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 
13 #include "SkRefCnt.h"
14 
15 #ifdef SK_DEBUG
16 #include "SkTHash.h"
17 #endif
18 
19 /**
20  * Allocates memory in blocks and parcels out space in the blocks for allocation
21  * requests. It is optimized for allocate / release speed over memory
22  * efficiency. The interface is designed to be used to implement operator new
23  * and delete overrides. All allocations are expected to be released before the
24  * pool's destructor is called. Allocations will be 8-byte aligned.
25  */
26 class GrMemoryPool {
27 public:
28     /**
29      * Prealloc size is the amount of space to allocate at pool creation
30      * time and keep around until pool destruction. The min alloc size is
31      * the smallest allowed size of additional allocations. Both sizes are
32      * adjusted to ensure that:
33      *   1. they are are 8-byte aligned
34      *   2. minAllocSize >= kSmallestMinAllocSize
35      *   3. preallocSize >= minAllocSize
36      *
37      * Both sizes is what the pool will end up allocating from the system, and
38      * portions of the allocated memory is used for internal bookkeeping.
39      */
40     GrMemoryPool(size_t preallocSize, size_t minAllocSize);
41 
42     ~GrMemoryPool();
43 
44     /**
45      * Allocates memory. The memory must be freed with release().
46      */
47     void* allocate(size_t size);
48 
49     /**
50      * p must have been returned by allocate()
51      */
52     void release(void* p);
53 
54     /**
55      * Returns true if there are no unreleased allocations.
56      */
isEmpty()57     bool isEmpty() const { return fTail == fHead && !fHead->fLiveCount; }
58 
59     /**
60      * Returns the total allocated size of the GrMemoryPool minus any preallocated amount
61      */
size()62     size_t size() const { return fSize; }
63 
64     /**
65      * Returns the preallocated size of the GrMemoryPool
66      */
preallocSize()67     size_t preallocSize() const { return fHead->fSize; }
68 
69     /**
70      * Minimum value of minAllocSize constructor argument.
71      */
72     constexpr static size_t kSmallestMinAllocSize = 1 << 10;
73 
74 private:
75     struct BlockHeader;
76 
77     static BlockHeader* CreateBlock(size_t size);
78 
79     static void DeleteBlock(BlockHeader* block);
80 
81     void validate();
82 
83     struct BlockHeader {
84 #ifdef SK_DEBUG
85         uint32_t     fBlockSentinal;  ///< known value to check for bad back pointers to blocks
86 #endif
87         BlockHeader* fNext;      ///< doubly-linked list of blocks.
88         BlockHeader* fPrev;
89         int          fLiveCount; ///< number of outstanding allocations in the
90                                  ///< block.
91         intptr_t     fCurrPtr;   ///< ptr to the start of blocks free space.
92         intptr_t     fPrevPtr;   ///< ptr to the last allocation made
93         size_t       fFreeSize;  ///< amount of free space left in the block.
94         size_t       fSize;      ///< total allocated size of the block
95     };
96 
97     static const uint32_t kAssignedMarker = 0xCDCDCDCD;
98     static const uint32_t kFreedMarker    = 0xEFEFEFEF;
99 
100     struct AllocHeader {
101 #ifdef SK_DEBUG
102         uint32_t fSentinal;      ///< known value to check for memory stomping (e.g., (CD)*)
103         int32_t fID;             ///< ID that can be used to track down leaks by clients.
104 #endif
105         BlockHeader* fHeader;    ///< pointer back to the block header in which an alloc resides
106     };
107 
108     size_t                            fSize;
109     size_t                            fMinAllocSize;
110     BlockHeader*                      fHead;
111     BlockHeader*                      fTail;
112 #ifdef SK_DEBUG
113     int                               fAllocationCnt;
114     int                               fAllocBlockCnt;
115     SkTHashSet<int32_t>               fAllocatedIDs;
116 #endif
117 
118 protected:
119     enum {
120         // We assume this alignment is good enough for everybody.
121         kAlignment    = 8,
122         kHeaderSize   = GR_CT_ALIGN_UP(sizeof(BlockHeader), kAlignment),
123         kPerAllocPad  = GR_CT_ALIGN_UP(sizeof(AllocHeader), kAlignment),
124     };
125 };
126 
127 class GrOp;
128 
129 // DDL TODO: for the DLL use case this could probably be the non-intrinsic-based style of
130 // ref counting
131 class GrOpMemoryPool : public SkRefCnt {
132 public:
GrOpMemoryPool(size_t preallocSize,size_t minAllocSize)133     GrOpMemoryPool(size_t preallocSize, size_t minAllocSize)
134             : fMemoryPool(preallocSize, minAllocSize) {
135     }
136 
137     template <typename Op, typename... OpArgs>
allocate(OpArgs &&...opArgs)138     std::unique_ptr<Op> allocate(OpArgs&&... opArgs) {
139         char* mem = (char*) fMemoryPool.allocate(sizeof(Op));
140         return std::unique_ptr<Op>(new (mem) Op(std::forward<OpArgs>(opArgs)...));
141     }
142 
allocate(size_t size)143     void* allocate(size_t size) {
144         return fMemoryPool.allocate(size);
145     }
146 
147     void release(std::unique_ptr<GrOp> op);
148 
isEmpty()149     bool isEmpty() const { return fMemoryPool.isEmpty(); }
150 
151 private:
152     GrMemoryPool fMemoryPool;
153 };
154 
155 #endif
156