1 files changed, 56 insertions, 0 deletions
diff --git a/pkg/copy/fileinfo.go b/pkg/copy/fileinfo.go
new file mode 100644
index 000000000..08b4eb377
--- /dev/null
+++ b/pkg/copy/fileinfo.go
@@ -0,0 +1,56 @@
+package copy
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+// XDockerContainerPathStatHeader is the *key* in http headers pointing to the
+// base64 encoded JSON payload of stating a path in a container.
+const XDockerContainerPathStatHeader = "X-Docker-Container-Path-Stat"
+
+// FileInfo describes a file or directory and is returned by
+// (*CopyItem).Stat().
+type FileInfo struct {
+	Name       string      `json:"name"`
+	Size       int64       `json:"size"`
+	Mode       os.FileMode `json:"mode"`
+	ModTime    time.Time   `json:"mtime"`
+	IsDir      bool        `json:"isDir"`
+	IsStream   bool        `json:"isStream"`
+	LinkTarget string      `json:"linkTarget"`
+}
+
+// EncodeFileInfo serializes the specified FileInfo as a base64 encoded JSON
+// payload.  Intended for Docker compat.
+func EncodeFileInfo(info *FileInfo) (string, error) {
+	buf, err := json.Marshal(&info)
+	if err != nil {
+		return "", errors.Wrap(err, "failed to serialize file stats")
+	}
+	return base64.URLEncoding.EncodeToString(buf), nil
+}
+
+// ExtractFileInfoFromHeader extracts a base64 encoded JSON payload of a
+// FileInfo in the http header.  If no such header entry is found, nil is
+// returned.  Intended for Docker compat.
+func ExtractFileInfoFromHeader(header *http.Header) (*FileInfo, error) {
+	rawData := header.Get(XDockerContainerPathStatHeader)
+	if len(rawData) == 0 {
+		return nil, nil
+	}
+
+	info := FileInfo{}
+	base64Decoder := base64.NewDecoder(base64.URLEncoding, strings.NewReader(rawData))
+	if err := json.NewDecoder(base64Decoder).Decode(&info); err != nil {
+		return nil, err
+	}
+
+	return &info, nil
+}