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Published: Feb 9, 2021 License: Apache-2.0 Imports: 7 Imported by: 0



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).


reference                       := name [ ":" tag ] [ "@" digest ]
name                            := [domain '/'] path-component ['/' path-component]*
domain                          := domain-component ['.' domain-component]* [':' port-number]
domain-component                := /([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])/
port-number                     := /[0-9]+/
path-component                  := alpha-numeric [separator alpha-numeric]*
alpha-numeric                   := /[a-z0-9]+/
separator                       := /[_.]|__|[-]*/

tag                             := /[\w][\w.-]{0,127}/

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,}/ ; At least 128 bit digest value

identifier                      := /[a-f0-9]{64}/
short-identifier                := /[a-f0-9]{6,64}/



View Source
const (
	// NameTotalLengthMax is the maximum total number of characters in a repository name.
	NameTotalLengthMax = 255


View Source
var (
	// ErrReferenceInvalidFormat represents an error while trying to parse a string as a reference.
	ErrReferenceInvalidFormat = errors.New("invalid reference format")

	// ErrTagInvalidFormat represents an error while trying to parse a string as a tag.
	ErrTagInvalidFormat = errors.New("invalid tag format")

	// ErrDigestInvalidFormat represents an error while trying to parse a string as a tag.
	ErrDigestInvalidFormat = errors.New("invalid digest format")

	// ErrNameContainsUppercase is returned for invalid repository names that contain uppercase characters.
	ErrNameContainsUppercase = errors.New("repository name must be lowercase")

	// 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 NameTotalLengthMax.
	ErrNameTooLong = fmt.Errorf("repository name must not be more than %v characters", NameTotalLengthMax)

	// ErrNameNotCanonical is returned when a name is not canonical.
	ErrNameNotCanonical = errors.New("repository name must be canonical")
View Source
var (

	// DomainRegexp defines the structure of potential domain components
	// that may be part of image names. This is purposely a subset of what is
	// allowed by DNS to ensure backwards compatibility with Docker image
	// names.
	DomainRegexp = expression(
		optional(repeated(literal(`.`), domainComponentRegexp)),
		optional(literal(`:`), match(`[0-9]+`)))

	// TagRegexp matches valid tag names. From docker/docker:graph/tags.go.
	TagRegexp = match(`[\w][\w.-]{0,127}`)

	// DigestRegexp matches valid digests.
	DigestRegexp = match(`[A-Za-z][A-Za-z0-9]*(?:[-_+.][A-Za-z][A-Za-z0-9]*)*[:][[:xdigit:]]{32,}`)

	// NameRegexp is the format for the name component of references. The
	// regexp has capturing groups for the domain and name part omitting
	// the separating forward slash from either.
	NameRegexp = expression(
		optional(DomainRegexp, literal(`/`)),
		optional(repeated(literal(`/`), nameComponentRegexp)))

	// ReferenceRegexp is the full supported format of a reference. The regexp
	// is anchored and has capturing groups for name, tag, and digest
	// components.
	ReferenceRegexp = anchored(capture(NameRegexp),
		optional(literal(":"), capture(TagRegexp)),
		optional(literal("@"), capture(DigestRegexp)))

	// IdentifierRegexp is the format for string identifier used as a
	// content addressable identifier using sha256. These identifiers
	// are like digests without the algorithm, since sha256 is used.
	IdentifierRegexp = match(`([a-f0-9]{64})`)

	// ShortIdentifierRegexp is the format used to represent a prefix
	// of an identifier. A prefix may be used to match a sha256 identifier
	// within a list of trusted identifiers.
	ShortIdentifierRegexp = match(`([a-f0-9]{6,64})`)


func Domain

func Domain(named Named) string

Domain returns the domain part of the Named reference

func FamiliarMatch

func FamiliarMatch(pattern string, ref Reference) (bool, error)

FamiliarMatch reports whether ref matches the specified pattern. See for supported patterns.

func FamiliarName

func FamiliarName(ref Named) string

FamiliarName returns the familiar name string for the given named, familiarizing if needed.

func FamiliarString

func FamiliarString(ref Reference) string

FamiliarString returns the familiar string representation for the given reference, familiarizing if needed.

func IsNameOnly

func IsNameOnly(ref Named) bool

IsNameOnly returns true if reference only contains a repo name.

func Path

func Path(named Named) (name string)

Path returns the name without the domain part of the Named reference

func SplitHostname

func SplitHostname(named Named) (string, string)

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 DEPRECATED: Use Domain or Path


type Canonical

type Canonical interface {
	Digest() digest.Digest

Canonical reference is an object with a fully unique name including a name with domain and digest

func WithDigest

func WithDigest(name Named, digest digest.Digest) (Canonical, error)

WithDigest combines the name from "name" and the digest from "digest" to form a reference incorporating both the name and the digest.

type Digested

type Digested interface {
	Digest() digest.Digest

Digested is an object which has a digest in which it can be referenced by

type Field

type Field struct {
	// contains filtered or unexported fields

Field provides a wrapper type for resolving correct reference types when working with encoding.

func AsField

func AsField(reference Reference) Field

AsField wraps a reference in a Field for encoding.

func (Field) MarshalText

func (f Field) MarshalText() (p []byte, err error)

MarshalText serializes the field to byte text which is the string of the reference.

func (Field) Reference

func (f Field) Reference() 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 (*Field) UnmarshalText

func (f *Field) UnmarshalText(p []byte) error

UnmarshalText parses text bytes by invoking the reference parser to ensure the appropriately typed reference object is wrapped by field.

type Named

type Named interface {
	Name() string

Named is an object with a full name

func ParseNamed

func ParseNamed(s string) (Named, error)

ParseNamed parses s and returns a syntactically valid reference implementing the Named interface. The reference must have a name and be in the canonical form, otherwise an error is returned. If an error was encountered it is returned, along with a nil Reference. NOTE: ParseNamed will not handle short digests.

func ParseNormalizedNamed

func ParseNormalizedNamed(s string) (Named, error)

ParseNormalizedNamed parses a string into a named reference transforming a familiar name from Docker UI to a fully qualified reference. If the value may be an identifier use ParseAnyReference.

func TagNameOnly

func TagNameOnly(ref Named) Named

TagNameOnly adds the default tag "latest" to a reference if it only has a repo name.

func TrimNamed

func TrimNamed(ref Named) Named

TrimNamed removes any tag or digest from the named reference.

func WithName

func WithName(name string) (Named, error)

WithName returns a named object representing the given string. If the input is invalid ErrReferenceInvalidFormat will be returned.

type NamedTagged

type NamedTagged interface {
	Tag() string

NamedTagged is an object including a name and tag.

func WithTag

func WithTag(name Named, tag string) (NamedTagged, error)

WithTag combines the name from "name" and the tag from "tag" to form a reference incorporating both the name and the tag.

type Reference

type Reference interface {
	// String returns the full reference
	String() string

Reference is an opaque object reference identifier that may include modifiers such as a hostname, name, tag, and digest.

func Parse

func Parse(s string) (Reference, error)

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 ParseAnyReference

func ParseAnyReference(ref string) (Reference, error)

ParseAnyReference parses a reference string as a possible identifier, full digest, or familiar name.

func ParseAnyReferenceWithSet

func ParseAnyReferenceWithSet(ref string, ds *digestset.Set) (Reference, error)

ParseAnyReferenceWithSet parses a reference string as a possible short identifier to be matched in a digest set, a full digest, or familiar name.

type Tagged

type Tagged interface {
	Tag() string

Tagged is an object which has a tag

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