distribution/reference/reference.go
Derek McGowan bcda04d6cd Add field type for serialization
Since reference itself may be represented by multiple types which implement the reference inteface, serialization can lead to ambiguous type which cannot be deserialized.
Field wraps the reference object to ensure that the correct type is always deserialized, requiring an extra unwrap of the reference after deserialization.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
2015-10-09 16:05:49 -07:00

283 lines
6.7 KiB
Go

// Package reference provides a general type to represent any way of referencing images within the registry.
// Its main purpose is to abstract tags and digests (content-addressable hash).
//
// Grammar
//
// reference := repository [ ":" tag ] [ "@" digest ]
//
// // repository.go
// repository := hostname ['/' component]+
// hostname := hostcomponent [':' port-number]
// component := alpha-numeric [separator alpha-numeric]*
// hostcomponent := [hostpart '.']* hostpart
// alpha-numeric := /[a-zA-Z0-9]+/
// separator := /[_-]/
// port-number := /[0-9]+/
// hostpart := /([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])/
//
// // tag.go
// tag := /[\w][\w.-]{0,127}/
//
// // from the digest package
// digest := digest-algorithm ":" digest-hex
// digest-algorithm := digest-algorithm-component [ digest-algorithm-separator digest-algorithm-component ]
// digest-algorithm-separator := /[+.-_]/
// digest-algorithm-component := /[A-Za-z][A-Za-z0-9]*/
// digest-hex := /[0-9a-fA-F]{32,}/ ; Atleast 128 bit digest value
package reference
import (
"errors"
"fmt"
"github.com/docker/distribution/digest"
)
const (
// NameTotalLengthMax is the maximum total number of characters in a repository name.
NameTotalLengthMax = 255
)
var (
// ErrReferenceInvalidFormat represents an error while trying to parse a string as a reference.
ErrReferenceInvalidFormat = errors.New("invalid reference format")
// ErrNameEmpty is returned for empty, invalid repository names.
ErrNameEmpty = errors.New("repository name must have at least one component")
// ErrNameTooLong is returned when a repository name is longer than
// RepositoryNameTotalLengthMax
ErrNameTooLong = fmt.Errorf("repository name must not be more than %v characters", NameTotalLengthMax)
)
// Reference is an opaque object reference identifier that may include
// modifiers such as a hostname, name, tag, and digest.
type Reference interface {
// String returns the full reference
String() string
}
// Field provides a wrapper type for resolving correct reference types when
// working with encoding.
type Field struct {
reference Reference
}
// AsField wraps a reference in a Field for encoding.
func AsField(reference Reference) Field {
return Field{reference}
}
// Reference unwraps the reference type from the field to
// return the Reference object. This object should be
// of the appropriate type to further check for different
// reference types.
func (f Field) Reference() Reference {
return f.reference
}
// MarshalText serializes the field to byte text which
// is the string of the reference.
func (f Field) MarshalText() (p []byte, err error) {
return []byte(f.reference.String()), nil
}
// UnmarshalText parses text bytes by invoking the
// reference parser to ensure the appropriately
// typed reference object is wrapped by field.
func (f *Field) UnmarshalText(p []byte) error {
r, err := Parse(string(p))
if err != nil {
return err
}
f.reference = r
return nil
}
// Named is an object with a full name
type Named interface {
Name() string
}
// Tagged is an object which has a tag
type Tagged interface {
Tag() string
}
// Digested is an object which has a digest
// in which it can be referenced by
type Digested interface {
Digest() digest.Digest
}
// Canonical reference is an object with a fully unique
// name including a name with hostname and digest
type Canonical interface {
Reference
Named
Digested
}
// SplitHostname splits a named reference into a
// hostname and name string. If no valid hostname is
// found, the hostname is empty and the full value
// is returned as name
func SplitHostname(named Named) (string, string) {
name := named.Name()
match := anchoredNameRegexp.FindStringSubmatch(name)
if match == nil || len(match) != 3 {
return "", name
}
return match[1], match[2]
}
// Parse parses s and returns a syntactically valid Reference.
// If an error was encountered it is returned, along with a nil Reference.
// NOTE: Parse will not handle short digests.
func Parse(s string) (Reference, error) {
matches := ReferenceRegexp.FindStringSubmatch(s)
if matches == nil {
if s == "" {
return nil, ErrNameEmpty
}
// TODO(dmcgowan): Provide more specific and helpful error
return nil, ErrReferenceInvalidFormat
}
if len(matches[1]) > NameTotalLengthMax {
return nil, ErrNameTooLong
}
ref := reference{
name: matches[1],
tag: matches[2],
}
if matches[3] != "" {
var err error
ref.digest, err = digest.ParseDigest(matches[3])
if err != nil {
return nil, err
}
}
r := getBestReferenceType(ref)
if r == nil {
return nil, ErrNameEmpty
}
return r, nil
}
// ParseNamed parses the input string and returns a named
// object representing the given string. If the input is
// invalid ErrReferenceInvalidFormat will be returned.
func ParseNamed(name string) (Named, error) {
if !anchoredNameRegexp.MatchString(name) {
return nil, ErrReferenceInvalidFormat
}
return repository(name), nil
}
func getBestReferenceType(ref reference) Reference {
if ref.name == "" {
// Allow digest only references
if ref.digest != "" {
return digestReference(ref.digest)
}
return nil
}
if ref.tag == "" {
if ref.digest != "" {
return canonicalReference{
name: ref.name,
digest: ref.digest,
}
}
return repository(ref.name)
}
if ref.digest == "" {
return taggedReference{
name: ref.name,
tag: ref.tag,
}
}
return ref
}
type reference struct {
name string
tag string
digest digest.Digest
}
func (r reference) String() string {
return r.name + ":" + r.tag + "@" + r.digest.String()
}
func (r reference) Name() string {
return r.name
}
func (r reference) Tag() string {
return r.tag
}
func (r reference) Digest() digest.Digest {
return r.digest
}
type repository string
func (r repository) String() string {
return string(r)
}
func (r repository) Name() string {
return string(r)
}
type digestReference digest.Digest
func (d digestReference) String() string {
return d.String()
}
func (d digestReference) Digest() digest.Digest {
return digest.Digest(d)
}
type taggedReference struct {
name string
tag string
}
func (t taggedReference) String() string {
return t.name + ":" + t.tag
}
func (t taggedReference) Name() string {
return t.name
}
func (t taggedReference) Tag() string {
return t.tag
}
type canonicalReference struct {
name string
digest digest.Digest
}
func (c canonicalReference) String() string {
return c.name + "@" + c.digest.String()
}
func (c canonicalReference) Name() string {
return c.name
}
func (c canonicalReference) Digest() digest.Digest {
return c.digest
}