gecko-dev/js/tamarin/MMgc/GCLargeAlloc.h

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 * "License"); you may not use this file except in compliance with the License. You may obtain 
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 * 
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 * WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 * language governing rights and limitations under the License. 
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 * The Original Code is [Open Source Virtual Machine.] 
 * 
 * The Initial Developer of the Original Code is Adobe System Incorporated.  Portions created 
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 * Reserved. 
 * 
 * Contributor(s): Adobe AS3 Team
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#ifndef __GCLargeAlloc__
#define __GCLargeAlloc__

namespace MMgc
{
	/**
	 * This is a garbage collecting allocator for large memory blocks.
	 */
	class GCLargeAlloc : public GCAllocObject
	{
		friend class GC;
	private:
		enum {
			kMarkFlag         = 0x1,
			kQueuedFlag       = 0x2,
			kFinalizeFlag     = 0x4,
			kHasWeakRef       = 0x8,
			kContainsPointers = 0x10,
			kRCObject         = 0x20
		};

	public:
		GCLargeAlloc(GC* gc);
		~GCLargeAlloc();

		void* Alloc(size_t size, int flags);
		void Free(void *ptr);
		void Finalize();
		void ClearMarks();

		static void SetHasWeakRef(const void *item, bool to)
		{
			if(to) {
				GetBlockHeader(item)->flags |= kHasWeakRef;
			} else {
				GetBlockHeader(item)->flags &= ~kHasWeakRef;
			}
		}

		static bool HasWeakRef(const void *item)
		{
			return (GetBlockHeader(item)->flags & kHasWeakRef) != 0;
		}

		static bool IsLargeBlock(const void *item)
		{
			// The pointer should be 4K aligned plus 16 bytes
		        // Mac inserts 16 bytes for new[] so make it more general
			return (((uintptr)item & 0xFFF) == sizeof(LargeBlock));
		}

		static bool SetMark(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			bool oldMark = (block->flags & kMarkFlag) != 0;
			block->flags |= kMarkFlag;
			block->flags &= ~kQueuedFlag;
			return oldMark;
		}

		static void SetQueued(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			block->flags |= kQueuedFlag;
		}

		static void SetFinalize(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			block->flags |= kFinalizeFlag;
		}
		
		static bool GetMark(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			return (block->flags & kMarkFlag) != 0;
		}

		static bool IsWhite(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			if(!IsLargeBlock(item))
				return false;
			return (block->flags & (kMarkFlag|kQueuedFlag)) == 0;
		}

		static void* FindBeginning(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			return (void*) (block+1);
		}

		static void ClearFinalized(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			block->flags &= ~kFinalizeFlag;
		}

		static bool ContainsPointers(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			return (block->flags & kContainsPointers) != 0;
		}
		
		static bool IsFinalized(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			return (block->flags & kFinalizeFlag) != 0;
		}

		static bool IsRCObject(const void *item)
		{
			LargeBlock *block = GetBlockHeader(item);
			return (block->flags & kRCObject) != 0;
		}

	private:
		struct LargeBlock
		{
			GC *gc;
			LargeBlock *next;
			uint32 usableSize;
			uint32 flags;

			int GetNumBlocks() const { return (usableSize + sizeof(LargeBlock)) / GCHeap::kBlockSize; }
		};

		static LargeBlock* GetBlockHeader(const void *addr)
		{
			return (LargeBlock*) ((uintptr)addr & ~0xFFF);
		}
		
		static bool NeedsFinalize(LargeBlock *block)
		{
			return (block->flags & kFinalizeFlag) != 0;
		}			
		
		// The list of chunk blocks
		LargeBlock* m_blocks;
		bool m_startedFinalize;
		static bool ConservativeGetMark(const void *item, bool bogusPointerReturnValue);

	protected:
		GC *m_gc;
	
	};
}

#endif /* __GCLargeAlloc__ */