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82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef MOZILLA_SHAREDBUFFER_H_
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#define MOZILLA_SHAREDBUFFER_H_
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#include "mozilla/CheckedInt.h"
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#include "mozilla/mozalloc.h"
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#include "nsCOMPtr.h"
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#include "nsAutoPtr.h"
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namespace mozilla {
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class AudioBlockBuffer;
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/**
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* Base class for objects with a thread-safe refcount and a virtual
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* destructor.
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*/
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class ThreadSharedObject {
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public:
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NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject)
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bool IsShared() { return mRefCnt.get() > 1; }
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virtual AudioBlockBuffer* AsAudioBlockBuffer() { return nullptr; };
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virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
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{
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return 0;
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}
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virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
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{
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return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
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}
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protected:
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// Protected destructor, to discourage deletion outside of Release():
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virtual ~ThreadSharedObject() {}
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};
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/**
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* Heap-allocated chunk of arbitrary data with threadsafe refcounting.
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* Typically you would allocate one of these, fill it in, and then treat it as
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* immutable while it's shared.
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* This only guarantees 4-byte alignment of the data. For alignment we simply
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* assume that the memory from malloc is at least 4-byte aligned and the
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* refcount's size is large enough that SharedBuffer's size is divisible by 4.
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*/
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class SharedBuffer : public ThreadSharedObject {
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public:
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void* Data() { return this + 1; }
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static already_AddRefed<SharedBuffer> Create(size_t aSize)
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{
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CheckedInt<size_t> size = sizeof(SharedBuffer);
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size += aSize;
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if (!size.isValid()) {
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MOZ_CRASH();
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}
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void* m = moz_xmalloc(size.value());
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RefPtr<SharedBuffer> p = new (m) SharedBuffer();
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NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0,
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"SharedBuffers should be at least 4-byte aligned");
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return p.forget();
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}
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size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override
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{
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return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
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}
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private:
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SharedBuffer() {}
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};
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} // namespace mozilla
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#endif /* MOZILLA_SHAREDBUFFER_H_ */
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