554 lines
11 KiB
C
554 lines
11 KiB
C
/*++
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Copyright (c) 1996 Microsoft Corporation
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Module Name:
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group.c
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Abstract:
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This module contains Group ID managment routines.
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Group IDs identify an AFD_GROUP_ENTRY structure in a lookup table.
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Each AFD_GROUP_ENTRY contains a reference count and a type (either
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GroupTypeConstrained or GroupTypeUnconstrained). Free group IDs are
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linked together in a doubly-linked list. As group IDs are allocated,
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they are removed from this list. Once the free list becomes empty,
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the lookup table is grown appropriately.
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Author:
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Keith Moore (keithmo) 06-Jun-1996
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Revision History:
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--*/
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#include "afdp.h"
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//
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// Private constants.
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//
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#define AFD_GROUP_TABLE_GROWTH 32 // entries
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//
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// Private types.
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//
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typedef struct _AFD_GROUP_ENTRY {
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union {
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LIST_ENTRY ListEntry;
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struct {
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AFD_GROUP_TYPE GroupType;
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LONG ReferenceCount;
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};
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};
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} AFD_GROUP_ENTRY, *PAFD_GROUP_ENTRY;
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//
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// Private globals.
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//
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PERESOURCE AfdGroupTableResource;
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PAFD_GROUP_ENTRY AfdGroupTable;
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LIST_ENTRY AfdFreeGroupList;
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LONG AfdGroupTableSize;
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//
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// Private functions.
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//
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PAFD_GROUP_ENTRY
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AfdMapGroupToEntry(
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IN LONG Group
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);
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#ifdef ALLOC_PRAGMA
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#pragma alloc_text( INIT, AfdInitializeGroup )
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#pragma alloc_text( PAGE, AfdTerminateGroup )
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#pragma alloc_text( PAGE, AfdReferenceGroup )
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#pragma alloc_text( PAGE, AfdDereferenceGroup )
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#pragma alloc_text( PAGE, AfdGetGroup )
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#endif
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BOOLEAN
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AfdInitializeGroup(
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VOID
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)
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/*++
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Routine Description:
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Initializes any globals necessary for the group ID package.
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Return Value:
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BOOLEAN - TRUE if successful, FALSE otherwise.
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--*/
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{
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//
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// Initialize the group globals.
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//
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AfdGroupTableResource = AFD_ALLOCATE_POOL_PRIORITY(
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NonPagedPool,
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sizeof(*AfdGroupTableResource),
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AFD_RESOURCE_POOL_TAG,
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HighPoolPriority
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);
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if( AfdGroupTableResource == NULL ) {
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return FALSE;
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}
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ExInitializeResourceLite( AfdGroupTableResource );
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AfdGroupTable = NULL;
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InitializeListHead( &AfdFreeGroupList );
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AfdGroupTableSize = 0;
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return TRUE;
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} // AfdInitializeGroup
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VOID
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AfdTerminateGroup(
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VOID
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)
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/*++
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Routine Description:
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Destroys any globals created for the group ID package.
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--*/
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{
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if( AfdGroupTableResource != NULL ) {
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ExDeleteResourceLite( AfdGroupTableResource );
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AFD_FREE_POOL(
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AfdGroupTableResource,
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AFD_RESOURCE_POOL_TAG
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);
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AfdGroupTableResource = NULL;
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}
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if( AfdGroupTable != NULL ) {
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AFD_FREE_POOL(
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AfdGroupTable,
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AFD_GROUP_POOL_TAG
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);
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AfdGroupTable = NULL;
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}
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InitializeListHead( &AfdFreeGroupList );
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AfdGroupTableSize = 0;
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} // AfdTerminateGroup
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BOOLEAN
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AfdReferenceGroup(
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IN LONG Group,
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OUT PAFD_GROUP_TYPE GroupType
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)
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/*++
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Routine Description:
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Bumps the reference count associated with the given group ID.
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Arguments:
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Group - The group ID to reference.
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GroupType - Returns the type of the group.
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Returns:
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BOOLEAN - TRUE if the group ID was valid, FALSE otherwise.
