Add diffservice to contrib

Signed-off-by: Derek McGowan <derek@mcg.dev>

contrib/diffservice/service.go

@@ -0,0 +1,140 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package diffservice
+
+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/typeurl/v2"
+	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+type service struct {
+	applier  diff.Applier
+	comparer diff.Comparer
+	diffapi.UnimplementedDiffServer
+}
+
+func FromApplierAndComparer(a diff.Applier, c diff.Comparer) diffapi.DiffServer {
+	return &service{
+		applier:  a,
+		comparer: c,
+	}
+}
+func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi.ApplyResponse, error) {
+	if s.applier == nil {
+		return nil, errdefs.ToGRPC(errdefs.ErrNotImplemented)
+	}
+
+	var (
+		ocidesc ocispec.Descriptor
+		err     error
+		desc    = toDescriptor(er.Diff)
+		mounts  = toMounts(er.Mounts)
+	)
+
+	var opts []diff.ApplyOpt
+	if er.Payloads != nil {
+		payloads := make(map[string]typeurl.Any)
+		for k, v := range er.Payloads {
+			payloads[k] = v
+		}
+		opts = append(opts, diff.WithPayloads(payloads))
+	}
+
+	ocidesc, err = s.applier.Apply(ctx, desc, mounts, opts...)
+	if err != nil {
+		return nil, errdefs.ToGRPC(err)
+	}
+
+	return &diffapi.ApplyResponse{
+		Applied: fromDescriptor(ocidesc),
+	}, nil
+}
+
+func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.DiffResponse, error) {
+	if s.comparer == nil {
+		return nil, errdefs.ToGRPC(errdefs.ErrNotImplemented)
+	}
+	var (
+		ocidesc ocispec.Descriptor
+		err     error
+		aMounts = toMounts(dr.Left)
+		bMounts = toMounts(dr.Right)
+	)
+
+	var opts []diff.Opt
+	if dr.MediaType != "" {
+		opts = append(opts, diff.WithMediaType(dr.MediaType))
+	}
+	if dr.Ref != "" {
+		opts = append(opts, diff.WithReference(dr.Ref))
+	}
+	if dr.Labels != nil {
+		opts = append(opts, diff.WithLabels(dr.Labels))
+	}
+	if dr.SourceDateEpoch != nil {
+		tm := dr.SourceDateEpoch.AsTime()
+		opts = append(opts, diff.WithSourceDateEpoch(&tm))
+	}
+
+	ocidesc, err = s.comparer.Compare(ctx, aMounts, bMounts, opts...)
+	if err != nil {
+		return nil, errdefs.ToGRPC(err)
+	}
+
+	return &diffapi.DiffResponse{
+		Diff: fromDescriptor(ocidesc),
+	}, nil
+}
+
+func toMounts(apim []*types.Mount) []mount.Mount {
+	mounts := make([]mount.Mount, len(apim))
+	for i, m := range apim {
+		mounts[i] = mount.Mount{
+			Type:    m.Type,
+			Source:  m.Source,
+			Target:  m.Target,
+			Options: m.Options,
+		}
+	}
+	return mounts
+}
+
+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,
+	}
+}