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77 lines
2.4 KiB
C++
77 lines
2.4 KiB
C++
//===--- ThreadSafeRefCounted.h - Thread-safe Refcounting Base --*- 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 - 2015 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 http://swift.org/LICENSE.txt for license information
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// See http://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_THREADSAFEREFCOUNTED_H
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#define SWIFT_BASIC_THREADSAFEREFCOUNTED_H
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#include "llvm/Support/Atomic.h"
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#include <cassert>
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namespace swift {
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/// A thread-safe version of \c llvm::RefCountedBase.
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///
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/// A generic base class for objects that wish to have their lifetimes managed
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/// using reference counts. Classes subclass \c ThreadSafeRefCountedBase to
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/// obtain such functionality, and are typically handled with
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/// \c IntrusiveRefCntPtr "smart pointers" which automatically handle the
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/// management of reference counts.
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/// FIXME: This should eventually move to llvm.
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template <class Derived>
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class ThreadSafeRefCountedBase {
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mutable llvm::sys::cas_flag ref_cnt;
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protected:
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ThreadSafeRefCountedBase() : ref_cnt(0) {}
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public:
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void Retain() const {
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llvm::sys::AtomicIncrement(&ref_cnt);
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}
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void Release() const {
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int refCount = static_cast<int>(llvm::sys::AtomicDecrement(&ref_cnt));
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assert(refCount >= 0 && "Reference count was already zero.");
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if (refCount == 0) delete static_cast<const Derived*>(this);
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}
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};
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/// A class that has the same function as \c ThreadSafeRefCountedBase, but with
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/// a virtual destructor.
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///
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/// Should be used instead of \c ThreadSafeRefCountedBase for classes that
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/// already have virtual methods to enforce dynamic allocation via 'new'.
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/// FIXME: This should eventually move to llvm.
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class ThreadSafeRefCountedBaseVPTR {
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mutable llvm::sys::cas_flag ref_cnt;
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virtual void anchor();
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protected:
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ThreadSafeRefCountedBaseVPTR() : ref_cnt(0) {}
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virtual ~ThreadSafeRefCountedBaseVPTR() {}
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public:
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void Retain() const {
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llvm::sys::AtomicIncrement(&ref_cnt);
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}
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void Release() const {
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int refCount = static_cast<int>(llvm::sys::AtomicDecrement(&ref_cnt));
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assert(refCount >= 0 && "Reference count was already zero.");
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if (refCount == 0) delete this;
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}
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};
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} // end namespace swift.
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#endif
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