Add GrMemoryPool as a helper to override operators new/delete

Review URL: http://codereview.appspot.com/6306090/



git-svn-id: http://skia.googlecode.com/svn/trunk@4282 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 153 insertions, 0 deletions

diff --git a/src/gpu/GrMemoryPool.cpp b/src/gpu/GrMemoryPool.cpp
new file mode 100644
index 0000000000..597f88cbb8
--- /dev/null
+++ b/src/gpu/GrMemoryPool.cpp
@@ -0,0 +1,153 @@
+/*
+ * 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"
+
+#if GR_DEBUG
+    #define VALIDATE this->validate()
+#else
+    #define VALIDATE
+#endif
+
+GrMemoryPool::GrMemoryPool(size_t preallocSize, size_t minAllocSize) {
+    GR_DEBUGCODE(fAllocationCnt = 0);
+
+    minAllocSize = GrMax<size_t>(minAllocSize, 1 << 10);
+    fMinAllocSize = GrSizeAlignUp(minAllocSize + kPerAllocPad, kAlignment),
+    fPreallocSize = GrSizeAlignUp(preallocSize + kPerAllocPad, kAlignment);
+    fPreallocSize = GrMax(fPreallocSize, fMinAllocSize);
+
+    fHead = CreateBlock(fPreallocSize);
+    fTail = fHead;
+    fHead->fNext = NULL;
+    fHead->fPrev = NULL;
+    VALIDATE;
+};
+
+GrMemoryPool::~GrMemoryPool() {
+    VALIDATE;
+    GrAssert(0 == fAllocationCnt);
+    GrAssert(fHead == fTail);
+    GrAssert(0 == fHead->fLiveCount);
+    DeleteBlock(fHead);
+};
+
+void* GrMemoryPool::allocate(size_t size) {
+    VALIDATE;
+    size = GrSizeAlignUp(size, kAlignment);
+    size += kPerAllocPad;
+    if (fTail->fFreeSize < size) {
+        int blockSize = size;
+        blockSize = GrMax<size_t>(blockSize, fMinAllocSize);
+        BlockHeader* block = CreateBlock(blockSize);
+
+        block->fPrev = fTail;
+        block->fNext = NULL;
+        GrAssert(NULL == fTail->fNext);
+        fTail->fNext = block;
+        fTail = block;
+    }
+    GrAssert(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->fCurrPtr += size;
+    fTail->fFreeSize -= size;
+    fTail->fLiveCount += 1;
+    GR_DEBUGCODE(++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;
+            GrAssert(prev);
+            prev->fNext = next;
+            if (next) {
+                next->fPrev = prev;
+            } else {
+                GrAssert(fTail == block);
+                fTail = prev;
+            }
+            DeleteBlock(block);
+        }
+    } else {
+        --block->fLiveCount;
+    }
+    GR_DEBUGCODE(--fAllocationCnt);
+    VALIDATE;
+}
+
+GrMemoryPool::BlockHeader* GrMemoryPool::CreateBlock(size_t size) {
+    BlockHeader* block =
+        reinterpret_cast<BlockHeader*>(GrMalloc(size + kHeaderSize));
+    // we assume malloc gives us aligned memory
+    GrAssert(!(reinterpret_cast<intptr_t>(block) % kAlignment));
+    block->fLiveCount = 0;
+    block->fFreeSize = size;
+    block->fCurrPtr = reinterpret_cast<intptr_t>(block) + kHeaderSize;
+    return block;
+}
+
+void GrMemoryPool::DeleteBlock(BlockHeader* block) {
+    GrFree(block);
+}
+
+void GrMemoryPool::validate() {
+    BlockHeader* block = fHead;
+    BlockHeader* prev = NULL;
+    GrAssert(block);
+    int allocCount = 0;
+    do {
+        allocCount += block->fLiveCount;
+        GrAssert(prev == block->fPrev);
+        if (NULL != prev) {
+            GrAssert(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;
+
+        GrAssert(!(b % kAlignment));
+        GrAssert(!(totalSize % kAlignment));
+        GrAssert(!(userSize % kAlignment));
+        GrAssert(!(block->fCurrPtr % kAlignment));
+        if (fHead != block) {
+            GrAssert(block->fLiveCount);
+            GrAssert(userSize >= fMinAllocSize);
+        } else {
+            GrAssert(userSize == fPreallocSize);
+        }
+        if (!block->fLiveCount) {
+            GrAssert(ptrOffset ==  kHeaderSize);
+            GrAssert(userStart == block->fCurrPtr);
+        } else {
+            GrAssert(block == *reinterpret_cast<BlockHeader**>(userStart));
+        }
+        prev = block;
+    } while ((block = block->fNext));
+    GrAssert(allocCount == fAllocationCnt);
+    GrAssert(prev == fTail);
+}
+