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/*
* Copyright © 2014 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authored by: Thomas Voß <thomas.voss@canonical.com>
*/
#ifndef CORE_LOCATION_SETTINGS_H_
#define CORE_LOCATION_SETTINGS_H_
#include <cstdint>
#include <memory>
#include <sstream>
#include <string>
namespace core
{
namespace location
{
// A simple interface for reading/writing values given a string key.
struct Settings
{
// To safe us some typing
typedef std::shared_ptr<Settings> Ptr;
// Collects possible exceptions reported from getters.
struct Error
{
Error() = delete;
// Thrown if no value of the specified type is available for
// the given key.
struct NoValueForKey : public std::runtime_error
{
NoValueForKey(const std::string& key);
};
};
// The usual boilerplate
Settings() = default;
Settings(const Settings&) = delete;
virtual ~Settings() = default;
Settings& operator=(const Settings&) = delete;
// Syncs the current settings to implementation-specific backends.
virtual void sync() = 0;
// Returns true iff a value is known for the given key.
virtual bool has_value_for_key(const std::string& key) const = 0;
// Convenience wrapper.
template <typename T>
inline T get_enum_for_key(const std::string& key, T default_value);
template <typename T>
inline T get_enum_for_key_or_throw(const std::string& key);
// Tries to read the value for the given key and returns the default_value if
// no value is known.
std::string get_string_for_key(const std::string& key, const std::string& default_value);
// Gets an integer value known for the given key, or throws Error::NoValueForKey.
virtual std::string get_string_for_key_or_throw(const std::string& key) = 0;
// Convenience wrapper.
template <typename T>
inline bool set_enum_for_key(const std::string& key, T value);
// Sets values known for the given key.
virtual bool set_string_for_key(const std::string& key, const std::string& value) = 0;
};
// A decorator that syncs whenever a value changes.
struct SyncingSettings : public Settings
{
SyncingSettings(const Settings::Ptr& impl) : impl{impl} {}
~SyncingSettings()
{
sync();
}
virtual void sync()
{
impl->sync();
}
virtual bool has_value_for_key(const std::string& key) const
{
return impl->has_value_for_key(key);
}
virtual std::string get_string_for_key_or_throw(const std::string& key)
{
return impl->get_string_for_key_or_throw(key);
}
virtual bool set_string_for_key(const std::string& key, const std::string& value)
{
auto result = impl->set_string_for_key(key, value);
if (result)
impl->sync();
return result;
}
Settings::Ptr impl;
};
template <typename T>
inline T Settings::get_enum_for_key(const std::string& key, T default_value)
{
static_assert(std::is_enum<T>::value, "Only enum types are supported.");
std::stringstream dss;
dss << default_value;
std::stringstream ss{get_string_for_key(key, dss.str())};
T result;
ss >> result;
return result;
}
template <typename T>
inline T Settings::get_enum_for_key_or_throw(const std::string& key)
{
static_assert(std::is_enum<T>::value, "Only enum types are supported.");
std::stringstream ss{get_string_for_key_or_throw(key)};
T result;
ss >> result;
return result;
}
template <typename T>
inline bool Settings::set_enum_for_key(const std::string& key, T value)
{
static_assert(std::is_enum<T>::value, "Only enum types are supported.");
std::stringstream ss;
ss << value;
return set_string_for_key(key, ss.str());
}
}
}
#endif // CORE_LOCATION_SETTINGS_H_
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