1 //===--- A self contained equivalent of std::mutex --------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_MUTEX_H 10 #define LLVM_LIBC_SRC___SUPPORT_CPP_MUTEX_H 11 12 #include "src/__support/macros/config.h" 13 14 namespace LIBC_NAMESPACE_DECL { 15 namespace cpp { 16 17 // Assume the calling thread has already obtained mutex ownership. 18 struct adopt_lock_t { 19 explicit adopt_lock_t() = default; 20 }; 21 22 // Tag used to make a scoped lock take ownership of a locked mutex. 23 constexpr adopt_lock_t adopt_lock{}; 24 25 // An RAII class for easy locking and unlocking of mutexes. 26 template <typename MutexType> class lock_guard { 27 MutexType &mutex; 28 29 public: 30 // Calls `m.lock()` upon resource acquisition. lock_guard(MutexType & m)31 explicit lock_guard(MutexType &m) : mutex(m) { mutex.lock(); } 32 33 // Acquires ownership of the mutex object `m` without attempting to lock 34 // it. The behavior is undefined if the current thread does not hold the 35 // lock on `m`. Does not call `m.lock()` upon resource acquisition. lock_guard(MutexType & m,adopt_lock_t)36 lock_guard(MutexType &m, adopt_lock_t /* t */) : mutex(m) {} 37 ~lock_guard()38 ~lock_guard() { mutex.unlock(); } 39 40 // non-copyable 41 lock_guard &operator=(const lock_guard &) = delete; 42 lock_guard(const lock_guard &) = delete; 43 }; 44 45 // Deduction guide for lock_guard to suppress CTAD warnings. 46 template <typename T> lock_guard(T &) -> lock_guard<T>; 47 48 } // namespace cpp 49 } // namespace LIBC_NAMESPACE_DECL 50 51 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_MUTEX_H 52