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509 lines
19 KiB
509 lines
19 KiB
#include <precomp.h>
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#include "ErrCtrl.h"
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#include "utils.h"
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#include "hash.h"
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//~~~~~~~~~~~~~~~~~~~~~~~~ PRIVATE HASH FUNCTIONS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Matches the keys one against the other.
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UINT // [RET] number of matching chars
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HshPrvMatchKeys(
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LPWSTR wszKey1, // [IN] key 1
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LPWSTR wszKey2) // [IN] key 2
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{
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UINT i = 0;
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while (*wszKey1 != L'\0' && *wszKey1 == *wszKey2)
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{
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wszKey1++; wszKey2++;
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i++;
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}
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return i;
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}
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// deletes all the pHash tree - doesn't touch the pObjects from
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// within (if any)
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VOID
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HshDestructor(
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PHASH_NODE pHash) // [IN] hash tree to delete
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{
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// pHash should not be NULL -- but who knows what the caller is doing!
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if (pHash != NULL)
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{
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while(!IsListEmpty(&(pHash->lstDown)))
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{
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PHASH_NODE pChild;
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pChild = CONTAINING_RECORD(pHash->lstDown.Flink, HASH_NODE, lstHoriz);
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HshDestructor(pChild);
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}
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RemoveEntryList(&(pHash->lstHoriz));
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MemFree(pHash->wszKey);
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MemFree(pHash);
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}
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}
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//~~~~~~~~~~~~~~~~~~~~~~~~ PUBLIC HASH FUNCTIONS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Initializes a HASH structure
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DWORD
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HshInitialize(PHASH pHash)
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{
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DWORD dwErr = ERROR_SUCCESS;
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if (pHash != NULL)
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{
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__try
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{
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InitializeCriticalSection(&(pHash->csMutex));
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pHash->bValid = TRUE;
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}
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__except(EXCEPTION_EXECUTE_HANDLER)
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{
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dwErr = GetExceptionCode();
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}
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pHash->pRoot = NULL;
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}
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else
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dwErr = ERROR_INVALID_PARAMETER;
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SetLastError(dwErr);
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return dwErr;
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}
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// Cleans all resources referenced by a HASH structures
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VOID
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HshDestroy(PHASH pHash)
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{
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HshDestructor(pHash->pRoot);
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if (pHash->bValid)
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{
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DeleteCriticalSection(&(pHash->csMutex));
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pHash->bValid = FALSE;
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}
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}
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// Inserts an opaque object into the cache. The object is keyed on a wstring
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// The call could alter the structure of the hash, hence it returns the reference
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// to the updated hash.
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DWORD // [RET] win32 error code
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HshInsertObjectRef(
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PHASH_NODE pHash, // [IN] hash to operate on
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LPWSTR wszKey, // [IN] key of the object to insert
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LPVOID pObject, // [IN] object itself to insert in the cache
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PHASH_NODE *ppOutHash) // [OUT] pointer to the updated hash
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{
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DWORD dwErr = ERROR_SUCCESS;
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_Asrt(ppOutHash != NULL, L"No output hash expected??");
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_Asrt(wszKey != NULL, L"Key info should not be NULL");
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// if the node passed in is NULL this means a new node
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// has to be created
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if (pHash == NULL)
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{
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// this node is definitely not in the hash
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// allocate the new node
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pHash = MemCAlloc(sizeof(HASH_NODE));
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if (pHash == NULL)
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{
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dwErr = GetLastError();
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goto exit;
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}
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// allocate mem for the new key
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pHash->wszKey = MemCAlloc(sizeof(WCHAR)*(wcslen(wszKey)+1));
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if (pHash->wszKey == NULL)
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{
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dwErr = GetLastError();
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MemFree(pHash);
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goto exit;
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}
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// copy the new key
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wcscpy(pHash->wszKey, wszKey);
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// initialize the horizontal and down lists
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InitializeListHead(&(pHash->lstHoriz));
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InitializeListHead(&(pHash->lstDown));
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// copy the reference to the object associated with the key
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pHash->pObject = pObject;
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// at this point we have a standalone newly created node:
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// no links are defined either on the horizontal, downwards or upwards
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// these will be set up (if needed) by the caller.
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*ppOutHash = pHash;
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}
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// if the node passed in is not NULL, we need to match as many
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// characters between wszKey and the node's key. Based on who's shorter
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// we decide to either set the reference (if keys identical) or
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// break the branch (if wszKey is shorter than the current one) or
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// to recurse down the insertion.
