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30 #include "wtf/Assertions.h"
31 #include "wtf/FastMalloc.h"
32 #include "wtf/Noncopyable.h"
33 #include "wtf/OwnPtr.h"
34 #include "wtf/PassOwnPtr.h"
35 #include "wtf/RefCounted.h"
36 #include "wtf/Vector.h"
40 // An arena which allocates only Plain Old Data (POD), or classes and
41 // structs bottoming out in Plain Old Data. NOTE: the constructors of
42 // the objects allocated in this arena are called, but _not_ their
45 class PODArena FINAL : public RefCounted<PODArena> {
47 // The arena is configured with an allocator, which is responsible
48 // for allocating and freeing chunks of memory at a time.
49 class Allocator : public RefCounted<Allocator> {
51 virtual void* allocate(size_t size) = 0;
52 virtual void free(void* ptr) = 0;
54 virtual ~Allocator() { }
55 friend class WTF::RefCounted<Allocator>;
58 // The Arena's default allocator, which uses fastMalloc and
59 // fastFree to allocate chunks of storage.
60 class FastMallocAllocator : public Allocator {
62 static PassRefPtr<FastMallocAllocator> create()
64 return adoptRef(new FastMallocAllocator);
67 virtual void* allocate(size_t size) OVERRIDE { return fastMalloc(size); }
68 virtual void free(void* ptr) OVERRIDE { fastFree(ptr); }
71 FastMallocAllocator() { }
74 // Creates a new PODArena configured with a FastMallocAllocator.
75 static PassRefPtr<PODArena> create()
77 return adoptRef(new PODArena);
80 // Creates a new PODArena configured with the given Allocator.
81 static PassRefPtr<PODArena> create(PassRefPtr<Allocator> allocator)
83 return adoptRef(new PODArena(allocator));
86 // Allocates an object from the arena.
87 template<class T> T* allocateObject()
89 return new (allocateBase<T>()) T();
92 // Allocates an object from the arena, calling a single-argument constructor.
93 template<class T, class Argument1Type> T* allocateObject(const Argument1Type& argument1)
95 return new (allocateBase<T>()) T(argument1);
98 // The initial size of allocated chunks; increases as necessary to
99 // satisfy large allocations. Mainly public for unit tests.
101 DefaultChunkSize = 16384
105 friend class WTF::RefCounted<PODArena>;
108 : m_allocator(FastMallocAllocator::create())
110 , m_currentChunkSize(DefaultChunkSize) { }
112 explicit PODArena(PassRefPtr<Allocator> allocator)
113 : m_allocator(allocator)
115 , m_currentChunkSize(DefaultChunkSize) { }
117 // Returns the alignment requirement for classes and structs on the
119 template <class T> static size_t minAlignment()
121 return WTF_ALIGN_OF(T);
124 template<class T> void* allocateBase()
127 size_t roundedSize = roundUp(sizeof(T), minAlignment<T>());
129 ptr = m_current->allocate(roundedSize);
132 if (roundedSize > m_currentChunkSize)
133 m_currentChunkSize = roundedSize;
134 m_chunks.append(adoptPtr(new Chunk(m_allocator.get(), m_currentChunkSize)));
135 m_current = m_chunks.last().get();
136 ptr = m_current->allocate(roundedSize);
141 // Rounds up the given allocation size to the specified alignment.
142 size_t roundUp(size_t size, size_t alignment)
144 ASSERT(!(alignment % 2));
145 return (size + alignment - 1) & ~(alignment - 1);
148 // Manages a chunk of memory and individual allocations out of it.
150 WTF_MAKE_NONCOPYABLE(Chunk);
152 // Allocates a block of memory of the given size from the passed
154 Chunk(Allocator* allocator, size_t size)
155 : m_allocator(allocator)
159 m_base = static_cast<uint8_t*>(m_allocator->allocate(size));
162 // Frees the memory allocated from the Allocator in the
166 m_allocator->free(m_base);
169 // Returns a pointer to "size" bytes of storage, or 0 if this
170 // Chunk could not satisfy the allocation.
171 void* allocate(size_t size)
173 // Check for overflow
174 if (m_currentOffset + size < m_currentOffset)
177 if (m_currentOffset + size > m_size)
180 void* result = m_base + m_currentOffset;
181 m_currentOffset += size;
186 Allocator* m_allocator;
189 size_t m_currentOffset;
192 RefPtr<Allocator> m_allocator;
194 size_t m_currentChunkSize;
195 Vector<OwnPtr<Chunk> > m_chunks;