Initial commit

vendor/github.com/hyperhq/hypercli/pkg/tarsum/versioning.go

@@ -0,0 +1,150 @@
+package tarsum
+
+import (
+	"archive/tar"
+	"errors"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Version is used for versioning of the TarSum algorithm
+// based on the prefix of the hash used
+// i.e. "tarsum+sha256:e58fcf7418d4390dec8e8fb69d88c06ec07039d651fedd3aa72af9972e7d046b"
+type Version int
+
+// Prefix of "tarsum"
+const (
+	Version0 Version = iota
+	Version1
+	// VersionDev this constant will be either the latest or an unsettled next-version of the TarSum calculation
+	VersionDev
+)
+
+// VersionLabelForChecksum returns the label for the given tarsum
+// checksum, i.e., everything before the first `+` character in
+// the string or an empty string if no label separator is found.
+func VersionLabelForChecksum(checksum string) string {
+	// Checksums are in the form: {versionLabel}+{hashID}:{hex}
+	sepIndex := strings.Index(checksum, "+")
+	if sepIndex < 0 {
+		return ""
+	}
+	return checksum[:sepIndex]
+}
+
+// GetVersions gets a list of all known tarsum versions.
+func GetVersions() []Version {
+	v := []Version{}
+	for k := range tarSumVersions {
+		v = append(v, k)
+	}
+	return v
+}
+
+var (
+	tarSumVersions = map[Version]string{
+		Version0:   "tarsum",
+		Version1:   "tarsum.v1",
+		VersionDev: "tarsum.dev",
+	}
+	tarSumVersionsByName = map[string]Version{
+		"tarsum":     Version0,
+		"tarsum.v1":  Version1,
+		"tarsum.dev": VersionDev,
+	}
+)
+
+func (tsv Version) String() string {
+	return tarSumVersions[tsv]
+}
+
+// GetVersionFromTarsum returns the Version from the provided string.
+func GetVersionFromTarsum(tarsum string) (Version, error) {
+	tsv := tarsum
+	if strings.Contains(tarsum, "+") {
+		tsv = strings.SplitN(tarsum, "+", 2)[0]
+	}
+	for v, s := range tarSumVersions {
+		if s == tsv {
+			return v, nil
+		}
+	}
+	return -1, ErrNotVersion
+}
+
+// Errors that may be returned by functions in this package
+var (
+	ErrNotVersion            = errors.New("string does not include a TarSum Version")
+	ErrVersionNotImplemented = errors.New("TarSum Version is not yet implemented")
+)
+
+// tarHeaderSelector is the interface which different versions
+// of tarsum should use for selecting and ordering tar headers
+// for each item in the archive.
+type tarHeaderSelector interface {
+	selectHeaders(h *tar.Header) (orderedHeaders [][2]string)
+}
+
+type tarHeaderSelectFunc func(h *tar.Header) (orderedHeaders [][2]string)
+
+func (f tarHeaderSelectFunc) selectHeaders(h *tar.Header) (orderedHeaders [][2]string) {
+	return f(h)
+}
+
+func v0TarHeaderSelect(h *tar.Header) (orderedHeaders [][2]string) {
+	return [][2]string{
+		{"name", h.Name},
+		{"mode", strconv.FormatInt(h.Mode, 10)},
+		{"uid", strconv.Itoa(h.Uid)},
+		{"gid", strconv.Itoa(h.Gid)},
+		{"size", strconv.FormatInt(h.Size, 10)},
+		{"mtime", strconv.FormatInt(h.ModTime.UTC().Unix(), 10)},
+		{"typeflag", string([]byte{h.Typeflag})},
+		{"linkname", h.Linkname},
+		{"uname", h.Uname},
+		{"gname", h.Gname},
+		{"devmajor", strconv.FormatInt(h.Devmajor, 10)},
+		{"devminor", strconv.FormatInt(h.Devminor, 10)},
+	}
+}
+
+func v1TarHeaderSelect(h *tar.Header) (orderedHeaders [][2]string) {
+	// Get extended attributes.
+	xAttrKeys := make([]string, len(h.Xattrs))
+	for k := range h.Xattrs {
+		xAttrKeys = append(xAttrKeys, k)
+	}
+	sort.Strings(xAttrKeys)
+
+	// Make the slice with enough capacity to hold the 11 basic headers
+	// we want from the v0 selector plus however many xattrs we have.
+	orderedHeaders = make([][2]string, 0, 11+len(xAttrKeys))
+
+	// Copy all headers from v0 excluding the 'mtime' header (the 5th element).
+	v0headers := v0TarHeaderSelect(h)
+	orderedHeaders = append(orderedHeaders, v0headers[0:5]...)
+	orderedHeaders = append(orderedHeaders, v0headers[6:]...)
+
+	// Finally, append the sorted xattrs.
+	for _, k := range xAttrKeys {
+		orderedHeaders = append(orderedHeaders, [2]string{k, h.Xattrs[k]})
+	}
+
+	return
+}
+
+var registeredHeaderSelectors = map[Version]tarHeaderSelectFunc{
+	Version0:   v0TarHeaderSelect,
+	Version1:   v1TarHeaderSelect,
+	VersionDev: v1TarHeaderSelect,
+}
+
+func getTarHeaderSelector(v Version) (tarHeaderSelector, error) {
+	headerSelector, ok := registeredHeaderSelectors[v]
+	if !ok {
+		return nil, ErrVersionNotImplemented
+	}
+
+	return headerSelector, nil
+}