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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
| commit | 0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d (patch) | |
| tree | a31f07c9bcca9d56ce61e9a1ffd30ef350d513aa /xpcom/threads/DataMutex.h | |
| parent | Initial commit. (diff) | |
| download | firefox-esr-upstream/115.8.0esr.tar.xz firefox-esr-upstream/115.8.0esr.zip | |
Adding upstream version 115.8.0esr.upstream/115.8.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'xpcom/threads/DataMutex.h')
| -rw-r--r-- | xpcom/threads/DataMutex.h | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/xpcom/threads/DataMutex.h b/xpcom/threads/DataMutex.h new file mode 100644 index 0000000000..44f0a35762 --- /dev/null +++ b/xpcom/threads/DataMutex.h @@ -0,0 +1,130 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this file, + * You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef DataMutex_h__ +#define DataMutex_h__ + +#include <utility> +#include "mozilla/Mutex.h" +#include "mozilla/StaticMutex.h" + +namespace mozilla { + +// A template to wrap a type with a mutex so that accesses to the type's +// data are required to take the lock before accessing it. This ensures +// that a mutex is explicitly associated with the data that it protects, +// and makes it impossible to access the data without first taking the +// associated mutex. +// +// This is based on Rust's std::sync::Mutex, which operates under the +// strategy of locking data, rather than code. +// +// Examples: +// +// DataMutex<uint32_t> u32DataMutex(1, "u32DataMutex"); +// auto x = u32DataMutex.Lock(); +// *x = 4; +// assert(*x, 4u); +// +// DataMutex<nsTArray<uint32_t>> arrayDataMutex("arrayDataMutex"); +// auto a = arrayDataMutex.Lock(); +// auto& x = a.ref(); +// x.AppendElement(1u); +// assert(x[0], 1u); +// +template <typename T, typename MutexType> +class DataMutexBase { + public: + template <typename V> + class MOZ_STACK_CLASS AutoLockBase { + public: + V* operator->() const& { return &ref(); } + V* operator->() const&& = delete; + + V& operator*() const& { return ref(); } + V& operator*() const&& = delete; + + // Like RefPtr, make this act like its underlying raw pointer type + // whenever it is used in a context where a raw pointer is expected. + operator V*() const& { return &ref(); } + + // Like RefPtr, don't allow implicit conversion of temporary to raw pointer. + operator V*() const&& = delete; + + V& ref() const& { + MOZ_ASSERT(mOwner); + return mOwner->mValue; + } + V& ref() const&& = delete; + + AutoLockBase(AutoLockBase&& aOther) : mOwner(aOther.mOwner) { + aOther.mOwner = nullptr; + } + + ~AutoLockBase() { + if (mOwner) { + mOwner->mMutex.Unlock(); + mOwner = nullptr; + } + } + + private: + friend class DataMutexBase; + + AutoLockBase(const AutoLockBase& aOther) = delete; + + explicit AutoLockBase(DataMutexBase<T, MutexType>* aDataMutex) + : mOwner(aDataMutex) { + MOZ_ASSERT(!!mOwner); + mOwner->mMutex.Lock(); + } + + DataMutexBase<T, MutexType>* mOwner; + }; + + using AutoLock = AutoLockBase<T>; + using ConstAutoLock = AutoLockBase<const T>; + + explicit DataMutexBase(const char* aName) : mMutex(aName) {} + + DataMutexBase(T&& aValue, const char* aName) + : mMutex(aName), mValue(std::move(aValue)) {} + + AutoLock Lock() { return AutoLock(this); } + ConstAutoLock ConstLock() { return ConstAutoLock(this); } + + const MutexType& Mutex() const { return mMutex; } + + private: + MutexType mMutex; + T mValue; +}; + +// Craft a version of StaticMutex that takes a const char* in its ctor. +// We need this so it works interchangeably with Mutex which requires a const +// char* aName in its ctor. +class StaticMutexNameless : public StaticMutex { + public: + explicit StaticMutexNameless(const char* aName) : StaticMutex() {} + + private: + // Disallow copy construction, `=`, `new`, and `delete` like BaseStaticMutex. +#ifdef DEBUG + StaticMutexNameless(StaticMutexNameless& aOther); +#endif // DEBUG + StaticMutexNameless& operator=(StaticMutexNameless* aRhs); + static void* operator new(size_t) noexcept(true); + static void operator delete(void*); +}; + +template <typename T> +using DataMutex = DataMutexBase<T, Mutex>; +template <typename T> +using StaticDataMutex = DataMutexBase<T, StaticMutexNameless>; + +} // namespace mozilla + +#endif // DataMutex_h__ |