Issue while execute tsql function - function

Question

I have written the following function:
CREATE FUNCTION dbo.GetData
(#value AS VARCHAR(MAX),
#pattern AS VARCHAR(MAX),
#masker AS VARCHAR,
#notMaskedCount AS INT)
RETURNS NCHAR(47)
AS BEGIN
DECLARE #nextPatIdx INT
SET #nextPatIdx = PATINDEX('%' + #pattern + '%', #value)
WHILE #nextPatIdx > 0 AND #nextPatIdx < LEN(#value) - #notMaskedCount
BEGIN
SET #value = Stuff(#value, #nextPatIdx, 1, #masker)
SET #nextPatIdx = PATINDEX('%' + #pattern + '%', #value)
END
RETURN CONVERT(NCHAR(40), #value) + '_data'
END
Run it with :
select dbo.GetData('152648494','[a-zA-Z0-9]', 'x', 4)
If I execute it throw C# and try readdata it throws exception
If I runt it viahttp://sqlfiddle.com/#!6/6ee81/1 I get an error
It doen`t complete the execution
What is wrong - the function / the way I call it?

Answer 1

You achieved a infinite loop as you can check using this piece of code:
---select dbo.GetData('152648494','[a-zA-Z0-9]', 'x', 4)
declare
#value AS VARCHAR(MAX) = '152648494',
#pattern AS VARCHAR(MAX) = '[a-zA-Z0-9]',
#masker AS VARCHAR(1) = 'x',
#notMaskedCount AS INT = 4
DECLARE #nextPatIdx INT
SET #nextPatIdx = PATINDEX('%' + #pattern + '%', #value)
WHILE #nextPatIdx > 0 AND #nextPatIdx < LEN(#value) - #notMaskedCount
BEGIN
SET #value = Stuff(#value, #nextPatIdx, 1, #masker)
SET #nextPatIdx = PATINDEX('%' + #pattern + '%', #value)
print #nextPatIdx;
END
print 'END'
select CONVERT(NCHAR(40), #value) + '_data'
Maybe if you change the inequality
#nextPatIdx > 0
to
#nextPatIdx > 1
It ill exit the infinite loop but I need more info to find out what you desired output
EDIT
I guess you need to change your loop to it.
WHILE #nextPatIdx > 0 AND #nextPatIdx <= LEN(#value) - #notMaskedCount
BEGIN
SET #value = Stuff(#value, #nextPatIdx, 1, #masker)
--SET #nextPatIdx = PATINDEX('%' + #pattern + '%', #value)
SET #nextPatIdx += 1
END