/src/mozilla-central/dom/media/SharedBuffer.h
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1 | | /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
2 | | /* This Source Code Form is subject to the terms of the Mozilla Public |
3 | | * License, v. 2.0. If a copy of the MPL was not distributed with this file, |
4 | | * You can obtain one at http://mozilla.org/MPL/2.0/. */ |
5 | | |
6 | | #ifndef MOZILLA_SHAREDBUFFER_H_ |
7 | | #define MOZILLA_SHAREDBUFFER_H_ |
8 | | |
9 | | #include "mozilla/CheckedInt.h" |
10 | | #include "mozilla/mozalloc.h" |
11 | | #include "mozilla/MemoryReporting.h" |
12 | | #include "nsISupportsImpl.h" |
13 | | |
14 | | namespace mozilla { |
15 | | |
16 | | class AudioBlockBuffer; |
17 | | class ThreadSharedFloatArrayBufferList; |
18 | | |
19 | | /** |
20 | | * Base class for objects with a thread-safe refcount and a virtual |
21 | | * destructor. |
22 | | */ |
23 | | class ThreadSharedObject { |
24 | | public: |
25 | | NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject) |
26 | | |
27 | 0 | bool IsShared() { return mRefCnt.get() > 1; } |
28 | | |
29 | 0 | virtual AudioBlockBuffer* AsAudioBlockBuffer() { return nullptr; }; |
30 | | virtual ThreadSharedFloatArrayBufferList* AsThreadSharedFloatArrayBufferList() |
31 | 0 | { |
32 | 0 | return nullptr; |
33 | 0 | }; |
34 | | |
35 | | virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const |
36 | 0 | { |
37 | 0 | return 0; |
38 | 0 | } |
39 | | |
40 | | virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const |
41 | 0 | { |
42 | 0 | return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); |
43 | 0 | } |
44 | | protected: |
45 | | // Protected destructor, to discourage deletion outside of Release(): |
46 | 0 | virtual ~ThreadSharedObject() {} |
47 | | }; |
48 | | |
49 | | /** |
50 | | * Heap-allocated chunk of arbitrary data with threadsafe refcounting. |
51 | | * Typically you would allocate one of these, fill it in, and then treat it as |
52 | | * immutable while it's shared. |
53 | | * This only guarantees 4-byte alignment of the data. For alignment we simply |
54 | | * assume that the memory from malloc is at least 4-byte aligned and the |
55 | | * refcount's size is large enough that SharedBuffer's size is divisible by 4. |
56 | | */ |
57 | | class SharedBuffer : public ThreadSharedObject { |
58 | | public: |
59 | 0 | void* Data() { return this + 1; } |
60 | | |
61 | | static already_AddRefed<SharedBuffer> Create(size_t aSize, const fallible_t&) |
62 | 0 | { |
63 | 0 | void* m = operator new(AllocSize(aSize), fallible); |
64 | 0 | if (!m) { |
65 | 0 | return nullptr; |
66 | 0 | } |
67 | 0 | RefPtr<SharedBuffer> p = new (m) SharedBuffer(); |
68 | 0 | return p.forget(); |
69 | 0 | } |
70 | | |
71 | | static already_AddRefed<SharedBuffer> Create(size_t aSize) |
72 | 0 | { |
73 | 0 | void* m = operator new(AllocSize(aSize)); |
74 | 0 | RefPtr<SharedBuffer> p = new (m) SharedBuffer(); |
75 | 0 | return p.forget(); |
76 | 0 | } |
77 | | |
78 | | size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override |
79 | 0 | { |
80 | 0 | return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); |
81 | 0 | } |
82 | | |
83 | | private: |
84 | | static size_t |
85 | | AllocSize(size_t aDataSize) |
86 | 0 | { |
87 | 0 | CheckedInt<size_t> size = sizeof(SharedBuffer); |
88 | 0 | size += aDataSize; |
89 | 0 | if (!size.isValid()) { |
90 | 0 | MOZ_CRASH(); |
91 | 0 | } |
92 | 0 | return size.value(); |
93 | 0 | } |
94 | | |
95 | | SharedBuffer() |
96 | 0 | { |
97 | 0 | NS_ASSERTION((reinterpret_cast<char*>(this + 1) - reinterpret_cast<char*>(this)) % 4 == 0, |
98 | 0 | "SharedBuffers should be at least 4-byte aligned"); |
99 | 0 | } |
100 | | }; |
101 | | |
102 | | } // namespace mozilla |
103 | | |
104 | | #endif /* MOZILLA_SHAREDBUFFER_H_ */ |