RxCreateMidAtlas function (midatlax.h)

Article
02/22/2024

RxCreateMidAtlas allocates a new instance of MID_ATLAS data structure and initializes it.

Syntax

PRX_MID_ATLAS RxCreateMidAtlas(
  USHORT MaximumNumberOfEntries,
  USHORT InitialAllocation
);

Parameters

MaximumNumberOfEntries

The maximum number of multiplex IDs (MIDs) to be allowed in the atlas.

InitialAllocation

The number of multiplex IDs allocated initially.

Return value

RxCreateMidAtlas returns a pointer to allocated and initialized MID_ATLAS data structure on success or a NULL pointer on failure.

Remarks

RDBSS defines a Multiplex ID (MID), a 16-bit value, that can be used by both the network client (mini-redirector) and the server to distinguish between the concurrently active requests on any connection.

The MID must be efficiently able to manage the unique tagging and identification of a number of MIDs (typically 50) from a possible combination of 65,536 values. In order to ensure a proper time space tradeoff, the lookup is organized as a three level hierarchy. The 16 bits used to represent a MID are split up into three bitfields. The length of the rightmost field (least significant ) is decided by the maximum number of MIDs that are to be allowed in the atlas. This maximum value is a parameter passed to RxCreateMidAtlas when the MID_ATLAS data structure is created. The remaining length is split up equally between the next two fields.

For example, if a maximum of 50 MIDs are to be allocated on creation , the length of the first field is 6 (64 ( 2 ** 6 ) is greater than 50 ). The remaining length is split into two fields of 5 bits each.

RxCreateMidAtlas allocates non-paged pool memory when creating a new MID_ATLAS data structure.

Requirements

Requirement	Value
Target Platform	Desktop
Header	midatlax.h (include Midatlax.h)
IRQL	<= APC_LEVEL