restic/backend/local.go

457 lines
8.8 KiB
Go

package backend
import (
"crypto/rand"
"crypto/sha256"
"errors"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"strings"
)
const (
dirMode = 0700
dataPath = "data"
snapshotPath = "snapshots"
treePath = "trees"
lockPath = "locks"
keyPath = "keys"
tempPath = "tmp"
versionFileName = "version"
idFileName = "id"
)
var ErrWrongData = errors.New("wrong data returned by backend, checksum does not match")
type Local struct {
p string
ver uint
id ID
}
// OpenLocal opens the local backend at dir.
func OpenLocal(dir string) (*Local, error) {
items := []string{
dir,
filepath.Join(dir, dataPath),
filepath.Join(dir, snapshotPath),
filepath.Join(dir, treePath),
filepath.Join(dir, lockPath),
filepath.Join(dir, keyPath),
filepath.Join(dir, tempPath),
}
// test if all necessary dirs and files are there
for _, d := range items {
if _, err := os.Stat(d); err != nil {
return nil, fmt.Errorf("%s does not exist", d)
}
}
// read version file
f, err := os.Open(filepath.Join(dir, versionFileName))
if err != nil {
return nil, fmt.Errorf("unable to read version file: %v\n", err)
}
var version uint
n, err := fmt.Fscanf(f, "%d", &version)
if err != nil {
return nil, err
}
if n != 1 {
return nil, errors.New("could not read version from file")
}
err = f.Close()
if err != nil {
return nil, err
}
// check version
if version != BackendVersion {
return nil, fmt.Errorf("wrong version %d", version)
}
// read ID
f, err = os.Open(filepath.Join(dir, idFileName))
if err != nil {
return nil, err
}
buf, err := ioutil.ReadAll(f)
if err != nil {
return nil, err
}
err = f.Close()
if err != nil {
return nil, err
}
id, err := ParseID(strings.TrimSpace(string(buf)))
if err != nil {
return nil, err
}
return &Local{p: dir, ver: version, id: id}, nil
}
// CreateLocal creates all the necessary files and directories for a new local
// backend at dir.
func CreateLocal(dir string) (*Local, error) {
versionFile := filepath.Join(dir, versionFileName)
idFile := filepath.Join(dir, idFileName)
dirs := []string{
dir,
filepath.Join(dir, dataPath),
filepath.Join(dir, snapshotPath),
filepath.Join(dir, treePath),
filepath.Join(dir, lockPath),
filepath.Join(dir, keyPath),
filepath.Join(dir, tempPath),
}
// test if files already exist
_, err := os.Lstat(versionFile)
if err == nil {
return nil, errors.New("version file already exists")
}
_, err = os.Lstat(idFile)
if err == nil {
return nil, errors.New("id file already exists")
}
// test if directories already exist
for _, d := range dirs[1:] {
if _, err := os.Stat(d); err == nil {
return nil, fmt.Errorf("dir %s already exists", d)
}
}
// create paths for data, refs and temp
for _, d := range dirs {
err := os.MkdirAll(d, dirMode)
if err != nil {
return nil, err
}
}
// create version file
f, err := os.Create(versionFile)
if err != nil {
return nil, err
}
_, err = fmt.Fprintf(f, "%d\n", BackendVersion)
if err != nil {
return nil, err
}
err = f.Close()
if err != nil {
return nil, err
}
// create ID file
id := make([]byte, sha256.Size)
_, err = rand.Read(id)
if err != nil {
return nil, err
}
f, err = os.Create(idFile)
if err != nil {
return nil, err
}
_, err = fmt.Fprintf(f, "%s\n", ID(id).String())
if err != nil {
return nil, err
}
err = f.Close()
if err != nil {
return nil, err
}
// open backend
return OpenLocal(dir)
}
// Location returns this backend's location (the directory name).
func (b *Local) Location() string {
return b.p
}
// Return temp directory in correct directory for this backend.
func (b *Local) tempFile() (*os.File, error) {
return ioutil.TempFile(filepath.Join(b.p, tempPath), "temp-")
}
// Rename temp file to final name according to type and ID.
func (b *Local) renameFile(file *os.File, t Type, id ID) error {
filename := b.filename(t, id)
oldname := file.Name()
if t == Data || t == Tree {
// create directories if necessary, ignore errors
os.MkdirAll(filepath.Dir(filename), dirMode)
}
err := os.Rename(oldname, filename)
if err != nil {
return err
}
// set mode to read-only
fi, err := os.Stat(filename)
if err != nil {
return err
}
return os.Chmod(filename, fi.Mode()&os.FileMode(^uint32(0222)))
}
// Construct directory for given Type.
