258 lines
4.7 KiB
C
258 lines
4.7 KiB
C
/*++
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Copyright (c) 1997 - 98, Microsoft Corporation
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Module Name:
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avltrie.c
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Abstract:
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Contains routines for a best matching
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prefix lookup using an PATRICIA trie.
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Author:
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Chaitanya Kodeboyina (chaitk) 24-Jun-1998
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Revision History:
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--*/
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#include "pattrie.h"
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DWORD
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WINAPI
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CreateTable(
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IN USHORT MaxBytes,
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OUT HANDLE *Table
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)
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{
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PPAT_TRIE NewTrie;
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ASSERT(sizeof(PAT_CONTEXT) <= sizeof(LOOKUP_CONTEXT));
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ASSERT(sizeof(PAT_LINKAGE) <= sizeof(DATA_ENTRY));
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if (MaxBytes)
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{
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if (NewTrie = AllocNZeroMemory(sizeof(PAT_TRIE)))
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{
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NewTrie->MaxKeyBytes = (MaxBytes + sizeof(ULONG) - 1) / sizeof(ULONG);
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#if _PROF_
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NewTrie->MemoryInUse = sizeof(PAT_TRIE);
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#endif
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*Table = NewTrie;
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return NO_ERROR;
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}
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else // if (NewTrie == NULL)
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{
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*Table = NULL;
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return ERROR_NOT_ENOUGH_MEMORY;
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}
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}
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else // (if MaxBytes == 0)
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{
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return ERROR_INVALID_PARAMETER;
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}
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}
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DWORD
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WINAPI
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SearchInTable(
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IN HANDLE Table,
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IN USHORT NumBits,
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IN PUCHAR KeyBits,
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OUT PLOOKUP_CONTEXT Context OPTIONAL,
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OUT PDATA_ENTRY *Data
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)
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{
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PPAT_TRIE Trie;
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PPAT_NODE PrevNode;
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PPAT_NODE CurrNode;
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PPAT_NODE BestNode;
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PAT_CHILD NextChild;
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ULONG Key;
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#if _PROF_
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UINT NumTravs1;
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UINT NumTravs2;
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#endif
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Trie = Table;
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#if DBG
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if (NumBits > Trie->MaxKeyBytes * BITS_IN_BYTE)
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{
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*Data = NULL;
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return ERROR_INVALID_PARAMETER;
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}
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#endif
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#if _PROF_
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NumTravs1 = 0;
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NumTravs2 = 0;
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#endif
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//
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// Go down the search trie matching the
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// next set of bits in key as u do so
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//
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Key = RtlUlongByteSwap(KeyBits);
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CurrNode = Trie->TrieRoot;
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PrevNode = NULL;
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NextChild = LCHILD;
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BestNode = NULL;
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while (CurrNode)
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{
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#if _PROF_
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NumTravs1++;
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if (CurrNode->Data)
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{
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NumTravs2++;
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}
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#endif
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}
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return NO_ERROR;
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}
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DWORD
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WINAPI
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BestMatchInTable(
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IN HANDLE Table,
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IN PUCHAR KeyBits,
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OUT PDATA_ENTRY *BestData
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)
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{
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PPAT_TRIE Trie;
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PPAT_NODE CurrNode;
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PAT_CHILD NextChild;
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UINT BitsLeft;
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ULONG Key;
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ULONG CurrMask;
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ULONG CurrBits;
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#if _PROF_
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UINT NumTravs1;
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UINT NumTravs2;
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#endif
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*BestData = NULL;
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Trie = Table;
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BytesLeft = Trie->MaxKeyBytes;
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#if _PROF_
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NumTravs1 = 0;
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NumTravs2 = 0;
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#endif
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//
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// Go down trie after trie until all bits done
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//
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while (BytesLeft)
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{
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//
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// Get the key for the next trie search
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//
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Key = RtlUlongByteSwap(*(ULONG *)KeyBits);
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KeyBits += sizeof(ULONG);
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BytesLeft -= sizeof(ULONG);
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//
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// Go down the current search trie
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//
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CurrNode = Trie->TrieRoot;
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BitsLeft = sizeof(ULONG) * BITS_IN_BYTE;
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Data = NULL;
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while (CurrNode)
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{
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#if _PROF_
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NumTravs1++;
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if (CurrNode->Data)
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{
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NumTravs2++;
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}
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#endif
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CurrMask = MaskBits(CurrNode->NumBits);
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CurrBits = CurrNode->KeyBits;
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//
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// Try to match bits in the current node
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//
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if ((Key & CurrMask) != CurrBits)
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{
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// Failed to match this node
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break;
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}
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//
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// Update node with best data so far
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//
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if (CurrNode->Data)
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{
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Data = CurrNode->Data;
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}
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//
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// Go down for more specific match
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//
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BitsLeft -= CurrNode->NumBits;
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Key <<= CurrNode->NumBits;
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NextChild = PickMostSigNBits(Key, 1);
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CurrNode = CurrNode->Child[NextChild];
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}
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//
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// Do we do a full match in this sub-trie
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// & do we have more sub-trees to work on
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//
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if (BitsLeft || (!IS_SUB_TRIE(Data)))
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{
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*BestData = Data;
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break;
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}
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Trie = GET_SUB_TRIE(*BestData);
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}
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#if _PROF_
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Print("Num Travs 1 = %5d, Travs 2 = %5d\n",
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NumTravs1,
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NumTravs2);
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#endif
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return BitsLeft ? ERROR_NOT_FOUND : NO_ERROR;
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}
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