69 lines
2.1 KiB
C
69 lines
2.1 KiB
C
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#pragma once
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/**
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* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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* SPDX-License-Identifier: Apache-2.0.
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*/
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#include <aws/common/assert.h>
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#include <memory>
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#include <mutex>
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namespace Aws
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{
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namespace Crt
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{
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/**
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* Inherit from RefCounted to allow reference-counting from C code,
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* which will keep your C++ object alive as long as the count is non-zero.
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*
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* A class must inherit from RefCounted and std::enable_shared_from_this.
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* Your class must always be placed inside a shared_ptr (do not create on
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* the stack, or keep on the heap as a raw pointer).
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*
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* Whenever the reference count goes from 0 to 1 a shared_ptr is created
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* internally to keep this object alive. Whenever the reference count
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* goes from 1 to 0 the internal shared_ptr is reset, allowing this object
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* to be destroyed.
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*/
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template <class T> class RefCounted
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{
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protected:
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RefCounted() {}
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~RefCounted() {}
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void AcquireRef()
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{
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m_mutex.lock();
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if (m_count++ == 0)
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{
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m_strongPtr = static_cast<T *>(this)->shared_from_this();
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}
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m_mutex.unlock();
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}
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void ReleaseRef()
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{
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// Move contents of m_strongPtr to a temp so that this
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// object can't be destroyed until the function exits.
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std::shared_ptr<T> tmpStrongPtr;
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m_mutex.lock();
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AWS_ASSERT(m_count > 0 && "refcount has gone negative");
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if (m_count-- == 1)
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{
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std::swap(m_strongPtr, tmpStrongPtr);
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}
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m_mutex.unlock();
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}
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private:
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RefCounted(const RefCounted &) = delete;
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RefCounted &operator=(const RefCounted &) = delete;
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size_t m_count = 0;
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std::shared_ptr<T> m_strongPtr;
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std::mutex m_mutex;
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};
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} // namespace Crt
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} // namespace Aws
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