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filesystem.go
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filesystem.go
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package filesystem
import (
"archive/tar"
"compress/gzip"
"io"
"io/ioutil"
"os"
"path/filepath"
"strings"
"time"
)
// Fileinfo is a struct that holds User, Group, and Mode
type Fileinfo struct {
User string
Group string
Mode os.FileMode
}
// Closer implements Close()
type Closer interface {
Close() error
}
// Reader provides read-related methods which are runnable on a bare filesystem
// or a tar.gz file
type Reader interface {
ReadFile(filename string) ([]byte, error)
}
// Writer provides write-related methods which are runnable on a bare filesystem
// or a tar.gz file
type Writer interface {
Mkdir(filename string, fileInfo Fileinfo) error
WriteFile(filename string, data []byte, fileInfo Fileinfo) error
}
// WriteCloser implements Writer and Closer
type WriteCloser interface {
Writer
Closer
}
// Filesystem implements Reader, Writer and Closer
type Filesystem interface {
Reader
Writer
Closer
}
type filesystem struct {
name string
}
var _ Filesystem = &filesystem{}
// NewFilesystem returns a Filesystem interface backed by a bare filesystem
func NewFilesystem(name string) (Filesystem, error) {
err := os.RemoveAll(name)
if err != nil {
return nil, err
}
err = os.MkdirAll(name, 0777)
if err != nil {
return nil, err
}
return &filesystem{name}, nil
}
// Mkdir makes a directory. Note that it does not chown/chgrp as that would
// require elevated privileges
func (f *filesystem) Mkdir(name string, fileInfo Fileinfo) error {
return os.Mkdir(name, fileInfo.Mode)
}
func (f *filesystem) mkdirAll(name string) error {
return os.MkdirAll(name, 0755)
}
func (f *filesystem) WriteFile(filename string, data []byte, fileInfo Fileinfo) error {
filePath := filepath.Join(f.name, filename)
err := f.mkdirAll(filepath.Dir(filePath))
if err != nil {
return err
}
return ioutil.WriteFile(filePath, data, fileInfo.Mode)
}
func (f *filesystem) ReadFile(filename string) ([]byte, error) {
return ioutil.ReadFile(filepath.Join(f.name, filename))
}
func (filesystem) Close() error {
return nil
}
type tgzwriter struct {
gz *gzip.Writer
tw *tar.Writer
now time.Time
dirs map[string]struct{}
}
var _ WriteCloser = &tgzwriter{}
// NewTGZWriter returns a WriteCloser interface backed by a tar.gz file
func NewTGZWriter(w io.Writer) (WriteCloser, error) {
gz := gzip.NewWriter(w)
tw := &tgzwriter{
gz: gz,
tw: tar.NewWriter(gz),
now: time.Now(),
dirs: map[string]struct{}{},
}
return tw, nil
}
func (t *tgzwriter) Mkdir(name string, fileInfo Fileinfo) error {
if _, exists := t.dirs[name]; exists {
return &os.PathError{Op: "mkdir", Path: name}
}
err := t.tw.WriteHeader(&tar.Header{
Name: name,
Mode: int64(fileInfo.Mode),
ModTime: t.now,
Typeflag: tar.TypeDir,
Uname: fileInfo.User,
Gname: fileInfo.Group,
})
if err != nil {
return err
}
t.dirs[name] = struct{}{}
return nil
}
func (t *tgzwriter) mkdirAll(name string) error {
parts := strings.Split(name, "/")
for i := 1; i < len(parts); i++ {
name = filepath.Join(parts[:i]...)
if _, exists := t.dirs[name]; exists {
continue
}
err := t.Mkdir(name, Fileinfo{Mode: 0755, User: "root", Group: "root"})
if err != nil {
return err
}
}
return nil
}
func (t *tgzwriter) WriteFile(filename string, data []byte, fileInfo Fileinfo) error {
err := t.mkdirAll(filepath.Dir(filename))
if err != nil {
return err
}
err = t.tw.WriteHeader(&tar.Header{
Name: filename,
Mode: int64(fileInfo.Mode),
Size: int64(len(data)),
ModTime: t.now,
Typeflag: tar.TypeReg,
Uname: fileInfo.User,
Gname: fileInfo.Group,
})
if err != nil {
return err
}
_, err = t.tw.Write(data)
return err
}
func (t *tgzwriter) Close() error {
err := t.tw.Close()
if err != nil {
return err
}
return t.gz.Close()
}
type tgzreader struct {
r io.ReadSeeker
}
var _ Reader = &tgzreader{}
// NewTGZReader returns a Reader interface backed by a tar.gz file
func NewTGZReader(r io.ReadSeeker) (Reader, error) {
return &tgzreader{r: r}, nil
}
func (t *tgzreader) ReadFile(filename string) ([]byte, error) {
_, err := t.r.Seek(0, io.SeekStart)
if err != nil {
return nil, err
}
gz, err := gzip.NewReader(t.r)
if err != nil {
return nil, err
}
tr := tar.NewReader(gz)
for {
h, err := tr.Next()
if err != nil {
return nil, err
}
if h.Name == filename {
return ioutil.ReadAll(tr)
}
}
}