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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 MOZILLA_SHAREDBUFFER_H_
#define MOZILLA_SHAREDBUFFER_H_
#include "mozilla/CheckedInt.h"
#include "mozilla/mozalloc.h"
#include "mozilla/MemoryReporting.h"
#include "nsISupportsImpl.h"
namespace mozilla {
class AudioBlockBuffer;
class ThreadSharedFloatArrayBufferList;
/**
* Base class for objects with a thread-safe refcount and a virtual
* destructor.
*/
class ThreadSharedObject {
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject)
bool IsShared() { return mRefCnt.get() > 1; }
virtual AudioBlockBuffer* AsAudioBlockBuffer() { return nullptr; };
virtual ThreadSharedFloatArrayBufferList*
AsThreadSharedFloatArrayBufferList() {
return nullptr;
};
virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
return 0;
}
virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
}
protected:
// Protected destructor, to discourage deletion outside of Release():
virtual ~ThreadSharedObject() = default;
};
/**
* Heap-allocated chunk of arbitrary data with threadsafe refcounting.
* Typically you would allocate one of these, fill it in, and then treat it as
* immutable while it's shared.
* This only guarantees 4-byte alignment of the data. For alignment we simply
* assume that the memory from malloc is at least 4-byte aligned and the
* refcount's size is large enough that SharedBuffer's size is divisible by 4.
*/
class SharedBuffer : public ThreadSharedObject {
public:
void* Data() { return this + 1; }
// Ensure that the caller has a CheckedInt. We have to take one by
// non-const reference to do that, because if we take one by const
// reference or value or rvalue reference the implicit constructor on
// CheckedInt will helpfully synthesize one for us at the callsite
// even if the caller passes a raw size_t.
static already_AddRefed<SharedBuffer> Create(CheckedInt<size_t>& aSize,
const fallible_t&) {
CheckedInt<size_t> allocSize = AllocSize(aSize, fallible);
if (!allocSize.isValid()) {
return nullptr;
}
void* m = operator new(allocSize.value(), fallible);
if (!m) {
return nullptr;
}
RefPtr<SharedBuffer> p = new (m) SharedBuffer();
return p.forget();
}
static already_AddRefed<SharedBuffer> Create(CheckedInt<size_t>& aSize) {
void* m = operator new(AllocSize(aSize));
RefPtr<SharedBuffer> p = new (m) SharedBuffer();
return p.forget();
}
size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override {
return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
}
private:
static CheckedInt<size_t> AllocSize(CheckedInt<size_t> aDataSize,
const fallible_t&) {
CheckedInt<size_t> size = sizeof(SharedBuffer);
size += aDataSize;
return size;
}
static size_t AllocSize(CheckedInt<size_t> aDataSize) {
CheckedInt<size_t> size = AllocSize(aDataSize, fallible);
if (!size.isValid()) {
MOZ_CRASH();
}
return size.value();
}
SharedBuffer() {
NS_ASSERTION(
(reinterpret_cast<char*>(this + 1) - reinterpret_cast<char*>(this)) %
4 ==
0,
"SharedBuffers should be at least 4-byte aligned");
}
};
} // namespace mozilla
#endif /* MOZILLA_SHAREDBUFFER_H_ */
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