Decode HTML Strings in SQL Server

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

-- EXEC UrlDecode '%c3%a1'
-- EXEC UrlDecode '\\Tul1ciprmw1\RichMediaAssets\Open\Telemundo\Al Rojo Vivo con Mar%c3%ada Celeste\_derived_jpg_q90_172x128_m1\3ARValx05Mar%c3%ada Celeste Arrar%c3%a1s.jpg'
-- EXEC UrlDecode '%4D'

ALTER PROCEDURE UrlDecode
-- Add the parameters for the stored procedure here
@URL varchar(2000)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

DECLARE @Position INT,
@Base CHAR(16),
@High TINYINT,
@Low TINYINT,
@NewHigh INT,
@Pattern CHAR(21)

SELECT @Base = '0123456789abcdef',
@Pattern = '%[%][0-9a-f][0-9a-f]%',
@Position = PATINDEX(@Pattern, @URL)

SELECT @High = CHARINDEX(SUBSTRING(@URL, @Position + 1, 1), @Base) -1,
@Low = CHARINDEX(SUBSTRING(@URL, @Position + 2, 1), @Base) -1

WHILE @Position > 0
BEGIN

IF (@High & 15) = 12 -- xC0
BEGIN
SELECT @NewHigh = @Low * POWER(2, 6) --Shift Low 6 bits

SELECT @High = CHARINDEX(SUBSTRING(@URL, @Position + 4, 1), @Base) -1
SELECT @Low = CHARINDEX(SUBSTRING(@URL, @Position + 5, 1), @Base) -1

SELECT @URL = STUFF(@URL, @Position, 6, CHAR(@NewHigh | (16 * @High) | @Low))

SELECT @High = 0, @Low = 0, @NewHigh = 0

END
ELSE
BEGIN
SELECT @URL = STUFF(@URL, @Position, 3, CHAR(16 * @High | @Low))

END

SELECT @Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
BEGIN
SELECT @High = CHARINDEX(SUBSTRING(@URL, @Position + 1, 1), @Base) -1,
@Low = CHARINDEX(SUBSTRING(@URL, @Position + 2, 1), @Base) -1
END
END

SELECT @URL

END
GO