1 files changed, 228 insertions, 0 deletions
diff --git a/third_party/nix/src/libutil/config.hh b/third_party/nix/src/libutil/config.hh
new file mode 100644
index 000000000000..81b1c80e0e97
--- /dev/null
+++ b/third_party/nix/src/libutil/config.hh
@@ -0,0 +1,228 @@
+#include <map>
+#include <set>
+
+#include "libutil/types.hh"
+
+#pragma once
+
+namespace nix {
+
+class Args;
+class AbstractSetting;
+class JSONPlaceholder;
+class JSONObject;
+
+class AbstractConfig {
+ protected:
+  StringMap unknownSettings;
+
+  explicit AbstractConfig(const StringMap& initials = {})
+      : unknownSettings(initials) {}
+
+ public:
+  virtual bool set(const std::string& name, const std::string& value) = 0;
+
+  struct SettingInfo {
+    std::string value;
+    std::string description;
+  };
+
+  virtual void getSettings(std::map<std::string, SettingInfo>& res,
+                           bool overridenOnly = false) = 0;
+
+  void applyConfigFile(const Path& path);
+
+  virtual void resetOverriden() = 0;
+
+  virtual void toJSON(JSONObject& out) = 0;
+
+  virtual void convertToArgs(Args& args, const std::string& category) = 0;
+
+  void warnUnknownSettings();
+
+  void reapplyUnknownSettings();
+};
+
+/* 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 : public AbstractConfig {
+  friend class AbstractSetting;
+
+ public:
+  struct SettingData {
+    bool isAlias;
+    AbstractSetting* setting;
+    SettingData(bool isAlias, AbstractSetting* setting)
+        : isAlias(isAlias), setting(setting) {}
+  };
+
+  typedef std::map<std::string, SettingData> Settings;
+
+ private:
+  Settings _settings;
+
+ public:
+  explicit Config(const StringMap& initials = {}) : AbstractConfig(initials) {}
+
+  bool set(const std::string& name, const std::string& value) override;
+
+  void addSetting(AbstractSetting* setting);
+
+  void getSettings(std::map<std::string, SettingInfo>& res,
+                   bool overridenOnly = false) override;
+
+  void resetOverriden() override;
+
+  void toJSON(JSONObject& out) override;
+
+  void convertToArgs(Args& args, const std::string& category) override;
+};
+
+class AbstractSetting {
+  friend class Config;
+
+ public:
+  const std::string name;
+  const std::string description;
+  const std::set<std::string> aliases;
+
+  int created = 123;
+
+  bool overriden = false;
+
+ protected:
+  AbstractSetting(std::string name, std::string description,
+                  std::set<std::string> aliases);
+
+  virtual ~AbstractSetting() {
+    // Check against a gcc miscompilation causing our constructor
+    // not to run (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431).
+    assert(created == 123);
+  }
+
+  virtual void set(const std::string& value) = 0;
+
+  virtual std::string to_string() = 0;
+
+  virtual void toJSON(JSONPlaceholder& out);
+
+  virtual void convertToArg(Args& args, const std::string& category);
+
+  bool isOverriden() { return overriden; }
+};
+
+/* A setting of type T. */
+template <typename T>
+class BaseSetting : public AbstractSetting {
+ protected:
+  T value;
+
+ public:
+  BaseSetting(const T& def, const std::string& name,
+              const std::string& description,
+              const std::set<std::string>& aliases = {})
+      : AbstractSetting(name, description, aliases), value(def) {}
+
+  operator const T&() const { return value; }
+  operator T&() { return value; }
+  const T& get() 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) { assign(v); }
+  virtual void assign(const T& v) { value = v; }
+
+  void set(const std::string& str) override;
+
+  virtual void override(const T& v) {
+    overriden = true;
+    value = v;
+  }
+
+  std::string to_string() override;
+
+  void convertToArg(Args& args, const std::string& category) override;
+
+  void toJSON(JSONPlaceholder& out) override;
+};
+
+template <typename T>
+std::ostream& operator<<(std::ostream& str, const BaseSetting<T>& opt) {
+  str << (const T&)opt;
+  return str;
+}
+
+template <typename T>
+bool operator==(const T& v1, const BaseSetting<T>& v2) {
+  return v1 == (const T&)v2;
+}
+
+template <typename T>
+class Setting : public BaseSetting<T> {
+ public:
+  Setting(Config* options, const T& def, const std::string& name,
+          const std::string& description,
+          const std::set<std::string>& aliases = {})
+      : BaseSetting<T>(def, name, description, aliases) {
+    options->addSetting(this);
+  }
+
+  void operator=(const T& v) { this->assign(v); }
+};
+
+/* A special setting for Paths. These are automatically canonicalised
+   (e.g. "/foo//bar/" becomes "/foo/bar"). */
+class PathSetting : public BaseSetting<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 = {})
+      : BaseSetting<Path>(def, name, description, aliases),
+        allowEmpty(allowEmpty) {
+    options->addSetting(this);
+  }
+
+  void set(const std::string& str) override;
+
+  Path operator+(const char* p) const { return value + p; }
+
+  void operator=(const Path& v) { this->assign(v); }
+};
+
+struct GlobalConfig : public AbstractConfig {
+  using ConfigRegistrations = std::vector<Config*>;
+  static ConfigRegistrations* configRegistrations;
+
+  bool set(const std::string& name, const std::string& value) override;
+
+  void getSettings(std::map<std::string, SettingInfo>& res,
+                   bool overridenOnly = false) override;
+
+  void resetOverriden() override;
+
+  void toJSON(JSONObject& out) override;
+
+  void convertToArgs(Args& args, const std::string& category) override;
+
+  struct Register {
+    explicit Register(Config* config);
+  };
+};
+
+extern GlobalConfig globalConfig;
+
+}  // namespace nix