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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012-2022 OpenVPN Inc.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License Version 3
// as published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program in the COPYING file.
// If not, see <http://www.gnu.org/licenses/>.
// Atomic file-handling methods.
#pragma once
#include <openvpn/common/platform.hpp>
#if defined(OPENVPN_PLATFORM_WIN)
#error atomic file methods not supported on Windows
#endif
#include <stdio.h> // for rename()
#include <unistd.h> // for unlink()
#include <errno.h>
#include <cstring>
#include <openvpn/common/file.hpp>
#include <openvpn/common/fileunix.hpp>
#include <openvpn/common/strerror.hpp>
#include <openvpn/common/tmpfilename.hpp>
namespace openvpn {
// Atomically write binary buffer to file (relies on
// the atomicity of rename())
inline void write_binary_atomic(const std::string &fn,
const std::string &tmpdir,
const mode_t mode,
const std::uint64_t mtime_ns, // set explicit modification-time in nanoseconds since epoch, or 0 to defer to system
const ConstBuffer &buf,
StrongRandomAPI &rng)
{
// generate temporary filename
const std::string tfn = tmp_filename(fn, tmpdir, rng);
// write to temporary file
write_binary_unix(tfn, mode, mtime_ns, buf);
// then move into position
if (::rename(tfn.c_str(), fn.c_str()) == -1)
{
const int eno = errno;
::unlink(tfn.c_str()); // move failed, so delete the temporary file
OPENVPN_THROW(file_unix_error, "error moving '" << tfn << "' -> '" << fn << "' : " << strerror_str(eno));
}
}
inline void write_binary_atomic(const std::string &fn,
const std::string &tmpdir,
const mode_t mode,
const std::uint64_t mtime_ns,
const Buffer &buf,
StrongRandomAPI &rng)
{
write_binary_atomic(fn, tmpdir, mode, mtime_ns, const_buffer_ref(buf), rng);
}
} // namespace openvpn
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