attachment_store.h revision 1320f92c476a1ad9d19dba2a48c72b75566198e9 
1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef SYNC_API_ATTACHMENTS_ATTACHMENT_STORE_H_
6#define SYNC_API_ATTACHMENTS_ATTACHMENT_STORE_H_
7
8#include "base/callback.h"
9#include "base/memory/ref_counted.h"
10#include "base/memory/scoped_ptr.h"
11#include "sync/api/attachments/attachment.h"
12#include "sync/api/attachments/attachment_id.h"
13#include "sync/base/sync_export.h"
14
15namespace base {
16class RefCountedMemory;
17}  // namespace base
18
19namespace syncer {
20
21class Attachment;
22class AttachmentId;
23
24// A place to locally store and access Attachments.
25//
26// Destroying this object does not necessarily cancel outstanding async
27// operations. If you need cancel like semantics, use WeakPtr in the callbacks.
28class SYNC_EXPORT AttachmentStore : public base::RefCounted<AttachmentStore> {
29 public:
30  AttachmentStore();
31
32  // TODO(maniscalco): Consider udpating Read and Write methods to support
33  // resumable transfers (bug 353292).
34
35  enum Result {
36    SUCCESS,            // No error, all completed successfully.
37    UNSPECIFIED_ERROR,  // An unspecified error occurred for one or more items.
38  };
39
40  typedef base::Callback<void(const Result&,
41                              scoped_ptr<AttachmentMap>,
42                              scoped_ptr<AttachmentIdList>)> ReadCallback;
43  typedef base::Callback<void(const Result&)> WriteCallback;
44  typedef base::Callback<void(const Result&)> DropCallback;
45
46  // Asynchronously reads the attachments identified by |ids|.
47  //
48  // |callback| will be invoked when finished. AttachmentStore will attempt to
49  // read all attachments specified in ids. If any of the attachments do not
50  // exist or could not be read, |callback|'s Result will be UNSPECIFIED_ERROR.
51  // Callback's AttachmentMap will contain all attachments that were
52  // successfully read, AttachmentIdList will contain attachment ids of
53  // attachments that are unavailable in attachment store, these need to be
54  // downloaded from server.
55  //
56  // Reads on individual attachments are treated atomically; |callback| will not
57  // read only part of an attachment.
58  virtual void Read(const AttachmentIdList& ids,
59                    const ReadCallback& callback) = 0;
60
61  // Asynchronously writes |attachments| to the store.
62  //
63  // Will not overwrite stored attachments. Attempting to overwrite an
64  // attachment that already exists is not an error.
65  //
66  // |callback| will be invoked when finished. If any of the attachments could
67  // not be written |callback|'s Result will be UNSPECIFIED_ERROR. When this
68  // happens, some or none of the attachments may have been written
69  // successfully.
70  virtual void Write(const AttachmentList& attachments,
71                     const WriteCallback& callback) = 0;
72
73  // Asynchronously drops |attchments| from this store.
74  //
75  // This does not remove attachments from the server.
76  //
77  // |callback| will be invoked when finished. Attempting to drop an attachment
78  // that does not exist is not an error. If any of the existing attachment
79  // could not be dropped, |callback|'s Result will be UNSPECIFIED_ERROR. When
80  // this happens, some or none of the attachments may have been dropped
81  // successfully.
82  virtual void Drop(const AttachmentIdList& ids,
83                    const DropCallback& callback) = 0;
84
85 protected:
86  friend class base::RefCounted<AttachmentStore>;
87  virtual ~AttachmentStore();
88};
89
90}  // namespace syncer
91
92#endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_STORE_H_
93