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// 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 := 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}/
package reference
import (
"errors"
"fmt"
"strings"
"github.com/opencontainers/go-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")
// 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")
)
// 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 {
Reference
Name() string
}
// Tagged is an object which has a tag
type Tagged interface {
Reference
Tag() string
}
// NamedTagged is an object including a name and tag.
type NamedTagged interface {
Named
Tag() string
}
// Digested is an object which has a digest
// in which it can be referenced by
type Digested interface {
Reference
Digest() digest.Digest
}
// Canonical reference is an object with a fully unique
// name including a name with domain and digest
type Canonical interface {
Named
Digest() digest.Digest
}
// namedRepository is a reference to a repository with a name.
// A namedRepository has both domain and path components.
type namedRepository interface {
Named
Domain() string
Path() string
}
// Domain returns the domain part of the Named reference
func Domain(named Named) string {
if r, ok := named.(namedRepository); ok {
return r.Domain()
}
domain, _ := splitDomain(named.Name())
return domain
}
// Path returns the name without the domain part of the Named reference
func Path(named Named) (name string) {
if r, ok := named.(namedRepository); ok {
return r.Path()
}
_, path := splitDomain(named.Name())
return path
}
func splitDomain(name string) (string, string) {
match := anchoredNameRegexp.FindStringSubmatch(name)
if len(match) != 3 {
return "", name
}
return match[1], match[2]
}
// 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
func SplitHostname(named Named) (string, string) {
if r, ok := named.(namedRepository); ok {
return r.Domain(), r.Path()
}
return splitDomain(named.Name())
}
// 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
}
if ReferenceRegexp.FindStringSubmatch(strings.ToLower(s)) != nil {
return nil, ErrNameContainsUppercase
}
return nil, ErrReferenceInvalidFormat
}
if len(matches[1]) > NameTotalLengthMax {
return nil, ErrNameTooLong
}
var repo repository
nameMatch := anchoredNameRegexp.FindStringSubmatch(matches[1])
if len(nameMatch) == 3 {
repo.domain = nameMatch[1]
repo.path = nameMatch[2]
} else {
repo.domain = ""
repo.path = matches[1]
}
ref := reference{
namedRepository: repo,
tag: matches[2],
}
if matches[3] != "" {
var err error
ref.digest, err = digest.Parse(matches[3])
if err != nil {
return nil, err
}
}
r := getBestReferenceType(ref)
if r == nil {
return nil, ErrNameEmpty
}
return r, nil
}
// 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 ParseNamed(s string) (Named, error) {
named, err := ParseNormalizedNamed(s)
if err != nil {
return nil, err
}
if named.String() != s {
return nil, ErrNameNotCanonical
}
return named, nil
}
// WithName returns a named object representing the given string. If the input
// is invalid ErrReferenceInvalidFormat will be returned.
func WithName(name string) (Named, error) {
if len(name) > NameTotalLengthMax {
return nil, ErrNameTooLong
}
match := anchoredNameRegexp.FindStringSubmatch(name)
if match == nil || len(match) != 3 {
return nil, ErrReferenceInvalidFormat
}
return repository{
domain: match[1],
path: match[2],
}, nil
}
// WithTag combines the name from "name" and the tag from "tag" to form a
// reference incorporating both the name and the tag.
func WithTag(name Named, tag string) (NamedTagged, error) {
if !anchoredTagRegexp.MatchString(tag) {
return nil, ErrTagInvalidFormat
}
var repo repository
if r, ok := name.(namedRepository); ok {
repo.domain = r.Domain()
repo.path = r.Path()
} else {
repo.path = name.Name()
}
if canonical, ok := name.(Canonical); ok {
return reference{
namedRepository: repo,
tag: tag,
digest: canonical.Digest(),
}, nil
}
return taggedReference{
namedRepository: repo,
tag: tag,
}, nil
}
// WithDigest combines the name from "name" and the digest from "digest" to form
// a reference incorporating both the name and the digest.
func WithDigest(name Named, digest digest.Digest) (Canonical, error) {
if !anchoredDigestRegexp.MatchString(digest.String()) {
return nil, ErrDigestInvalidFormat
}
var repo repository
if r, ok := name.(namedRepository); ok {
repo.domain = r.Domain()
repo.path = r.Path()
} else {
repo.path = name.Name()
}
if tagged, ok := name.(Tagged); ok {
return reference{
namedRepository: repo,
tag: tagged.Tag(),
digest: digest,
}, nil
}
return canonicalReference{
namedRepository: repo,
digest: digest,
}, nil
}
// TrimNamed removes any tag or digest from the named reference.
func TrimNamed(ref Named) Named {
domain, path := SplitHostname(ref)
return repository{
domain: domain,
path: path,
}
}
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{
namedRepository: ref.namedRepository,
digest: ref.digest,
}
}
return ref.namedRepository
}
if ref.digest == "" {
return taggedReference{
namedRepository: ref.namedRepository,
tag: ref.tag,
}
}
return ref
}
type reference struct {
namedRepository
tag string
digest digest.Digest
}
func (r reference) String() string {
return r.Name() + ":" + r.tag + "@" + r.digest.String()
}
func (r reference) Tag() string {
return r.tag
}
func (r reference) Digest() digest.Digest {
return r.digest
}
type repository struct {
domain string
path string
}
func (r repository) String() string {
return r.Name()
}
func (r repository) Name() string {
if r.domain == "" {
return r.path
}
return r.domain + "/" + r.path
}
func (r repository) Domain() string {
return r.domain
}
func (r repository) Path() string {
return r.path
}
type digestReference digest.Digest
func (d digestReference) String() string {
return digest.Digest(d).String()
}
func (d digestReference) Digest() digest.Digest {
return digest.Digest(d)
}
type taggedReference struct {
namedRepository
tag string
}
func (t taggedReference) String() string {
return t.Name() + ":" + t.tag
}
func (t taggedReference) Tag() string {
return t.tag
}
type canonicalReference struct {
namedRepository
digest digest.Digest
}
func (c canonicalReference) String() string {
return c.Name() + "@" + c.digest.String()
}
func (c canonicalReference) Digest() digest.Digest {
return c.digest
}
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