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 #include "GrMemoryPool.h"
9
10 #ifdef SK_DEBUG
11 #define VALIDATE this->validate()
12 #else
13 #define VALIDATE
14 #endif
15
GrMemoryPool(size_t preallocSize,size_t minAllocSize)16 GrMemoryPool::GrMemoryPool(size_t preallocSize, size_t minAllocSize) {
17 SkDEBUGCODE(fAllocationCnt = 0);
18
19 minAllocSize = SkTMax<size_t>(minAllocSize, 1 << 10);
20 fMinAllocSize = GrSizeAlignUp(minAllocSize + kPerAllocPad, kAlignment),
21 fPreallocSize = GrSizeAlignUp(preallocSize + kPerAllocPad, kAlignment);
22 fPreallocSize = SkTMax(fPreallocSize, fMinAllocSize);
23
24 fHead = CreateBlock(fPreallocSize);
25 fTail = fHead;
26 fHead->fNext = NULL;
27 fHead->fPrev = NULL;
28 VALIDATE;
29 };
30
~GrMemoryPool()31 GrMemoryPool::~GrMemoryPool() {
32 VALIDATE;
33 SkASSERT(0 == fAllocationCnt);
34 SkASSERT(fHead == fTail);
35 SkASSERT(0 == fHead->fLiveCount);
36 DeleteBlock(fHead);
37 };
38
allocate(size_t size)39 void* GrMemoryPool::allocate(size_t size) {
40 VALIDATE;
41 size = GrSizeAlignUp(size, kAlignment);
42 size += kPerAllocPad;
43 if (fTail->fFreeSize < size) {
44 size_t blockSize = size;
45 blockSize = SkTMax<size_t>(blockSize, fMinAllocSize);
46 BlockHeader* block = CreateBlock(blockSize);
47
48 block->fPrev = fTail;
49 block->fNext = NULL;
50 SkASSERT(NULL == fTail->fNext);
51 fTail->fNext = block;
52 fTail = block;
53 }
54 SkASSERT(fTail->fFreeSize >= size);
55 intptr_t ptr = fTail->fCurrPtr;
56 // We stash a pointer to the block header, just before the allocated space,
57 // so that we can decrement the live count on delete in constant time.
58 *reinterpret_cast<BlockHeader**>(ptr) = fTail;
59 ptr += kPerAllocPad;
60 fTail->fPrevPtr = fTail->fCurrPtr;
61 fTail->fCurrPtr += size;
62 fTail->fFreeSize -= size;
63 fTail->fLiveCount += 1;
64 SkDEBUGCODE(++fAllocationCnt);
65 VALIDATE;
66 return reinterpret_cast<void*>(ptr);
67 }
68
release(void * p)69 void GrMemoryPool::release(void* p) {
70 VALIDATE;
71 intptr_t ptr = reinterpret_cast<intptr_t>(p) - kPerAllocPad;
72 BlockHeader* block = *reinterpret_cast<BlockHeader**>(ptr);
73 if (1 == block->fLiveCount) {
74 // the head block is special, it is reset rather than deleted
75 if (fHead == block) {
76 fHead->fCurrPtr = reinterpret_cast<intptr_t>(fHead) +
77 kHeaderSize;
78 fHead->fLiveCount = 0;
79 fHead->fFreeSize = fPreallocSize;
80 } else {
81 BlockHeader* prev = block->fPrev;
82 BlockHeader* next = block->fNext;
83 SkASSERT(prev);
84 prev->fNext = next;
85 if (next) {
86 next->fPrev = prev;
87 } else {
88 SkASSERT(fTail == block);
89 fTail = prev;
90 }
91 DeleteBlock(block);
92 }
93 } else {
94 --block->fLiveCount;
95 // Trivial reclaim: if we're releasing the most recent allocation, reuse it
96 if (block->fPrevPtr == ptr) {
97 block->fFreeSize += (block->fCurrPtr - block->fPrevPtr);
98 block->fCurrPtr = block->fPrevPtr;
99 }
100 }
101 SkDEBUGCODE(--fAllocationCnt);
102 VALIDATE;
103 }
104
CreateBlock(size_t size)105 GrMemoryPool::BlockHeader* GrMemoryPool::CreateBlock(size_t size) {
106 BlockHeader* block =
107 reinterpret_cast<BlockHeader*>(sk_malloc_throw(size + kHeaderSize));
108 // we assume malloc gives us aligned memory
109 SkASSERT(!(reinterpret_cast<intptr_t>(block) % kAlignment));
110 block->fLiveCount = 0;
111 block->fFreeSize = size;
112 block->fCurrPtr = reinterpret_cast<intptr_t>(block) + kHeaderSize;
113 block->fPrevPtr = 0; // gcc warns on assigning NULL to an intptr_t.
114 return block;
115 }
116
DeleteBlock(BlockHeader * block)117 void GrMemoryPool::DeleteBlock(BlockHeader* block) {
118 sk_free(block);
119 }
120
validate()121 void GrMemoryPool::validate() {
122 #ifdef SK_DEBUG
123 BlockHeader* block = fHead;
124 BlockHeader* prev = NULL;
125 SkASSERT(block);
126 int allocCount = 0;
127 do {
128 allocCount += block->fLiveCount;
129 SkASSERT(prev == block->fPrev);
130 if (prev) {
131 SkASSERT(prev->fNext == block);
132 }
133
134 intptr_t b = reinterpret_cast<intptr_t>(block);
135 size_t ptrOffset = block->fCurrPtr - b;
136 size_t totalSize = ptrOffset + block->fFreeSize;
137 size_t userSize = totalSize - kHeaderSize;
138 intptr_t userStart = b + kHeaderSize;
139
140 SkASSERT(!(b % kAlignment));
141 SkASSERT(!(totalSize % kAlignment));
142 SkASSERT(!(userSize % kAlignment));
143 SkASSERT(!(block->fCurrPtr % kAlignment));
144 if (fHead != block) {
145 SkASSERT(block->fLiveCount);
146 SkASSERT(userSize >= fMinAllocSize);
147 } else {
148 SkASSERT(userSize == fPreallocSize);
149 }
150 if (!block->fLiveCount) {
151 SkASSERT(ptrOffset == kHeaderSize);
152 SkASSERT(userStart == block->fCurrPtr);
153 } else {
154 SkASSERT(block == *reinterpret_cast<BlockHeader**>(userStart));
155 }
156 prev = block;
157 } while ((block = block->fNext));
158 SkASSERT(allocCount == fAllocationCnt);
159 SkASSERT(prev == fTail);
160 #endif
161 }
162