Line data Source code
1 : /*
2 : * Copyright 2012 Google Inc.
3 : *
4 : * Use of this source code is governed by a BSD-style license that can be
5 : * found in the LICENSE file.
6 : */
7 :
8 : #ifndef GrMemoryPool_DEFINED
9 : #define GrMemoryPool_DEFINED
10 :
11 : #include "GrTypes.h"
12 : #ifdef SK_DEBUG
13 : #include "SkTHash.h"
14 : #endif
15 :
16 : /**
17 : * Allocates memory in blocks and parcels out space in the blocks for allocation
18 : * requests. It is optimized for allocate / release speed over memory
19 : * efficiency. The interface is designed to be used to implement operator new
20 : * and delete overrides. All allocations are expected to be released before the
21 : * pool's destructor is called. Allocations will be 8-byte aligned.
22 : */
23 : class GrMemoryPool {
24 : public:
25 : /**
26 : * Prealloc size is the amount of space to allocate at pool creation
27 : * time and keep around until pool destruction. The min alloc size is
28 : * the smallest allowed size of additional allocations. Both sizes are
29 : * adjusted to ensure that:
30 : * 1. they are are 8-byte aligned
31 : * 2. minAllocSize >= kSmallestMinAllocSize
32 : * 3. preallocSize >= minAllocSize
33 : *
34 : * Both sizes is what the pool will end up allocating from the system, and
35 : * portions of the allocated memory is used for internal bookkeeping.
36 : */
37 : GrMemoryPool(size_t preallocSize, size_t minAllocSize);
38 :
39 : ~GrMemoryPool();
40 :
41 : /**
42 : * Allocates memory. The memory must be freed with release().
43 : */
44 : void* allocate(size_t size);
45 :
46 : /**
47 : * p must have been returned by allocate()
48 : */
49 : void release(void* p);
50 :
51 : /**
52 : * Returns true if there are no unreleased allocations.
53 : */
54 0 : bool isEmpty() const { return fTail == fHead && !fHead->fLiveCount; }
55 :
56 : /**
57 : * Returns the total allocated size of the GrMemoryPool minus any preallocated amount
58 : */
59 0 : size_t size() const { return fSize; }
60 :
61 : /**
62 : * Returns the preallocated size of the GrMemoryPool
63 : */
64 : size_t preallocSize() const { return fHead->fSize; }
65 :
66 : /**
67 : * Minimum value of minAllocSize constructor argument.
68 : */
69 : constexpr static size_t kSmallestMinAllocSize = 1 << 10;
70 :
71 : private:
72 : struct BlockHeader;
73 :
74 : static BlockHeader* CreateBlock(size_t size);
75 :
76 : static void DeleteBlock(BlockHeader* block);
77 :
78 : void validate();
79 :
80 : struct BlockHeader {
81 : #ifdef SK_DEBUG
82 : uint32_t fBlockSentinal; ///< known value to check for bad back pointers to blocks
83 : #endif
84 : BlockHeader* fNext; ///< doubly-linked list of blocks.
85 : BlockHeader* fPrev;
86 : int fLiveCount; ///< number of outstanding allocations in the
87 : ///< block.
88 : intptr_t fCurrPtr; ///< ptr to the start of blocks free space.
89 : intptr_t fPrevPtr; ///< ptr to the last allocation made
90 : size_t fFreeSize; ///< amount of free space left in the block.
91 : size_t fSize; ///< total allocated size of the block
92 : };
93 :
94 : static const uint32_t kAssignedMarker = 0xCDCDCDCD;
95 : static const uint32_t kFreedMarker = 0xEFEFEFEF;
96 :
97 : struct AllocHeader {
98 : #ifdef SK_DEBUG
99 : uint32_t fSentinal; ///< known value to check for memory stomping (e.g., (CD)*)
100 : int32_t fID; ///< ID that can be used to track down leaks by clients.
