c9aaff00f8
To allow generic manifest walking, we define an interface method of `References` that returns the referenced items in the manifest. The current implementation does not return the config target from schema2, making this useless for most applications. The garbage collector has been modified to show the utility of this correctly formed `References` method. We may be able to make more generic traversal methods with this, as well. Signed-off-by: Stephen J Day <stephen.day@docker.com>
134 lines
4 KiB
Go
134 lines
4 KiB
Go
package schema2
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import (
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"encoding/json"
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"errors"
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"fmt"
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"github.com/docker/distribution"
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"github.com/docker/distribution/digest"
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"github.com/docker/distribution/manifest"
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)
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const (
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// MediaTypeManifest specifies the mediaType for the current version.
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MediaTypeManifest = "application/vnd.docker.distribution.manifest.v2+json"
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// MediaTypeConfig specifies the mediaType for the image configuration.
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MediaTypeConfig = "application/vnd.docker.container.image.v1+json"
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// MediaTypePluginConfig specifies the mediaType for plugin configuration.
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MediaTypePluginConfig = "application/vnd.docker.plugin.image.v0+json"
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// MediaTypeLayer is the mediaType used for layers referenced by the
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// manifest.
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MediaTypeLayer = "application/vnd.docker.image.rootfs.diff.tar.gzip"
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// MediaTypeForeignLayer is the mediaType used for layers that must be
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// downloaded from foreign URLs.
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MediaTypeForeignLayer = "application/vnd.docker.image.rootfs.foreign.diff.tar.gzip"
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)
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var (
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// SchemaVersion provides a pre-initialized version structure for this
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// packages version of the manifest.
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SchemaVersion = manifest.Versioned{
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SchemaVersion: 2,
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MediaType: MediaTypeManifest,
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}
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)
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func init() {
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schema2Func := func(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
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m := new(DeserializedManifest)
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err := m.UnmarshalJSON(b)
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if err != nil {
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return nil, distribution.Descriptor{}, err
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}
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dgst := digest.FromBytes(b)
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return m, distribution.Descriptor{Digest: dgst, Size: int64(len(b)), MediaType: MediaTypeManifest}, err
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}
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err := distribution.RegisterManifestSchema(MediaTypeManifest, schema2Func)
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if err != nil {
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panic(fmt.Sprintf("Unable to register manifest: %s", err))
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}
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}
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// Manifest defines a schema2 manifest.
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type Manifest struct {
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manifest.Versioned
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// Config references the image configuration as a blob.
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Config distribution.Descriptor `json:"config"`
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// Layers lists descriptors for the layers referenced by the
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// configuration.
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Layers []distribution.Descriptor `json:"layers"`
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}
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// References returnes the descriptors of this manifests references.
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func (m Manifest) References() []distribution.Descriptor {
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references := make([]distribution.Descriptor, 0, 1+len(m.Layers))
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references = append(references, m.Config)
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references = append(references, m.Layers...)
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return references
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}
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// Target returns the target of this signed manifest.
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func (m Manifest) Target() distribution.Descriptor {
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return m.Config
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}
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// DeserializedManifest wraps Manifest with a copy of the original JSON.
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// It satisfies the distribution.Manifest interface.
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type DeserializedManifest struct {
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Manifest
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// canonical is the canonical byte representation of the Manifest.
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canonical []byte
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}
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// FromStruct takes a Manifest structure, marshals it to JSON, and returns a
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// DeserializedManifest which contains the manifest and its JSON representation.
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func FromStruct(m Manifest) (*DeserializedManifest, error) {
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var deserialized DeserializedManifest
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deserialized.Manifest = m
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var err error
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deserialized.canonical, err = json.MarshalIndent(&m, "", " ")
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return &deserialized, err
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}
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// UnmarshalJSON populates a new Manifest struct from JSON data.
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func (m *DeserializedManifest) UnmarshalJSON(b []byte) error {
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m.canonical = make([]byte, len(b), len(b))
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// store manifest in canonical
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copy(m.canonical, b)
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// Unmarshal canonical JSON into Manifest object
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var manifest Manifest
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if err := json.Unmarshal(m.canonical, &manifest); err != nil {
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return err
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}
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m.Manifest = manifest
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return nil
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}
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// MarshalJSON returns the contents of canonical. If canonical is empty,
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// marshals the inner contents.
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func (m *DeserializedManifest) MarshalJSON() ([]byte, error) {
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if len(m.canonical) > 0 {
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return m.canonical, nil
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}
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return nil, errors.New("JSON representation not initialized in DeserializedManifest")
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}
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// Payload returns the raw content of the manifest. The contents can be used to
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// calculate the content identifier.
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func (m DeserializedManifest) Payload() (string, []byte, error) {
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return m.MediaType, m.canonical, nil
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}
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