RtlEnumerateGenericTableWithoutSplaying function (ntddk.h)

Article
02/28/2023

The RtlEnumerateGenericTableWithoutSplaying routine is used to enumerate the elements in a generic table.

Syntax

NTSYSAPI PVOID RtlEnumerateGenericTableWithoutSplaying(
  [in]      PRTL_GENERIC_TABLE Table,
  [in, out] PVOID              *RestartKey
);

Parameters

[in] Table

A pointer to the generic table (RTL_GENERIC_TABLE). The table must have been initialized by calling RtlInitializeGenericTable.

[in, out] RestartKey

An address of the element returned by the previous call to RtlEnumerateGenericTableWithoutSplaying. Should be set to NULL if the enumeration is to start at the first element in the table.

To enumerate all elements in the table, use RtlEnumerateGenericTableWithoutSplaying as follows:

RestartKey = NULL;
for (ptr = RtlEnumerateGenericTableWithoutSplaying(Table, &RestartKey);
     ptr != NULL;
     ptr = RtlEnumerateGenericTableWithoutSplaying(Table, &RestartKey)) {
        // Process the element pointed to by ptr
}

Return value

RtlEnumerateGenericTableWithoutSplaying returns a pointer to the caller-defined structure associated with the element. It returns NULL if RestartKey is NULL and the table has no elements or if RestartKey is a returned pointer and there is no next element.

Remarks

Unlike RtlEnumerateGenericTable, RtlEnumerateGenericTableWithoutSplaying does not flatten the generic table by converting it from a splay tree into a sorted linked list. RtlEnumerateGenericTableWithoutSplaying is more efficient and multiprocessor-safe than RtlEnumerateGenericTable.

RtlEnumerateGenericTableWithoutSplaying can be called repeatedly to process the caller's data in each element of a generic table.

Callers of the Rtl..GenericTable routines are responsible for exclusively synchronizing access to the generic table. An exclusive fast mutex is the most efficient synchronization mechanism to use for this purpose.

By default, the operating system uses splay trees to implement generic tables. 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. For example, use the RtlEnumerateGenericTableWithoutSplaying routine instead of RtlEnumerateGenericTableWithoutSplayingAvl. In the call to RtlEnumerateGenericTableWithoutSplayingAvl, the caller must pass a RTL_AVL_TABLE table structure rather than RTL_GENERIC_TABLE.

Callers of RtlEnumerateGenericTableWithoutSplaying must be running at IRQL < DISPATCH_LEVEL if the caller-allocated memory for the generic table is pageable.

Requirements

Requirement	Value
Target Platform	Universal
Header	ntddk.h (include Ntddk.h, Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	See Remarks section.