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// 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.
#include <string>
#include <vector>
#include "base/callback.h"
#include "base/macros.h"
#include "sync/base/sync_export.h"
namespace base {
class SequencedTaskRunner;
} // namespace base
namespace syncer_v2 {
// ModelTypeStore is leveldb backed store for model type's data, metadata and
// global metadata.
// Store keeps records for entries identified by ids. For each entry store keeps
// data and metadata. Also store keeps one record for global metadata.
// To create store call one of Create*Store static factory functions. Model type
// controls store's lifetime with returned scoped_ptr. Call to Create*Store
// function triggers asynchronous store backend initialization, callback will be
// called with results when initialization is done.
// Read operations are asynchronous, initiated with one of Read* functions,
// provided callback will be called with result code and output of read
// operation.
// Write operations are done in context of write batch. To get one call
// CreateWriteBatch(). After that pass write batch object to Write/Delete
// functions. WriteBatch only accumulates pending changes, doesn't actually do
// data modification. Calling CommitWriteBatch writes all accumulated changes to
// disk atomically. Callback passed to CommitWriteBatch will be called with
// result of write operation. If write batch object is destroyed without
// comitting accumulated write operations will not be persisted.
// Destroying store object doesn't necessarily cancel asynchronous operations
// issued previously. You should be prepared to handle callbacks from those
// operations.
class SYNC_EXPORT ModelTypeStore {
// Result of store operations.
enum class Result {
// Output of read operations is passed back as list of Record structures.
struct Record {
Record(const std::string& id, const std::string& value)
: id(id), value(value) {}
std::string id;
std::string value;
// WriteBatch object is used in all modification operations.
class SYNC_EXPORT WriteBatch {
virtual ~WriteBatch();
friend class MockModelTypeStore;
typedef std::vector<Record> RecordList;
typedef std::vector<std::string> IdList;
typedef base::Callback<void(Result result, scoped_ptr<ModelTypeStore> store)>
typedef base::Callback<void(Result result)> CallbackWithResult;
typedef base::Callback<void(Result result,
scoped_ptr<RecordList> data_records,
scoped_ptr<IdList> missing_id_list)>
typedef base::Callback<void(Result result,
scoped_ptr<RecordList> data_records)>
typedef base::Callback<void(Result result,
scoped_ptr<RecordList> metadata_records,
const std::string& global_metadata)>
// CreateStore takes |path| and |blocking_task_runner|. Here is how to get
// task runner in production code:
// base::SequencedWorkerPool* worker_pool =
// content::BrowserThread::GetBlockingPool();
// scoped_refptr<base::SequencedTaskRunner> blocking_task_runner(
// worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
// worker_pool->GetSequenceToken(),
// base::SequencedWorkerPool::SKIP_ON_SHUTDOWN));
// In test get task runner from MessageLoop::task_runner().
static void CreateStore(
const std::string& path,
scoped_refptr<base::SequencedTaskRunner> blocking_task_runner,
const InitCallback& callback);
// Creates store object backed by in-memory leveldb database. It is used in
// tests.
static void CreateInMemoryStoreForTest(const InitCallback& callback);
virtual ~ModelTypeStore();
// Read operations return records either for all entries or only for ones
// identified in |id_list|. Result is SUCCESS if all records were read
// successfully. If reading any of records fails result is UNSPECIFIED_ERROR
// and RecordList contains some records that were read successfully. There is
// no guarantee that RecordList will contain all successfully read records in
// this case.
// Callback for ReadData (ReadDataCallback) in addition receives list of ids
// that were not found in store (missing_id_list).
virtual void ReadData(const IdList& id_list,
const ReadDataCallback& callback) = 0;
virtual void ReadAllData(const ReadAllDataCallback& callback) = 0;
// ReadMetadataCallback will be invoked with three parameters: result of
// operation, list of metadata records and global metadata.
virtual void ReadAllMetadata(const ReadMetadataCallback& callback) = 0;
// Creates write batch for write operations.
virtual scoped_ptr<WriteBatch> CreateWriteBatch() = 0;
// Commits write operations accumulated in write batch. If write operation
// fails result is UNSPECIFIED_ERROR and write operations will not be
// reflected in the store.
virtual void CommitWriteBatch(scoped_ptr<WriteBatch> write_batch,
const CallbackWithResult& callback) = 0;
// Write operations.
virtual void WriteData(WriteBatch* write_batch,
const std::string& id,
const std::string& value) = 0;
virtual void WriteMetadata(WriteBatch* write_batch,
const std::string& id,
const std::string& value) = 0;
virtual void WriteGlobalMetadata(WriteBatch* write_batch,
const std::string& value) = 0;
virtual void DeleteData(WriteBatch* write_batch, const std::string& id) = 0;
virtual void DeleteMetadata(WriteBatch* write_batch,
const std::string& id) = 0;
virtual void DeleteGlobalMetadata(WriteBatch* write_batch) = 0;
// TODO(pavely): Consider implementing DeleteAllMetadata with following
// signature:
// virtual void DeleteAllMetadata(const CallbackWithResult& callback) = 0.
// It will delete all metadata records and global metadata record.
} // namespace syncer_v2