forked from lix-project/lix
165 lines
4.3 KiB
C++
165 lines
4.3 KiB
C++
#include "profiles.hh"
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#include "store-api.hh"
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#include "util.hh"
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdio.h>
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namespace nix {
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static bool cmpGensByNumber(const Generation & a, const Generation & b)
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{
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return a.number < b.number;
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}
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/* Parse a generation name of the format
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`<profilename>-<number>-link'. */
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static int parseName(const string & profileName, const string & name)
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{
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if (string(name, 0, profileName.size() + 1) != profileName + "-") return -1;
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string s = string(name, profileName.size() + 1);
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string::size_type p = s.find("-link");
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if (p == string::npos) return -1;
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int n;
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if (string2Int(string(s, 0, p), n) && n >= 0)
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return n;
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else
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return -1;
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}
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Generations findGenerations(Path profile, int & curGen)
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{
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Generations gens;
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Path profileDir = dirOf(profile);
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string profileName = baseNameOf(profile);
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for (auto & i : readDirectory(profileDir)) {
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int n;
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if ((n = parseName(profileName, i.name)) != -1) {
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Generation gen;
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gen.path = profileDir + "/" + i.name;
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gen.number = n;
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struct stat st;
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if (lstat(gen.path.c_str(), &st) != 0)
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throw SysError(format("statting ‘%1%’") % gen.path);
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gen.creationTime = st.st_mtime;
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gens.push_back(gen);
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}
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}
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gens.sort(cmpGensByNumber);
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curGen = pathExists(profile)
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? parseName(profileName, readLink(profile))
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: -1;
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return gens;
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}
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static void makeName(const Path & profile, unsigned int num,
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Path & outLink)
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{
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Path prefix = (format("%1%-%2%") % profile % num).str();
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outLink = prefix + "-link";
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}
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Path createGeneration(Path profile, Path outPath)
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{
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/* The new generation number should be higher than old the
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previous ones. */
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int dummy;
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Generations gens = findGenerations(profile, dummy);
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unsigned int num;
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if (gens.size() > 0) {
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Generation last = gens.back();
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if (readLink(last.path) == outPath) {
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/* We only create a new generation symlink if it differs
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from the last one.
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This helps keeping gratuitous installs/rebuilds from piling
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up uncontrolled numbers of generations, cluttering up the
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UI like grub. */
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return last.path;
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}
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num = gens.back().number;
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} else {
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num = 0;
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}
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/* Create the new generation. Note that addPermRoot() blocks if
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the garbage collector is running to prevent the stuff we've
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built from moving from the temporary roots (which the GC knows)
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to the permanent roots (of which the GC would have a stale
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view). If we didn't do it this way, the GC might remove the
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user environment etc. we've just built. */
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Path generation;
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makeName(profile, num + 1, generation);
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addPermRoot(*store, outPath, generation, false, true);
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return generation;
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}
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static void removeFile(const Path & path)
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{
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if (remove(path.c_str()) == -1)
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throw SysError(format("cannot unlink ‘%1%’") % path);
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}
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void deleteGeneration(const Path & profile, unsigned int gen)
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{
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Path generation;
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makeName(profile, gen, generation);
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removeFile(generation);
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}
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void switchLink(Path link, Path target)
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{
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/* Hacky. */
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if (dirOf(target) == dirOf(link)) target = baseNameOf(target);
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Path tmp = canonPath(dirOf(link) + "/.new_" + baseNameOf(link));
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createSymlink(target, tmp);
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/* The rename() system call is supposed to be essentially atomic
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on Unix. That is, if we have links `current -> X' and
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`new_current -> Y', and we rename new_current to current, a
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process accessing current will see X or Y, but never a
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file-not-found or other error condition. This is sufficient to
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atomically switch user environments. */
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if (rename(tmp.c_str(), link.c_str()) != 0)
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throw SysError(format("renaming ‘%1%’ to ‘%2%’") % tmp % link);
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}
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void lockProfile(PathLocks & lock, const Path & profile)
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{
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lock.lockPaths(singleton<PathSet>(profile),
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(format("waiting for lock on profile ‘%1%’") % profile).str());
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lock.setDeletion(true);
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}
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string optimisticLockProfile(const Path & profile)
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{
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return pathExists(profile) ? readLink(profile) : "";
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}
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}
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