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manifest.go
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manifest.go
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package ocischema
import (
"encoding/json"
"errors"
"fmt"
"github.com/nlandolfi/distribution/v3"
"github.com/nlandolfi/distribution/v3/manifest"
"github.com/opencontainers/go-digest"
v1 "github.com/opencontainers/image-spec/specs-go/v1"
)
// SchemaVersion provides a pre-initialized version structure for OCI Image
// Manifests
var SchemaVersion = manifest.Versioned{
SchemaVersion: 2,
MediaType: v1.MediaTypeImageManifest,
}
func init() {
ocischemaFunc := func(b []byte) (distribution.Manifest, distribution.Descriptor, error) {
if err := validateManifest(b); err != nil {
return nil, distribution.Descriptor{}, err
}
m := new(DeserializedManifest)
err := m.UnmarshalJSON(b)
if err != nil {
return nil, distribution.Descriptor{}, err
}
dgst := digest.FromBytes(b)
return m, distribution.Descriptor{Digest: dgst, Size: int64(len(b)), MediaType: v1.MediaTypeImageManifest}, err
}
err := distribution.RegisterManifestSchema(v1.MediaTypeImageManifest, ocischemaFunc)
if err != nil {
panic(fmt.Sprintf("Unable to register manifest: %s", err))
}
}
// Manifest defines a ocischema manifest.
type Manifest struct {
manifest.Versioned
// Config references the image configuration as a blob.
Config distribution.Descriptor `json:"config"`
// Layers lists descriptors for the layers referenced by the
// configuration.
Layers []distribution.Descriptor `json:"layers"`
// Annotations contains arbitrary metadata for the image manifest.
Annotations map[string]string `json:"annotations,omitempty"`
}
// References returns the descriptors of this manifests references.
func (m Manifest) References() []distribution.Descriptor {
references := make([]distribution.Descriptor, 0, 1+len(m.Layers))
references = append(references, m.Config)
references = append(references, m.Layers...)
return references
}
// Target returns the target of this manifest.
func (m Manifest) Target() distribution.Descriptor {
return m.Config
}
// DeserializedManifest wraps Manifest with a copy of the original JSON.
// It satisfies the distribution.Manifest interface.
type DeserializedManifest struct {
Manifest
// canonical is the canonical byte representation of the Manifest.
canonical []byte
}
// FromStruct takes a Manifest structure, marshals it to JSON, and returns a
// DeserializedManifest which contains the manifest and its JSON representation.
func FromStruct(m Manifest) (*DeserializedManifest, error) {
var deserialized DeserializedManifest
deserialized.Manifest = m
var err error
deserialized.canonical, err = json.MarshalIndent(&m, "", " ")
return &deserialized, err
}
// UnmarshalJSON populates a new Manifest struct from JSON data.
func (m *DeserializedManifest) UnmarshalJSON(b []byte) error {
m.canonical = make([]byte, len(b))
// store manifest in canonical
copy(m.canonical, b)
// Unmarshal canonical JSON into Manifest object
var mfst Manifest
if err := json.Unmarshal(m.canonical, &mfst); err != nil {
return err
}
if mfst.MediaType != "" && mfst.MediaType != v1.MediaTypeImageManifest {
return fmt.Errorf("if present, mediaType in manifest should be '%s' not '%s'",
v1.MediaTypeImageManifest, mfst.MediaType)
}
m.Manifest = mfst
return nil
}
// MarshalJSON returns the contents of canonical. If canonical is empty,
// marshals the inner contents.
func (m *DeserializedManifest) MarshalJSON() ([]byte, error) {
if len(m.canonical) > 0 {
return m.canonical, nil
}
return nil, errors.New("JSON representation not initialized in DeserializedManifest")
}
// Payload returns the raw content of the manifest. The contents can be used to
// calculate the content identifier.
func (m DeserializedManifest) Payload() (string, []byte, error) {
return v1.MediaTypeImageManifest, m.canonical, nil
}
// validateManifest returns an error if the byte slice is invalid JSON or if it
// contains fields that belong to a index
func validateManifest(b []byte) error {
var doc struct {
Manifests interface{} `json:"manifests,omitempty"`
}
if err := json.Unmarshal(b, &doc); err != nil {
return err
}
if doc.Manifests != nil {
return errors.New("ocimanifest: expected manifest but found index")
}
return nil
}