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Diffstat (limited to 'src/utils/cpp/file_locking.hpp')
-rw-r--r-- | src/utils/cpp/file_locking.hpp | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/src/utils/cpp/file_locking.hpp b/src/utils/cpp/file_locking.hpp new file mode 100644 index 00000000..a92b874a --- /dev/null +++ b/src/utils/cpp/file_locking.hpp @@ -0,0 +1,65 @@ +// Copyright 2022 Huawei Cloud Computing Technology Co., Ltd. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef INCLUDED_SRC_OTHER_TOOLS_FILE_LOCKING_HPP +#define INCLUDED_SRC_OTHER_TOOLS_FILE_LOCKING_HPP + +#include <filesystem> +#include <memory> +#include <optional> + +#include "gsl-lite/gsl-lite.hpp" + +/* \brief Thread- and process-safe file locking mechanism for paths. + * User guarantees write access in the parent directory of the path given, as + * the lock will be placed there and missing tree directories will be created. + * Lock path and name conventions: a/b.c, a/b/, a/b => a/b.lock; / => /.lock; + */ +class LockFile { + public: + // no default ctor + LockFile() = delete; + + /// \brief Destroy the LockFile object. + /// It only closes the open file descriptor, but does not explicitly unlock. + ~LockFile() noexcept; + + // no copies, only moves + LockFile(LockFile const&) = delete; + LockFile(LockFile&& other) noexcept; + auto operator=(LockFile const&) = delete; + auto operator=(LockFile&& other) noexcept -> LockFile&; + + /// \brief Tries to acquire a lock file in the given directory path. + /// Missing directories will be created if write permission exists. + /// Returns the lock file object on success, nullopt on failure. + [[nodiscard]] static auto Acquire(std::filesystem::path const& fspath, + bool is_shared) noexcept + -> std::optional<LockFile>; + + private: + gsl::owner<FILE*> file_handle_{nullptr}; + std::filesystem::path lock_file_{}; + + /// \brief Private ctor. Instances are only created by Acquire method. + explicit LockFile(gsl::owner<FILE*> file_handle, + std::filesystem::path lock_file) noexcept + : file_handle_{file_handle}, lock_file_{std::move(lock_file)} {}; + + [[nodiscard]] static auto GetLockFilePath( + std::filesystem::path const& fspath) noexcept + -> std::optional<std::filesystem::path>; +}; + +#endif // FILE_LOCKING |