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package contenthash
import (
"archive/tar"
"io"
"sort"
"strconv"
"strings"
)
// WriteV1TarsumHeaders writes a tar header to a writer in V1 tarsum format.
func WriteV1TarsumHeaders(h *tar.Header, w io.Writer) {
for _, elem := range v1TarHeaderSelect(h) {
w.Write([]byte(elem[0] + elem[1]))
}
}
// Functions below are from docker legacy tarsum implementation.
// There is no valid technical reason to continue using them.
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) {
pax := h.PAXRecords
if len(h.Xattrs) > 0 { //nolint:staticcheck // field deprecated in stdlib
if pax == nil {
pax = map[string]string{}
for k, v := range h.Xattrs { //nolint:staticcheck // field deprecated in stdlib
pax["SCHILY.xattr."+k] = v
}
}
}
// Get extended attributes.
xAttrKeys := make([]string, 0, len(h.PAXRecords))
for k := range pax {
if strings.HasPrefix(k, "SCHILY.xattr.") {
k = strings.TrimPrefix(k, "SCHILY.xattr.")
if k == "security.capability" || !strings.HasPrefix(k, "security.") && !strings.HasPrefix(k, "system.") {
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.PAXRecords["SCHILY.xattr."+k]})
}
return
}
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