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Merge pull request #13412 from xokdvium/read-directory-caching

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libutil: Use caching `directory_entry` API in `PosixSourceAccessor::r…
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Eelco Dolstra 2025-07-01 16:59:40 +02:00 • committed by GitHub
commit 9600eaef2e
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1 changed files with 30 additions and 19 deletions
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49
src/libutil/posix-source-accessor.cc
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@ -141,33 +141,44 @@ SourceAccessor::DirEntries PosixSourceAccessor::readDirectory(const CanonPath &
for (auto & entry : DirectoryIterator{makeAbsPath(path)}) {
checkInterrupt();
auto type = [&]() -> std::optional<Type> {
std::filesystem::file_type nativeType;
try {
nativeType = entry.symlink_status().type();
/* WARNING: We are specifically not calling symlink_status()
* here, because that always translates to `stat` call and
* doesn't make use of any caching. Instead, we have to
* rely on the myriad of `is_*` functions, which actually do
* the caching. If you are in doubt then take a look at the
* libstdc++ implementation [1] and the standard proposal
* about the caching variations of directory_entry [2].
* [1]: https://github.com/gcc-mirror/gcc/blob/8ea555b7b4725dbc5d9286f729166cd54ce5b615/libstdc%2B%2B-v3/include/bits/fs_dir.h#L341-L348
* [2]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0317r1.html
*/
/* Check for symlink first, because other getters follow symlinks. */
if (entry.is_symlink())
return tSymlink;
if (entry.is_regular_file())
return tRegular;
if (entry.is_directory())
return tDirectory;
if (entry.is_character_file())
return tChar;
if (entry.is_block_file())
return tBlock;
if (entry.is_fifo())
return tFifo;
if (entry.is_socket())
return tSocket;
return tUnknown;
} catch (std::filesystem::filesystem_error & e) {
// We cannot always stat the child. (Ideally there is no
// stat because the native directory entry has the type
// already, but this isn't always the case.)
if (e.code() == std::errc::permission_denied || e.code() == std::errc::operation_not_permitted)
return std::nullopt;
else throw;
else
throw;
}
// cannot exhaustively enumerate because implementation-specific
// additional file types are allowed.
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wswitch-enum"
switch (nativeType) {
case std::filesystem::file_type::regular: return Type::tRegular; break;
case std::filesystem::file_type::symlink: return Type::tSymlink; break;
case std::filesystem::file_type::directory: return Type::tDirectory; break;
case std::filesystem::file_type::character: return Type::tChar; break;
case std::filesystem::file_type::block: return Type::tBlock; break;
case std::filesystem::file_type::fifo: return Type::tFifo; break;
case std::filesystem::file_type::socket: return Type::tSocket; break;
default: return tUnknown;
}
#pragma GCC diagnostic pop
}();
res.emplace(entry.path().filename().string(), type);
}