lix/src/libstore/profiles.cc
Eelco Dolstra bbe97dff8b Make the Store API more type-safe
Most functions now take a StorePath argument rather than a Path (which
is just an alias for std::string). The StorePath constructor ensures
that the path is syntactically correct (i.e. it looks like
<store-dir>/<base32-hash>-<name>). Similarly, functions like
buildPaths() now take a StorePathWithOutputs, rather than abusing Path
by adding a '!<outputs>' suffix.

Note that the StorePath type is implemented in Rust. This involves
some hackery to allow Rust values to be used directly in C++, via a
helper type whose destructor calls the Rust type's drop()
function. The main issue is the dynamic nature of C++ move semantics:
after we have moved a Rust value, we should not call the drop function
on the original value. So when we move a value, we set the original
value to bitwise zero, and the destructor only calls drop() if the
value is not bitwise zero. This should be sufficient for most types.

Also lots of minor cleanups to the C++ API to make it more modern
(e.g. using std::optional and std::string_view in some places).
2019-12-10 22:06:05 +01:00

260 lines
6.7 KiB
C++

#include "profiles.hh"
#include "store-api.hh"
#include "util.hh"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
namespace nix {
static bool cmpGensByNumber(const Generation & a, const Generation & b)
{
return a.number < b.number;
}
/* Parse a generation name of the format
`<profilename>-<number>-link'. */
static int parseName(const string & profileName, const string & name)
{
if (string(name, 0, profileName.size() + 1) != profileName + "-") return -1;
string s = string(name, profileName.size() + 1);
string::size_type p = s.find("-link");
if (p == string::npos) return -1;
int n;
if (string2Int(string(s, 0, p), n) && n >= 0)
return n;
else
return -1;
}
Generations findGenerations(Path profile, int & curGen)
{
Generations gens;
Path profileDir = dirOf(profile);
auto profileName = std::string(baseNameOf(profile));
for (auto & i : readDirectory(profileDir)) {
int n;
if ((n = parseName(profileName, i.name)) != -1) {
Generation gen;
gen.path = profileDir + "/" + i.name;
gen.number = n;
struct stat st;
if (lstat(gen.path.c_str(), &st) != 0)
throw SysError(format("statting '%1%'") % gen.path);
gen.creationTime = st.st_mtime;
gens.push_back(gen);
}
}
gens.sort(cmpGensByNumber);
curGen = pathExists(profile)
? parseName(profileName, readLink(profile))
: -1;
return gens;
}
static void makeName(const Path & profile, unsigned int num,
Path & outLink)
{
Path prefix = (format("%1%-%2%") % profile % num).str();
outLink = prefix + "-link";
}
Path createGeneration(ref<LocalFSStore> store, Path profile, Path outPath)
{
/* The new generation number should be higher than old the
previous ones. */
int dummy;
Generations gens = findGenerations(profile, dummy);
unsigned int num;
if (gens.size() > 0) {
Generation last = gens.back();
if (readLink(last.path) == outPath) {
/* We only create a new generation symlink if it differs
from the last one.
This helps keeping gratuitous installs/rebuilds from piling
up uncontrolled numbers of generations, cluttering up the
UI like grub. */
return last.path;
}
num = gens.back().number;
} else {
num = 0;
}
/* Create the new generation. Note that addPermRoot() blocks if
the garbage collector is running to prevent the stuff we've
built from moving from the temporary roots (which the GC knows)
to the permanent roots (of which the GC would have a stale
view). If we didn't do it this way, the GC might remove the
user environment etc. we've just built. */
Path generation;
makeName(profile, num + 1, generation);
store->addPermRoot(store->parseStorePath(outPath), generation, false, true);
return generation;
}
static void removeFile(const Path & path)
{
if (remove(path.c_str()) == -1)
throw SysError(format("cannot unlink '%1%'") % path);
}
void deleteGeneration(const Path & profile, unsigned int gen)
{
Path generation;
makeName(profile, gen, generation);
removeFile(generation);
}
static void deleteGeneration2(const Path & profile, unsigned int gen, bool dryRun)
{
if (dryRun)
printInfo(format("would remove generation %1%") % gen);
else {
printInfo(format("removing generation %1%") % gen);
deleteGeneration(profile, gen);
}
}
void deleteGenerations(const Path & profile, const std::set<unsigned int> & gensToDelete, bool dryRun)
{
PathLocks lock;
lockProfile(lock, profile);
int curGen;
Generations gens = findGenerations(profile, curGen);
if (gensToDelete.find(curGen) != gensToDelete.end())
throw Error(format("cannot delete current generation of profile %1%'") % profile);
for (auto & i : gens) {
if (gensToDelete.find(i.number) == gensToDelete.end()) continue;
deleteGeneration2(profile, i.number, dryRun);
}
}
void deleteGenerationsGreaterThan(const Path & profile, int max, bool dryRun)
{
PathLocks lock;
lockProfile(lock, profile);
int curGen;
bool fromCurGen = false;
Generations gens = findGenerations(profile, curGen);
for (auto i = gens.rbegin(); i != gens.rend(); ++i) {
if (i->number == curGen) {
fromCurGen = true;
max--;
continue;
}
if (fromCurGen) {
if (max) {
max--;
continue;
}
deleteGeneration2(profile, i->number, dryRun);
}
}
}
void deleteOldGenerations(const Path & profile, bool dryRun)
{
PathLocks lock;
lockProfile(lock, profile);
int curGen;
Generations gens = findGenerations(profile, curGen);
for (auto & i : gens)
if (i.number != curGen)
deleteGeneration2(profile, i.number, dryRun);
}
void deleteGenerationsOlderThan(const Path & profile, time_t t, bool dryRun)
{
PathLocks lock;
lockProfile(lock, profile);
int curGen;
Generations gens = findGenerations(profile, curGen);
bool canDelete = false;
for (auto i = gens.rbegin(); i != gens.rend(); ++i)
if (canDelete) {
assert(i->creationTime < t);
if (i->number != curGen)
deleteGeneration2(profile, i->number, dryRun);
} else if (i->creationTime < t) {
/* We may now start deleting generations, but we don't
delete this generation yet, because this generation was
still the one that was active at the requested point in
time. */
canDelete = true;
}
}
void deleteGenerationsOlderThan(const Path & profile, const string & timeSpec, bool dryRun)
{
time_t curTime = time(0);
string strDays = string(timeSpec, 0, timeSpec.size() - 1);
int days;
if (!string2Int(strDays, days) || days < 1)
throw Error(format("invalid number of days specifier '%1%'") % timeSpec);
time_t oldTime = curTime - days * 24 * 3600;
deleteGenerationsOlderThan(profile, oldTime, dryRun);
}
void switchLink(Path link, Path target)
{
/* Hacky. */
if (dirOf(target) == dirOf(link)) target = baseNameOf(target);
replaceSymlink(target, link);
}
void lockProfile(PathLocks & lock, const Path & profile)
{
lock.lockPaths({profile}, (format("waiting for lock on profile '%1%'") % profile).str());
lock.setDeletion(true);
}
string optimisticLockProfile(const Path & profile)
{
return pathExists(profile) ? readLink(profile) : "";
}
}