124 lines
3.8 KiB
C
124 lines
3.8 KiB
C
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/*++ BUILD Version: 0009 // Increment this if a change has global effects
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Copyright (c) 1987-1993 Microsoft Corporation
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Module Name:
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midatlas.h
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Abstract:
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This module defines the data structure used in mapping MIDS to the corresponding requests/
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contexts associated with them.
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Author:
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Balan Sethu Raman (SethuR) 26-Aug-95 Created
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Notes:
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MID (Multiplex ID) is used at both the server and the client ( redirector ) to distinguish
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between the concurrently active requests on any connection. This data structure has been
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designed to meet the following criterion.
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1) It should scale well to handle the differing capabilities of a server, e.g., the typical
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NT server permits 50 outstanding requests on any connection. The CORE level servers can go as
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low as one and on Gateway machines the desired number can be very high ( in the oreder of thousands)
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2) The two primary operations that need to be handled well are
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i) mapping a MID to the context associated with it.
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-- This routine will be invoked to process every packet received along any connection
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at both the server and the client.
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ii) generating a new MID for sending requests to the server.
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-- This will be used at the client both for max. command enforcement as well as
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tagging each concurrent request with a unique id.
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The most common case is that of a connection between a NT client and a NT server. All
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design decisions have been made in order to ensure that the solutions are optimal
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for this case.
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The MID data structure must be efficiently able to manage the unique tagging and identification
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of a number of mids ( typically 50 ) from a possible combination of 65536 values. In order to
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ensure a proper time space tradeoff the lookup is organized as a three level hierarchy.
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The 16 bits used to represent a MID are split upinto three bit fields. The length of the
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rightmost field ( least signifiant ) is decided by the number of mids that are to be
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allocated on creation. The remaining length is split up equally between the next two
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fields, e.g., if 50 mids are to be allocated on creation , the length of the first field
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is 6 ( 64 ( 2 ** 6 ) is greater than 50 ), 5 and 5.
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--*/
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#ifndef _MIDATLAX_H_
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#define _MIDATLAX_H_
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typedef struct _RX_MID_ATLAS {
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USHORT MaximumNumberOfMids;
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USHORT MidsAllocated;
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USHORT NumberOfMidsInUse;
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USHORT NumberOfMidsDiscarded;
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USHORT MaximumMidFieldWidth;
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USHORT Reserved;
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USHORT MidQuantum;
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UCHAR MidQuantumFieldWidth;
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UCHAR NumberOfLevels;
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LIST_ENTRY MidMapFreeList;
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LIST_ENTRY MidMapExpansionList;
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struct _MID_MAP_ *pRootMidMap;
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} RX_MID_ATLAS, *PRX_MID_ATLAS;
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typedef
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VOID (*PCONTEXT_DESTRUCTOR)(
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PVOID pContext);
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typedef
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VOID (*PCONTEXT_ITERATOR)(
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PVOID pContext);
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#define RxGetMaximumNumberOfMids(pMidAtlas) \
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((pMidAtlas)->MaximumNumberOfMids)
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#define RxGetNumberOfMidsInUse(pMidAtlas) \
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((pMidAtlas)->NumberOfMidsInUse)
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PRX_MID_ATLAS
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RxCreateMidAtlas(
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USHORT MaximumNumberOfEntries,
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USHORT InitialAllocation);
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VOID
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RxDestroyMidAtlas(
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PRX_MID_ATLAS pMidAtlas,
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PCONTEXT_DESTRUCTOR pContextDestructor);
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void
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RxIterateMidAtlasAndRemove(
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PRX_MID_ATLAS pMidAtlas,
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PCONTEXT_ITERATOR pContextIterator);
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PVOID
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RxMapMidToContext(
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PRX_MID_ATLAS pMidAtlas,
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USHORT Mid);
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NTSTATUS
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RxAssociateContextWithMid(
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PRX_MID_ATLAS pMidAtlas,
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PVOID pContext,
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PUSHORT pNewMid);
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NTSTATUS
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RxMapAndDissociateMidFromContext(
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PRX_MID_ATLAS pMidAtlas,
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USHORT Mid,
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PVOID *pContextPointer);
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NTSTATUS
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RxReassociateMid(
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PRX_MID_ATLAS pMidAtlas,
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USHORT Mid,
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PVOID pNewContext);
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#endif
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