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else
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{
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UINT nMatch;
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PHASH_NODE pChild;
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enum { MATCH, SUBSET, SUPERSET, UNDECIDED, RECURSE} nAnalysis;
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nMatch = HshPrvMatchKeys(wszKey, pHash->wszKey);
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// analyze the given key with respect to the current node;
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if (wszKey[nMatch] == L'\0' && pHash->wszKey[nMatch] == L'\0')
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// the key matches the current node
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nAnalysis = MATCH;
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else if (wszKey[nMatch] == L'\0')
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// the key is a subset of the current node
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nAnalysis = SUBSET;
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else
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{
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// so far undecided - further see if this translates to SUPERSET
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// or even better, if SUPERSET can be handled by a child, hence
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// RECURSE.
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nAnalysis = UNDECIDED;
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if (pHash->wszKey[nMatch] == L'\0')
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{
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PLIST_ENTRY pEntry;
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// the new key is a superset of the current nod
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nAnalysis = SUPERSET;
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// the new key could be covered by one of the existent children.
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// check then if it is the case to send the work down to some child
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for (pEntry = pHash->lstDown.Flink;
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pEntry != &(pHash->lstDown);
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pEntry = pEntry->Flink)
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{
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pChild = CONTAINING_RECORD(pEntry, HASH_NODE, lstHoriz);
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if (wszKey[nMatch] == pChild->wszKey[0])
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{
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// the child to follow up has been located and saved
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// in pChild. Set nAnalysis to UNDECIDED and break;
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nAnalysis = RECURSE;
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break;
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}
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}
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}
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}
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// if the key matches exactly the current node
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// then is only a matter of setting the object's reference
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if (nAnalysis == MATCH)
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{
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// if the node is already referencing an object..
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if (pHash->pObject != NULL)
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{
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// signal out ERROR_DUPLICATE_TAG
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dwErr = ERROR_DUPLICATE_TAG;
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}
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else
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{
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// just insert the reference and get out with success.
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pHash->pObject = pObject;
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// save the Out hash pointer
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*ppOutHash = pHash;
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}
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}
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// if a child has been identified, let pChild (saved previously)
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// to follow up
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else if (nAnalysis == RECURSE)
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{
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dwErr = HshInsertObjectRef(
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pChild,
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wszKey+nMatch,
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pObject,
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ppOutHash);
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if (dwErr == ERROR_SUCCESS)
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*ppOutHash = pHash;
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}
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// if any of SUBSET, SUPERSET or UNDECIDED
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else
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{
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PHASH_NODE pParent = NULL;
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LPWSTR wszTrailKey = NULL;
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UINT nTrailLen = 0;
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// [C = common part; c = current key; n = new key]
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// (SUBSET) (UNDECIDED)
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// current: CCCCCccc or current: CCCCCccc
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// new: CCCCC new: CCCCCnnnnn
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//
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// In both cases, the current node splits.
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// Create first a new node, containing just CCCCC
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if (nAnalysis != SUPERSET)
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{
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// get the number of chars in pHash's key that are not matching
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nTrailLen = wcslen(pHash->wszKey) - nMatch;
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// create first the trailing part of the key (allocate the number of
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// chars from the current node that didn't match)
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wszTrailKey = MemCAlloc(sizeof(WCHAR)*(nTrailLen+1));
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if (wszTrailKey == NULL)
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{
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// if anything went wrong, just go out with the error.
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// hash hasn't been modified.
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dwErr = GetLastError();
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goto exit;
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}
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// wcsncpy doesn't append the null terminator but the string
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// is already nulled out and it has the right size
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wcsncpy(wszTrailKey, pHash->wszKey+nMatch, nTrailLen);
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// create then the node that will act as the common parent
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pHash->wszKey[nMatch] = L'\0';
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dwErr = HshInsertObjectRef(
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NULL, // request a new node to be created
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pHash->wszKey, // common part of the current keys
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NULL, // this node is not referencing any object
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&pParent); // get back the newly created pointer.
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pHash->wszKey[nMatch] = wszTrailKey[0];
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// in case anything went wrong, the hash has not been altered,
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// we just need to bubble up the error.
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if (dwErr != ERROR_SUCCESS)
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{
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MemFree(wszTrailKey);
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goto exit;
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}
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// set the new parent up link
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pParent->pUpLink = pHash->pUpLink;
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}
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// (SUPERSET) (UNDECIDED)
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// current: CCCCC or current: CCCCCccccc
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// new: CCCCCnnn new: CCCCCnnn
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// In both cases a new node has to be created for the "nnn" part.
