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// Copyright (c) 2012 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_SYNCABLE_DIRECTORY_BACKING_STORE_H_
#define SYNC_SYNCABLE_DIRECTORY_BACKING_STORE_H_
#pragma once
#include <string>
#include "base/memory/scoped_ptr.h"
#include "base/threading/non_thread_safe.h"
#include "sql/connection.h"
#include "sql/statement.h"
#include "sync/syncable/dir_open_result.h"
#include "sync/syncable/model_type.h"
#include "sync/syncable/syncable.h"
namespace sync_pb {
class EntitySpecifics;
}
namespace syncable {
struct ColumnSpec;
typedef Directory::MetahandlesIndex MetahandlesIndex;
// Interface that provides persistence for a syncable::Directory object. You can
// load all the persisted data to prime a syncable::Directory on startup by
// invoking Load. The only other thing you (or more correctly, a Directory) can
// do here is save any changes that have occurred since calling Load, which can
// be done periodically as often as desired.
//
// The DirectoryBackingStore will own an sqlite lock on its database for most of
// its lifetime. You must not have two DirectoryBackingStore objects accessing
// the database simultaneously. Because the lock exists at the database level,
// not even two separate browser instances would be able to acquire it
// simultaneously.
//
// This class is abstract so that we can extend it in interesting ways for use
// in tests. The concrete class used in non-test scenarios is
// OnDiskDirectoryBackingStore.
class DirectoryBackingStore : public base::NonThreadSafe {
public:
explicit DirectoryBackingStore(const std::string& dir_name);
virtual ~DirectoryBackingStore();
// Loads and drops all currently persisted meta entries into |entry_bucket|
// and loads appropriate persisted kernel info into |info_bucket|.
//
// This function can perform some cleanup tasks behind the scenes. It will
// clean up unused entries from the database and migrate to the latest
// database version. The caller can safely ignore these details.
//
// NOTE: On success (return value of OPENED), the buckets are populated with
// newly allocated items, meaning ownership is bestowed upon the caller.
virtual DirOpenResult Load(MetahandlesIndex* entry_bucket,
Directory::KernelLoadInfo* kernel_load_info) = 0;
// Updates the on-disk store with the input |snapshot| as a database
// transaction. Does NOT open any syncable transactions as this would cause
// opening transactions elsewhere to block on synchronous I/O.
// DO NOT CALL THIS FROM MORE THAN ONE THREAD EVER. Also, whichever thread
// calls SaveChanges *must* be the thread that owns/destroys |this|.
virtual bool SaveChanges(const Directory::SaveChangesSnapshot& snapshot);
protected:
// For test classes.
DirectoryBackingStore(const std::string& dir_name,
sql::Connection* connection);
// General Directory initialization and load helpers.
bool InitializeTables();
bool CreateTables();
// Create 'share_info' or 'temp_share_info' depending on value of
// is_temporary. Returns an sqlite
bool CreateShareInfoTable(bool is_temporary);
bool CreateShareInfoTableVersion71(bool is_temporary);
// Create 'metas' or 'temp_metas' depending on value of is_temporary.
bool CreateMetasTable(bool is_temporary);
bool CreateModelsTable();
bool CreateV71ModelsTable();
// We don't need to load any synced and applied deleted entries, we can
// in fact just purge them forever on startup.
bool DropDeletedEntries();
// Drops a table if it exists, harmless if the table did not already exist.
bool SafeDropTable(const char* table_name);
// Load helpers for entries and attributes.
bool LoadEntries(MetahandlesIndex* entry_bucket);
bool LoadInfo(Directory::KernelLoadInfo* info);
// Save/update helpers for entries. Return false if sqlite commit fails.
bool SaveEntryToDB(const EntryKernel& entry);
bool SaveNewEntryToDB(const EntryKernel& entry);
bool UpdateEntryToDB(const EntryKernel& entry);
DirOpenResult DoLoad(MetahandlesIndex* entry_bucket,
Directory::KernelLoadInfo* kernel_load_info);
// Close save_dbhandle_. Broken out for testing.
void EndSave();
// Removes each entry whose metahandle is in |handles| from the database.
// Does synchronous I/O. Returns false on error.
bool DeleteEntries(const MetahandleSet& handles);
// Drop all tables in preparation for reinitialization.
void DropAllTables();
// Serialization helpers for syncable::ModelType. These convert between
// the ModelType enum and the values we persist in the database to identify
// a model. We persist a default instance of the specifics protobuf as the
// ID, rather than the enum value.
static ModelType ModelIdToModelTypeEnum(const void* data, int length);
static std::string ModelTypeEnumToModelId(ModelType model_type);
static std::string GenerateCacheGUID();
// Runs an integrity check on the current database. If the
// integrity check fails, false is returned and error is populated
// with an error message.
bool CheckIntegrity(sqlite3* handle, std::string* error) const;
// Migration utilities.
bool RefreshColumns();
bool SetVersion(int version);
int GetVersion();
bool MigrateToSpecifics(const char* old_columns,
const char* specifics_column,
void(*handler_function) (
sql::Statement* old_value_query,
int old_value_column,
sync_pb::EntitySpecifics* mutable_new_value));
// Individual version migrations.
bool MigrateVersion67To68();
bool MigrateVersion68To69();
bool MigrateVersion69To70();
bool MigrateVersion70To71();
bool MigrateVersion71To72();
bool MigrateVersion72To73();
bool MigrateVersion73To74();
bool MigrateVersion74To75();
bool MigrateVersion75To76();
bool MigrateVersion76To77();
bool MigrateVersion77To78();
scoped_ptr<sql::Connection> db_;
sql::Statement save_entry_statement_;
std::string dir_name_;
// Set to true if migration left some old columns around that need to be
// discarded.
bool needs_column_refresh_;
DISALLOW_COPY_AND_ASSIGN(DirectoryBackingStore);
};
} // namespace syncable
#endif // SYNC_SYNCABLE_DIRECTORY_BACKING_STORE_H_