content/media/SharedBuffer.h@97036ab72558 (annotated)
content/media/SharedBuffer.h
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| michael@0 | 2 | /* This Source Code Form is subject to the terms of the Mozilla Public |
| michael@0 | 3 | * License, v. 2.0. If a copy of the MPL was not distributed with this file, |
| michael@0 | 4 | * You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| michael@0 | 5 | |
| michael@0 | 6 | #ifndef MOZILLA_SHAREDBUFFER_H_ |
| michael@0 | 7 | #define MOZILLA_SHAREDBUFFER_H_ |
| michael@0 | 8 | |
| michael@0 | 9 | #include "mozilla/CheckedInt.h" |
| michael@0 | 10 | #include "mozilla/mozalloc.h" |
| michael@0 | 11 | #include "nsCOMPtr.h" |
| michael@0 | 12 | #include "nsAutoPtr.h" |
| michael@0 | 13 | |
| michael@0 | 14 | namespace mozilla { |
| michael@0 | 15 | |
| michael@0 | 16 | /** |
| michael@0 | 17 | * Base class for objects with a thread-safe refcount and a virtual |
| michael@0 | 18 | * destructor. |
| michael@0 | 19 | */ |
| michael@0 | 20 | class ThreadSharedObject { |
| michael@0 | 21 | public: |
| michael@0 | 22 | NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject) |
| michael@0 | 23 | |
| michael@0 | 24 | bool IsShared() { return mRefCnt.get() > 1; } |
| michael@0 | 25 | |
| michael@0 | 26 | virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const |
| michael@0 | 27 | { |
| michael@0 | 28 | return 0; |
| michael@0 | 29 | } |
| michael@0 | 30 | |
| michael@0 | 31 | virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const |
| michael@0 | 32 | { |
| michael@0 | 33 | return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); |
| michael@0 | 34 | } |
| michael@0 | 35 | protected: |
| michael@0 | 36 | // Protected destructor, to discourage deletion outside of Release(): |
| michael@0 | 37 | virtual ~ThreadSharedObject() {} |
| michael@0 | 38 | }; |
| michael@0 | 39 | |
| michael@0 | 40 | /** |
| michael@0 | 41 | * Heap-allocated chunk of arbitrary data with threadsafe refcounting. |
| michael@0 | 42 | * Typically you would allocate one of these, fill it in, and then treat it as |
| michael@0 | 43 | * immutable while it's shared. |
| michael@0 | 44 | * This only guarantees 4-byte alignment of the data. For alignment we |
| michael@0 | 45 | * simply assume that the refcount is at least 4-byte aligned and its size |
| michael@0 | 46 | * is divisible by 4. |
| michael@0 | 47 | */ |
| michael@0 | 48 | class SharedBuffer : public ThreadSharedObject { |
| michael@0 | 49 | public: |
| michael@0 | 50 | void* Data() { return this + 1; } |
| michael@0 | 51 | |
| michael@0 | 52 | static already_AddRefed<SharedBuffer> Create(size_t aSize) |
| michael@0 | 53 | { |
| michael@0 | 54 | CheckedInt<size_t> size = sizeof(SharedBuffer); |
| michael@0 | 55 | size += aSize; |
| michael@0 | 56 | if (!size.isValid()) { |
| michael@0 | 57 | MOZ_CRASH(); |
| michael@0 | 58 | } |
| michael@0 | 59 | void* m = moz_xmalloc(size.value()); |
| michael@0 | 60 | nsRefPtr<SharedBuffer> p = new (m) SharedBuffer(); |
| michael@0 | 61 | NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0, |
| michael@0 | 62 | "SharedBuffers should be at least 4-byte aligned"); |
| michael@0 | 63 | return p.forget(); |
| michael@0 | 64 | } |
| michael@0 | 65 | |
| michael@0 | 66 | virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const MOZ_OVERRIDE |
| michael@0 | 67 | { |
| michael@0 | 68 | return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); |
| michael@0 | 69 | } |
| michael@0 | 70 | |
| michael@0 | 71 | private: |
| michael@0 | 72 | SharedBuffer() {} |
| michael@0 | 73 | }; |
| michael@0 | 74 | |
| michael@0 | 75 | } |
| michael@0 | 76 | |
| michael@0 | 77 | #endif /* MOZILLA_SHAREDBUFFER_H_ */ |
