nix-super/src/libstore/profiles.hh

#pragma once
///@file

 #include "types.hh"
#include "pathlocks.hh"

#include <time.h>


namespace nix {

class StorePath;


typedef uint64_t GenerationNumber;

struct Generation
{
    GenerationNumber number;
    Path path;
    time_t creationTime;
};

typedef std::list<Generation> Generations;


/**
 * Returns the list of currently present generations for the specified
 * profile, sorted by generation number. Also returns the number of
 * the current generation.
 */
std::pair<Generations, std::optional<GenerationNumber>> findGenerations(Path profile);

class LocalFSStore;

Path createGeneration(ref<LocalFSStore> store, Path profile, StorePath outPath);

void deleteGeneration(const Path & profile, GenerationNumber gen);

void deleteGenerations(const Path & profile, const std::set<GenerationNumber> & gensToDelete, bool dryRun);

void deleteGenerationsGreaterThan(const Path & profile, GenerationNumber max, bool dryRun);

void deleteOldGenerations(const Path & profile, bool dryRun);

void deleteGenerationsOlderThan(const Path & profile, time_t t, bool dryRun);

void deleteGenerationsOlderThan(const Path & profile, std::string_view timeSpec, bool dryRun);

void switchLink(Path link, Path target);

/**
 * Roll back a profile to the specified generation, or to the most
 * recent one older than the current.
 */
void switchGeneration(
    const Path & profile,
    std::optional<GenerationNumber> dstGen,
    bool dryRun);

/**
 * Ensure exclusive access to a profile.  Any command that modifies
 * the profile first acquires this lock.
 */
void lockProfile(PathLocks & lock, const Path & profile);

/**
 * Optimistic locking is used by long-running operations like `nix-env
 * -i'.  Instead of acquiring the exclusive lock for the entire
 * duration of the operation, we just perform the operation
 * optimistically (without an exclusive lock), and check at the end
 * whether the profile changed while we were busy (i.e., the symlink
 * target changed).  If so, the operation is restarted.  Restarting is
 * generally cheap, since the build results are still in the Nix
 * store.  Most of the time, only the user environment has to be
 * rebuilt.
 */
std::string optimisticLockProfile(const Path & profile);

/**
 * Create and return the path to a directory suitable for storing the user’s
 * profiles.
 */
Path profilesDir();

/**
 * Return the path to the profile directory for root (but don't try creating it)
 */
Path rootProfilesDir();

/**
 * Create and return the path to the file used for storing the users's channels
 */
Path defaultChannelsDir();

/**
 * Return the path to the channel directory for root (but don't try creating it)
 */
Path rootChannelsDir();

/**
 * Resolve the default profile (~/.nix-profile by default,
 * $XDG_STATE_HOME/nix/profile if XDG Base Directory Support is enabled),
 * and create if doesn't exist
 */
Path getDefaultProfile();

}