/
imageref.go
137 lines (123 loc) · 4.33 KB
/
imageref.go
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/******************************************************************************
*
* Copyright 2020 SAP SE
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
******************************************************************************/
package models
import (
"fmt"
"net/url"
"strings"
"github.com/opencontainers/go-digest"
)
const (
defaultHostName = "registry-1.docker.io"
defaultTagName = "latest"
)
// ImageReference refers to an image that can be pulled from a registry.
type ImageReference struct {
Host string // either a plain hostname or a host:port like "example.org:443"
RepoName string
Reference ManifestReference
}
// String returns the most compact string representation of this reference.
func (r ImageReference) String() string {
var result string
if r.Reference.IsDigest() {
// digests are appended with "@"
result = fmt.Sprintf("%s@%s", r.RepoName, r.Reference.Digest)
} else {
// tag names are appended with ":"
if r.Reference.Tag == defaultTagName {
result = r.RepoName
} else {
result = fmt.Sprintf("%s:%s", r.RepoName, r.Reference.Tag)
}
}
if r.Host == defaultHostName {
// strip leading "library/" from repo name; e.g.
// "registry-1.docker.io/library/alpine:3.9" becomes just "alpine:3.9"
return strings.TrimPrefix(result, "library/")
}
return fmt.Sprintf("%s/%s", r.Host, result)
}
// ParseImageReference parses an image reference string like
// "registry.example.org/alpine:3.9" into an ImageReference struct.
// Both on success and on error, an additional string is returned indicating how
// the input was interpreted (e.g. which defaults were inferred). This can be
// shown to the user to help them understand how the reference was parsed.
func ParseImageReference(input string) (ImageReference, string, error) {
// prepend hostname for default registry if input does not include a hostname or host:port
inputParts := strings.SplitN(input, "/", 2)
hadNoHostName := false
if len(inputParts) == 1 || !looksLikeHostName(inputParts[0]) {
input = fmt.Sprintf("%s/%s", defaultHostName, input)
hadNoHostName = true
}
// reformat into a URL for parsing purposes
input = "docker-pullable://" + input
imageURL, err := url.Parse(input)
if err != nil {
return ImageReference{}, input, err
}
var ref ImageReference
switch {
case strings.Contains(imageURL.Path, "@"):
// input references a digest
pathParts := ImageReferenceRx.FindStringSubmatch(imageURL.Path)
parsedDigest, err := digest.Parse(pathParts[len(pathParts)-1])
if err != nil {
return ImageReference{}, input, fmt.Errorf("invalid digest: %q", ref.Reference)
}
ref = ImageReference{
Host: imageURL.Host,
RepoName: strings.TrimPrefix(pathParts[1], "/"),
Reference: ManifestReference{Digest: parsedDigest},
}
case strings.Contains(imageURL.Path, ":"):
// input references a tag name
pathParts := strings.SplitN(imageURL.Path, ":", 2)
ref = ImageReference{
Host: imageURL.Host,
RepoName: strings.TrimPrefix(pathParts[0], "/"),
Reference: ManifestReference{Tag: pathParts[1]},
}
default:
// input references no tag or digest - use default tag
ref = ImageReference{
Host: imageURL.Host,
RepoName: strings.TrimPrefix(imageURL.Path, "/"),
Reference: ManifestReference{Tag: "latest"},
}
}
if !RepoNameWithLeadingSlashRx.MatchString("/" + ref.RepoName) {
return ImageReference{}, input, fmt.Errorf("invalid repository name: %q", ref.RepoName)
}
if hadNoHostName {
// on the default registry, single-word repo names like "alpine" are
// actually shorthands for "library/alpine" etc.
if !strings.Contains(ref.RepoName, "/") {
ref.RepoName = "library/" + ref.RepoName
}
}
return ref, input, nil
}
func looksLikeHostName(host string) bool {
if strings.Contains(host, ":") {
// looks like "host:port"
return true
}
return strings.Contains(host, ".") || host == "localhost"
}