func Unzip()

in zip/zip.go [745:811]
59 lines of code
16 McCabe index (conditional complexity)

func Unzip(dir string, m module.Version, zipFile string) (err error) {
	defer func() {
		if err != nil {
			err = &zipError{verb: "unzip", path: zipFile, err: err}
		}
	}()

	// Check that the directory is empty. Don't create it yet in case there's
	// an error reading the zip.
	if files, _ := ioutil.ReadDir(dir); len(files) > 0 {
		return fmt.Errorf("target directory %v exists and is not empty", dir)
	}

	// Open the zip and check that it satisfies all restrictions.
	f, err := os.Open(zipFile)
	if err != nil {
		return err
	}
	defer f.Close()
	z, cf, err := checkZip(m, f)
	if err != nil {
		return err
	}
	if err := cf.Err(); err != nil {
		return err
	}

	// Unzip, enforcing sizes declared in the zip file.
	prefix := fmt.Sprintf("%s@%s/", m.Path, m.Version)
	if err := os.MkdirAll(dir, 0777); err != nil {
		return err
	}
	for _, zf := range z.File {
		name := zf.Name[len(prefix):]
		if name == "" || strings.HasSuffix(name, "/") {
			continue
		}
		dst := filepath.Join(dir, name)
		if err := os.MkdirAll(filepath.Dir(dst), 0777); err != nil {
			return err
		}
		w, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0444)
		if err != nil {
			return err
		}
		r, err := zf.Open()
		if err != nil {
			w.Close()
			return err
		}
		lr := &io.LimitedReader{R: r, N: int64(zf.UncompressedSize64) + 1}
		_, err = io.Copy(w, lr)
		r.Close()
		if err != nil {
			w.Close()
			return err
		}
		if err := w.Close(); err != nil {
			return err
		}
		if lr.N <= 0 {
			return fmt.Errorf("uncompressed size of file %s is larger than declared size (%d bytes)", zf.Name, zf.UncompressedSize64)
		}
	}

	return nil
}