Method CreateDelta

src/engine/shared/snapshot.cpp:298–379

TODO: OPT: this should be made much faster

// TODO: OPT: this should be made much faster
int CSnapshotDelta::CreateDelta(const CSnapshot *pFrom, const CSnapshot *pTo, void *pDstData)
{
	CData *pDelta = (CData *)pDstData;
	int *pData = (int *)pDelta->m_aData;

	pDelta->m_NumDeletedItems = 0;
	pDelta->m_NumUpdateItems = 0;
	pDelta->m_NumTempItems = 0;

	CItemList aHashlist[HASHLIST_SIZE];
	GenerateHash(aHashlist, pTo);

	// pack deleted stuff
	for(int i = 0; i < pFrom->NumItems(); i++)
	{
		const CSnapshotItem *pFromItem = pFrom->GetItem(i);
		if(GetItemIndexHashed(pFromItem->Key(), aHashlist) == -1)
		{
			// deleted
			pDelta->m_NumDeletedItems++;
			*pData = pFromItem->Key();
			pData++;
		}
	}

	GenerateHash(aHashlist, pFrom);

	// fetch previous indices
	// we do this as a separate pass because it helps the cache
	int aPastIndices[CSnapshot::MAX_ITEMS];
	const int NumItems = pTo->NumItems();
	for(int i = 0; i < NumItems; i++)
	{
		const CSnapshotItem *pCurItem = pTo->GetItem(i); // O(1) .. O(n)
		aPastIndices[i] = GetItemIndexHashed(pCurItem->Key(), aHashlist); // O(n) .. O(n^n)
	}

	for(int i = 0; i < NumItems; i++)
	{
		// do delta
		const int ItemSize = pTo->GetItemSize(i); // O(1) .. O(n)
		const CSnapshotItem *pCurItem = pTo->GetItem(i); // O(1) .. O(n)
		const int PastIndex = aPastIndices[i];
		const bool IncludeSize = pCurItem->Type() >= MAX_NETOBJSIZES || !m_aItemSizes[pCurItem->Type()];

		if(PastIndex != -1)
		{
			int *pItemDataDst = pData + 3;

			const CSnapshotItem *pPastItem = pFrom->GetItem(PastIndex);

			if(!IncludeSize)
				pItemDataDst = pData + 2;

			if(DiffItem(pPastItem->Data(), pCurItem->Data(), pItemDataDst, ItemSize / sizeof(int32_t)))
			{
				*pData++ = pCurItem->Type();
				*pData++ = pCurItem->Id();