61 lines
1.7 KiB
Go
61 lines
1.7 KiB
Go
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package contenthash
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import (
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"archive/tar"
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"io"
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"sort"
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"strconv"
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)
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// WriteV1TarsumHeaders writes a tar header to a writer in V1 tarsum format.
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func WriteV1TarsumHeaders(h *tar.Header, w io.Writer) {
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for _, elem := range v1TarHeaderSelect(h) {
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w.Write([]byte(elem[0] + elem[1]))
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}
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}
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// Functions below are from docker legacy tarsum implementation.
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// There is no valid technical reason to continue using them.
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func v0TarHeaderSelect(h *tar.Header) (orderedHeaders [][2]string) {
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return [][2]string{
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{"name", h.Name},
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{"mode", strconv.FormatInt(h.Mode, 10)},
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{"uid", strconv.Itoa(h.Uid)},
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{"gid", strconv.Itoa(h.Gid)},
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{"size", strconv.FormatInt(h.Size, 10)},
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{"mtime", strconv.FormatInt(h.ModTime.UTC().Unix(), 10)},
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{"typeflag", string([]byte{h.Typeflag})},
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{"linkname", h.Linkname},
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{"uname", h.Uname},
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{"gname", h.Gname},
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{"devmajor", strconv.FormatInt(h.Devmajor, 10)},
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{"devminor", strconv.FormatInt(h.Devminor, 10)},
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}
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}
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func v1TarHeaderSelect(h *tar.Header) (orderedHeaders [][2]string) {
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// Get extended attributes.
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xAttrKeys := make([]string, len(h.Xattrs))
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for k := range h.Xattrs {
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xAttrKeys = append(xAttrKeys, k)
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}
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sort.Strings(xAttrKeys)
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// Make the slice with enough capacity to hold the 11 basic headers
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// we want from the v0 selector plus however many xattrs we have.
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orderedHeaders = make([][2]string, 0, 11+len(xAttrKeys))
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// Copy all headers from v0 excluding the 'mtime' header (the 5th element).
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v0headers := v0TarHeaderSelect(h)
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orderedHeaders = append(orderedHeaders, v0headers[0:5]...)
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orderedHeaders = append(orderedHeaders, v0headers[6:]...)
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// Finally, append the sorted xattrs.
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for _, k := range xAttrKeys {
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orderedHeaders = append(orderedHeaders, [2]string{k, h.Xattrs[k]})
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}
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return
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}
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