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--*/
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{
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PAFD_GROUP_ENTRY groupEntry;
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AFD_GROUP_TYPE groupType;
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groupEntry = AfdMapGroupToEntry( Group );
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if( groupEntry != NULL ) {
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groupType = groupEntry->GroupType;
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if( groupType == GroupTypeConstrained ||
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groupType == GroupTypeUnconstrained ) {
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groupEntry->ReferenceCount++;
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*GroupType = groupType;
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} else {
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groupEntry = NULL;
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}
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ExReleaseResourceLite( AfdGroupTableResource );
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KeLeaveCriticalRegion ();
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}
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return (BOOLEAN)( groupEntry != NULL );
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} // AfdReferenceGroup
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BOOLEAN
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AfdDereferenceGroup(
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IN LONG Group
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)
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/*++
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Routine Description:
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Decrements the reference count associated with the given group ID.
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If the ref count drops to zero, the group ID is freed.
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Arguments:
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Group - The group ID to dereference.
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Returns:
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BOOLEAN - TRUE if the group ID was valid, FALSE otherwise.
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--*/
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{
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PAFD_GROUP_ENTRY groupEntry;
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AFD_GROUP_TYPE groupType;
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groupEntry = AfdMapGroupToEntry( Group );
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if( groupEntry != NULL ) {
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groupType = groupEntry->GroupType;
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if( groupType == GroupTypeConstrained ||
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groupType == GroupTypeUnconstrained ) {
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ASSERT( groupEntry->ReferenceCount > 0 );
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groupEntry->ReferenceCount--;
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if( groupEntry->ReferenceCount == 0 ) {
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InsertTailList(
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&AfdFreeGroupList,
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&groupEntry->ListEntry
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);
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}
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} else {
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groupEntry = NULL;
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}
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ExReleaseResourceLite( AfdGroupTableResource );
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KeLeaveCriticalRegion ();
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}
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return (BOOLEAN)( groupEntry != NULL );
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} // AfdDereferenceGroup
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BOOLEAN
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AfdGetGroup(
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IN OUT PLONG Group,
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OUT PAFD_GROUP_TYPE GroupType
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)
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/*++
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Routine Description:
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Examines the incoming group. If is zero, then nothing is done. If it
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is SG_CONSTRAINED_GROUP, then a new constrained group ID is created.
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If it is SG_UNCONSTRAINED_GROUP, then a new unconstrained group ID is
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created. Otherwise, it must identify an existing group, so that group
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is referenced.
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Arguments:
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Group - Points to the group ID to examine/modify.
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GroupType - Returns the type of the group.
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Return Value:
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BOOLEAN - TRUE if successful, FALSE otherwise.
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--*/
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{
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LONG groupValue;
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PAFD_GROUP_ENTRY groupEntry;
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PAFD_GROUP_ENTRY newGroupTable;
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LONG newGroupTableSize;
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LONG i;
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PLIST_ENTRY listEntry;
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groupValue = *Group;
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//
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// Zero means "no group", so just ignore it.
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//
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if( groupValue == 0 ) {
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*GroupType = GroupTypeNeither;
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return TRUE;
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}
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//
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// If we're being asked to create a new group, do it.
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//
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if( groupValue == SG_CONSTRAINED_GROUP ||
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groupValue == SG_UNCONSTRAINED_GROUP ) {
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//
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// Lock the table.
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//
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//
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// Make sure the thread in which we execute cannot get
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// suspeneded in APC while we own the global resource.
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//
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KeEnterCriticalRegion ();
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ExAcquireResourceExclusiveLite( AfdGroupTableResource, TRUE );
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//
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// See if there's room at the inn.
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//
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if( IsListEmpty( &AfdFreeGroupList ) ) {
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//
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// No room, we'll need to create/expand the table.
