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// This source code is released into the public domain.
export module nihil.posix:tempfile;
import nihil.std;
import nihil.util;
import :fd;
import :getenv;
import :open;
import :unlink;
// tempfile: create a temporary file.
namespace nihil {
struct tempfile_flags_tag
{
};
export using tempfile_flags = flagset<std::uint8_t, tempfile_flags_tag>;
// No flags.
export inline constexpr auto tempfile_none = tempfile_flags();
// Unlink the tempfile immediately after creating it
export inline constexpr auto tempfile_unlink = tempfile_flags::bit<0>();
export struct temporary_file final
{
// Fetch the file's fd.
[[nodiscard]] auto fd(this temporary_file &self) -> nihil::fd &
{
if (!self.m_fd)
throw std::logic_error("fd() called on empty temporary_file");
return self.m_fd;
}
// Fetch the name of this file. If tempfile_unlink was specified,
// throws std::logic_error.
[[nodiscard]] auto path(this temporary_file const &self) -> std::filesystem::path const &
{
if (self.m_path.empty())
throw std::logic_error("path() called on unlinked temporary_file");
return self.m_path;
}
// Release this temporary file, causing it to be closed and deleted immediately
// Throws std::logic_error if the file has already been released.
auto release(this temporary_file &self) -> void
{
if (!self.m_fd)
throw std::logic_error("release() called on already-released tempfile");
if (!self.m_path.empty()) {
std::ignore = unlink(self.path());
self.m_path.clear();
}
std::ignore = self.m_fd.close();
}
// Destructor; unlink the file if we didn't already.
~temporary_file() // NOLINT
{
if (m_fd)
release();
}
// Not copyable.
temporary_file(temporary_file const &) = delete;
// Movable.
temporary_file(temporary_file &&other) noexcept = default;
// Not assignable.
auto operator=(this temporary_file &, temporary_file const &) -> temporary_file & = delete;
auto
operator=(this temporary_file &, temporary_file &&) noexcept -> temporary_file & = delete;
private:
// The file descriptor for the file.
nihil::fd m_fd;
std::filesystem::path m_path;
temporary_file(nihil::fd &&fd, std::filesystem::path path) noexcept
: m_fd(std::move(fd))
, m_path(std::move(path))
{
}
explicit temporary_file(nihil::fd &&fd) noexcept
: m_fd(std::move(fd))
{
}
friend auto tempfile(tempfile_flags flags) -> std::expected<temporary_file, error>;
};
/*
* Create a temporary file and return it.
*/
export [[nodiscard]] auto
tempfile(tempfile_flags flags = tempfile_none) -> std::expected<temporary_file, error>
{
auto rng = std::default_random_engine(std::random_device{}());
auto random_name = [&] -> std::string {
auto constexpr length = std::size_t{12};
auto constexpr randchars = std::string_view("abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"0123456789");
auto dist = std::uniform_int_distribution<>(0, randchars.size() - 1);
auto ret = std::string(length, 0);
std::ranges::generate_n(ret.begin(), length,
[&] -> char { return randchars[dist(rng)]; });
return ret;
};
auto dir = std::filesystem::path(getenv("TMPDIR").value_or("/tmp")); // NOLINT
// Keep trying until we don't get EEXIST.
for (;;) {
auto filename = dir / (random_name() + ".tmp");
auto fd =
nihil::open(filename, open_readwrite | open_create | open_exclusive, 0600);
if (!fd) {
if (fd.error() == std::errc::file_exists)
continue;
return std::unexpected(fd.error());
}
if (flags & tempfile_unlink) {
std::ignore = unlink(filename);
return temporary_file(std::move(*fd));
}
return temporary_file(std::move(*fd), std::move(filename));
}
}
} // namespace nihil
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