptorFromProto(resp.Applied), nil
 }
 
 func (r *diffRemote) Compare(ctx context.Context, a, b []mount.Mount, opts ...diff.Opt) (ocispec.Descriptor, error) {
@@ -96,26 +95,5 @@ func (r *diffRemote) Compare(ctx context.Context, a, b []mount.Mount, opts ...di
 	if err != nil {
 		return ocispec.Descriptor{}, errdefs.FromGRPC(err)
 	}
-	return toDescriptor(resp.Diff), nil
+	return oci.DescriptorFromProto(resp.Diff), nil
-}
-
-func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
-	if d == nil {
-		return ocispec.Descriptor{}
-	}
-	return ocispec.Descriptor{
-		MediaType:   d.MediaType,
-		Digest:      digest.Digest(d.Digest),
-		Size:        d.Size,
-		Annotations: d.Annotations,
-	}
-}
-
-func fromDescriptor(d ocispec.Descriptor) *types.Descriptor {
-	return &types.Descriptor{
-		MediaType:   d.MediaType,
-		Digest:      d.Digest.String(),
-		Size:        d.Size,
-		Annotations: d.Annotations,
-	}
 }

oci/spec.go

@@ -21,8 +21,11 @@ import (
 	"path/filepath"
 	"runtime"
 
+	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/opencontainers/runtime-spec/specs-go"
 
+	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/containers"
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/platforms"
@@ -220,3 +223,25 @@ func populateDefaultDarwinSpec(s *Spec) error {
 	}
 	return nil
 }
+
+// DescriptorFromProto converts containerds protobuf [types.Descriptor]
+// to the OCI image specs [ocispec.Descriptor].
+func DescriptorFromProto(d *types.Descriptor) ocispec.Descriptor {
+	return ocispec.Descriptor{
+		MediaType:   d.MediaType,
+		Digest:      digest.Digest(d.Digest),
+		Size:        d.Size,
+		Annotations: d.Annotations,
+	}
+}
+
+// DescriptorToProto converts the OCI image specs [ocispec.Descriptor]
+// to containerds protobuf [types.Descriptor].
+func DescriptorToProto(d ocispec.Descriptor) *types.Descriptor {
+	return &types.Descriptor{
+		MediaType:   d.MediaType,
+		Digest:      d.Digest.String(),
+		Size:        d.Size,
+		Annotations: d.Annotations,
+	}
+}

services/diff/local.go

@@ -21,14 +21,13 @@ import (
 	"fmt"
 
 	diffapi "github.com/containerd/containerd/api/services/diff/v1"
-	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
+	"github.com/containerd/containerd/oci"
 	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/services"
 	"github.com/containerd/typeurl/v2"
-	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"google.golang.org/grpc"
 )
@@ -97,7 +96,7 @@ func (l *local) Apply(ctx context.Context, er *diffapi.ApplyRequest, _ ...grpc.C
 	var (
 		ocidesc ocispec.Descriptor
 		err     error
-		desc    = toDescriptor(er.Diff)
+		desc    = oci.DescriptorFromProto(er.Diff)
 		mounts  = mount.FromProto(er.Mounts)
 	)
 
@@ -122,7 +121,7 @@ func (l *local) Apply(ctx context.Context, er *diffapi.ApplyRequest, _ ...grpc.C
 	}
 
 	return &diffapi.ApplyResponse{
-		Applied: fromDescriptor(ocidesc),
+		Applied: oci.DescriptorToProto(ocidesc),
 	}, nil
 
 }
@@ -161,24 +160,6 @@ func (l *local) Diff(ctx context.Context, dr *diffapi.DiffRequest, _ ...grpc.Cal
 	}
 
 	return &diffapi.DiffResponse{
-		Diff: fromDescriptor(ocidesc),
+		Diff: oci.DescriptorToProto(ocidesc),
 	}, nil
 }
-
-func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
-	return ocispec.Descriptor{
-		MediaType:   d.MediaType,
-		Digest:      digest.Digest(d.Digest),
-		Size:        d.Size,
-		Annotations: d.Annotations,
-	}
-}
-
-func fromDescriptor(d ocispec.Descriptor) *types.Descriptor {
-	return &types.Descriptor{
-		MediaType:   d.MediaType,
-		Digest:      d.Digest.String(),
-		Size:        d.Size,
-		Annotations: d.Annotations,
-	}
-}