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
diff --git a/src/gpu/GrMemoryPool.h b/src/gpu/GrMemoryPool.h
new file mode 100644
index 0000000..08c9ee2
--- /dev/null
+++ b/src/gpu/GrMemoryPool.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrMemoryPool_DEFINED
+#define GrMemoryPool_DEFINED
+
+#include "GrTypes.h"
+
+/**
+ * Allocates memory in blocks and parcels out space in the blocks for allocation
+ * requests. It is optimized for allocate / release speed over memory
+ * effeciency. The interface is designed to be used to implement operator new
+ * and delete overrides. All allocations are expected to be released before the
+ * pool's destructor is called. Allocations will be 8-byte aligned.
+ */
+class GrMemoryPool {
+public:
+ /**
+ * Prealloc size is the amount of space to make available at pool creation
+ * time and keep around until pool destruction. The min alloc size is the
+ * smallest allowed size of additional allocations.
+ */
+ GrMemoryPool(size_t preallocSize, size_t minAllocSize);
+
+ ~GrMemoryPool();
+
+ /**
+ * Allocates memory. The memory must be freed with release().
+ */
+ void* allocate(size_t size);
+
+ /**
+ * p must have been returned by allocate()
+ */
+ void release(void* p);
+
+ /**
+ * Returns true if there are no unreleased allocations.
+ */
+ bool isEmpty() const { return fTail == fHead && !fHead->fLiveCount; }
+
+private:
+ struct BlockHeader;
+
+ BlockHeader* CreateBlock(size_t size);
+
+ void DeleteBlock(BlockHeader* block);
+
+ void validate();
+
+ struct BlockHeader {
+ BlockHeader* fNext; // doubly-linked list of blocks.
+ BlockHeader* fPrev;
+ int fLiveCount; // number of outstanding allocations in the
+ // block.
+ intptr_t fCurrPtr; // ptr to the start of blocks free space.
+ size_t fFreeSize; // amount of free space left in the block.
+ };
+
+ enum {
+ // We assume this alignment is good enough for everybody.
+ kAlignment = 8,
+ kHeaderSize = GR_CT_ALIGN_UP(sizeof(BlockHeader), kAlignment),
+ kPerAllocPad = GR_CT_ALIGN_UP(sizeof(BlockHeader*), kAlignment),
+ };
+ size_t fPreallocSize;
+ size_t fMinAllocSize;
+ BlockHeader* fHead;
+ BlockHeader* fTail;
+#if GR_DEBUG
+ int fAllocationCnt;
+#endif
+};
+
+#endif