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[NTOSKNRL]

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Improve performance of FsRtlIsNameInExpression by using a stack buffer for backtracking of wildcard expressions. See also CR-60

svn path=/trunk/; revision=64369
This commit is contained in:
Timo Kreuzer
2014-09-28 18:17:14 +00:00
parent 1f933c38fc
commit edc042092f
1 changed files with 32 additions and 18 deletions
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reactos/ntoskrnl/fsrtl/name.c
+32 -18
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@@ -24,7 +24,10 @@ FsRtlIsNameInExpressionPrivate(IN PUNICODE_STRING Expression,
IN PWCHAR UpcaseTable OPTIONAL)
{
SHORT StarFound = -1, DosStarFound = -1;
PUSHORT BackTracking = NULL, DosBackTracking = NULL;
USHORT BackTrackingBuffer[5], DosBackTrackingBuffer[5];
PUSHORT BackTracking = BackTrackingBuffer, DosBackTracking = DosBackTrackingBuffer;
SHORT BackTrackingSize = RTL_NUMBER_OF(BackTrackingBuffer);
SHORT DosBackTrackingSize = RTL_NUMBER_OF(DosBackTrackingBuffer);
UNICODE_STRING IntExpression;
USHORT ExpressionPosition = 0, NamePosition = 0, MatchingChars, LastDot;
WCHAR CompareChar;
@@ -127,23 +130,28 @@ FsRtlIsNameInExpressionPrivate(IN PUNICODE_STRING Expression,
ExpressionPosition++;
}
/* Save star position */
if (!BackTracking)
{
BackTracking = ExAllocatePoolWithTag(PagedPool | POOL_RAISE_IF_ALLOCATION_FAILURE,
(Expression->Length / sizeof(WCHAR)) * sizeof(USHORT),
'nrSF');
}
BackTracking[++StarFound] = ExpressionPosition++;
/* If star is at the end, then eat all rest and leave */
if (ExpressionPosition == Expression->Length / sizeof(WCHAR))
{
NamePosition = Name->Length / sizeof(WCHAR);
break;
}
/* Save star position */
StarFound++;
if (StarFound >= BackTrackingSize)
{
BackTrackingSize = Expression->Length / sizeof(WCHAR);
BackTracking = ExAllocatePoolWithTag(PagedPool | POOL_RAISE_IF_ALLOCATION_FAILURE,
BackTrackingSize * sizeof(USHORT),
'nrSF');
RtlCopyMemory(BackTracking, BackTrackingBuffer, sizeof(BackTrackingBuffer));
}
BackTracking[StarFound] = ExpressionPosition++;
/* Allow null matching */
else if (Expression->Buffer[ExpressionPosition] != L'?' &&
if (Expression->Buffer[ExpressionPosition] != L'?' &&
Expression->Buffer[ExpressionPosition] != Name->Buffer[NamePosition])
{
NamePosition++;
@@ -179,10 +187,16 @@ FsRtlIsNameInExpressionPrivate(IN PUNICODE_STRING Expression,
*/
if (MatchingChars != Name->Length || LastDot == (USHORT)-1)
{
if (!DosBackTracking) DosBackTracking = ExAllocatePoolWithTag(PagedPool | POOL_RAISE_IF_ALLOCATION_FAILURE,
(Expression->Length / sizeof(WCHAR)) * sizeof(USHORT),
'nrSF');
DosBackTracking[++DosStarFound] = ExpressionPosition++;
DosStarFound++;
if (DosStarFound >= DosBackTrackingSize)
{
DosBackTrackingSize = Expression->Length / sizeof(WCHAR);
DosBackTracking = ExAllocatePoolWithTag(PagedPool | POOL_RAISE_IF_ALLOCATION_FAILURE,
DosBackTrackingSize * sizeof(USHORT),
'nrSF');
RtlCopyMemory(DosBackTracking, DosBackTrackingBuffer, sizeof(DosBackTrackingBuffer));
}
DosBackTracking[DosStarFound] = ExpressionPosition++;
/* Not the same char, start exploring */
if (Expression->Buffer[ExpressionPosition] != Name->Buffer[NamePosition])
@@ -206,7 +220,7 @@ FsRtlIsNameInExpressionPrivate(IN PUNICODE_STRING Expression,
NamePosition++;
}
/* Try to explore later on for null matching */
else if ((ExpressionPosition + 1 < (USHORT)(Expression->Length / sizeof(WCHAR))) &&
else if ((ExpressionPosition + 1 < (USHORT)(Expression->Length / sizeof(WCHAR))) &&
(Name->Buffer[NamePosition] == Expression->Buffer[ExpressionPosition + 1]))
{
NamePosition++;
@@ -262,11 +276,11 @@ FsRtlIsNameInExpressionPrivate(IN PUNICODE_STRING Expression,
}
}
if (BackTracking)
if (BackTracking != BackTrackingBuffer)
{
ExFreePoolWithTag(BackTracking, 'nrSF');
}
if (DosBackTracking)
if (DosBackTracking != DosBackTrackingBuffer)
{
ExFreePoolWithTag(DosBackTracking, 'nrSF');
}