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f5bdb858e0
Moved all the threading code to one place. Added explicit support for Darwin, Linux, Pthreads, C11 threads and Win32 threads, including new implementations of Once for Linux, Pthreads, C11 and Win32. rdar://90776105
91 lines
2.5 KiB
C++
91 lines
2.5 KiB
C++
//===--- Lazy.h - A lazily-initialized object -------------------*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_BASIC_LAZY_H
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#define SWIFT_BASIC_LAZY_H
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#include <memory>
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#include "swift/Basic/Malloc.h"
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#include "swift/Basic/type_traits.h"
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#include "swift/Threading/Once.h"
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namespace swift {
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/// A template for lazily-constructed, zero-initialized, leaked-on-exit
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/// global objects.
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template <class T> class Lazy {
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alignas(T) char Value[sizeof(T)] = { 0 };
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swift::once_t OnceToken = {};
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static void defaultInitCallback(void *ValueAddr) {
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::new (ValueAddr) T();
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}
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public:
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using Type = T;
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T &get(void (*initCallback)(void *) = defaultInitCallback);
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template<typename Arg1>
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T &getWithInit(Arg1 &&arg1);
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/// Get the value, assuming it must have already been initialized by this
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/// point.
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T &unsafeGetAlreadyInitialized() { return *reinterpret_cast<T *>(&Value); }
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constexpr Lazy() = default;
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T *operator->() { return &get(); }
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T &operator*() { return get(); }
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private:
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Lazy(const Lazy &) = delete;
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Lazy &operator=(const Lazy &) = delete;
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};
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template <typename T> inline T &Lazy<T>::get(void (*initCallback)(void*)) {
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static_assert(std::is_literal_type<Lazy<T>>::value,
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"Lazy<T> must be a literal type");
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swift::once(OnceToken, initCallback, &Value);
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return unsafeGetAlreadyInitialized();
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}
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template <typename T>
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template <typename Arg1> inline T &Lazy<T>::getWithInit(Arg1 &&arg1) {
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struct Data {
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void *address;
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Arg1 &&arg1;
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static void init(void *context) {
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Data *data = static_cast<Data *>(context);
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::new (data->address) T(static_cast<Arg1&&>(data->arg1));
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}
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} data{&Value, static_cast<Arg1&&>(arg1)};
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swift::once(OnceToken, &Data::init, &data);
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return unsafeGetAlreadyInitialized();
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}
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} // end namespace swift
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#define SWIFT_LAZY_CONSTANT(INITIAL_VALUE) \
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([]{ \
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using T = ::std::remove_reference<decltype(INITIAL_VALUE)>::type; \
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static ::swift::Lazy<T> TheLazy; \
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return TheLazy.get([](void *ValueAddr){ ::new(ValueAddr) T{INITIAL_VALUE}; });\
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}())
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#endif // SWIFT_BASIC_LAZY_H
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