mirror of
https://github.com/restic/restic.git
synced 2024-12-25 17:27:25 +00:00
f69a39cff5
This allows identifying a repository regardless if it's accessed over SFTP or locally. Introduced for having a per-repository cache.
567 lines
11 KiB
Go
567 lines
11 KiB
Go
package backend
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import (
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"crypto/rand"
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"crypto/sha256"
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"encoding/hex"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"log"
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"os"
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"os/exec"
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"path/filepath"
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"strings"
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"github.com/pkg/sftp"
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)
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const (
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tempfileRandomSuffixLength = 10
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)
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type SFTP struct {
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c *sftp.Client
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p string
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ver uint
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id ID
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cmd *exec.Cmd
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}
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func start_client(program string, args ...string) (*SFTP, error) {
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// Connect to a remote host and request the sftp subsystem via the 'ssh'
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// command. This assumes that passwordless login is correctly configured.
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cmd := exec.Command(program, args...)
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// send errors from ssh to stderr
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cmd.Stderr = os.Stderr
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// get stdin and stdout
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wr, err := cmd.StdinPipe()
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if err != nil {
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log.Fatal(err)
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}
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rd, err := cmd.StdoutPipe()
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if err != nil {
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log.Fatal(err)
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}
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// start the process
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if err := cmd.Start(); err != nil {
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log.Fatal(err)
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}
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// open the SFTP session
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client, err := sftp.NewClientPipe(rd, wr)
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if err != nil {
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log.Fatal(err)
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}
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return &SFTP{c: client, cmd: cmd}, nil
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}
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// OpenSFTP opens an sftp backend. When the command is started via
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// exec.Command, it is expected to speak sftp on stdin/stdout. The backend
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// is expected at the given path.
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func OpenSFTP(dir string, program string, args ...string) (*SFTP, error) {
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sftp, err := start_client(program, args...)
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if err != nil {
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return nil, err
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}
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// test if all necessary dirs and files are there
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items := []string{
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dir,
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filepath.Join(dir, dataPath),
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filepath.Join(dir, snapshotPath),
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filepath.Join(dir, treePath),
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filepath.Join(dir, lockPath),
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filepath.Join(dir, keyPath),
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filepath.Join(dir, tempPath),
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}
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for _, d := range items {
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if _, err := sftp.c.Lstat(d); err != nil {
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return nil, fmt.Errorf("%s does not exist", d)
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}
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}
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// read version file
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f, err := sftp.c.Open(filepath.Join(dir, versionFileName))
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if err != nil {
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return nil, fmt.Errorf("unable to read version file: %v\n", err)
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}
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var version uint
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n, err := fmt.Fscanf(f, "%d", &version)
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if err != nil {
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return nil, err
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}
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if n != 1 {
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return nil, errors.New("could not read version from file")
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}
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err = f.Close()
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if err != nil {
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return nil, err
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}
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// check version
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if version != BackendVersion {
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return nil, fmt.Errorf("wrong version %d", version)
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}
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// read ID
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f, err = sftp.c.Open(filepath.Join(dir, idFileName))
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if err != nil {
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return nil, err
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}
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buf, err := ioutil.ReadAll(f)
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if err != nil {
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return nil, err
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}
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err = f.Close()
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if err != nil {
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return nil, err
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}
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id, err := ParseID(strings.TrimSpace(string(buf)))
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if err != nil {
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return nil, err
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}
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sftp.id = id
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sftp.p = dir
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return sftp, nil
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}
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// CreateSFTP creates all the necessary files and directories for a new sftp
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// backend at dir.
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func CreateSFTP(dir string, program string, args ...string) (*SFTP, error) {
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sftp, err := start_client(program, args...)
