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#include <map>
#include <set>
#include "types.hh"
#pragma once
namespace nix {
class Args;
class AbstractSetting;
/* A class to simplify providing configuration settings. The typical
use is to inherit Config and add Setting<T> members:
class MyClass : private Config
{
Setting<int> foo{this, 123, "foo", "the number of foos to use"};
Setting<std::string> bar{this, "blabla", "bar", "the name of the bar"};
MyClass() : Config(readConfigFile("/etc/my-app.conf"))
{
std::cout << foo << "\n"; // will print 123 unless overriden
}
};
*/
class Config
{
friend class AbstractSetting;
struct SettingData
{
bool isAlias = false;
AbstractSetting * setting;
};
std::map<std::string, SettingData> _settings;
StringMap initials;
public:
Config(const StringMap & initials)
: initials(initials)
{ }
void set(const std::string & name, const std::string & value);
void add(AbstractSetting * setting);
void warnUnused();
std::string dump();
};
class AbstractSetting
{
friend class Config;
public:
const std::string name;
const std::string description;
const std::set<std::string> aliases;
int created = 123;
protected:
AbstractSetting(
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases);
virtual ~AbstractSetting()
{
// Check against a gcc miscompilation causing our constructor
// not to run.
assert(created == 123);
}
virtual void set(const std::string & value) = 0;
virtual std::string to_string() = 0;
};
/* A setting of type T. */
template<typename T>
class Setting : public AbstractSetting
{
protected:
T value;
public:
Setting(Config * options,
const T & def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: AbstractSetting(name, description, aliases)
, value(def)
{
options->add(this);
}
operator const T &() const { return value; }
bool operator ==(const T & v2) const { return value == v2; }
bool operator !=(const T & v2) const { return value != v2; }
void operator =(const T & v) { value = v; }
void set(const std::string & str) override;
std::string to_string() override;
};
template<typename T>
std::ostream & operator <<(std::ostream & str, const Setting<T> & opt)
{
str << (const T &) opt;
return str;
}
/* A special setting for Paths. These are automatically canonicalised
(e.g. "/foo//bar/" becomes "/foo/bar"). */
class PathSetting : public Setting<Path>
{
bool allowEmpty;
public:
PathSetting(Config * options,
bool allowEmpty,
const Path & def,
const std::string & name,
const std::string & description,
const std::set<std::string> & aliases = {})
: Setting<Path>(options, def, name, description, aliases)
, allowEmpty(allowEmpty)
{
set(value);
}
void set(const std::string & str) override;
Path operator +(const char * p) const { return value + p; }
};
}
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