distribution/manifests.go
Stephen J Day 9c88801a12
context: remove definition of Context
Back in the before time, the best practices surrounding usage of Context
weren't quite worked out. We defined our own type to make usage easier.
As this packaged was used elsewhere, it make it more and more
challenging to integrate with the forked `Context` type. Now that it is
available in the standard library, we can just use that one directly.

To make usage more consistent, we now use `dcontext` when referring to
the distribution context package.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
2017-08-11 15:53:31 -07:00

125 lines
4.2 KiB
Go

package distribution
import (
"context"
"fmt"
"mime"
"github.com/opencontainers/go-digest"
)
// Manifest represents a registry object specifying a set of
// references and an optional target
type Manifest interface {
// References returns a list of objects which make up this manifest.
// A reference is anything which can be represented by a
// distribution.Descriptor. These can consist of layers, resources or other
// manifests.
//
// While no particular order is required, implementations should return
// them from highest to lowest priority. For example, one might want to
// return the base layer before the top layer.
References() []Descriptor
// Payload provides the serialized format of the manifest, in addition to
// the media type.
Payload() (mediaType string, payload []byte, err error)
}
// ManifestBuilder creates a manifest allowing one to include dependencies.
// Instances can be obtained from a version-specific manifest package. Manifest
// specific data is passed into the function which creates the builder.
type ManifestBuilder interface {
// Build creates the manifest from his builder.
Build(ctx context.Context) (Manifest, error)
// References returns a list of objects which have been added to this
// builder. The dependencies are returned in the order they were added,
// which should be from base to head.
References() []Descriptor
// AppendReference includes the given object in the manifest after any
// existing dependencies. If the add fails, such as when adding an
// unsupported dependency, an error may be returned.
//
// The destination of the reference is dependent on the manifest type and
// the dependency type.
AppendReference(dependency Describable) error
}
// ManifestService describes operations on image manifests.
type ManifestService interface {
// Exists returns true if the manifest exists.
Exists(ctx context.Context, dgst digest.Digest) (bool, error)
// Get retrieves the manifest specified by the given digest
Get(ctx context.Context, dgst digest.Digest, options ...ManifestServiceOption) (Manifest, error)
// Put creates or updates the given manifest returning the manifest digest
Put(ctx context.Context, manifest Manifest, options ...ManifestServiceOption) (digest.Digest, error)
// Delete removes the manifest specified by the given digest. Deleting
// a manifest that doesn't exist will return ErrManifestNotFound
Delete(ctx context.Context, dgst digest.Digest) error
}
// ManifestEnumerator enables iterating over manifests
type ManifestEnumerator interface {
// Enumerate calls ingester for each manifest.
Enumerate(ctx context.Context, ingester func(digest.Digest) error) error
}
// Describable is an interface for descriptors
type Describable interface {
Descriptor() Descriptor
}
// ManifestMediaTypes returns the supported media types for manifests.
func ManifestMediaTypes() (mediaTypes []string) {
for t := range mappings {
if t != "" {
mediaTypes = append(mediaTypes, t)
}
}
return
}
// UnmarshalFunc implements manifest unmarshalling a given MediaType
type UnmarshalFunc func([]byte) (Manifest, Descriptor, error)
var mappings = make(map[string]UnmarshalFunc, 0)
// UnmarshalManifest looks up manifest unmarshal functions based on
// MediaType
func UnmarshalManifest(ctHeader string, p []byte) (Manifest, Descriptor, error) {
// Need to look up by the actual media type, not the raw contents of
// the header. Strip semicolons and anything following them.
var mediaType string
if ctHeader != "" {
var err error
mediaType, _, err = mime.ParseMediaType(ctHeader)
if err != nil {
return nil, Descriptor{}, err
}
}
unmarshalFunc, ok := mappings[mediaType]
if !ok {
unmarshalFunc, ok = mappings[""]
if !ok {
return nil, Descriptor{}, fmt.Errorf("unsupported manifest media type and no default available: %s", mediaType)
}
}
return unmarshalFunc(p)
}
// RegisterManifestSchema registers an UnmarshalFunc for a given schema type. This
// should be called from specific
func RegisterManifestSchema(mediaType string, u UnmarshalFunc) error {
if _, ok := mappings[mediaType]; ok {
return fmt.Errorf("manifest media type registration would overwrite existing: %s", mediaType)
}
mappings[mediaType] = u
return nil
}