components/sync/model/attachments/attachment.h

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SYNC_MODEL_ATTACHMENTS_ATTACHMENT_H_
#define COMPONENTS_SYNC_MODEL_ATTACHMENTS_ATTACHMENT_H_

#include <stdint.h>

#include <map>
#include <memory>
#include <vector>

#include "base/memory/ref_counted.h"
#include "base/memory/ref_counted_memory.h"
#include "components/sync/model/attachments/attachment_id.h"

namespace syncer {

// A blob of in-memory data attached to a sync item.
//
// While Attachment objects themselves aren't immutable (they are assignable)
// the data they wrap is immutable.
//
// It is cheap to copy Attachments. Feel free to store and return by value.
class Attachment {
 public:
  Attachment(const Attachment& other);
  ~Attachment();

  // Default copy and assignment are welcome.

  // Creates an attachment with a unique id and the supplied data.
  //
  // Used when creating a brand new attachment.
  static Attachment Create(const scoped_refptr<base::RefCountedMemory>& data);

  // Creates an attachment with the supplied id and data.
  //
  // Used when you want to recreate a specific attachment. E.g. creating a local
  // copy of an attachment that already exists on the sync server.
  static Attachment CreateFromParts(
      const AttachmentId& id,
      const scoped_refptr<base::RefCountedMemory>& data);

  // Returns this attachment's id.
  const AttachmentId& GetId() const;

  // Returns this attachment's data.
  const scoped_refptr<base::RefCountedMemory>& GetData() const;

  // Returns precomputed crc32c hash of data. In ideal case this hash is
  // computed when attachment is first created. It is then passed around through
  // local attachment store and attachment server. Crc is verified when
  // attachment is downloaded from server or loaded from local storage.
  uint32_t GetCrc32c() const;

 private:
  AttachmentId id_;
  scoped_refptr<base::RefCountedMemory> data_;

  Attachment(const AttachmentId& id,
             const scoped_refptr<base::RefCountedMemory>& data);
};

using AttachmentList = std::vector<Attachment>;
using AttachmentMap = std::map<AttachmentId, Attachment>;

}  // namespace syncer

#endif  // COMPONENTS_SYNC_MODEL_ATTACHMENTS_ATTACHMENT_H_