move dependencies to vendor

vendor/github.com/docker/distribution/digest/tarsum.go

@@ -0,0 +1,70 @@
+package digest
+
+import (
+	"fmt"
+
+	"regexp"
+)
+
+// TarSumRegexp defines a regular expression to match tarsum identifiers.
+var TarsumRegexp = regexp.MustCompile("tarsum(?:.[a-z0-9]+)?\\+[a-zA-Z0-9]+:[A-Fa-f0-9]+")
+
+// TarsumRegexpCapturing defines a regular expression to match tarsum identifiers with
+// capture groups corresponding to each component.
+var TarsumRegexpCapturing = regexp.MustCompile("(tarsum)(.([a-z0-9]+))?\\+([a-zA-Z0-9]+):([A-Fa-f0-9]+)")
+
+// TarSumInfo contains information about a parsed tarsum.
+type TarSumInfo struct {
+	// Version contains the version of the tarsum.
+	Version string
+
+	// Algorithm contains the algorithm for the final digest
+	Algorithm string
+
+	// Digest contains the hex-encoded digest.
+	Digest string
+}
+
+// InvalidTarSumError provides informations about a TarSum that cannot be parsed
+// by ParseTarSum.
+type InvalidTarSumError string
+
+func (e InvalidTarSumError) Error() string {
+	return fmt.Sprintf("invalid tarsum: %q", string(e))
+}
+
+// ParseTarSum parses a tarsum string into its components of interest. For
+// example, this method may receive the tarsum in the following format:
+//
+//		tarsum.v1+sha256:220a60ecd4a3c32c282622a625a54db9ba0ff55b5ba9c29c7064a2bc358b6a3e
+//
+// The function will return the following:
+//
+//		TarSumInfo{
+//			Version: "v1",
+//			Algorithm: "sha256",
+//			Digest: "220a60ecd4a3c32c282622a625a54db9ba0ff55b5ba9c29c7064a2bc358b6a3e",
+//		}
+//
+func ParseTarSum(tarSum string) (tsi TarSumInfo, err error) {
+	components := TarsumRegexpCapturing.FindStringSubmatch(tarSum)
+
+	if len(components) != 1+TarsumRegexpCapturing.NumSubexp() {
+		return TarSumInfo{}, InvalidTarSumError(tarSum)
+	}
+
+	return TarSumInfo{
+		Version:   components[3],
+		Algorithm: components[4],
+		Digest:    components[5],
+	}, nil
+}
+
+// String returns the valid, string representation of the tarsum info.
+func (tsi TarSumInfo) String() string {
+	if tsi.Version == "" {
+		return fmt.Sprintf("tarsum+%s:%s", tsi.Algorithm, tsi.Digest)
+	}
+
+	return fmt.Sprintf("tarsum.%s+%s:%s", tsi.Version, tsi.Algorithm, tsi.Digest)
+}