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if err != nil {
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return nil, err
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}
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versionFile := filepath.Join(dir, versionFileName)
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idFile := filepath.Join(dir, idFileName)
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dirs := []string{
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dir,
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filepath.Join(dir, dataPath),
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filepath.Join(dir, snapshotPath),
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filepath.Join(dir, treePath),
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filepath.Join(dir, lockPath),
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filepath.Join(dir, keyPath),
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filepath.Join(dir, tempPath),
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}
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// test if files already exist
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_, err = sftp.c.Lstat(versionFile)
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if err == nil {
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return nil, errors.New("version file already exists")
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}
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_, err = sftp.c.Lstat(idFile)
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if err == nil {
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return nil, errors.New("id file already exists")
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}
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// test if directories already exist
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for _, d := range dirs[1:] {
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if _, err := sftp.c.Lstat(d); err == nil {
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return nil, fmt.Errorf("dir %s already exists", d)
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}
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}
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// create paths for data, refs and temp blobs
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for _, d := range dirs {
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err = sftp.mkdirAll(d, dirMode)
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if err != nil {
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return nil, err
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}
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}
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// create version file
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f, err := sftp.c.Create(versionFile)
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if err != nil {
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return nil, err
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}
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_, err = fmt.Fprintf(f, "%d\n", BackendVersion)
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if err != nil {
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return nil, err
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}
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err = f.Close()
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if err != nil {
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return nil, err
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}
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// create ID file
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id := make([]byte, sha256.Size)
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_, err = rand.Read(id)
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if err != nil {
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return nil, err
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}
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f, err = sftp.c.Create(idFile)
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if err != nil {
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return nil, err
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}
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_, err = fmt.Fprintf(f, "%s\n", ID(id).String())
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if err != nil {
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return nil, err
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}
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err = f.Close()
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if err != nil {
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return nil, err
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}
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err = sftp.c.Close()
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if err != nil {
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return nil, err
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}
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err = sftp.cmd.Wait()
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if err != nil {
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return nil, err
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}
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// open backend
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return OpenSFTP(dir, program, args...)
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}
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// Location returns this backend's location (the directory name).
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func (r *SFTP) Location() string {
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return r.p
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}
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// Return temp directory in correct directory for this backend.
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func (r *SFTP) tempFile() (string, *sftp.File, error) {
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// choose random suffix
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buf := make([]byte, tempfileRandomSuffixLength)
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n, err := io.ReadFull(rand.Reader, buf)
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if err != nil {
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return "", nil, err
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}
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if n != len(buf) {
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return "", nil, errors.New("unable to generate enough random bytes for temp file")
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}
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// construct tempfile name
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name := filepath.Join(r.p, tempPath, fmt.Sprintf("temp-%s", hex.EncodeToString(buf)))
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// create file in temp dir
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f, err := r.c.Create(name)
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if err != nil {
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return "", nil, err
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}
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return name, f, nil
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}
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func (r *SFTP) mkdirAll(dir string, mode os.FileMode) error {
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// check if directory already exists
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fi, err := r.c.Lstat(dir)
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if err == nil {
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if fi.IsDir() {
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return nil
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}
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return fmt.Errorf("mkdirAll(%s): entry exists but is not a directory", dir)
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}
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// create parent directories
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errMkdirAll := r.mkdirAll(filepath.Dir(dir), dirMode)
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// create directory
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errMkdir := r.c.Mkdir(dir)
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// test if directory was created successfully
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fi, err = r.c.Lstat(dir)
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if err != nil {
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// return previous errors
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return fmt.Errorf("mkdirAll(%s): unable to create directories: %v, %v", dir, errMkdirAll, errMkdir)
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}
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if !fi.IsDir() {
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return fmt.Errorf("mkdirAll(%s): entry exists but is not a directory", dir)
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}
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// set mode
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return r.c.Chmod(dir, mode)
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}
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// Rename temp file to final name according to type and ID.
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func (r *SFTP) renameFile(oldname string, t Type, id ID) error {
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newname := r.filename(t, id)
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// create directories if necessary
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if t == Data || t == Tree {
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err := r.mkdirAll(filepath.Dir(newname), dirMode)
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if err != nil {
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return err
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}
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}
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return r.c.Rename(oldname, newname)
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}
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// Construct directory for given Type.
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func (r *SFTP) dirname(t Type, id ID) string {
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var n string
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switch t {
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case Data:
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n = dataPath
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if id != nil {
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n = filepath.Join(dataPath, fmt.Sprintf("%02x", id[0]))
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}
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case Snapshot:
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n = snapshotPath
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case Tree:
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n = treePath
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if id != nil {
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n = filepath.Join(treePath, fmt.Sprintf("%02x", id[0]))
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}
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case Lock:
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n = lockPath
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case Key:
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n = keyPath
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}
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return filepath.Join(r.p, n)
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}
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type sftpBlob struct {
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f *sftp.File
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name string
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hw *HashingWriter
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backend *SFTP
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tpe Type
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id ID
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size uint
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closed bool
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}
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func (sb *sftpBlob) Close() error {
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if sb.closed {
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return errors.New("Close() called on closed file")
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}
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sb.closed = true
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err := sb.f.Close()
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if err != nil {
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return fmt.Errorf("sftp: file.Close: %v", err)
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}
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// get ID
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sb.id = ID(sb.hw.Sum(nil))
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// check for duplicate ID
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res, err := sb.backend.Test(sb.tpe, sb.id)
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if err != nil {
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return fmt.Errorf("testing presence of ID %v failed: %v", sb.id, err)
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}
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if res {
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return ErrAlreadyPresent
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}
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// rename file
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err = sb.backend.renameFile(sb.name, sb.tpe, sb.id)
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if err != nil {
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return err
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}
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return nil
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}
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func (sb *sftpBlob) Write(p []byte) (int, error) {
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n, err := sb.hw.Write(p)
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sb.size += uint(n)
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return n, err
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}
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func (sb *sftpBlob) Size() uint {
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return sb.size
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}
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func (sb *sftpBlob) ID() (ID, error) {
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if sb.id == nil {
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return nil, errors.New("blob is not closed, ID unavailable")
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}
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return sb.id, nil
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}
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// Create creates a new blob of type t. Blob implements io.WriteCloser. Once
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// Close() has been called, ID() can be used to retrieve the ID. If the blob is
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// already present, Close() returns ErrAlreadyPresent.
