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#ifndef MOZC_STORAGE_STORAGE_INTERFACE_H_
#define MOZC_STORAGE_STORAGE_INTERFACE_H_

#include <string>

#include "base/port.h"

namespace mozc {
namespace storage {

class StorageInterface {
 public:
  // Binds |filename| to the storage but the interpretation of the
  // |filename| depends on the implementation. implementations can
  // - ignore the specified |filename|.
  // - load the existing data from |filename|.
  // - return true if the specified |filename| does not exist.
  // Despite its name, an implementation may not keep the underlaying
  // data storage specified by |filename| opened.
  // StorageInterface::Sync may try to open |filename| again but it
  // may fail even when this method returns true.
  virtual bool Open(const std::string &filename) = 0;

  // Flushes on-memory data into persistent storage (usually on
  // disk) specified by |filename|.
  virtual bool Sync() = 0;

  // Looks up key and returns the value.
  // If key is not found, returns false.
  // It is not guaranteed that the data is synced to the disk.
  virtual bool Lookup(const std::string &key, std::string *value) const = 0;

  // Inserts key and value.
  // It is not guaranteed that the data is synced to the disk.
  virtual bool Insert(const std::string &key, const std::string &value) = 0;

  // Erases the key-value pair specified by |key|.
  // It is not guaranteed that the data is synced to the disk
  virtual bool Erase(const std::string &key) = 0;

  // clears internal keys and values
  // Sync() is automatically called.
  virtual bool Clear() = 0;

  // Returns the number of keys, not a number of bytes.
  virtual size_t Size() const = 0;

  StorageInterface() {}
  virtual ~StorageInterface() {}
};

}  // namespace storage
}  // namespace mozc

#endif  // MOZC_STORAGE_STORAGE_INTERFACE_H_
