Merge pull request #10393 from thaJeztah/improve_reference

pkg/reference: reduce allocations and improve GoDoc

pkg/reference/reference.go

@@ -18,7 +18,6 @@ package reference
 
 import (
 	"errors"
-	"fmt"
 	"net/url"
 	"path"
 	"regexp"
@@ -136,8 +135,12 @@ func (r Spec) Hostname() string {
 // Digest returns the digest portion of the reference spec. This may be a
 // partial or invalid digest, which may be used to lookup a complete digest.
 func (r Spec) Digest() digest.Digest {
-	_, dgst := SplitObject(r.Object)
+	i := strings.Index(r.Object, "@")
-	return dgst
+
+	if i < 0 {
+		return ""
+	}
+	return digest.Digest(r.Object[i+1:])
 }
 
 // String returns the normalized string for the ref.
@@ -146,21 +149,29 @@ func (r Spec) String() string {
 		return r.Locator
 	}
 	if r.Object[:1] == "@" {
-		return fmt.Sprintf("%v%v", r.Locator, r.Object)
+		return r.Locator + r.Object
 	}
 
-	return fmt.Sprintf("%v:%v", r.Locator, r.Object)
+	return r.Locator + ":" + r.Object
 }
 
-// SplitObject provides two parts of the object spec, delimited by an `@`
+// SplitObject provides two parts of the object spec, delimited by an "@"
-// symbol.
+// symbol. It does not perform any validation on correctness of the values
+// returned, and it's the callers' responsibility to validate the result.
 //
-// Either may be empty and it is the callers job to validate them
+// If an "@" delimiter is found, it returns the part *including* the "@"
-// appropriately.
+// delimiter as "tag", and the part after the "@" as digest.
+//
+// The example below produces "docker.io/library/ubuntu:latest@" and
+// "sha256:deadbeef";
+//
+//	t, d := SplitObject("docker.io/library/ubuntu:latest@sha256:deadbeef")
+//	fmt.Println(t) // docker.io/library/ubuntu:latest@
+//	fmt.Println(d) // sha256:deadbeef
 func SplitObject(obj string) (tag string, dgst digest.Digest) {
-	parts := strings.SplitAfterN(obj, "@", 2)
+	if i := strings.Index(obj, "@"); i >= 0 {
-	if len(parts) < 2 {
+		// Offset by one so preserve the "@" in the tag returned.
-		return parts[0], ""
+		return obj[:i+1], digest.Digest(obj[i+1:])
 	}
-	return parts[0], digest.Digest(parts[1])
+	return obj, ""
 }

pkg/reference/reference_test.go

@@ -192,3 +192,33 @@ func TestReferenceParser(t *testing.T) {
 		})
 	}
 }
+
+func BenchmarkSplitObject(b *testing.B) {
+	inputs := []string{
+		"",
+		"@",
+		"docker.io@",
+		"@digest",
+		"docker.io/library/redis:foo?fooo=asdf",
+		"docker.io/library/redis:foo@sha256:abcdef?fooo=asdf",
+		"docker.io/library/redis@sha256:abcdef?fooo=asdf",
+		"docker.io/library/redis:obj@abcdef?fooo=asdf",
+		"localhost:5000/library/redis:obj@abcdef?fooo=asdf",
+		"/docker.io/library/redis:obj@abcdef?fooo=asdf",
+		"docker.io/library/redis?fooo=asdf",
+		"sub-dom1.foo.com/bar/baz/quux:latest",
+		"sub-dom1.foo.com/bar/baz/quux:some-long-tag",
+		"b.gcr.io/test.example.com/my-app:test.example.com",
+		"xn--n3h.com/myimage:xn--n3h.com", // ☃.com in punycode
+		"xn--7o8h.com/myimage:xn--7o8h.com@sha512:fffffff",
+		"http://xn--7o8h.com/myimage:xn--7o8h.com@sha512:fffffff",
+	}
+
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		for _, input := range inputs {
+			_, _ = SplitObject(input)
+		}
+	}
+}