src/session/generic_storage_manager.h

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#ifndef MOZC_SESSION_GENERIC_STORAGE_MANAGER_H_
#define MOZC_SESSION_GENERIC_STORAGE_MANAGER_H_

#include "base/port.h"
#include "base/scoped_ptr.h"
#include "session/commands.pb.h"

namespace mozc {

class GenericStorageInterface;

// For unit test.
class GenericLruStorageProxy;

namespace storage {
class LRUStorage;
}  // namespace storage

// Override and set the subclass's instance to
// GenericStorageManager for unit test.
class GenericStorageManagerInterface {
 public:
  GenericStorageManagerInterface() {}
  virtual ~GenericStorageManagerInterface() {}
  virtual GenericStorageInterface *GetStorage(
     commands::GenericStorageEntry::StorageType storage_type) = 0;
};

// Manages generic storages.
class GenericStorageManagerFactory {
 public:
  // Returns corresponding storage's instance.
  // If no instance is available, NULL is returned.
  static GenericStorageInterface *GetStorage(
     commands::GenericStorageEntry::StorageType storage_type);
  // For unit test.
  static void SetGenericStorageManager(GenericStorageManagerInterface *manager);

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(GenericStorageManagerFactory);
};

// Generic interface for storages.
// This class defines only the interfaces.
// Detailed behaviors depend on the subclass's
// backend.
class GenericStorageInterface {
 public:
  GenericStorageInterface() {}
  virtual ~GenericStorageInterface() {}

  // Inserts new entry.
  // If something goes wrong, returns false.
  // value should be terminated by '\0'.
  virtual bool Insert(const string &key, const char *value) = 0;
  // Looks up the value.
  // If something goes wrong, returns NULL.
  virtual const char *Lookup(const string &key) = 0;
  // Lists all the values.
  // If something goes wrong, returns false.
  virtual bool GetAllValues(vector<string> *values) = 0;
  // Clears all the entries.
  virtual bool Clear() = 0;
};

// Storage class of which backend is LRUStorage.
class GenericLruStorage : public GenericStorageInterface {
 public:
  GenericLruStorage(
      const char *file_name, size_t value_size, size_t size, uint32 seed);
  virtual ~GenericLruStorage();

  // If the storage has |key|, this method overwrites
  // the old value.
  // If the entiry's size is over GetSize(),
  // the oldest value is disposed.
  virtual bool Insert(const string &key, const char *value);

  virtual const char *Lookup(const string &key);

  // The order is new to old.
  virtual bool GetAllValues(vector<string> *values);

  virtual bool Clear();

 protected:
  // Opens the storage if not opened yet.
  // If something goes wrong, returns false.
  bool EnsureStorage();

 private:
  friend class GenericLruStorageProxy;
  scoped_ptr<mozc::storage::LRUStorage> lru_storage_;
  const string file_name_;
  const size_t value_size_;
  const size_t size_;
  const uint32 seed_;
  // Temporary buffer to insert a value into this storage.
  scoped_ptr<char[]> value_buffer_;

  DISALLOW_COPY_AND_ASSIGN(GenericLruStorage);
};

}  // namespace mozc

#endif  // MOZC_SESSION_GENERIC_STORAGE_MANAGER_H_