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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "GrMemoryPool.h"
#ifdef SK_DEBUG
#define VALIDATE this->validate()
#else
#define VALIDATE
#endif
GrMemoryPool::GrMemoryPool(size_t preallocSize, size_t minAllocSize) {
SkDEBUGCODE(fAllocationCnt = 0);
minAllocSize = SkTMax<size_t>(minAllocSize, 1 << 10);
fMinAllocSize = GrSizeAlignUp(minAllocSize + kPerAllocPad, kAlignment),
fPreallocSize = GrSizeAlignUp(preallocSize + kPerAllocPad, kAlignment);
fPreallocSize = SkTMax(fPreallocSize, fMinAllocSize);
fHead = CreateBlock(fPreallocSize);
fTail = fHead;
fHead->fNext = NULL;
fHead->fPrev = NULL;
VALIDATE;
};
GrMemoryPool::~GrMemoryPool() {
VALIDATE;
SkASSERT(0 == fAllocationCnt);
SkASSERT(fHead == fTail);
SkASSERT(0 == fHead->fLiveCount);
DeleteBlock(fHead);
};
void* GrMemoryPool::allocate(size_t size) {
VALIDATE;
size = GrSizeAlignUp(size, kAlignment);
size += kPerAllocPad;
if (fTail->fFreeSize < size) {
size_t blockSize = size;
blockSize = SkTMax<size_t>(blockSize, fMinAllocSize);
BlockHeader* block = CreateBlock(blockSize);
block->fPrev = fTail;
block->fNext = NULL;
SkASSERT(NULL == fTail->fNext);
fTail->fNext = block;
fTail = block;
}
SkASSERT(fTail->fFreeSize >= size);
intptr_t ptr = fTail->fCurrPtr;
// We stash a pointer to the block header, just before the allocated space,
// so that we can decrement the live count on delete in constant time.
*reinterpret_cast<BlockHeader**>(ptr) = fTail;
ptr += kPerAllocPad;
fTail->fPrevPtr = fTail->fCurrPtr;
fTail->fCurrPtr += size;
fTail->fFreeSize -= size;
fTail->fLiveCount += 1;
SkDEBUGCODE(++fAllocationCnt);
VALIDATE;
return reinterpret_cast<void*>(ptr);
}
void GrMemoryPool::release(void* p) {
VALIDATE;
intptr_t ptr = reinterpret_cast<intptr_t>(p) - kPerAllocPad;
BlockHeader* block = *reinterpret_cast<BlockHeader**>(ptr);
if (1 == block->fLiveCount) {
// the head block is special, it is reset rather than deleted
if (fHead == block) {
fHead->fCurrPtr = reinterpret_cast<intptr_t>(fHead) +
kHeaderSize;
fHead->fLiveCount = 0;
fHead->fFreeSize = fPreallocSize;
} else {
BlockHeader* prev = block->fPrev;
BlockHeader* next = block->fNext;
SkASSERT(prev);
prev->fNext = next;
if (next) {
next->fPrev = prev;
} else {
SkASSERT(fTail == block);
fTail = prev;
}
DeleteBlock(block);
}
} else {
--block->fLiveCount;
// Trivial reclaim: if we're releasing the most recent allocation, reuse it
if (block->fPrevPtr == ptr) {
block->fFreeSize += (block->fCurrPtr - block->fPrevPtr);
block->fCurrPtr = block->fPrevPtr;
}
}
SkDEBUGCODE(--fAllocationCnt);
VALIDATE;
}
GrMemoryPool::BlockHeader* GrMemoryPool::CreateBlock(size_t size) {
BlockHeader* block =
reinterpret_cast<BlockHeader*>(sk_malloc_throw(size + kHeaderSize));
// we assume malloc gives us aligned memory
SkASSERT(!(reinterpret_cast<intptr_t>(block) % kAlignment));
block->fLiveCount = 0;
block->fFreeSize = size;
block->fCurrPtr = reinterpret_cast<intptr_t>(block) + kHeaderSize;
block->fPrevPtr = 0; // gcc warns on assigning NULL to an intptr_t.
return block;
}
void GrMemoryPool::DeleteBlock(BlockHeader* block) {
sk_free(block);
}
void GrMemoryPool::validate() {
#ifdef SK_DEBUG
BlockHeader* block = fHead;
BlockHeader* prev = NULL;
SkASSERT(block);
int allocCount = 0;
do {
allocCount += block->fLiveCount;
SkASSERT(prev == block->fPrev);
if (NULL != prev) {
SkASSERT(prev->fNext == block);
}
intptr_t b = reinterpret_cast<intptr_t>(block);
size_t ptrOffset = block->fCurrPtr - b;
size_t totalSize = ptrOffset + block->fFreeSize;
size_t userSize = totalSize - kHeaderSize;
intptr_t userStart = b + kHeaderSize;
SkASSERT(!(b % kAlignment));
SkASSERT(!(totalSize % kAlignment));
SkASSERT(!(userSize % kAlignment));
SkASSERT(!(block->fCurrPtr % kAlignment));
if (fHead != block) {
SkASSERT(block->fLiveCount);
SkASSERT(userSize >= fMinAllocSize);
} else {
SkASSERT(userSize == fPreallocSize);
}
if (!block->fLiveCount) {
SkASSERT(ptrOffset == kHeaderSize);
SkASSERT(userStart == block->fCurrPtr);
} else {
SkASSERT(block == *reinterpret_cast<BlockHeader**>(userStart));
}
prev = block;
} while ((block = block->fNext));
SkASSERT(allocCount == fAllocationCnt);
SkASSERT(prev == fTail);
#endif
}
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