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package containerd
import (
"context"
"reflect"
"strings"
"github.com/docker/docker/api/types/container"
imagetype "github.com/docker/docker/api/types/image"
"github.com/docker/docker/builder"
"github.com/docker/docker/image"
)
// MakeImageCache creates a stateful image cache.
func (i *ImageService) MakeImageCache(ctx context.Context, cacheFrom []string) (builder.ImageCache, error) {
images := []*image.Image{}
for _, c := range cacheFrom {
im, err := i.GetImage(ctx, c, imagetype.GetImageOpts{})
if err != nil {
return nil, err
}
images = append(images, im)
}
return &imageCache{images: images, c: i}, nil
}
type imageCache struct {
images []*image.Image
c *ImageService
}
func (ic *imageCache) GetCache(parentID string, cfg *container.Config) (imageID string, err error) {
ctx := context.TODO()
parent, err := ic.c.GetImage(ctx, parentID, imagetype.GetImageOpts{})
if err != nil {
return "", err
}
for _, localCachedImage := range ic.images {
if isMatch(localCachedImage, parent, cfg) {
return localCachedImage.ID().String(), nil
}
}
children, err := ic.c.Children(ctx, parent.ID())
if err != nil {
return "", err
}
for _, children := range children {
childImage, err := ic.c.GetImage(ctx, children.String(), imagetype.GetImageOpts{})
if err != nil {
return "", err
}
if isMatch(childImage, parent, cfg) {
return children.String(), nil
}
}
return "", nil
}
// isMatch checks whether a given target can be used as cache for the given
// parent image/config combination.
// A target can only be an immediate child of the given parent image. For
// a parent image with `n` history entries, a valid target must have `n+1`
// entries and the extra entry must match the provided config
func isMatch(target, parent *image.Image, cfg *container.Config) bool {
if target == nil || parent == nil || cfg == nil {
return false
}
if len(target.History) != len(parent.History)+1 ||
len(target.RootFS.DiffIDs) != len(parent.RootFS.DiffIDs)+1 {
return false
}
for i := range parent.History {
if !reflect.DeepEqual(parent.History[i], target.History[i]) {
return false
}
}
childCreatedBy := target.History[len(target.History)-1].CreatedBy
return childCreatedBy == strings.Join(cfg.Cmd, " ")
}
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