CHECKSUM Replacement For IMAGE And TEXT

With this discussion here http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=70328
I started to thinkn about Microsoft really calculated checksum value.

This code is 100% compatible with MS original. That is, the result is identical.
You can use it "as is", or you can use it to see that MS function does not produce that unique values one could expect.

With text/varchar/image data, call with SELECT BINARY_CHECKSUM('abcdefghijklmnop'), dbo.fnPesoBinaryChecksum('abcdefghijklmnop')
With integer data, call with SELECT BINARY_CHECKSUM(123), dbo.fnPesoBinaryChecksum(CAST(123 AS VARBINARY))
I haven't figured out how to calculate checksum for integers greater than 255 yet.CREATE FUNCTION dbo.fnPesoBinaryChecksum
(
@Data IMAGE
)
RETURNS INT
AS

BEGIN
DECLARE@Index INT,
@MaxIndex INT,
@SUM BIGINT,
@Overflow TINYINT

SELECT@Index = 1,
@MaxIndex = DATALENGTH(@Data),
@SUM = 0

WHILE @Index <= @MaxIndex
SELECT@SUM = (16 * @SUM) ^ SUBSTRING(@Data, @Index, 1),
@Overflow = @SUM / 4294967296,
@SUM = @SUM - @Overflow * 4294967296,
@SUM = @SUM ^ @Overflow,
@Index = @Index + 1

IF @SUM > 2147483647
SELECT @SUM = @SUM - 4294967296

RETURN @SUM
ENDActually this is an improvement of MS function, since it accepts TEXT and IMAGE data.CREATE FUNCTION dbo.fnPesoTextChecksum
(
@Data TEXT
)
RETURNS INT
AS

BEGIN
DECLARE@Index INT,
@MaxIndex INT,
@SUM BIGINT,
@Overflow TINYINT

SELECT@Index = 1,
@MaxIndex = DATALENGTH(@Data),
@SUM = 0

WHILE @Index <= @MaxIndex
SELECT@SUM = (16 * @SUM) ^ ASCII(SUBSTRING(@Data, @Index, 1)),
@Overflow = @SUM / 4294967296,
@SUM = @SUM - @Overflow * 4294967296,
@SUM = @SUM ^ @Overflow,
@Index = @Index + 1

IF @SUM > 2147483647
SELECT @SUM = @SUM - 4294967296

RETURN @SUM
END
Peter Larsson
Helsingborg, Sweden