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, 79 insertions, 0 deletions

diff --git a/src/gpu/GrMemoryPool.h b/src/gpu/GrMemoryPool.h
new file mode 100644
index 0000000000..08c9ee2bbe
--- /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