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 "nsCOMPtr.h" 12 13 namespace mozilla { 14 15 class AudioBlockBuffer; 16 17 /** 18 * Base class for objects with a thread-safe refcount and a virtual 19 * destructor. 20 */ 21 class ThreadSharedObject { 22 public: NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject)23 NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadSharedObject) 24 25 bool IsShared() { return mRefCnt.get() > 1; } 26 AsAudioBlockBuffer()27 virtual AudioBlockBuffer* AsAudioBlockBuffer() { return nullptr; }; 28 SizeOfExcludingThis(MallocSizeOf aMallocSizeOf)29 virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const 30 { 31 return 0; 32 } 33 SizeOfIncludingThis(MallocSizeOf aMallocSizeOf)34 virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const 35 { 36 return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); 37 } 38 protected: 39 // Protected destructor, to discourage deletion outside of Release(): ~ThreadSharedObject()40 virtual ~ThreadSharedObject() {} 41 }; 42 43 /** 44 * Heap-allocated chunk of arbitrary data with threadsafe refcounting. 45 * Typically you would allocate one of these, fill it in, and then treat it as 46 * immutable while it's shared. 47 * This only guarantees 4-byte alignment of the data. For alignment we simply 48 * assume that the memory from malloc is at least 4-byte aligned and the 49 * refcount's size is large enough that SharedBuffer's size is divisible by 4. 50 */ 51 class SharedBuffer : public ThreadSharedObject { 52 public: Data()53 void* Data() { return this + 1; } 54 Create(size_t aSize)55 static already_AddRefed<SharedBuffer> Create(size_t aSize) 56 { 57 CheckedInt<size_t> size = sizeof(SharedBuffer); 58 size += aSize; 59 if (!size.isValid()) { 60 MOZ_CRASH(); 61 } 62 void* m = moz_xmalloc(size.value()); 63 RefPtr<SharedBuffer> p = new (m) SharedBuffer(); 64 NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0, 65 "SharedBuffers should be at least 4-byte aligned"); 66 return p.forget(); 67 } 68 SizeOfIncludingThis(MallocSizeOf aMallocSizeOf)69 size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override 70 { 71 return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf); 72 } 73 74 private: SharedBuffer()75 SharedBuffer() {} 76 }; 77 78 } // namespace mozilla 79 80 #endif /* MOZILLA_SHAREDBUFFER_H_ */ 81