Initial commit

1 files changed, 166 insertions, 0 deletions

diff --git a/archive.go b/archive.go
new file mode 100644
index 0000000..fa1886f
--- /dev/null
+++ b/archive.go
@@ -0,0 +1,166 @@
+package pkgtools
+
+import (
+	"archive/tar"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+)
+
+type ArchiveReader interface {
+	Next() (*tar.Header, error)
+	Read([]byte) (int, error)
+}
+
+const NewDirMod = 0755
+
+func tarCreateBlockDev(target string, header *tar.Header) error {
+	mode := uint32(header.Mode & 07777)
+	mode |= unix.S_IFBLK
+	dev := unix.Mkdev(uint32(header.Devmajor), uint32(header.Devminor))
+	err := unix.Mknod(target, mode, int(dev))
+	return err
+}
+
+func tarCreateCharDev(target string, header *tar.Header) error {
+	mode := uint32(header.Mode & 07777)
+	mode |= unix.S_IFCHR
+	dev := unix.Mkdev(uint32(header.Devmajor), uint32(header.Devminor))
+	err := unix.Mknod(target, mode, int(dev))
+	return err
+}
+
+func tarCreateDir(target string) error {
+	err := os.MkdirAll(target, NewDirMod)
+	return err
+}
+
+func tarCreateFifo(target string, header *tar.Header) error {
+	mode := uint32(header.Mode & 07777)
+	mode |= unix.S_IFIFO
+	dev := unix.Mkdev(uint32(header.Devmajor), uint32(header.Devminor))
+	err := unix.Mknod(target, mode, int(dev))
+	return err
+}
+
+func tarCreateReg(target string, r io.Reader, header *tar.Header) error {
+	f, err := os.OpenFile(
+		target,
+		os.O_CREATE|os.O_RDWR,
+		os.FileMode(header.Mode),
+	)
+	if err != nil {
+		// it could be an error due to writing over a running executable.
+		err = os.Remove(target)
+		if err != nil {
+			return err
+		}
+
+		f, err = os.OpenFile(
+			target,
+			os.O_CREATE|os.O_RDWR,
+			os.FileMode(header.Mode),
+		)
+		if err != nil {
+			return err
+		}
+	}
+	defer f.Close()
+
+	// copy over contents
+	if _, err := io.Copy(f, r); err != nil {
+		return err
+	}
+	return nil
+}
+
+func tarCreateLink(root string, header *tar.Header) error {
+	oldName := filepath.Join(root, header.Linkname)
+	if filepath.IsAbs(header.Linkname) {
+		filepath.Join(root, oldName)
+	}
+	newName := filepath.Join(root, header.Name)
+	err := os.Link(oldName, newName)
+	if err != nil {
+		_ = os.Remove(newName)
+		err = os.Link(oldName, newName)
+	}
+	return err
+}
+
+func tarCreateSymlink(root string, header *tar.Header) error {
+	oldName := filepath.Join(root, header.Linkname)
+	if filepath.IsAbs(header.Linkname) {
+		filepath.Join(root, oldName)
+	}
+	newName := filepath.Join(root, header.Name)
+	err := os.Symlink(oldName, newName)
+	if err != nil {
+		_ = os.Remove(newName)
+		err = os.Symlink(oldName, newName)
+	}
+	return err
+}
+
+type InstallArchiveCfg struct {
+	Root  string
+	Chown bool
+	Chmod bool
+}
+
+func InstallArchive(
+	r ArchiveReader,
+	cfg *InstallArchiveCfg,
+) error {
+	for {
+		header, err := r.Next()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return err
+		}
+		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)
+			}
+		}
+	}
+
+	return nil
+}