[Sync] Implementation of ModelTypeStoreBackend

sync/internal_api/public/model_type_store_backend.h

Index: sync/internal_api/public/model_type_store_backend.h
diff --git a/sync/internal_api/public/model_type_store_backend.h b/sync/internal_api/public/model_type_store_backend.h
index cdbcd7b892bd6b44ec219ed50297b209a0ff7715..47ff50d8f729358ebc89dd40fe3f586b8de765ef 100644
--- a/sync/internal_api/public/model_type_store_backend.h
+++ b/sync/internal_api/public/model_type_store_backend.h
@@ -5,20 +5,79 @@
 #ifndef SYNC_INTERNAL_API_PUBLIC_MODEL_TYPE_STORE_BACKEND_H_
 #define SYNC_INTERNAL_API_PUBLIC_MODEL_TYPE_STORE_BACKEND_H_
 
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.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 ModelTypeStoreBackend : public base::NonThreadSafe {
+class SYNC_EXPORT_PRIVATE ModelTypeStoreBackend : public base::NonThreadSafe {
  public:
   ModelTypeStoreBackend();
   ~ModelTypeStoreBackend();
 
-  ModelTypeStore::Result Init();
+  // Helper function to create in memory environment for leveldb.
+  static scoped_ptr<leveldb::Env> CreateInMemoryEnv();
+
+  // Take ownership of env from consumer of ModelTypeStoreBackend object. env
+  // will be deleted right after db_ is deleted. This function allows tests to
+  // create in-memory store without requiring them to manage env ownership.
+  void TakeEnvOwnership(scoped_ptr<leveldb::Env> env);
+
+  // 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, leveldb::Env* env);
+
+  // 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(
+      scoped_ptr<leveldb::WriteBatch> write_batch);
+
+ private:
+  // 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.
+  scoped_ptr<leveldb::Env> env_;
+
+  scoped_ptr<leveldb::DB> db_;
+
+  DISALLOW_COPY_AND_ASSIGN(ModelTypeStoreBackend);
 };
 
 }  // namespace syncer_v2