mirror of https://github.com/perkeep/perkeep.git
99 lines
2.6 KiB
Go
99 lines
2.6 KiB
Go
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/*
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Copyright 2012 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package localdisk
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import (
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"bytes"
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"crypto/rand"
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"fmt"
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"io"
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"io/ioutil"
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"os"
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"path/filepath"
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"time"
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"camlistore.org/pkg/blobserver"
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)
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var _ blobserver.Generationer = (*DiskStorage)(nil)
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func (ds *DiskStorage) generationFile() string {
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return filepath.Join(ds.root, "GENERATION.dat")
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}
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func (ds *DiskStorage) StorageGeneration() (initTime time.Time, random string, err error) {
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if ds.partition != "" {
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err = fmt.Errorf("localdisk: can't call StorageGeneration on queue partition %q", ds.partition)
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return
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}
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f, err := os.Open(ds.generationFile())
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if os.IsNotExist(err) {
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if err = ds.ResetStorageGeneration(); err != nil {
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return
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}
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f, err = os.Open(ds.generationFile())
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}
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if err != nil {
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return
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}
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defer f.Close()
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bs, err := ioutil.ReadAll(f)
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if err != nil {
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return
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}
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if i := bytes.IndexByte(bs, '\n'); i != -1 {
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bs = bs[:i]
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}
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if fi, err := f.Stat(); err == nil {
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initTime = fi.ModTime()
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}
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random = string(bs)
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return
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}
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func (ds *DiskStorage) ResetStorageGeneration() error {
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if ds.partition != "" {
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return fmt.Errorf("localdisk: can't call StorageGeneration on queue partition %q", ds.partition)
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}
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var buf bytes.Buffer
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if _, err := io.CopyN(&buf, rand.Reader, 20); err != nil {
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return err
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}
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hex := fmt.Sprintf("%x", buf.Bytes())
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buf.Reset()
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buf.WriteString(hex)
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buf.WriteString(`
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This file's random string on the first line is an optimization and
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paranoia facility for clients.
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If the client sees the same random string in multiple upload sessions,
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it assumes that the blobserver still has all the same blobs, and also
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it's the same server. This mechanism is not fundamental to
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Camlistore's operation: the client could also check each blob before
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uploading, or enumerate all blobs from the server too. This is purely
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an optimization so clients can mix this value into their "is this file
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uploaded?" local cache keys.
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If you deleted any blobs (or suspect any were corrupted), it's best to
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delete this file so clients can safely re-upload them.
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`)
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return ioutil.WriteFile(ds.generationFile(), buf.Bytes(), 0644)
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}
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