archive: move stat-header handling into copy package

Move handling the stat header into `pkg/copy`.  All copy-related should
ideally be located in this package to increase locality and reduce
scattering where possible.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

3 files changed, 56 insertions, 14 deletions

diff --git a/pkg/copy/copy.go b/pkg/copy/copy.go
index 0e68eb450..3993b532e 100644
--- a/pkg/copy/copy.go
+++ b/pkg/copy/copy.go
@@ -114,7 +114,6 @@ func enforceCopyRules(source, destination *CopyItem) error {
 		return nil
 	}
 
-	// Source is a *stream*.
 	if source.info.IsStream {
 		if !(destination.info.IsDir || destination.info.IsStream) {
 			return errors.New("destination must be a directory or stream when copying from a stream")
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
+}
diff --git a/pkg/copy/item.go b/pkg/copy/item.go
index db6bca610..df8bf30b9 100644
--- a/pkg/copy/item.go
+++ b/pkg/copy/item.go
@@ -5,7 +5,6 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"time"
 
 	buildahCopiah "github.com/containers/buildah/copier"
 	"github.com/containers/buildah/pkg/chrootuser"
@@ -75,18 +74,6 @@ type CopyItem struct {
 // deferFunc allows for returning functions that must be deferred at call sites.
 type deferFunc func()
 
-// 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"`
-}
-
 // Stat returns the FileInfo.
 func (item *CopyItem) Stat() (*FileInfo, error) {
 	return &item.info, item.statError