diff options
Diffstat (limited to 'src/libutil/filesystem.cc')
| -rw-r--r-- | src/libutil/filesystem.cc | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/src/libutil/filesystem.cc b/src/libutil/filesystem.cc new file mode 100644 index 000000000..403389e60 --- /dev/null +++ b/src/libutil/filesystem.cc @@ -0,0 +1,172 @@ +#include <sys/time.h> +#include <filesystem> + +#include "finally.hh" +#include "util.hh" +#include "types.hh" + +namespace fs = std::filesystem; + +namespace nix { + +static Path tempName(Path tmpRoot, const Path & prefix, bool includePid, + int & counter) +{ + tmpRoot = canonPath(tmpRoot.empty() ? getEnv("TMPDIR").value_or("/tmp") : tmpRoot, true); + if (includePid) + return (format("%1%/%2%-%3%-%4%") % tmpRoot % prefix % getpid() % counter++).str(); + else + return (format("%1%/%2%-%3%") % tmpRoot % prefix % counter++).str(); +} + +Path createTempDir(const Path & tmpRoot, const Path & prefix, + bool includePid, bool useGlobalCounter, mode_t mode) +{ + static int globalCounter = 0; + int localCounter = 0; + int & counter(useGlobalCounter ? globalCounter : localCounter); + + while (1) { + checkInterrupt(); + Path tmpDir = tempName(tmpRoot, prefix, includePid, counter); + if (mkdir(tmpDir.c_str(), mode) == 0) { +#if __FreeBSD__ + /* Explicitly set the group of the directory. This is to + work around around problems caused by BSD's group + ownership semantics (directories inherit the group of + the parent). For instance, the group of /tmp on + FreeBSD is "wheel", so all directories created in /tmp + will be owned by "wheel"; but if the user is not in + "wheel", then "tar" will fail to unpack archives that + have the setgid bit set on directories. */ + if (chown(tmpDir.c_str(), (uid_t) -1, getegid()) != 0) + throw SysError("setting group of directory '%1%'", tmpDir); +#endif + return tmpDir; + } + if (errno != EEXIST) + throw SysError("creating directory '%1%'", tmpDir); + } +} + + +std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix) +{ + Path tmpl(getEnv("TMPDIR").value_or("/tmp") + "/" + prefix + ".XXXXXX"); + // Strictly speaking, this is UB, but who cares... + // FIXME: use O_TMPFILE. + AutoCloseFD fd(mkstemp((char *) tmpl.c_str())); + if (!fd) + throw SysError("creating temporary file '%s'", tmpl); + closeOnExec(fd.get()); + return {std::move(fd), tmpl}; +} + +void createSymlink(const Path & target, const Path & link, + std::optional<time_t> mtime) +{ + if (symlink(target.c_str(), link.c_str())) + throw SysError("creating symlink from '%1%' to '%2%'", link, target); + if (mtime) { + struct timeval times[2]; + times[0].tv_sec = *mtime; + times[0].tv_usec = 0; + times[1].tv_sec = *mtime; + times[1].tv_usec = 0; + if (lutimes(link.c_str(), times)) + throw SysError("setting time of symlink '%s'", link); + } +} + +void replaceSymlink(const Path & target, const Path & link, + std::optional<time_t> mtime) +{ + for (unsigned int n = 0; true; n++) { + Path tmp = canonPath(fmt("%s/.%d_%s", dirOf(link), n, baseNameOf(link))); + + try { + createSymlink(target, tmp, mtime); + } catch (SysError & e) { + if (e.errNo == EEXIST) continue; + throw; + } + + renameFile(tmp, link); + + break; + } +} + +void setWriteTime(const fs::path & p, const struct stat & st) +{ + struct timeval times[2]; + times[0] = { + .tv_sec = st.st_atime, + .tv_usec = 0, + }; + times[1] = { + .tv_sec = st.st_mtime, + .tv_usec = 0, + }; + if (lutimes(p.c_str(), times) != 0) + throw SysError("changing modification time of '%s'", p); +} + +void copy(const fs::directory_entry & from, const fs::path & to, bool andDelete) +{ + // TODO: Rewrite the `is_*` to use `symlink_status()` + auto statOfFrom = lstat(from.path().c_str()); + auto fromStatus = from.symlink_status(); + + // Mark the directory as writable so that we can delete its children + if (andDelete && fs::is_directory(fromStatus)) { + fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow); + } + + + if (fs::is_symlink(fromStatus) || fs::is_regular_file(fromStatus)) { + fs::copy(from.path(), to, fs::copy_options::copy_symlinks | fs::copy_options::overwrite_existing); + } else if (fs::is_directory(fromStatus)) { + fs::create_directory(to); + for (auto & entry : fs::directory_iterator(from.path())) { + copy(entry, to / entry.path().filename(), andDelete); + } + } else { + throw Error("file '%s' has an unsupported type", from.path()); + } + + setWriteTime(to, statOfFrom); + if (andDelete) { + if (!fs::is_symlink(fromStatus)) + fs::permissions(from.path(), fs::perms::owner_write, fs::perm_options::add | fs::perm_options::nofollow); + fs::remove(from.path()); + } +} + +void renameFile(const Path & oldName, const Path & newName) +{ + fs::rename(oldName, newName); +} + +void moveFile(const Path & oldName, const Path & newName) +{ + try { + renameFile(oldName, newName); + } catch (fs::filesystem_error & e) { + auto oldPath = fs::path(oldName); + auto newPath = fs::path(newName); + // For the move to be as atomic as possible, copy to a temporary + // directory + fs::path temp = createTempDir(newPath.parent_path(), "rename-tmp"); + Finally removeTemp = [&]() { fs::remove(temp); }; + auto tempCopyTarget = temp / "copy-target"; + if (e.code().value() == EXDEV) { + fs::remove(newPath); + warn("Can’t rename %s as %s, copying instead", oldName, newName); + copy(fs::directory_entry(oldPath), tempCopyTarget, true); + renameFile(tempCopyTarget, newPath); + } + } +} + +} |