Move diff to core/diff

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

core/diff/diff.go

@@ -0,0 +1,148 @@
+/*
+   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 diff
+
+import (
+	"context"
+	"io"
+	"time"
+
+	"github.com/containerd/containerd/v2/mount"
+	"github.com/containerd/typeurl/v2"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// Config is used to hold parameters needed for a diff operation
+type Config struct {
+	// MediaType is the type of diff to generate
+	// Default depends on the differ,
+	// i.e. application/vnd.oci.image.layer.v1.tar+gzip
+	MediaType string
+
+	// Reference is the content upload reference
+	// Default will use a random reference string
+	Reference string
+
+	// Labels are the labels to apply to the generated content
+	Labels map[string]string
+
+	// Compressor is a function to compress the diff stream
+	// instead of the default gzip compressor. Differ passes
+	// the MediaType of the target diff content to the compressor.
+	// When using this config, MediaType must be specified as well.
+	Compressor func(dest io.Writer, mediaType string) (io.WriteCloser, error)
+
+	// SourceDateEpoch specifies the SOURCE_DATE_EPOCH without touching the env vars.
+	SourceDateEpoch *time.Time
+}
+
+// Opt is used to configure a diff operation
+type Opt func(*Config) error
+
+// Comparer allows creation of filesystem diffs between mounts
+type Comparer interface {
+	// Compare computes the difference between two mounts and returns a
+	// descriptor for the computed diff. The options can provide
+	// a ref which can be used to track the content creation of the diff.
+	// The media type which is used to determine the format of the created
+	// content can also be provided as an option.
+	Compare(ctx context.Context, lower, upper []mount.Mount, opts ...Opt) (ocispec.Descriptor, error)
+}
+
+// ApplyConfig is used to hold parameters needed for a apply operation
+type ApplyConfig struct {
+	// ProcessorPayloads specifies the payload sent to various processors
+	ProcessorPayloads map[string]typeurl.Any
+	// SyncFs is to synchronize the underlying filesystem containing files
+	SyncFs bool
+}
+
+// ApplyOpt is used to configure an Apply operation
+type ApplyOpt func(context.Context, ocispec.Descriptor, *ApplyConfig) error
+
+// Applier allows applying diffs between mounts
+type Applier interface {
+	// Apply applies the content referred to by the given descriptor to
+	// the provided mount. The method of applying is based on the
+	// implementation and content descriptor. For example, in the common
+	// case the descriptor is a file system difference in tar format,
+	// that tar would be applied on top of the mounts.
+	Apply(ctx context.Context, desc ocispec.Descriptor, mount []mount.Mount, opts ...ApplyOpt) (ocispec.Descriptor, error)
+}
+
+// WithCompressor sets the function to be used to compress the diff stream.
+func WithCompressor(f func(dest io.Writer, mediaType string) (io.WriteCloser, error)) Opt {
+	return func(c *Config) error {
+		c.Compressor = f
+		return nil
+	}
+}
+
+// WithMediaType sets the media type to use for creating the diff, without
+// specifying the differ will choose a default.
+func WithMediaType(m string) Opt {
+	return func(c *Config) error {
+		c.MediaType = m
+		return nil
+	}
+}
+
+// WithReference is used to set the content upload reference used by
+// the diff operation. This allows the caller to track the upload through
+// the content store.
+func WithReference(ref string) Opt {
+	return func(c *Config) error {
+		c.Reference = ref
+		return nil
+	}
+}
+
+// WithLabels is used to set content labels on the created diff content.
+func WithLabels(labels map[string]string) Opt {
+	return func(c *Config) error {
+		c.Labels = labels
+		return nil
+	}
+}
+
+// WithPayloads sets the apply processor payloads to the config
+func WithPayloads(payloads map[string]typeurl.Any) ApplyOpt {
+	return func(_ context.Context, _ ocispec.Descriptor, c *ApplyConfig) error {
+		c.ProcessorPayloads = payloads
+		return nil
+	}
+}
+
+// WithSyncFs sets sync flag to the config.
+func WithSyncFs(sync bool) ApplyOpt {
+	return func(_ context.Context, _ ocispec.Descriptor, c *ApplyConfig) error {
+		c.SyncFs = sync
+		return nil
+	}
+}
+
+// WithSourceDateEpoch specifies the timestamp used to provide control for reproducibility.
+// See also https://reproducible-builds.org/docs/source-date-epoch/ .
+//
+// Since containerd v2.0, the whiteout timestamps are set to zero (1970-01-01),
+// not to the source date epoch.
+func WithSourceDateEpoch(tm *time.Time) Opt {
+	return func(c *Config) error {
+		c.SourceDateEpoch = tm
+		return nil
+	}
+}