Leaked source code of windows server 2003
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/*++
Copyright (c) 1989 Microsoft Corporation
Module Name:
smsesnid.c
Abstract:
Session Manager Session ID Management
Author:
Mark Lucovsky (markl) 04-Oct-1989
Revision History:
--*/
#include "smsrvp.h"
#include <string.h>
ULONG SmpAllocateSessionId( IN PSMPKNOWNSUBSYS OwningSubsystem, IN PSMPKNOWNSUBSYS CreatorSubsystem OPTIONAL )
/*++
Routine Description:
This function allocates a session ID.
Arguments:
OwningSubsystem - Supplies the address of the subsystem that should become the owner of this session.
CreatorSubsystem - An optional parameter that supplies the address of the subsystem requesting the creation of this session. This subsystem is notified when the session completes.
Return Value:
This function returns the session ID for this session.
--*/
{
ULONG SessionId; PLIST_ENTRY SessionIdListInsertPoint; PSMPSESSION Session;
RtlEnterCriticalSection(&SmpSessionListLock);
//
// SessionIds are allocated by incrementing a 32 bit counter.
// If the counter wraps, then session IDs are allocated by
// scanning the sorted list of current session IDs for a hole.
//
SessionId = SmpNextSessionId++; SessionIdListInsertPoint = SmpSessionListHead.Blink;
if ( !SmpNextSessionIdScanMode ) {
if ( SmpNextSessionId == 0 ) {
//
// We have used up 32 bits worth of session IDs so
// enable scan mode session ID allocation.
//
SmpNextSessionIdScanMode = TRUE; }
} else {
//
// Compute a session ID by scanning the sorted session ID list
// until a hole is found. When an ID is found, then save it,
// and recalculate the insert point.
//
#if DBG
DbgPrint("SMSS: SessionId's Wrapped\n"); DbgBreakPoint(); #endif
}
Session = RtlAllocateHeap(SmpHeap, MAKE_TAG( SM_TAG ), sizeof(SMPSESSION));
if (Session) { Session->SessionId = SessionId; Session->OwningSubsystem = OwningSubsystem; Session->CreatorSubsystem = CreatorSubsystem;
InsertTailList(SessionIdListInsertPoint,&Session->SortedSessionIdListLinks); } else { DbgPrint("SMSS: Unable to keep track of session ID -- no memory available\n"); } RtlLeaveCriticalSection(&SmpSessionListLock);
return SessionId; }
PSMPSESSION SmpSessionIdToSession( IN ULONG SessionId )
/*++
Routine Description:
This function locates the session structure for the specified session ID.
It is assumed that the caller holds the session list lock.
Arguments:
SessionId - Supplies the session ID to locate the structure for.
Return Value:
NULL - No session matches the specified session.
NON-NULL - Returns a pointer to the session structure associated with the specified session ID.
--*/
{
PLIST_ENTRY Next; PSMPSESSION Session;
Next = SmpSessionListHead.Flink; while ( Next != &SmpSessionListHead ) { Session = CONTAINING_RECORD(Next, SMPSESSION, SortedSessionIdListLinks );
if ( Session->SessionId == SessionId ) { return Session; } Next = Session->SortedSessionIdListLinks.Flink; }
return NULL; }
VOID SmpDeleteSession( IN ULONG SessionId )
/*++
Routine Description:
This function locates and deletes a session ID.
Arguments:
SessionId - Supplies the session ID to delete.
Return Value:
None.
--*/
{ PSMPSESSION Session;
RtlEnterCriticalSection(&SmpSessionListLock);
Session = SmpSessionIdToSession(SessionId);
if ( Session ) {
RemoveEntryList(&Session->SortedSessionIdListLinks);
RtlLeaveCriticalSection(&SmpSessionListLock);
RtlFreeHeap(SmpHeap,0,Session);
} else {
RtlLeaveCriticalSection(&SmpSessionListLock); }
return; }
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