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//
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newGroupTableSize = AfdGroupTableSize + AFD_GROUP_TABLE_GROWTH;
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newGroupTable = AFD_ALLOCATE_POOL(
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PagedPool,
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newGroupTableSize * sizeof(AFD_GROUP_ENTRY),
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AFD_GROUP_POOL_TAG
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);
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if( newGroupTable == NULL ) {
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ExReleaseResourceLite( AfdGroupTableResource );
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KeLeaveCriticalRegion ();
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return FALSE;
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}
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if( AfdGroupTable == NULL ) {
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//
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// This is the initial table allocation, so reserve the
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// first three entries (0, SG_UNCONSTRAINED_GROUP, and
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// SG_CONSTRAINED_GROUP).
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//
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for( ;
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AfdGroupTableSize <= SG_CONSTRAINED_GROUP ||
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AfdGroupTableSize <= SG_UNCONSTRAINED_GROUP ;
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AfdGroupTableSize++ ) {
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newGroupTable[AfdGroupTableSize].ReferenceCount = 0;
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newGroupTable[AfdGroupTableSize].GroupType = GroupTypeNeither;
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}
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} else {
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//
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// Copy the old table into the new table, then free the
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// old table.
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//
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RtlCopyMemory(
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newGroupTable,
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AfdGroupTable,
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AfdGroupTableSize * sizeof(AFD_GROUP_ENTRY)
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);
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AFD_FREE_POOL(
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AfdGroupTable,
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AFD_GROUP_POOL_TAG
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);
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}
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//
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// Add the new entries to the free list.
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//
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for( i = newGroupTableSize - 1 ; i >= AfdGroupTableSize ; i-- ) {
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InsertHeadList(
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&AfdFreeGroupList,
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&newGroupTable[i].ListEntry
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);
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}
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AfdGroupTable = newGroupTable;
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AfdGroupTableSize = newGroupTableSize;
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}
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//
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// Pull the next free entry off the list.
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//
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ASSERT( !IsListEmpty( &AfdFreeGroupList ) );
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listEntry = RemoveHeadList( &AfdFreeGroupList );
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groupEntry = CONTAINING_RECORD(
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listEntry,
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AFD_GROUP_ENTRY,
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ListEntry
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);
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groupEntry->ReferenceCount = 1;
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groupEntry->GroupType = (AFD_GROUP_TYPE)groupValue;
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*Group = (LONG)( groupEntry - AfdGroupTable );
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*GroupType = groupEntry->GroupType;
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ExReleaseResourceLite( AfdGroupTableResource );
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KeLeaveCriticalRegion ();
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return TRUE;
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}
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//
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// Otherwise, just reference the group.
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//
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return AfdReferenceGroup( groupValue, GroupType );
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} // AfdGetGroup
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PAFD_GROUP_ENTRY
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AfdMapGroupToEntry(
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IN LONG Group
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)
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/*++
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Routine Description:
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Maps the given group ID to the corresponding AFD_GROUP_ENTRY structure.
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N.B. This routine returns with AfdGroupTableResource held if successful.
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Arguments:
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Group - The group ID to map.
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Return Value:
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PAFD_GROUP_ENTRY - The entry corresponding to the group ID if successful,
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NULL otherwise.
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--*/
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{
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PAFD_GROUP_ENTRY groupEntry;
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//
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// Lock the table.
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//
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//
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// Make sure the thread in which we execute cannot get
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// suspeneded in APC while we own the global resource.
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//
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KeEnterCriticalRegion ();
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ExAcquireResourceExclusiveLite( AfdGroupTableResource, TRUE );
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//
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// Validate the group ID.
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//
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if( Group > 0 && Group < AfdGroupTableSize ) {
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groupEntry = AfdGroupTable + Group;
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//
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// The group ID is within legal range. Ensure it's in use.
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// In the AFD_GROUP_ENTRY structure, the GroupType field is
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// overlayed with ListEntry.Flink due to the internal union.
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// We can use this knowledge to quickly validate that this
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// entry is in use.
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//
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if( groupEntry->GroupType == GroupTypeConstrained ||
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groupEntry->GroupType == GroupTypeUnconstrained ) {
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return groupEntry;
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}
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}
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//
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// Invalid group ID, fail it.
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//
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ExReleaseResourceLite( AfdGroupTableResource );
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KeLeaveCriticalRegion ();
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return NULL;
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} // AfdMapGroupToEntry
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