shill/key_value_store.h

// Copyright 2018 The Chromium OS 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 SHILL_KEY_VALUE_STORE_H_
#define SHILL_KEY_VALUE_STORE_H_

#include <map>
#include <string>
#include <vector>

#include <brillo/type_list.h>
#include <brillo/type_name_undecorate.h>
#include <brillo/variant_dictionary.h>

#include "shill/data_types.h"

namespace shill {

class KeyValueStore;

using KeyValueTypes = brillo::TypeList<bool,
                                       uint8_t,
                                       uint16_t,
                                       uint32_t,
                                       int16_t,
                                       int32_t,
                                       int64_t,
                                       double,

                                       std::vector<bool>,
                                       std::vector<uint8_t>,
                                       std::vector<std::vector<uint8_t>>,
                                       std::vector<uint32_t>,
                                       std::vector<int32_t>,
                                       std::vector<int64_t>,
                                       std::vector<double>,

                                       KeyValueStore,
                                       std::string,
                                       Stringmap,
                                       Strings,
                                       RpcIdentifier,
                                       RpcIdentifiers>;

class KeyValueStore {
  // A simple store for key-value pairs, which supports (a limited set of)
  // heterogeneous value types, as defined in the KeyValueTypes typelist above.
  //
  // Compare to PropertyStore, which enables a class to (selectively)
  // expose its instance members as properties accessible via
  // RPC. (RPC support for ProperyStore is implemented in a
  // protocol-specific adaptor. e.g. dbus_adpator.)
  //
  // Implemented separately from PropertyStore, to avoid complicating
  // the PropertyStore interface. In particular, objects implementing the
  // PropertyStore interface always provide the storage themselves. In
  // contrast, users of KeyValueStore expect KeyValueStore to provide
  // storage.
 public:
  KeyValueStore();

  // Required for equality comparison when KeyValueStore is wrapped inside a
  // brillo::Any object.
  bool operator==(const KeyValueStore& rhs) const;
  bool operator!=(const KeyValueStore& rhs) const;

  const brillo::VariantDictionary& properties() const { return properties_; }

  void Clear();
  void CopyFrom(const KeyValueStore& b);
  bool IsEmpty();

  void Remove(const std::string& name);

  bool ContainsVariant(const std::string& name) const;
  const brillo::Any& GetVariant(const std::string& name) const;
  void SetVariant(const std::string& name, const brillo::Any& value);

  template <typename T, typename = brillo::EnableIfIsOneOf<T, KeyValueTypes>>
  bool Contains(const std::string& name) const {
    return ContainsVariant(name) &&
           properties_.find(name)->second.IsTypeCompatible<T>();
  }

  template <typename T,
            typename brillo::EnableIfIsOneOfArithmetic<T, KeyValueTypes> = 0>
  T Get(const std::string& name) const {
    const auto& value = GetVariant(name);
    CHECK(value.IsTypeCompatible<T>())
        << "for " << brillo::GetTypeTag<T>() << " property " << name;
    return value.Get<T>();
  }

  template <typename T,
            typename brillo::EnableIfIsOneOfNonArithmetic<T, KeyValueTypes> = 0>
  const T& Get(const std::string& name) const {
    const auto& value = GetVariant(name);
    CHECK(value.IsTypeCompatible<T>())
        << "for " << brillo::GetTypeTag<T>() << " property " << name;
    return value.Get<T>();
  }

  template <typename T,
            typename brillo::EnableIfIsOneOfArithmetic<T, KeyValueTypes> = 0>
  void Set(const std::string& name, T value) {
    SetVariant(name, brillo::Any(value));
  }

  template <typename T,
            typename brillo::EnableIfIsOneOfNonArithmetic<T, KeyValueTypes> = 0>
  void Set(const std::string& name, const T& value) {
    SetVariant(name, brillo::Any(value));
  }

  // If |name| is in this store returns its value, otherwise returns
  // |default_value|.
  template <typename T,
            typename brillo::EnableIfIsOneOfArithmetic<T, KeyValueTypes> = 0>
  T Lookup(const std::string& name, T default_value) const {
    const auto it(properties_.find(name));
    if (it == properties_.end()) {
      return default_value;
    }
    CHECK(it->second.IsTypeCompatible<T>())
        << "for " << brillo::GetTypeTag<T>() << " property " << name;
    return it->second.Get<T>();
  }

  template <typename T,
            typename brillo::EnableIfIsOneOfNonArithmetic<T, KeyValueTypes> = 0>
  const T& Lookup(const std::string& name, const T& default_value) const {
    const auto it(properties_.find(name));
    if (it == properties_.end()) {
      return default_value;
    }
    CHECK(it->second.IsTypeCompatible<T>())
        << "for " << brillo::GetTypeTag<T>() << " property " << name;
    return it->second.Get<T>();
  }

  // Conversion function between KeyValueStore and brillo::VariantDictionary.
  // Since we already use brillo::VariantDictionary for storing key value
  // pairs, all conversions will be trivial except nested KeyValueStore and
  // nested brillo::VariantDictionary.
  static brillo::VariantDictionary ConvertToVariantDictionary(
      const KeyValueStore& in_store);
  static KeyValueStore ConvertFromVariantDictionary(
      const brillo::VariantDictionary& in_dict);

 private:
  brillo::VariantDictionary properties_;
};

}  // namespace shill

#endif  // SHILL_KEY_VALUE_STORE_H_