src/storage/registry.h

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#ifndef MOZC_STORAGE_REGISTRY_H_
#define MOZC_STORAGE_REGISTRY_H_

#include <cstring>
#include <string>

#include "base/port.h"
#include "base/logging.h"

namespace mozc {
namespace storage {

class StorageInterface;

// The idea of Registry module is the same as Windows Registry.
// You can use it for saving small data like timestamp, auth_token.
// DO NOT USE it to save big data or data which are frequently updated.
// Lookup() and Insert() do process-wide global lock and it may be slow.
// All methods are thread-safe.
//
// TODO(taku): Currently, Registry won't guarantee that two processes
// can con-currently share the same data. We will replace the backend
// of Registry (Storage Interface) with sqlite
//
// Example:
//  uint64 timestamp = 0;
//  CHECK(Registry::Lookup<uint64>("timestamp", &timestamp));
//
//  string value = "hello world";
//  CHECK(Registry::Insert<string>("hello", value));
class Registry {
 public:
  template <typename T>
  static bool Lookup(const string &key, T *value) {
    DCHECK(value);
    string tmp;
    if (!LookupInternal(key, &tmp)) {
      return false;
    }
    if (sizeof(*value) != tmp.size()) {
      return false;
    }
    memcpy(reinterpret_cast<char *>(value),
           tmp.data(), tmp.size());
    return true;
  }

  static bool Lookup(const string &key, string *value) {
    return LookupInternal(key, value);
  }

  static bool Lookup(const string &key, bool *value) {
    uint8 v = 0;
    const bool result = Lookup<uint8>(key, &v);
    *value = (v != 0);
    return result;
  }

  // insert key and data
  // It is not guaranteed that the data is synced to the disk
  template <typename T>
  static bool Insert(const string &key, const T &value) {
    string tmp(reinterpret_cast<const char *>(&value), sizeof(value));
    return InsertInternal(key, tmp);
  }

  // Insert key and string value
  // It is not guaranteed that the data is synced to the disk
  static bool Insert(const string &key, const string &value) {
    return InsertInternal(key, value);
  }

  // Insert key and bool value
  // It is not guaranteed that the data is synced to the disk
  static bool Insert(const string &key, const bool &value) {
    const uint8 tmp = static_cast<uint8>(value);
    return Insert<uint8>(key, tmp);
  }

  // Syncing the data into disk
  static bool Sync();

  // Erase key
  static bool Erase(const string &key);

  // clear internal keys and values
  static bool Clear();

  // Inject internal storage for unittesting.
  // TinyStorage is used by default
  // TODO(taku) replace it with SQLITE
  static void SetStorage(StorageInterface *handler);

 private:
  static bool LookupInternal(const string &key, string *value);
  static bool InsertInternal(const string &key, const string &value);

  DISALLOW_IMPLICIT_CONSTRUCTORS(Registry);
};
}  // namespace storage
}  // namespace mozc
#endif  // MOZC_STORAGE_REGISTRY_H_