func (b *Local) dirname(t Type, id ID) string {
var n string
switch t {
case Data:
n = dataPath
if id != nil {
n = filepath.Join(dataPath, fmt.Sprintf("%02x", id[0]))
}
case Snapshot:
n = snapshotPath
case Tree:
n = treePath
if id != nil {
n = filepath.Join(treePath, fmt.Sprintf("%02x", id[0]))
}
case Lock:
n = lockPath
case Key:
n = keyPath
}
return filepath.Join(b.p, n)
}
type localBlob struct {
f *os.File
hw *HashingWriter
backend *Local
tpe Type
id ID
size uint
closed bool
}
func (lb *localBlob) Close() error {
if lb.closed {
return errors.New("Close() called on closed file")
}
lb.closed = true
err := lb.f.Close()
if err != nil {
return fmt.Errorf("local: file.Close: %v", err)
}
// get ID
lb.id = ID(lb.hw.Sum(nil))
// check for duplicate ID
res, err := lb.backend.Test(lb.tpe, lb.id)
if err != nil {
return fmt.Errorf("testing presence of ID %v failed: %v", lb.id, err)
}
if res {
return ErrAlreadyPresent
}
// rename file
err = lb.backend.renameFile(lb.f, lb.tpe, lb.id)
if err != nil {
return err
}
return nil
}
func (lb *localBlob) Write(p []byte) (int, error) {
n, err := lb.hw.Write(p)
lb.size += uint(n)
return n, err
}
func (lb *localBlob) ID() (ID, error) {
if lb.id == nil {
return nil, errors.New("blob is not closed, ID unavailable")
}
return lb.id, nil
}
func (lb *localBlob) Size() uint {
return lb.size
}
// Create creates a new blob of type t. Blob implements io.WriteCloser. Once
// Close() has been called, ID() can be used to retrieve the ID. If the blob is
// already present, Close() returns ErrAlreadyPresent.
func (b *Local) Create(t Type) (Blob, error) {
// TODO: make sure that tempfile is removed upon error
// create tempfile in backend
file, err := b.tempFile()
if err != nil {
return nil, err
}
hw := NewHashingWriter(file, newHash())
blob := localBlob{
hw: hw,
f: file,
backend: b,
tpe: t,
}
return &blob, nil
}
// Construct path for given Type and ID.
func (b *Local) filename(t Type, id ID) string {
return filepath.Join(b.dirname(t, id), id.String())
}
// Get returns the content stored under the given ID. If the data doesn't match
// the requested ID, ErrWrongData is returned.
func (b *Local) Get(t Type, id ID) ([]byte, error) {
if id == nil {
return nil, errors.New("unable to load nil ID")
}
// try to open file
file, err := os.Open(b.filename(t, id))
defer file.Close()
if err != nil {
return nil, err
}
// read all
buf, err := ioutil.ReadAll(file)
if err != nil {
return nil, err
}
// check id
if !Hash(buf).Equal(id) {
return nil, ErrWrongData
}
return buf, nil
}
// GetReader returns a reader that yields the content stored under the given
// ID. The content is not verified. The reader should be closed after draining
// it.
func (b *Local) GetReader(t Type, id ID) (io.ReadCloser, error) {
if id == nil {
return nil, errors.New("unable to load nil ID")
}
// try to open file
file, err := os.Open(b.filename(t, id))
if err != nil {
return nil, err
}
return file, nil
}
// Test returns true if a blob of the given type and ID exists in the backend.
func (b *Local) Test(t Type, id ID) (bool, error) {
// try to open file
file, err := os.Open(b.filename(t, id))
defer func() {
file.Close()
}()
if err != nil {
if os.IsNotExist(err) {
return false, nil
}
return false, err
}
return true, nil
}
// Remove removes the content stored at ID.
func (b *Local) Remove(t Type, id ID) error {
return os.Remove(b.filename(t, id))
}
// List lists all objects of a given type.
func (b *Local) List(t Type) (IDs, error) {
// TODO: use os.Open() and d.Readdirnames() instead of Glob()
var pattern string
if t == Data || t == Tree {
pattern = filepath.Join(b.dirname(t, nil), "*", "*")
} else {
pattern = filepath.Join(b.dirname(t, nil), "*")
}
matches, err := filepath.Glob(pattern)
if err != nil {
return nil, err
}
ids := make(IDs, 0, len(matches))
for _, m := range matches {
base := filepath.Base(m)
if base == "" {
continue
}
id, err := ParseID(base)
if err != nil {
continue
}
ids = append(ids, id)
}
return ids, nil
}
// Version returns the version of this local backend.
func (b *Local) Version() uint {
return b.ver
}
// ID returns the ID of this local backend.
func (b *Local) ID() ID {
return b.id
}
// Close closes the backend
func (b *Local) Close() error {
return nil
}
// Delete removes the repository and all files.
func (b *Local) Delete() error {
return os.RemoveAll(b.p)
}