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#pragma once
///@file
#include "local-fs-store.hh"
namespace nix {
/**
* Mix-in class for implementing permanent roots as a pair of a direct
* (strong) reference and indirect weak reference to the first
* reference.
*
* See methods for details on the operations it represents.
*/
struct IndirectRootStore : public virtual LocalFSStore
{
inline static std::string operationName = "Indirect GC roots registration";
/**
* Implementation of `LocalFSStore::addPermRoot` where the permanent
* root is a pair of
*
* - The user-facing symlink which all implementations must create
*
* - An additional weak reference known as the "indirect root" that
* points to that symlink.
*
* The garbage collector will automatically remove the indirect root
* when it finds that the symlink has disappeared.
*
* The implementation of this method is concrete, but it delegates
* to `addIndirectRoot()` which is abstract.
*/
Path addPermRoot(const StorePath & storePath, const Path & gcRoot) override final;
/**
* Add an indirect root, which is a weak reference to the
* user-facing symlink created by `addPermRoot()`.
*
* @param path user-facing and user-controlled symlink to a store
* path.
*
* The form this weak-reference takes is implementation-specific.
*/
virtual void addIndirectRoot(const Path & path) = 0;
};
}
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