Move remotes to core/remotes

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

core/remotes/docker/handler.go

@@ -0,0 +1,149 @@
+/*
+   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 docker
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"strings"
+
+	"github.com/containerd/containerd/v2/core/content"
+	"github.com/containerd/containerd/v2/core/images"
+	"github.com/containerd/containerd/v2/labels"
+	"github.com/containerd/containerd/v2/reference"
+	"github.com/containerd/log"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// AppendDistributionSourceLabel updates the label of blob with distribution source.
+func AppendDistributionSourceLabel(manager content.Manager, ref string) (images.HandlerFunc, error) {
+	refspec, err := reference.Parse(ref)
+	if err != nil {
+		return nil, err
+	}
+
+	u, err := url.Parse("dummy://" + refspec.Locator)
+	if err != nil {
+		return nil, err
+	}
+
+	source, repo := u.Hostname(), strings.TrimPrefix(u.Path, "/")
+	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
+		info, err := manager.Info(ctx, desc.Digest)
+		if err != nil {
+			return nil, err
+		}
+
+		key := distributionSourceLabelKey(source)
+
+		originLabel := ""
+		if info.Labels != nil {
+			originLabel = info.Labels[key]
+		}
+		value := appendDistributionSourceLabel(originLabel, repo)
+
+		// The repo name has been limited under 256 and the distribution
+		// label might hit the limitation of label size, when blob data
+		// is used as the very, very common layer.
+		if err := labels.Validate(key, value); err != nil {
+			log.G(ctx).Warnf("skip to append distribution label: %s", err)
+			return nil, nil
+		}
+
+		info = content.Info{
+			Digest: desc.Digest,
+			Labels: map[string]string{
+				key: value,
+			},
+		}
+		_, err = manager.Update(ctx, info, fmt.Sprintf("labels.%s", key))
+		return nil, err
+	}, nil
+}
+
+func appendDistributionSourceLabel(originLabel, repo string) string {
+	repos := []string{}
+	if originLabel != "" {
+		repos = strings.Split(originLabel, ",")
+	}
+	repos = append(repos, repo)
+
+	// use empty string to present duplicate items
+	for i := 1; i < len(repos); i++ {
+		tmp, j := repos[i], i-1
+		for ; j >= 0 && repos[j] >= tmp; j-- {
+			if repos[j] == tmp {
+				tmp = ""
+			}
+			repos[j+1] = repos[j]
+		}
+		repos[j+1] = tmp
+	}
+
+	i := 0
+	for ; i < len(repos) && repos[i] == ""; i++ {
+	}
+
+	return strings.Join(repos[i:], ",")
+}
+
+func distributionSourceLabelKey(source string) string {
+	return labels.LabelDistributionSource + "." + source
+}
+
+// selectRepositoryMountCandidate will select the repo which has longest
+// common prefix components as the candidate.
+func selectRepositoryMountCandidate(refspec reference.Spec, sources map[string]string) string {
+	u, err := url.Parse("dummy://" + refspec.Locator)
+	if err != nil {
+		// NOTE: basically, it won't be error here
+		return ""
+	}
+
+	source, target := u.Hostname(), strings.TrimPrefix(u.Path, "/")
+	repoLabel, ok := sources[distributionSourceLabelKey(source)]
+	if !ok || repoLabel == "" {
+		return ""
+	}
+
+	n, match := 0, ""
+	components := strings.Split(target, "/")
+	for _, repo := range strings.Split(repoLabel, ",") {
+		// the target repo is not a candidate
+		if repo == target {
+			continue
+		}
+
+		if l := commonPrefixComponents(components, repo); l >= n {
+			n, match = l, repo
+		}
+	}
+	return match
+}
+
+func commonPrefixComponents(components []string, target string) int {
+	targetComponents := strings.Split(target, "/")
+
+	i := 0
+	for ; i < len(components) && i < len(targetComponents); i++ {
+		if components[i] != targetComponents[i] {
+			break
+		}
+	}
+	return i
+}