120 lines
3.1 KiB
C++
120 lines
3.1 KiB
C++
/*
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* Tencent is pleased to support the open source community by making
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* MMKV available.
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*
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* Copyright (C) 2018 THL A29 Limited, a Tencent company.
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* All rights reserved.
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*
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* Licensed under the BSD 3-Clause License (the "License"); you may not use
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* this file except in compliance with the License. You may obtain a copy of
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* the License at
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*
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* https://opensource.org/licenses/BSD-3-Clause
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef MMKV_INTERPROCESSLOCK_H
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#define MMKV_INTERPROCESSLOCK_H
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#ifdef __cplusplus
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#include "MMKVPredef.h"
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#include <fcntl.h>
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namespace mmkv {
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enum LockType {
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SharedLockType,
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ExclusiveLockType,
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};
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// a recursive POSIX file-lock wrapper
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// handles lock upgrade & downgrade correctly
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class FileLock {
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MMKVFileHandle_t m_fd;
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size_t m_sharedLockCount;
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size_t m_exclusiveLockCount;
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bool doLock(LockType lockType, bool wait);
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bool platformLock(LockType lockType, bool wait, bool unLockFirstIfNeeded);
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bool platformUnLock(bool unLockFirstIfNeeded);
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#ifndef MMKV_WIN32
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bool isFileLockValid() { return m_fd >= 0; }
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# ifdef MMKV_ANDROID
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const bool m_isAshmem;
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struct flock m_lockInfo;
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bool ashmemLock(LockType lockType, bool wait, bool unLockFirstIfNeeded);
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bool ashmemUnLock(bool unLockFirstIfNeeded);
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# endif
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#else // defined(MMKV_WIN32)
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OVERLAPPED m_overLapped;
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bool isFileLockValid() { return m_fd != INVALID_HANDLE_VALUE; }
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#endif // MMKV_WIN32
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public:
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#ifndef MMKV_WIN32
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# ifndef MMKV_ANDROID
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explicit FileLock(MMKVFileHandle_t fd) : m_fd(fd), m_sharedLockCount(0), m_exclusiveLockCount(0) {}
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# else
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explicit FileLock(MMKVFileHandle_t fd, bool isAshmem = false);
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# endif // MMKV_ANDROID
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#else // defined(MMKV_WIN32)
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explicit FileLock(MMKVFileHandle_t fd) : m_fd(fd), m_overLapped{}, m_sharedLockCount(0), m_exclusiveLockCount(0) {}
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#endif // MMKV_WIN32
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bool lock(LockType lockType);
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bool try_lock(LockType lockType);
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bool unlock(LockType lockType);
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// just forbid it for possibly misuse
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explicit FileLock(const FileLock &other) = delete;
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FileLock &operator=(const FileLock &other) = delete;
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};
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class InterProcessLock {
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FileLock *m_fileLock;
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LockType m_lockType;
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public:
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InterProcessLock(FileLock *fileLock, LockType lockType)
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: m_fileLock(fileLock), m_lockType(lockType), m_enable(true) {
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MMKV_ASSERT(m_fileLock);
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}
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bool m_enable;
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void lock() {
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if (m_enable) {
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m_fileLock->lock(m_lockType);
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}
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}
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bool try_lock() {
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if (m_enable) {
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return m_fileLock->try_lock(m_lockType);
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}
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return false;
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}
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void unlock() {
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if (m_enable) {
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m_fileLock->unlock(m_lockType);
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}
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}
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};
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} // namespace mmkv
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#endif
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#endif //MMKV_INTERPROCESSLOCK_H
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