1 files changed, 62 insertions, 1 deletions
diff --git a/libgo/go/archive/tar/common.go b/libgo/go/archive/tar/common.go
index fc7a40923cd..921b9fe9bdd 100644
--- a/libgo/go/archive/tar/common.go
+++ b/libgo/go/archive/tar/common.go
@@ -11,7 +11,12 @@
 //   http://www.gnu.org/software/tar/manual/html_node/Standard.html
 package tar
 
-import "time"
+import (
+	"errors"
+	"fmt"
+	"os"
+	"time"
+)
 
 const (
 	blockSize = 512
@@ -49,6 +54,62 @@ type Header struct {
 	ChangeTime time.Time // status change time
 }
 
+// sysStat, if non-nil, populates h from system-dependent fields of fi.
+var sysStat func(fi os.FileInfo, h *Header) error
+
+// Mode constants from the tar spec.
+const (
+	c_ISDIR  = 040000
+	c_ISFIFO = 010000
+	c_ISREG  = 0100000
+	c_ISLNK  = 0120000
+	c_ISBLK  = 060000
+	c_ISCHR  = 020000
+	c_ISSOCK = 0140000
+)
+
+// FileInfoHeader creates a partially-populated Header from fi.
+// If fi describes a symlink, FileInfoHeader records link as the link target.
+func FileInfoHeader(fi os.FileInfo, link string) (*Header, error) {
+	if fi == nil {
+		return nil, errors.New("tar: FileInfo is nil")
+	}
+	h := &Header{
+		Name:    fi.Name(),
+		ModTime: fi.ModTime(),
+		Mode:    int64(fi.Mode().Perm()), // or'd with c_IS* constants later
+	}
+	switch {
+	case fi.Mode()&os.ModeType == 0:
+		h.Mode |= c_ISREG
+		h.Typeflag = TypeReg
+		h.Size = fi.Size()
+	case fi.IsDir():
+		h.Typeflag = TypeDir
+		h.Mode |= c_ISDIR
+	case fi.Mode()&os.ModeSymlink != 0:
+		h.Typeflag = TypeSymlink
+		h.Mode |= c_ISLNK
+		h.Linkname = link
+	case fi.Mode()&os.ModeDevice != 0:
+		if fi.Mode()&os.ModeCharDevice != 0 {
+			h.Mode |= c_ISCHR
+			h.Typeflag = TypeChar
+		} else {
+			h.Mode |= c_ISBLK
+			h.Typeflag = TypeBlock
+		}
+	case fi.Mode()&os.ModeSocket != 0:
+		h.Mode |= c_ISSOCK
+	default:
+		return nil, fmt.Errorf("archive/tar: unknown file mode %v", fi.Mode())
+	}
+	if sysStat != nil {
+		return h, sysStat(fi, h)
+	}
+	return h, nil
+}
+
 var zeroBlock = make([]byte, blockSize)
 
 // POSIX specifies a sum of the unsigned byte values, but the Sun tar uses signed byte values.