101 : #endif
102 : BlockHeader* fHeader; ///< pointer back to the block header in which an alloc resides
103 : };
104 :
105 : size_t fSize;
106 : size_t fMinAllocSize;
107 : BlockHeader* fHead;
108 : BlockHeader* fTail;
109 : #ifdef SK_DEBUG
110 : int fAllocationCnt;
111 : int fAllocBlockCnt;
112 : SkTHashSet<int32_t> fAllocatedIDs;
113 : #endif
114 :
115 : protected:
116 : enum {
117 : // We assume this alignment is good enough for everybody.
118 : kAlignment = 8,
119 : kHeaderSize = GR_CT_ALIGN_UP(sizeof(BlockHeader), kAlignment),
120 : kPerAllocPad = GR_CT_ALIGN_UP(sizeof(AllocHeader), kAlignment),
121 : };
122 : };
123 :
124 : /**
125 : * Variant of GrMemoryPool that can only allocate objects of a single type. It is
126 : * not as flexible as GrMemoryPool, but it has more convenient allocate() method,
127 : * and more importantly, it guarantees number of objects that are preallocated at
128 : * construction or when adding a new memory block. I.e.
129 : *
130 : * GrMemoryPool pool(3 * sizeof(T), 1000 * sizeof(T));
131 : * pool.allocate(sizeof(T));
132 : * pool.allocate(sizeof(T));
133 : * pool.allocate(sizeof(T));
134 : *
135 : * will preallocate 3 * sizeof(T) bytes and use some of those bytes for internal
136 : * structures. Because of that, last allocate() call will end up allocating a new
137 : * block of 1000 * sizeof(T) bytes. In contrast,
138 : *
139 : * GrObjectMemoryPool<T> pool(3, 1000);
140 : * pool.allocate();
141 : * pool.allocate();
142 : * pool.allocate();
143 : *
144 : * guarantees to preallocate enough memory for 3 objects of sizeof(T), so last
145 : * allocate() will use preallocated memory and won't cause allocation of a new block.
146 : *
147 : * Same thing is true for the second (minAlloc) ctor argument: this class guarantees
148 : * that a newly added block will have enough space for 1000 objects of sizeof(T), while
149 : * GrMemoryPool does not.
150 : */
151 : template <class T>
152 0 : class GrObjectMemoryPool: public GrMemoryPool {
153 : public:
154 : /**
155 : * Preallocates memory for preallocCount objects, and sets new block size to be
156 : * enough to hold minAllocCount objects.
157 : */
158 0 : GrObjectMemoryPool(size_t preallocCount, size_t minAllocCount)
159 : : GrMemoryPool(CountToSize(preallocCount),
160 0 : CountToSize(SkTMax(minAllocCount, kSmallestMinAllocCount))) {
161 0 : }
162 :
163 : /**
164 : * Allocates memory for an object, but doesn't construct or otherwise initialize it.
165 : * The memory must be freed with release().
166 : */
167 0 : T* allocate() { return static_cast<T*>(GrMemoryPool::allocate(sizeof(T))); }
168 :
169 : private:
170 : constexpr static size_t kTotalObjectSize =
171 : kPerAllocPad + GR_CT_ALIGN_UP(sizeof(T), kAlignment);
172 :
173 0 : constexpr static size_t CountToSize(size_t count) {
174 0 : return kHeaderSize + count * kTotalObjectSize;
175 : }
176 :
177 : public:
178 : /**
179 : * Minimum value of minAllocCount constructor argument.
180 : */
181 : constexpr static size_t kSmallestMinAllocCount =
182 : (GrMemoryPool::kSmallestMinAllocSize - kHeaderSize + kTotalObjectSize - 1) /
183 : kTotalObjectSize;
184 : };
185 :
186 : template <class T>
187 : constexpr size_t GrObjectMemoryPool<T>::kSmallestMinAllocCount;
188 :
189 : #endif
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