restic/internal/cache/file.go
Alexander Neumann 9be24a1c9f Add cache
This commits adds rudimentary support for a cache directory, enabled by
default. The cache directory is created if it does not exist. The cache
is used if there's anything in it, newly created snapshot and index
files are written to the cache automatically.
2017-09-24 21:54:53 +02:00

194 lines
3.9 KiB
Go

package cache
import (
"io"
"os"
"path/filepath"
"github.com/pkg/errors"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/fs"
"github.com/restic/restic/internal/restic"
)
func (c *Cache) filename(h restic.Handle) string {
if len(h.Name) < 2 {
panic("Name is empty or too short")
}
subdir := h.Name[:2]
return filepath.Join(c.Path, cacheLayoutPaths[h.Type], subdir, h.Name)
}
func (c *Cache) canBeCached(t restic.FileType) bool {
if c == nil {
return false
}
if _, ok := cacheLayoutPaths[t]; !ok {
return false
}
return true
}
type readCloser struct {
io.Reader
io.Closer
}
// Load returns a reader that yields the contents of the file with the
// given handle. rd must be closed after use. If an error is returned, the
// ReadCloser is nil.
func (c *Cache) Load(h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
debug.Log("Load from cache: %v", h)
if !c.canBeCached(h.Type) {
return nil, errors.New("cannot be cached")
}
f, err := fs.Open(c.filename(h))
if err != nil {
return nil, errors.Wrap(err, "Open")
}
if offset > 0 {
if _, err = f.Seek(offset, io.SeekStart); err != nil {
f.Close()
return nil, err
}
}
rd := readCloser{Reader: f, Closer: f}
if length > 0 {
rd.Reader = io.LimitReader(f, int64(length))
}
return rd, nil
}
// SaveWriter returns a writer for the cache object h. It must be closed after writing is finished.
func (c *Cache) SaveWriter(h restic.Handle) (io.WriteCloser, error) {
debug.Log("Save to cache: %v", h)
if !c.canBeCached(h.Type) {
return nil, errors.New("cannot be cached")
}
p := c.filename(h)
err := fs.MkdirAll(filepath.Dir(p), 0700)
if err != nil {
return nil, errors.Wrap(err, "MkdirAll")
}
f, err := fs.OpenFile(p, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0400)
if err != nil {
return nil, errors.Wrap(err, "Create")
}
return f, err
}
// Save saves a file in the cache.
func (c *Cache) Save(h restic.Handle, rd io.Reader) error {
debug.Log("Save to cache: %v", h)
if rd == nil {
return errors.New("Save() called with nil reader")
}
f, err := c.SaveWriter(h)
if err != nil {
return err
}
if _, err = io.Copy(f, rd); err != nil {
_ = f.Close()
_ = c.Remove(h)
return errors.Wrap(err, "Copy")
}
if err = f.Close(); err != nil {
return errors.Wrap(err, "Close")
}
return nil
}
// Remove deletes a file. When the file is not cache, no error is returned.
func (c *Cache) Remove(h restic.Handle) error {
if !c.Has(h) {
return nil
}
return fs.Remove(c.filename(h))
}
// Clear removes all files of type t from the cache that are not contained in
// the set valid.
func (c *Cache) Clear(t restic.FileType, valid restic.IDSet) error {
debug.Log("Clearing cache for %v: %v valid files", t, len(valid))
if !c.canBeCached(t) {
return nil
}
list, err := c.list(t)
if err != nil {
return err
}
for id := range list {
if valid.Has(id) {
continue
}
if err = fs.Remove(c.filename(restic.Handle{Type: t, Name: id.String()})); err != nil {
return err
}
}
return nil
}
func isFile(fi os.FileInfo) bool {
return fi.Mode()&(os.ModeType|os.ModeCharDevice) == 0
}
// list returns a list of all files of type T in the cache.
func (c *Cache) list(t restic.FileType) (restic.IDSet, error) {
if !c.canBeCached(t) {
return nil, errors.New("cannot be cached")
}
list := restic.NewIDSet()
dir := filepath.Join(c.Path, cacheLayoutPaths[t])
err := filepath.Walk(dir, func(name string, fi os.FileInfo, err error) error {
if err != nil {
return errors.Wrap(err, "Walk")
}
if !isFile(fi) {
return nil
}
id, err := restic.ParseID(filepath.Base(name))
if err != nil {
return nil
}
list.Insert(id)
return nil
})
return list, err
}
// Has returns true if the file is cached.
func (c *Cache) Has(h restic.Handle) bool {
if !c.canBeCached(h.Type) {
return false
}
_, err := fs.Stat(c.filename(h))
if err == nil {
return true
}
return false
}