package sdk

import (

"archive/tar"

"compress/gzip"

"io"

"os"

"path/filepath"

"github.com/spf13/afero"

)

// IsTar returns true if the content is a tar

func IsTar(buf []byte) bool {

return len(buf) > 261 &&

buf[257] == 0x75 && buf[258] == 0x73 &&

buf[259] == 0x74 && buf[260] == 0x61 &&

buf[261] == 0x72

}

// IsGz returns true if the content is gzipped

func IsGz(buf []byte) bool {

return len(buf) > 2 &&

buf[0] == 0x1F && buf[1] == 0x8B && buf[2] == 0x8

}

// UntarGz takes a destination path and a reader; a tar.gz reader loops over the tarfile

// creating the file structure at 'dst' along the way, and writing any files

func UntarGz(fs afero.Fs, dst string, r io.Reader) error {

gzr, err := gzip.NewReader(r)

if err != nil {

return err

}

defer gzr.Close()

return Untar(fs, dst, gzr)

}

// Untar takes a destination path and a reader; a tar reader loops over the tarfile

// creating the file structure at 'dst' along the way, and writing any files

func Untar(fs afero.Fs, dst string, r io.Reader) error {

tr := tar.NewReader(r)

for {

header, err := tr.Next()

switch {

case err == io.EOF:

return nil

case err != nil:

return err

case header == nil:

continue

}

target := filepath.Join(dst, header.Name)

// check the file type

switch header.Typeflag {

case tar.TypeDir:

if _, err := fs.Stat(target); err != nil {

if err := fs.MkdirAll(target, 0755); err != nil {

return err

}

}

case tar.TypeReg:

f, err := fs.OpenFile(target, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))

if err != nil {

return err

}

if _, err := io.Copy(f, tr); err != nil {

return err

}

f.Close()

}

}

}