Move transfer and unpack packages

Packages related to transfer and unpacking provide core interfaces which
use other core interfaces and part of common functionality.

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

core/transfer/transfer.go

@@ -0,0 +1,136 @@
+/*
+   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 transfer
+
+import (
+	"context"
+	"io"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+	"github.com/containerd/containerd/v2/core/content"
+	"github.com/containerd/containerd/v2/core/images"
+)
+
+type Transferrer interface {
+	Transfer(ctx context.Context, source interface{}, destination interface{}, opts ...Opt) error
+}
+
+type ImageResolver interface {
+	Resolve(ctx context.Context) (name string, desc ocispec.Descriptor, err error)
+}
+
+type ImageFetcher interface {
+	ImageResolver
+
+	Fetcher(ctx context.Context, ref string) (Fetcher, error)
+}
+
+type ImagePusher interface {
+	Pusher(context.Context, ocispec.Descriptor) (Pusher, error)
+}
+
+type Fetcher interface {
+	Fetch(context.Context, ocispec.Descriptor) (io.ReadCloser, error)
+}
+
+type Pusher interface {
+	Push(context.Context, ocispec.Descriptor) (content.Writer, error)
+}
+
+// ImageFilterer is used to filter out child objects of an image
+type ImageFilterer interface {
+	ImageFilter(images.HandlerFunc, content.Store) images.HandlerFunc
+}
+
+// ImageStorer is a type which is capable of storing images for
+// the provided descriptor. The descriptor may be any type of manifest
+// including an index with multiple image references.
+type ImageStorer interface {
+	Store(context.Context, ocispec.Descriptor, images.Store) ([]images.Image, error)
+}
+
+// ImageGetter is type which returns an image from an image store
+type ImageGetter interface {
+	Get(context.Context, images.Store) (images.Image, error)
+}
+
+// ImageLookup is a type which returns images from an image store
+// based on names or prefixes
+type ImageLookup interface {
+	Lookup(context.Context, images.Store) ([]images.Image, error)
+}
+
+// ImageExporter exports images to a writer
+type ImageExporter interface {
+	Export(context.Context, content.Store, []images.Image) error
+}
+
+// ImageImporter imports an image into a content store
+type ImageImporter interface {
+	Import(context.Context, content.Store) (ocispec.Descriptor, error)
+}
+
+// ImageImportStreamer returns an import streamer based on OCI or
+// Docker image tar archives. The stream should be a raw tar stream
+// and without compression.
+type ImageImportStreamer interface {
+	ImportStream(context.Context) (io.Reader, string, error)
+}
+
+type ImageExportStreamer interface {
+	ExportStream(context.Context) (io.WriteCloser, string, error)
+}
+
+type ImageUnpacker interface {
+	UnpackPlatforms() []UnpackConfiguration
+}
+
+// UnpackConfiguration specifies the platform and snapshotter to use for resolving
+// the unpack Platform, if snapshotter is not specified the platform default will
+// be used.
+type UnpackConfiguration struct {
+	Platform    ocispec.Platform
+	Snapshotter string
+}
+
+type ProgressFunc func(Progress)
+
+type Config struct {
+	Progress ProgressFunc
+}
+
+type Opt func(*Config)
+
+func WithProgress(f ProgressFunc) Opt {
+	return func(opts *Config) {
+		opts.Progress = f
+	}
+}
+
+// Progress is used to represent a particular progress event or incremental
+// update for the provided named object. The parents represent the names of
+// the objects which initiated the progress for the provided named object.
+// The name and what object it represents is determined by the implementation.
+type Progress struct {
+	Event    string
+	Name     string
+	Parents  []string
+	Progress int64
+	Total    int64
+	Desc     *ocispec.Descriptor // since containerd v2.0
+}