Add support for packed resource files

updater/file.go

@@ -1,6 +1,13 @@
 package updater
 
-import "github.com/safing/portbase/log"
+import (
+	"io"
+	"os"
+	"strings"
+
+	"github.com/safing/portbase/log"
+	"github.com/safing/portbase/utils"
+)
 
 // File represents a file from the update system.
 type File struct {
@@ -42,3 +49,55 @@ func (file *File) markActiveWithLocking() {
 		file.resource.ActiveVersion = file.version
 	}
 }
+
+// Unpacker describes the function that is passed to
+// File.Unpack. It receives a reader to the compressed/packed
+// file and should return a reader that provides
+// unpacked file contents. If the returned reader implements
+// io.Closer it's close method is invoked when an error
+// or io.EOF is returned from Read().
+type Unpacker func(io.Reader) (io.Reader, error)
+
+// Unpack returns the path to the unpacked version of file and
+// unpacks it on demand using unpacker.
+func (file *File) Unpack(suffix string, unpacker Unpacker) (string, error) {
+	path := strings.TrimSuffix(file.Path(), suffix)
+
+	if suffix == "" {
+		path += "-unpacked"
+	}
+
+	_, err := os.Stat(path)
+	if err == nil {
+		return path, nil
+	}
+
+	if !os.IsNotExist(err) {
+		return "", err
+	}
+
+	f, err := os.Open(file.Path())
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	r, err := unpacker(f)
+	if err != nil {
+		return "", err
+	}
+
+	ioErr := utils.CreateAtomic(path, r, &utils.AtomicFileOptions{
+		TempDir: file.resource.registry.TmpDir().Path,
+	})
+
+	if c, ok := r.(io.Closer); ok {
+		if err := c.Close(); err != nil && ioErr == nil {
+			// if ioErr is already set we ignore the error from
+			// closing the unpacker.
+			ioErr = err
+		}
+	}
+
+	return path, ioErr
+}

updater/get.go

@@ -13,7 +13,8 @@ var (
 	ErrNotAvailableLocally = errors.New("the requested file is not available locally")
 )
 
-// GetFile returns the selected (mostly newest) file with the given identifier or an error, if it fails.
+// GetFile returns the selected (mostly newest) file with the given
+// identifier or an error, if it fails.
 func (reg *ResourceRegistry) GetFile(identifier string) (*File, error) {
 	reg.RLock()
 	res, ok := reg.resources[identifier]

updater/packers.go

@@ -0,0 +1,13 @@
+package updater
+
+import (
+	"compress/gzip"
+	"io"
+)
+
+// UnpackGZIP unpacks a GZIP compressed reader r
+// and returns a new reader. It's suitable to be
+// used with registry.GetPackedFile.
+func UnpackGZIP(r io.Reader) (io.Reader, error) {
+	return gzip.NewReader(r)
+}

utils/atomic.go

@@ -0,0 +1,101 @@
+package utils
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/google/renameio"
+)
+
+// AtomicFileOptions holds additional options for manipulating
+// the behavior of CreateAtomic and friends.
+type AtomicFileOptions struct {
+	// Mode is the file mode for the new file. If
+	// 0, the file mode will be set to 0600.
+	Mode os.FileMode
+
+	// TempDir is the path to the temp-directory
+	// that should be used. If empty, it defaults
+	// to the system temp.
+	TempDir string
+}
+
+// CreateAtomic creates or overwrites a file at dest atomically using
+// data from r. Atomic means that even in case of a power outage,
+// dest will never be a zero-length file. It will always either contain
+// the previous data (or not exist) or the new data but never anything
+// in between.
+func CreateAtomic(dest string, r io.Reader, opts *AtomicFileOptions) error {
+	if opts == nil {
+		opts = &AtomicFileOptions{}
+	}
+
+	tmpFile, err := renameio.TempFile(opts.TempDir, dest)
+	if err != nil {
+		return fmt.Errorf("failed to create temp file: %w", err)
+	}
+	defer tmpFile.Cleanup() //nolint:errcheck
+
+	if opts.Mode != 0 {
+		if err := tmpFile.Chmod(opts.Mode); err != nil {
+			return fmt.Errorf("failed to update mode bits of temp file: %w", err)
+		}
+	}
+
+	if _, err := io.Copy(tmpFile, r); err != nil {
+		return fmt.Errorf("failed to copy source file: %w", err)
+	}
+
+	if err := tmpFile.CloseAtomicallyReplace(); err != nil {
+		return fmt.Errorf("failed to rename temp file to %q", dest)
+	}
+
+	return nil
+}
+
+// CopyFileAtomic is like CreateAtomic but copies content from
+// src to dest. If opts.Mode is 0 CopyFileAtomic tries to set
+// the file mode of src to dest.
+func CopyFileAtomic(dest string, src string, opts *AtomicFileOptions) error {
+	if opts == nil {
+		opts = &AtomicFileOptions{}
+	}
+
+	if opts.Mode == 0 {
+		stat, err := os.Stat(src)
+		if err != nil {
+			return err
+		}
+		opts.Mode = stat.Mode()
+	}
+
+	f, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	return CreateAtomic(dest, f, opts)
+}
+
+// ReplaceFileAtomic replaces the file at dest with the content from src.
+// If dest exists it's file mode copied and used for the replacement. If
+// not, dest will get the same file mode as src. See CopyFileAtomic and
+// CreateAtomic for more information.
+func ReplaceFileAtomic(dest string, src string, opts *AtomicFileOptions) error {
+	if opts == nil {
+		opts = &AtomicFileOptions{}
+	}
+
+	if opts.Mode == 0 {
+		stat, err := os.Stat(dest)
+		if err == nil {
+			opts.Mode = stat.Mode()
+		} else if !os.IsNotExist(err) {
+			return err
+		}
+	}
+
+	return CopyFileAtomic(dest, src, opts)
+}