1/*
2 * Copyright (C) 2011 Apple Inc.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef PODFreeListArena_h
27#define PODFreeListArena_h
28
29#include "platform/PODArena.h"
30
31namespace blink {
32
33template <class T>
34class PODFreeListArena : public RefCounted<PODFreeListArena<T> > {
35public:
36    static PassRefPtr<PODFreeListArena> create()
37    {
38        return adoptRef(new PODFreeListArena);
39    }
40
41    // Creates a new PODFreeListArena configured with the given Allocator.
42    static PassRefPtr<PODFreeListArena> create(PassRefPtr<PODArena::Allocator> allocator)
43    {
44        return adoptRef(new PODFreeListArena(allocator));
45    }
46
47    // Allocates an object from the arena.
48    T* allocateObject()
49    {
50        void* ptr = allocateFromFreeList();
51
52        if (ptr) {
53            // Use placement operator new to allocate a T at this location.
54            new(ptr) T();
55            return static_cast<T*>(ptr);
56        }
57
58        // PODArena::allocateObject calls T's constructor.
59        return static_cast<T*>(m_arena->allocateObject<T>());
60    }
61
62    template<class Argument1Type> T* allocateObject(const Argument1Type& argument1)
63    {
64        void* ptr = allocateFromFreeList();
65
66        if (ptr) {
67            // Use placement operator new to allocate a T at this location.
68            new(ptr) T(argument1);
69            return static_cast<T*>(ptr);
70        }
71
72        // PODArena::allocateObject calls T's constructor.
73        return static_cast<T*>(m_arena->allocateObject<T>(argument1));
74    }
75
76    void freeObject(T* ptr)
77    {
78        FixedSizeMemoryChunk* oldFreeList = m_freeList;
79
80        m_freeList = reinterpret_cast<FixedSizeMemoryChunk*>(ptr);
81        m_freeList->next = oldFreeList;
82    }
83
84private:
85    PODFreeListArena()
86        : m_arena(PODArena::create()), m_freeList(0) { }
87
88    explicit PODFreeListArena(PassRefPtr<PODArena::Allocator> allocator)
89        : m_arena(PODArena::create(allocator)), m_freeList(0) { }
90
91    ~PODFreeListArena() { }
92
93    void* allocateFromFreeList()
94    {
95        if (m_freeList) {
96            void* memory = m_freeList;
97            m_freeList = m_freeList->next;
98            return memory;
99        }
100        return 0;
101    }
102
103    int getFreeListSizeForTesting() const
104    {
105        int total = 0;
106        for (FixedSizeMemoryChunk* cur = m_freeList; cur; cur = cur->next) {
107            total++;
108        }
109        return total;
110    }
111
112    RefPtr<PODArena> m_arena;
113
114    // This free list contains pointers within every chunk that's been allocated so
115    // far. None of the individual chunks can be freed until the arena is
116    // destroyed.
117    struct FixedSizeMemoryChunk {
118        FixedSizeMemoryChunk* next;
119    };
120    FixedSizeMemoryChunk* m_freeList;
121
122    COMPILE_ASSERT(sizeof(T) >= sizeof(FixedSizeMemoryChunk), PODFreeListArena_type_should_be_larger);
123
124    friend class WTF::RefCounted<PODFreeListArena>;
125    friend class PODFreeListArenaTest;
126};
127
128} // namespace blink
129
130#endif
131