1 files changed, 88 insertions, 36 deletions

diff --git a/archive.go b/archive.go
index fa1886f..6610936 100644
--- a/archive.go
+++ b/archive.go
@@ -12,7 +12,7 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-type ArchiveReader interface {
+type TarReader interface {
 	Next() (*tar.Header, error)
 	Read([]byte) (int, error)
 }
@@ -107,15 +107,78 @@ func tarCreateSymlink(root string, header *tar.Header) error {
 	return err
 }
 
-type InstallArchiveCfg struct {
+type TarFilter interface {
+	FilterTar(header *tar.Header, r io.Reader) error
+}
+
+type TarFilterFunc func(
+	header *tar.Header,
+	r io.Reader,
+) error
+
+func (f TarFilterFunc) FilterTar(h *tar.Header, r io.Reader) error {
+	return f(h, r)
+}
+
+type TarCfg struct {
 	Root  string
 	Chown bool
 	Chmod bool
 }
 
-func InstallArchive(
-	r ArchiveReader,
-	cfg *InstallArchiveCfg,
+type TarExtracter struct {
+	cfg *TarCfg
+}
+
+func NewTarExtractor(cfg *TarCfg) *TarExtracter {
+	return &TarExtracter{cfg}
+}
+
+func (s *TarExtracter) FilterTar(
+	header *tar.Header,
+	r io.Reader,
+) error {
+	target := path.Join(s.cfg.Root, header.Name)
+
+	var err error
+	switch header.Typeflag {
+	case tar.TypeBlock:
+		err = tarCreateBlockDev(target, header)
+	case tar.TypeChar:
+		err = tarCreateCharDev(target, header)
+	case tar.TypeFifo:
+		err = tarCreateFifo(target, header)
+	case tar.TypeDir:
+		err = tarCreateDir(target)
+	case tar.TypeReg:
+		err = tarCreateReg(target, r, header)
+	case tar.TypeLink:
+		err = tarCreateLink(s.cfg.Root, header)
+	case tar.TypeSymlink:
+		err = tarCreateSymlink(s.cfg.Root, header)
+	default:
+		err = errors.Errorf("unhandled file type '%c'", header.Typeflag)
+	}
+	if err != nil {
+		return errors.Wrap(err, "unpacking tar archive")
+	}
+
+	if s.cfg.Chown {
+		if err = os.Chown(target, header.Uid, header.Gid); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+		}
+	}
+	if s.cfg.Chmod {
+		if err = os.Chmod(target, header.FileInfo().Mode()); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+		}
+	}
+	return nil
+}
+
+func FilterTar(
+	r TarReader,
+	filters ...TarFilter,
 ) error {
 	for {
 		header, err := r.Next()
@@ -127,40 +190,29 @@ func InstallArchive(
 		if header == nil {
 			continue
 		}
-		target := path.Join(cfg.Root, header.Name)
-
-		switch header.Typeflag {
-		case tar.TypeBlock:
-			err = tarCreateBlockDev(target, header)
-		case tar.TypeChar:
-			err = tarCreateCharDev(target, header)
-		case tar.TypeFifo:
-			err = tarCreateFifo(target, header)
-		case tar.TypeDir:
-			err = tarCreateDir(target)
-		case tar.TypeReg:
-			err = tarCreateReg(target, r, header)
-		case tar.TypeLink:
-			err = tarCreateLink(cfg.Root, header)
-		case tar.TypeSymlink:
-			err = tarCreateSymlink(cfg.Root, header)
-		default:
-			err = errors.Errorf("unhandled file type '%c'", header.Typeflag)
-		}
-		if err != nil {
-			return errors.Wrap(err, "unpacking tar archive")
-		}
-		if cfg.Chown {
-			if err = os.Chown(target, header.Uid, header.Gid); err != nil {
-				fmt.Fprintln(os.Stderr, err)
-			}
-		}
-		if cfg.Chmod {
-			if err = os.Chmod(target, header.FileInfo().Mode()); err != nil {
-				fmt.Fprintln(os.Stderr, err)
+
+		for _, f := range filters {
+			// TODO: how do we dup r?
+			err := f.FilterTar(header, r)
+			if err != nil {
+				return err
 			}
 		}
 	}
 
 	return nil
 }
+
+func ExtractTar(
+	cfg *TarCfg,
+	fp string,
+) error {
+	f, err := os.Open(fp)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	r := tar.NewReader(f)
+	err = FilterTar(r, NewTarExtractor(cfg))
+	return errors.Wrap(err, "extracting tar file")
+}