1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/SharedBuffer.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,77 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this file,
1.7 + * You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef MOZILLA_SHAREDBUFFER_H_
1.10 +#define MOZILLA_SHAREDBUFFER_H_
1.11 +
1.12 +#include "mozilla/CheckedInt.h"
1.13 +#include "mozilla/mozalloc.h"
1.14 +#include "nsCOMPtr.h"
1.15 +#include "nsAutoPtr.h"
1.16 +
1.17 +namespace mozilla {
1.18 +
1.19 +/**
1.20 + * Base class for objects with a thread-safe refcount and a virtual
1.21 + * destructor.
1.22 + */
1.23 +class ThreadSharedObject {
1.24 +public:
1.25 + NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject)
1.26 +
1.27 + bool IsShared() { return mRefCnt.get() > 1; }
1.28 +
1.29 + virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
1.30 + {
1.31 + return 0;
1.32 + }
1.33 +
1.34 + virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
1.35 + {
1.36 + return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
1.37 + }
1.38 +protected:
1.39 + // Protected destructor, to discourage deletion outside of Release():
1.40 + virtual ~ThreadSharedObject() {}
1.41 +};
1.42 +
1.43 +/**
1.44 + * Heap-allocated chunk of arbitrary data with threadsafe refcounting.
1.45 + * Typically you would allocate one of these, fill it in, and then treat it as
1.46 + * immutable while it's shared.
1.47 + * This only guarantees 4-byte alignment of the data. For alignment we
1.48 + * simply assume that the refcount is at least 4-byte aligned and its size
1.49 + * is divisible by 4.
1.50 + */
1.51 +class SharedBuffer : public ThreadSharedObject {
1.52 +public:
1.53 + void* Data() { return this + 1; }
1.54 +
1.55 + static already_AddRefed<SharedBuffer> Create(size_t aSize)
1.56 + {
1.57 + CheckedInt<size_t> size = sizeof(SharedBuffer);
1.58 + size += aSize;
1.59 + if (!size.isValid()) {
1.60 + MOZ_CRASH();
1.61 + }
1.62 + void* m = moz_xmalloc(size.value());
1.63 + nsRefPtr<SharedBuffer> p = new (m) SharedBuffer();
1.64 + NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0,
1.65 + "SharedBuffers should be at least 4-byte aligned");
1.66 + return p.forget();
1.67 + }
1.68 +
1.69 + virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const MOZ_OVERRIDE
1.70 + {
1.71 + return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
1.72 + }
1.73 +
1.74 +private:
1.75 + SharedBuffer() {}
1.76 +};
1.77 +
1.78 +}
1.79 +
1.80 +#endif /* MOZILLA_SHAREDBUFFER_H_ */
