[Sync] Move //sync to //components/sync.

sync/internal_api/public/model_type_store_backend.h

-// Copyright 2015 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 SYNC_INTERNAL_API_PUBLIC_MODEL_TYPE_STORE_BACKEND_H_
-#define SYNC_INTERNAL_API_PUBLIC_MODEL_TYPE_STORE_BACKEND_H_
-
-#include <memory>
-#include <string>
-#include <unordered_map>
-
-#include "base/lazy_instance.h"
-#include "base/macros.h"
-#include "base/threading/thread_collision_warner.h"
-#include "sync/api/model_type_store.h"
-#include "sync/base/sync_export.h"
-
-namespace leveldb {
-class DB;
-class Env;
-class WriteBatch;
-}  // namespace leveldb
-
-namespace syncer_v2 {
-
-// ModelTypeStoreBackend handles operations with leveldb. It is oblivious of the
-// fact that it is called from separate thread (with the exception of ctor),
-// meaning it shouldn't deal with callbacks and task_runners.
-class SYNC_EXPORT ModelTypeStoreBackend
-    : public base::RefCountedThreadSafe<ModelTypeStoreBackend> {
- public:
-  typedef std::unordered_map<std::string, ModelTypeStoreBackend*> BackendMap;
-
-  // Helper function to create in memory environment for leveldb.
-  static std::unique_ptr<leveldb::Env> CreateInMemoryEnv();
-
-  // GetOrCreateBackend will check if |backend_map_| has a backend with same
-  // |path|. If |backend_map_| has one, wrap that backend to scoped_refptr and
-  // return. If |backend_map_| does not have, create a backend and store it into
-  // |backend_map_|.
-  static scoped_refptr<ModelTypeStoreBackend> GetOrCreateBackend(
-      const std::string& path,
-      std::unique_ptr<leveldb::Env> env,
-      ModelTypeStore::Result* result);
-
-  // Reads records with keys formed by prepending ids from |id_list| with
-  // |prefix|. If the record is found its id (without prefix) and value is
-  // appended to record_list. If record is not found its id is appended to
-  // |missing_id_list|. It is not an error that records for ids are not found so
-  // function will still return success in this case.
-  ModelTypeStore::Result ReadRecordsWithPrefix(
-      const std::string& prefix,
-      const ModelTypeStore::IdList& id_list,
-      ModelTypeStore::RecordList* record_list,
-      ModelTypeStore::IdList* missing_id_list);
-
-  // Reads all records with keys starting with |prefix|. Prefix is removed from
-  // key before it is added to |record_list|.
-  ModelTypeStore::Result ReadAllRecordsWithPrefix(
-      const std::string& prefix,
-      ModelTypeStore::RecordList* record_list);
-
-  // Writes modifications accumulated in |write_batch| to database.
-  ModelTypeStore::Result WriteModifications(
-      std::unique_ptr<leveldb::WriteBatch> write_batch);
-
- private:
-  friend class base::RefCountedThreadSafe<ModelTypeStoreBackend>;
-  friend class ModelTypeStoreBackendTest;
-
-  ModelTypeStoreBackend(const std::string& path);
-  ~ModelTypeStoreBackend();
-
-  // In some scenarios ModelTypeStoreBackend holds ownership of env. Typical
-  // example is when test creates in memory environment with CreateInMemoryEnv
-  // and wants it to be destroyed along with backend. This is achieved by
-  // passing ownership of env to TakeEnvOwnership function.
-  //
-  // env_ declaration should appear before declaration of db_ because
-  // environment object should still be valid when db_'s destructor is called.
-  std::unique_ptr<leveldb::Env> env_;
-
-  std::unique_ptr<leveldb::DB> db_;
-
-  std::string path_;
-
-  // backend_map_ holds raw pointer of backend, and when stores ask for backend,
-  // GetOrCreateBackend will return scoped_refptr of backend. backend_map_
-  // doesn't take reference to backend, therefore doesn't block backend
-  // destruction.
-  static base::LazyInstance<BackendMap> backend_map_;
-
-  // Init opens database at |path|. If database doesn't exist it creates one.
-  // Normally |env| should be nullptr, this causes leveldb to use default disk
-  // based environment from leveldb::Env::Default().
-  // Providing |env| allows to override environment used by leveldb for tests
-  // with in-memory or faulty environment.
-  ModelTypeStore::Result Init(const std::string& path,
-                              std::unique_ptr<leveldb::Env> env);
-
-  // Macro wrapped mutex to guard against concurrent calls in debug builds.
-  DFAKE_MUTEX(push_pop_);
-
-  DISALLOW_COPY_AND_ASSIGN(ModelTypeStoreBackend);
-};
-
-}  // namespace syncer_v2
-
-#endif  // SYNC_INTERNAL_API_PUBLIC_MODEL_TYPE_STORE_BACKEND_H_