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func (r *SFTP) Create(t Type) (Blob, error) {
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// TODO: make sure that tempfile is removed upon error
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// create tempfile in backend
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filename, file, err := r.tempFile()
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if err != nil {
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return nil, err
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}
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blob := sftpBlob{
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hw: NewHashingWriter(file, newHash()),
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f: file,
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name: filename,
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backend: r,
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tpe: t,
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}
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return &blob, nil
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}
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// Construct path for given Type and ID.
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func (r *SFTP) filename(t Type, id ID) string {
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return filepath.Join(r.dirname(t, id), id.String())
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}
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// Get returns the content stored under the given ID. If the data doesn't match
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// the requested ID, ErrWrongData is returned.
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func (r *SFTP) Get(t Type, id ID) ([]byte, error) {
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if id == nil {
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return nil, errors.New("unable to load nil ID")
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}
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// try to open file
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file, err := r.c.Open(r.filename(t, id))
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defer func() {
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// TODO: report bug against sftp client, ignore Close() for nil file
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if file != nil {
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file.Close()
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}
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}()
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if err != nil {
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return nil, err
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}
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// read all
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buf, err := ioutil.ReadAll(file)
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if err != nil {
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return nil, err
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}
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// check id
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if !Hash(buf).Equal(id) {
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return nil, ErrWrongData
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}
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return buf, nil
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}
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// GetReader returns a reader that yields the content stored under the given
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// ID. The content is not verified. The reader should be closed after draining
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// it.
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func (r *SFTP) GetReader(t Type, id ID) (io.ReadCloser, error) {
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if id == nil {
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return nil, errors.New("unable to load nil ID")
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}
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// try to open file
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file, err := r.c.Open(r.filename(t, id))
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if err != nil {
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return nil, err
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}
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return file, nil
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}
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// Test returns true if a blob of the given type and ID exists in the backend.
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func (r *SFTP) Test(t Type, id ID) (bool, error) {
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file, err := r.c.Open(r.filename(t, id))
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defer func() {
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if file != nil {
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file.Close()
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}
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}()
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if err != nil {
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if _, ok := err.(*sftp.StatusError); ok {
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return false, nil
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}
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return false, err
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}
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return true, nil
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}
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// Remove removes the content stored at ID.
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func (r *SFTP) Remove(t Type, id ID) error {
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return r.c.Remove(r.filename(t, id))
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}
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// List lists all objects of a given type.
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func (r *SFTP) List(t Type) (IDs, error) {
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list := []os.FileInfo{}
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var err error
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if t == Data || t == Tree {
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// read first level
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basedir := r.dirname(t, nil)
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list1, err := r.c.ReadDir(basedir)
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if err != nil {
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return nil, err
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}
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// read files
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for _, dir := range list1 {
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entries, err := r.c.ReadDir(filepath.Join(basedir, dir.Name()))
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if err != nil {
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return nil, err
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}
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for _, entry := range entries {
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list = append(list, entry)
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}
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}
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} else {
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list, err = r.c.ReadDir(r.dirname(t, nil))
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if err != nil {
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return nil, err
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}
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}
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ids := make(IDs, 0, len(list))
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for _, item := range list {
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id, err := ParseID(item.Name())
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// ignore everything that does not parse as an ID
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if err != nil {
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continue
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}
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ids = append(ids, id)
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}
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return ids, nil
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}
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// Version returns the version of this local backend.
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func (r *SFTP) Version() uint {
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return r.ver
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}
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// ID returns the ID of this local backend.
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func (r *SFTP) ID() ID {
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return r.id
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}
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// Close closes the sftp connection and terminates the underlying command.
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func (s *SFTP) Close() error {
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s.c.Close()
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// TODO: add timeout after which the process is killed
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return s.cmd.Wait()
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}
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