util/tar/tar.go

// Copyright (C) 2019-2020 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand.  If not, see <https://www.gnu.org/licenses/>.

package tar

import (
	"archive/tar"
	"compress/gzip"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

// CompressFolder takes the name of a folder to compress, and the name of a file in which to store it.
func CompressFolder(src, filename string) error {
	f, err := os.Create(filename)
	if err != nil {
		return err
	}
	return Compress(src, f)
}

// Compress takes a source and variable writers and walks 'source' writing each file
// found to the tar writer; the purpose for accepting multiple writers is to allow
// for multiple outputs (for example a file, or md5 hash)
// Copied with minor modifications from https://medium.com/@skdomino/taring-untaring-files-in-go-6b07cf56bc07
func Compress(src string, writers ...io.Writer) error {

	// ensure the src actually exists before trying to tar it
	if _, err := os.Stat(src); err != nil {
		return fmt.Errorf("Unable to tar files - %v", err.Error())
	}

	mw := io.MultiWriter(writers...)

	gzw := gzip.NewWriter(mw)
	defer gzw.Close()

	tw := tar.NewWriter(gzw)
	defer tw.Close()

	// walk path
	return filepath.Walk(src, func(file string, fi os.FileInfo, err error) error {

		// return on any error
		if err != nil {
			return err
		}

		// create a new dir/file header
		header, err := tar.FileInfoHeader(fi, fi.Name())
		if err != nil {
			return err
		}

		// update the name to correctly reflect the desired destination when untaring
		header.Name = strings.TrimPrefix(strings.Replace(file, src, "", -1), string(filepath.Separator))

		// write the header
		if err := tw.WriteHeader(header); err != nil {
			return err
		}

		// return on non-regular files (thanks to [kumo](https://medium.com/@komuw/just-like-you-did-fbdd7df829d3) for this suggested update)
		if !header.FileInfo().Mode().IsRegular() {
			return nil
		}

		// open files for taring
		f, err := os.Open(file)
		if err != nil {
			return err
		}

		// copy file data into tar writer
		if _, err := io.Copy(tw, f); err != nil {
			return err
		}

		// manually close here after each file operation; defering would cause each file close
		// to wait until all operations have completed.
		f.Close()

		return nil
	})
}