restic/storage/storage.go
Alexander Neumann d156b2d245 Add storage
2014-04-19 19:37:34 +02:00

231 lines
4.3 KiB
Go

package storage
import (
"bytes"
"crypto/sha256"
"encoding/hex"
"errors"
"hash"
"io"
"io/ioutil"
"net/url"
"os"
"path"
"github.com/fd0/khepri/hashing"
)
const (
dirMode = 0700
objectPath = "objects"
refPath = "refs"
tempPath = "tmp"
)
type Repository interface {
Put(reader io.Reader) (ID, error)
PutFile(path string) (ID, error)
Get(ID) (io.Reader, error)
Test(ID) (bool, error)
Link(name string, id ID) error
Unlink(name string) error
Resolve(name string) (ID, error)
}
var (
ErrIDDoesNotExist = errors.New("ID does not exist")
)
// References content within a repository.
type ID []byte
func (id ID) String() string {
return hex.EncodeToString(id)
}
// Equal compares an ID to another other.
func (id ID) Equal(other ID) bool {
return bytes.Equal(id, other)
}
// EqualString compares this ID to another one, given as a string.
func (id ID) EqualString(other string) (bool, error) {
s, err := hex.DecodeString(other)
if err != nil {
return false, err
}
return id.Equal(ID(s)), nil
}
// Name stands for the alias given to an ID.
type Name string
func (n Name) Encode() string {
return url.QueryEscape(string(n))
}
type Dir struct {
path string
hash func() hash.Hash
}
// NewDir creates a new dir-baked repository at the given path.
func NewDir(path string) (*Dir, error) {
d := &Dir{
path: path,
hash: sha256.New,
}
err := d.create()
if err != nil {
return nil, err
}
return d, nil
}
func (r *Dir) create() error {
dirs := []string{
r.path,
path.Join(r.path, objectPath),
path.Join(r.path, refPath),
path.Join(r.path, tempPath),
}
for _, dir := range dirs {
err := os.MkdirAll(dir, dirMode)
if err != nil {
return err
}
}
return nil
}
// SetHash changes the hash function used for deriving IDs. Default is SHA256.
func (r *Dir) SetHash(h func() hash.Hash) {
r.hash = h
}
// Path returns the directory used for this repository.
func (r *Dir) Path() string {
return r.path
}
// Put saves content and returns the ID.
func (r *Dir) Put(reader io.Reader) (ID, error) {
// save contents to tempfile, hash while writing
file, err := ioutil.TempFile(path.Join(r.path, tempPath), "temp-")
if err != nil {
return nil, err
}
rd := hashing.NewReader(reader, r.hash)
_, err = io.Copy(file, rd)
if err != nil {
return nil, err
}
err = file.Close()
if err != nil {
return nil, err
}
// move file to final name using hash of contents
id := ID(rd.Hash())
filename := path.Join(r.path, objectPath, id.String())
err = os.Rename(file.Name(), filename)
if err != nil {
return nil, err
}
return id, nil
}
// PutFile saves a file's content to the repository and returns the ID.
func (r *Dir) PutFile(path string) (ID, error) {
f, err := os.Open(path)
defer f.Close()
if err != nil {
return nil, err
}
return r.Put(f)
}
// Test returns true if the given ID exists in the repository.
func (r *Dir) Test(id ID) (bool, error) {
// try to open file
file, err := os.Open(path.Join(r.path, objectPath, id.String()))
defer func() {
file.Close()
}()
if err != nil {
if os.IsNotExist(err) {
return false, nil
}
return false, err
}
return true, nil
}
// Get returns a reader for the content stored under the given ID.
func (r *Dir) Get(id ID) (io.Reader, error) {
// try to open file
file, err := os.Open(path.Join(r.path, objectPath, id.String()))
if err != nil {
return nil, err
}
return file, nil
}
// Unlink removes a named ID.
func (r *Dir) Unlink(name string) error {
return os.Remove(path.Join(r.path, refPath, Name(name).Encode()))
}
// Link assigns a name to an ID. Name must be unique in this repository and ID must exist.
func (r *Dir) Link(name string, id ID) error {
exist, err := r.Test(id)
if err != nil {
return err
}
if !exist {
return ErrIDDoesNotExist
}
// create file, write id
f, err := os.Create(path.Join(r.path, refPath, Name(name).Encode()))
defer f.Close()
if err != nil {
return err
}
f.Write(id)
return nil
}
// Resolve returns the ID associated with the given name.
func (r *Dir) Resolve(name string) (ID, error) {
f, err := os.Open(path.Join(r.path, refPath, Name(name).Encode()))
defer f.Close()
if err != nil {
return nil, err
}
id := make([]byte, r.hash().Size())
_, err = io.ReadFull(f, id)
if err != nil {
return nil, err
}
return ID(id), nil
}