1 files changed, 117 insertions, 0 deletions
diff --git a/workhorse/internal/zipartifacts/metadata.go b/workhorse/internal/zipartifacts/metadata.go
new file mode 100644
index 00000000000..1ecf52deafb
--- /dev/null
+++ b/workhorse/internal/zipartifacts/metadata.go
@@ -0,0 +1,117 @@
+package zipartifacts
+
+import (
+	"archive/zip"
+	"compress/gzip"
+	"encoding/binary"
+	"encoding/json"
+	"io"
+	"path"
+	"sort"
+	"strconv"
+)
+
+type metadata struct {
+	Modified int64  `json:"modified,omitempty"`
+	Mode     string `json:"mode,omitempty"`
+	CRC      uint32 `json:"crc,omitempty"`
+	Size     uint64 `json:"size,omitempty"`
+	Zipped   uint64 `json:"zipped,omitempty"`
+	Comment  string `json:"comment,omitempty"`
+}
+
+const MetadataHeaderPrefix = "\x00\x00\x00&" // length of string below, encoded properly
+const MetadataHeader = "GitLab Build Artifacts Metadata 0.0.2\n"
+
+func newMetadata(file *zip.File) metadata {
+	if file == nil {
+		return metadata{}
+	}
+
+	return metadata{
+		//lint:ignore SA1019 Remove this once the minimum supported version is go 1.10 (go 1.9 and down do not support an alternative)
+		Modified: file.ModTime().Unix(),
+		Mode:     strconv.FormatUint(uint64(file.Mode().Perm()), 8),
+		CRC:      file.CRC32,
+		Size:     file.UncompressedSize64,
+		Zipped:   file.CompressedSize64,
+		Comment:  file.Comment,
+	}
+}
+
+func (m metadata) writeEncoded(output io.Writer) error {
+	j, err := json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	j = append(j, byte('\n'))
+	return writeBytes(output, j)
+}
+
+func writeZipEntryMetadata(output io.Writer, path string, entry *zip.File) error {
+	if err := writeString(output, path); err != nil {
+		return err
+	}
+
+	if err := newMetadata(entry).writeEncoded(output); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func GenerateZipMetadata(w io.Writer, archive *zip.Reader) error {
+	output := gzip.NewWriter(w)
+	defer output.Close()
+
+	if err := writeString(output, MetadataHeader); err != nil {
+		return err
+	}
+
+	// Write empty error header that we may need in the future
+	if err := writeString(output, "{}"); err != nil {
+		return err
+	}
+
+	// Create map of files in zip archive
+	zipMap := make(map[string]*zip.File, len(archive.File))
+
+	// Add missing entries
+	for _, entry := range archive.File {
+		zipMap[entry.Name] = entry
+
+		for d := path.Dir(entry.Name); d != "." && d != "/"; d = path.Dir(d) {
+			entryDir := d + "/"
+			if _, ok := zipMap[entryDir]; !ok {
+				zipMap[entryDir] = nil
+			}
+		}
+	}
+
+	// Sort paths
+	sortedPaths := make([]string, 0, len(zipMap))
+	for path := range zipMap {
+		sortedPaths = append(sortedPaths, path)
+	}
+	sort.Strings(sortedPaths)
+
+	// Write all files
+	for _, path := range sortedPaths {
+		if err := writeZipEntryMetadata(output, path, zipMap[path]); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func writeBytes(output io.Writer, data []byte) error {
+	err := binary.Write(output, binary.BigEndian, uint32(len(data)))
+	if err == nil {
+		_, err = output.Write(data)
+	}
+	return err
+}
+
+func writeString(output io.Writer, str string) error {
+	return writeBytes(output, []byte(str))
+}