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if (nAnalysis != SUBSET)
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{
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dwErr = HshInsertObjectRef(
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NULL,
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wszKey + nMatch,
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pObject,
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&pChild);
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if (dwErr != ERROR_SUCCESS)
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{
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// second creation failed, clean up everything and bail out
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MemFree(wszTrailKey);
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if (pParent != NULL)
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{
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MemFree(pParent->wszKey);
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MemFree(pParent);
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}
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// hash structure is not altered at this point.
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goto exit;
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}
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// link it up to the corresponding parent.
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pChild->pUpLink = (nAnalysis == SUPERSET) ? pHash : pParent;
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}
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// NO WAY BACK FROM NOW ON - hash is about to be altered
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// success is guaranteed
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// at this point, pChild is a non null pointer, with all the
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// LIST_ENTRIES from within the HASH_NODE initialized correctly.
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// (SUBSET) (UNDECIDED)
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// current: CCCCCccccc or current: CCCCCccccc
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// new: CCCCC new: CCCCCnnn
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// if the node has split, put the new parent in its place
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if (nAnalysis != SUPERSET)
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{
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// set the current key to the shrinked unmatched trailing part
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MemFree(pHash->wszKey);
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pHash->wszKey = wszTrailKey;
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// set the current upLink to the new pParent node
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pHash->pUpLink = pParent;
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// insert the new parent into its place
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InsertHeadList(&(pHash->lstHoriz), &(pParent->lstHoriz));
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// remove the node from its previous parent
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RemoveEntryList(&(pHash->lstHoriz));
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// reset the current node's list
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InitializeListHead(&(pHash->lstHoriz));
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// insert the node to its new parent down list.
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InsertHeadList(&(pParent->lstDown), &(pHash->lstHoriz));
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}
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// (SUPERSET) (UNDECIDED)
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// current: CCCCC or current: CCCCCccccc
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// new: CCCCCnnn new: CCCCCnnn
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// if a new child node has been created, link it in the hash
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if (nAnalysis != SUBSET)
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{
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// if the given key was either a superset of the
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// current key or derived from the current key,
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// there is a separated node for it. Insert it in the down list
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if (nAnalysis == SUPERSET)
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{
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InsertTailList(&(pHash->lstDown), &(pChild->lstHoriz));
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}
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else
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{
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InsertTailList(&(pParent->lstDown), &(pChild->lstHoriz));
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}
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}
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else
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{
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// set the new parent's reference to this data.
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pParent->pObject = pObject;
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}
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*ppOutHash = (nAnalysis == SUPERSET) ? pHash : pParent;
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// and that's all - we're done successfully!
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}
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}
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exit:
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SetLastError(dwErr);
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return dwErr;
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}
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// Retrieves an object from the hash. The hash structure is not touched in
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// any manner.
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DWORD // [RET] win32 error code
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HshQueryObjectRef(
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PHASH_NODE pHash, // [IN] hash to operate on
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LPWSTR wszKey, // [IN] key of the object to retrieve
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PHASH_NODE *ppHashNode) // [OUT] hash node referencing the queried object
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{
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DWORD dwErr = ERROR_FILE_NOT_FOUND;
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INT nDiff;
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if (wszKey == NULL)
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{
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dwErr = ERROR_INVALID_PARAMETER;
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goto exit;
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}
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if (pHash == NULL)
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{
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dwErr = ERROR_FILE_NOT_FOUND;
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goto exit;
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}
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nDiff = wcscmp(wszKey, pHash->wszKey);
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if (nDiff == 0)
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{
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// The key is identical with the one in this node
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if (pHash->pObject != NULL)
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{
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if (ppHashNode != NULL)
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{
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*ppHashNode = pHash;
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}
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dwErr = ERROR_SUCCESS;
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}
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// If there is no object in this node, this means
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// the query failed with FILE_NOT_FOUND
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}
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else if (nDiff > 0)
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{
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// The key is larger than the current node's key
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UINT nTrail = wcslen(pHash->wszKey);
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PLIST_ENTRY pEntry;
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// The trailing part of the key could be covered by one of
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// the children nodes. Scan then the Down list.
