UNHEXING to integer (as opposed to a string)...

I've tried several ways to get my hex-encoded string representation of
an integer to convert back to an integer, but none of them work (the
input string '1a4b' should evaluate to 6731):

(Note that this is not an endianness problem. The hex string is in
little endian byte order (since it represents a 2-byte integer or
short) and this is running on a little endian system. Also, method 4
(below) works with a string literal, but not a string variable, as
explained in the notes for method 4...)


method 1

SET @string := '1a4b';
SELECT UNHEX(@string);

+----------------+
| UNHEX(@string) |
+----------------+
| K |
+----------------+



method 2

SET @string := '1a4b';
SELECT CAST(@string AS UNSIGNED);

+---------------------------+
| CAST(@string AS UNSIGNED) |
+---------------------------+
| 1 |
+---------------------------+



method 3

SET @string := '1a4b';

SELECT CONCAT('0x', @string) into @string;
SELECT @string + 0;

+-------------+
| @string + 0 |
+-------------+
| 0 |
+-------------+



method 4

SELECT CAST(X'1a4b' AS UNSIGNED);

+---------------------------+
| CAST(X'1a4b' AS UNSIGNED) |
+---------------------------+
| 6731 |
+---------------------------+

-- that is the correct result, but this method seems to only work
with literals...



SET @string := '1a4b';
SELECT CAST(X@string AS UNSIGNED);

-- syntax error



SET @string := '1a4b';
SELECT CAST(X'@string' AS UNSIGNED);

-- syntax error



SET @string := '1a4b';
SELECT CAST(X"@string" AS UNSIGNED);

-- syntax error



SET @string := '1a4b';
SELECT CAST('X@string' AS UNSIGNED);

-- syntax error



SET @string := '1a4b';
SELECT CAST(X @string AS UNSIGNED);

-- syntax error







.... so, what can I do?






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Re: UNHEXING to integer (as opposed to a string)...

Oops: This little bit doesn't make sense, logically: "The hex string is
in little endian byte order (since it represents a 2-byte integer or
short)"... What I was trying to say is that the integer that this hex
string represents is multi-byte, so the order of the hex bytes **is**
important... but I ensure that the bytes are in little endian order
when sending the string to the server, and the server itself is little
endian, so endianness is not the problem with this conversion that I'm
trying to do.




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Re: UNHEXING to integer (as opposed to a string)...

Oops: This little bit doesn't make sense, logically: "The hex string is
in little endian byte order (since it represents a 2-byte integer or
short)"... What I was trying to say is that the integer that this hex
string represents is multi-byte, so the order of the hex bytes **is**
important... but I ensure that the bytes are in little endian order
when sending the string to the server, and the server itself is little
endian, so endianness is not the problem with this conversion that I'm
trying to do.




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Re: UNHEXING to integer (as opposed to a string)...

> SET @string := '1a4b';
> SELECT CONV(@string,16,10);
> +---------------------+
> | CONV(@string,16,10) |
> +---------------------+
> | 6731


Thanks. That works perfectly.

Much appreciated.







On February 28, 2010, Michael Dykman wrote:

> It's still a string, but this should accomplish what you are after.
> No endian issues apply here.
>
> SET @string := '1a4b';
> SELECT CONV(@string,16,10);
> +---------------------+
> | CONV(@string,16,10) |
> +---------------------+
> | 6731
>
> - michael dykman
>
>
> On Sun, Feb 28, 2010 at 12:08 PM, mysql.list@juun.com
> wrote:
>>
>>
>> Oops: This little bit doesn't make sense, logically: "The hex string is in
>> little endian byte order (since it represents a 2-byte integer or
>> short)"...
>> What I was trying to say is that the integer that this hex string
>> represents
>> is multi-byte, so the order of the hex bytes **is** important... but I
>> ensure that the bytes are in little endian order when sending the string to
>> the server, and the server itself is little endian, so endianness is
>> not the
>> problem with this conversion that I'm trying to do.
>>
>>
>>
>>
>> --
>> MySQL General Mailing List
>> For list archives: http://lists.mysql.com/mysql
>> To unsubscribe:    http://lists.mysql.com/mysql?unsub=mdykman@gmail.com
>>
>>
>
>
>
> --
> - michael dykman
> - mdykman@gmail.com
>
> May the Source be with you.
>
>




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