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RtlLookupFirstMatchingElementGenericTableAvl function (ntddk.h)

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The RtlLookupFirstMatchingElementGenericTableAvl routine finds the left-most element in the tree that matches the indicated data.

Syntax

NTSYSAPI PVOID RtlLookupFirstMatchingElementGenericTableAvl(
  [in]  PRTL_AVL_TABLE Table,
  [in]  PVOID          Buffer,
  [out] PVOID          *RestartKey
);

Parameters

[in] Table

A pointer to the generic Adelson-Velsky/Landis (AVL) table (RTL_AVL_TABLE).

[in] Buffer

A buffer that contains the search data.

[out] RestartKey

On output, contains a search context to use with an enumeration routine, such as RtlEnumerateGenericTableWithoutSplayingAvl.

Return value

The RtlLookupFirstMatchingElementGenericTableAvlroutine returns a pointer to the matched data, or NULL if no match was found.

Remarks

A tree that implements a generic table might contain several file names that differ only in case. A search algorithm can use this routine to locate the first match, without reference to case, and use an enumeration routine, such as RtlEnumerateGenericTableWithoutSplayingAvl, to return each subsequent match.

By default, the operating system uses splay trees to implement generic tables, but the RtlLookupFirstMatchingElementGenericTableAvlroutine only works with Adelson-Velsky/Landis (AVL) trees. Under some circumstances, operations on a splay tree will make the tree deep and narrow and might even turn it into a straight line. Very deep trees degrade the performance of searches. You can ensure a more balanced, shallower tree implementation of generic tables by using Adelson-Velsky/Landis (AVL) trees. If you want to configure the generic table routines to use AVL trees instead of splay trees in your driver, insert the following define statement in a common header file before including Ntddk.h:

#define RTL_USE_AVL_TABLES 0

If RTL_USE_AVL_TABLES is not defined, you must use the AVL form of the generic table routines.

Callers of RtlLookupFirstMatchingElementGenericTableAvl must be running at <= APC_LEVEL if either of the following conditions holds:

  • The caller-allocated memory at Table or at Buffer is pageable.
  • The caller-supplied CompareRoutine contains pageable code.

Requirements

Requirement Value
Minimum supported client Available starting with Windows Vista.
Target Platform Universal
Header ntddk.h (include FltKernel.h, Ntifs.h, Ntddk.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
IRQL <= APC_LEVEL (see Remarks section)

See also

RtlEnumerateGenericTableWithoutSplayingAvl