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for (pEntry = pHash->lstDown.Flink;
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pEntry != &(pHash->lstDown);
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pEntry = pEntry->Flink)
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{
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PHASH_NODE pChild;
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pChild = CONTAINING_RECORD(pEntry, HASH_NODE, lstHoriz);
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if (wszKey[nTrail] == pChild->wszKey[0])
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{
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// the child to follow up has been located and saved
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// in pChild. Try to match the trailing key against this node
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dwErr = HshQueryObjectRef(pChild, wszKey+nTrail, ppHashNode);
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break;
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}
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}
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// if no child has been located, dwErr is the default FILE_NOT_FOUND
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}
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// if nDiff < 0 - meaning key is included in the current node's key then
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// dwErr is the default FILE_NOT_FOUND which is good.
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exit:
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SetLastError(dwErr);
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return dwErr;
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}
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// Removes the object referenced by the pHash node. This could lead to one or
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// more hash node removals (if a leaf node on an isolated branch) but it could
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// also let the hash node untouched (i.e. internal node).
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// It is the caller's responsibility to clean up the object pointed by ppObject
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DWORD // [RET] win32 error code
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HshRemoveObjectRef(
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PHASH_NODE pHash, // [IN] hash to operate on
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PHASH_NODE pRemoveNode, // [IN] hash node to clear the reference to pObject
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LPVOID *ppObject, // [OUT] pointer to the object whose reference has been cleared
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PHASH_NODE *ppOutHash) // [OUT] pointer to the updated hash
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{
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DWORD dwErr = ERROR_SUCCESS;
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PHASH_NODE pNewRoot = NULL;
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_Asrt(ppObject != NULL, L"No output object expected??");
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_Asrt(ppOutHash != NULL, L"No output hash expected??");
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_Asrt(pRemoveNode != NULL, L"No node to remove??");
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// if the node contains no reference, return FILE_NOT_FOUND
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if (pRemoveNode->pObject == NULL)
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{
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dwErr = ERROR_FILE_NOT_FOUND;
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goto exit;
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}
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// remove the reference to the object at this moment
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*ppObject = pRemoveNode->pObject;
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pRemoveNode->pObject = NULL;
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// now climb the tree up to the root (!! - well it's a reversed tree) and merge
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// whatever nodes can be merged.
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// Merging: A node not referencing any object and having 0 or at most 1
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// successor can be deleted from the hash tree structure.
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while ((pRemoveNode != NULL) &&
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(pRemoveNode->pObject == NULL) &&
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(pRemoveNode->lstDown.Flink->Flink == &(pRemoveNode->lstDown)))
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{
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PHASH_NODE pUp = pRemoveNode->pUpLink;
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// if there is exactly 1 successor, its key needs to be prefixed with
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// the key of the node that is about to be removed. The successor also
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// needs to replace its parent in the hash tree structure.
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if (!IsListEmpty(&(pRemoveNode->lstDown)))
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{
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PHASH_NODE pDown;
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LPWSTR wszNewKey;
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pDown = CONTAINING_RECORD(pRemoveNode->lstDown.Flink, HASH_NODE, lstHoriz);
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wszNewKey = MemCAlloc(sizeof(WCHAR)*(wcslen(pRemoveNode->wszKey)+wcslen(pDown->wszKey)+1));
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if (wszNewKey == NULL)
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{
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// if the allocation failed, bail out with the error code.
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// the reference had already been removed, the hash might
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// not be compacted but it is still valid!
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dwErr = GetLastError();
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goto exit;
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}
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wcscpy(wszNewKey, pRemoveNode->wszKey);
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wcscat(wszNewKey, pDown->wszKey);
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MemFree(pDown->wszKey);
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pDown->wszKey = wszNewKey;
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// now raise the child node as a replacement of its parent
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pDown->pUpLink = pRemoveNode->pUpLink;
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InsertHeadList(&(pRemoveNode->lstHoriz), &(pDown->lstHoriz));
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pNewRoot = pDown;
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}
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// remove the current node
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RemoveEntryList(&(pRemoveNode->lstHoriz));
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// cleanup all its memory
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MemFree(pRemoveNode->wszKey);
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MemFree(pRemoveNode);
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// finally go and check the upper level node (if there is any)
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pRemoveNode = pUp;
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}
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// if pRemoveNode ended up to be NULL, this means either the whole hash has been cleared
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// or a "brother" took the role of the root. pNewRoot has the right value in both cases
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// if pRemoveNode is not NULL, since it walked up the chain constantly it means pHash (the
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// original root) was not affected. Hence, return it out.
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*ppOutHash = (pRemoveNode == NULL) ? pNewRoot : pHash;
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|
|
exit:
|
|
SetLastError(dwErr);
|
|
return dwErr;
|
|
}
|