GuEdgeCache.h

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#ifndef GU_EDGECACHE_H
#define GU_EDGECACHE_H
 
#include "foundation/PxMemory.h"
#include "foundation/PxAllocator.h"
#include "foundation/PxHash.h"
 
namespace physx
{
namespace Gu
{
    class EdgeCache
    {
#define NUM_EDGES_IN_CACHE 64       //must be power of 2.   32 lines result in 10% extra work (due to cache misses), 64 lines in 6% extra work, 128 lines in 4%.
    public:
        EdgeCache()
        {
            PxMemZero(cacheLines, NUM_EDGES_IN_CACHE*sizeof(CacheLine));
        }
 
        PxU32 hash(PxU32 key)   const
        {
            return (NUM_EDGES_IN_CACHE - 1) & PxComputeHash(key);       //Only a 16 bit hash would be needed here.
        }
 
        bool isInCache(PxU8 vertex0, PxU8 vertex1)
        {
            PX_ASSERT(vertex1 >= vertex0);
            PxU16 key = PxU16((vertex0 << 8) | vertex1);
            PxU32 h = hash(key);
            CacheLine& cl = cacheLines[h];
            if (cl.fullKey == key)
            {
                return true;
            }
            else    //cache the line now as it's about to be processed
            {
                cl.fullKey = key;
                return false;
            }
        }
 
    private:
        struct CacheLine
        {
            PxU16 fullKey;
        };
        CacheLine cacheLines[NUM_EDGES_IN_CACHE];
#undef NUM_EDGES_IN_CACHE
    };
}
 
}
 
#endif