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#pragma once
///@file
#include "store-api.hh"
namespace nix {
/**
* Garbage-collector roots, referring to a store path
*/
typedef std::unordered_map<StorePath, std::unordered_set<std::string>> Roots;
/**
* Possible garbage collector roots, referring to any path
*/
typedef std::unordered_map<Path, std::unordered_set<std::string>> UncheckedRoots;
struct GCOptions
{
/**
* Garbage collector operation:
*
* - `gcReturnLive`: return the set of paths reachable from
* (i.e. in the closure of) the roots.
*
* - `gcReturnDead`: return the set of paths not reachable from
* the roots.
*
* - `gcDeleteDead`: actually delete the latter set.
*
* - `gcDeleteSpecific`: delete the paths listed in
* `pathsToDelete`, insofar as they are not reachable.
*/
typedef enum {
gcReturnLive,
gcReturnDead,
gcDeleteDead,
gcDeleteSpecific,
} GCAction;
GCAction action{gcDeleteDead};
/**
* If `ignoreLiveness` is set, then reachability from the roots is
* ignored (dangerous!). However, the paths must still be
* unreferenced *within* the store (i.e., there can be no other
* store paths that depend on them).
*/
bool ignoreLiveness{false};
/**
* For `gcDeleteSpecific`, the paths to delete.
*/
StorePathSet pathsToDelete;
/**
* Stop after at least `maxFreed` bytes have been freed.
*/
uint64_t maxFreed{std::numeric_limits<uint64_t>::max()};
};
struct GCResults
{
/**
* Depending on the action, the GC roots, or the paths that would
* be or have been deleted.
*/
PathSet paths;
/**
* For `gcReturnDead`, `gcDeleteDead` and `gcDeleteSpecific`, the
* number of bytes that would be or was freed.
*/
uint64_t bytesFreed = 0;
};
/**
* Mix-in class for \ref Store "stores" which expose a notion of garbage
* collection.
*
* Garbage collection will allow deleting paths which are not
* transitively "rooted".
*
* The notion of GC roots actually not part of this class.
*
* - The base `Store` class has `Store::addTempRoot()` because for a store
* that doesn't support garbage collection at all, a temporary GC root is
* safely implementable as no-op.
*
* @todo actually this is not so good because stores are *views*.
* Some views have only a no-op temp roots even though others to the
* same store allow triggering GC. For instance one can't add a root
* over ssh, but that doesn't prevent someone from gc-ing that store
* accesed via SSH locally).
*
* - The derived `LocalFSStore` class has `LocalFSStore::addPermRoot`,
* which is not part of this class because it relies on the notion of
* an ambient file system. There are stores (`ssh-ng://`, for one),
* that *do* support garbage collection but *don't* expose any file
* system, and `LocalFSStore::addPermRoot` thus does not make sense
* for them.
*/
struct GcStore : public virtual Store
{
inline static std::string operationName = "Garbage collection";
/**
* Find the roots of the garbage collector. Each root is a pair
* `(link, storepath)` where `link` is the path of the symlink
* outside of the Nix store that point to `storePath`. If
* `censor` is true, privacy-sensitive information about roots
* found in `/proc` is censored.
*/
virtual Roots findRoots(bool censor) = 0;
/**
* Perform a garbage collection.
*/
virtual void collectGarbage(const GCOptions & options, GCResults & results) = 0;
};
}
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