Re: Convert from hex to string

Thanks a lot.

All works fine.

On Wed, Nov 25, 2015 at 9:49 PM, Francisco Olarte <folarte(at)peoplecall(dot)com>
wrote:

> Mail pingpong day. ;-)
>
> On Wed, Nov 25, 2015 at 7:27 PM, Adrian Klaver
> <adrian(dot)klaver(at)aklaver(dot)com> wrote:
>
> > postgres(at)latin1_db=# \encoding
> > UTF8
>
> This does not matter, as you are sending/receiving hex data, and the
> encoding done when sending query results to you gets reverted when you
> send queries back to the server.
>
>
> > postgres(at)latin1_db=# select convert_from('\xe9', 'latin1');
> > convert_from
> > --------------
> > é
> > (1 row)
>
> This DOES matter, you've had to change the query for it to work, you
> had to look up ( or know beforehand ) the database encoding and change
> it accordingly. . I mean, when you do encode('text',....) what you are
> really asking for is encode( implicit_text_to_bytea_conversion(text),
> ....), so you save one step, but them you have to change your query to
> the 'latin1' encoding you discovered. This is what I meant, you had to
> look at the database properties. But if you do an explicit
> convert_form with any encoding capable of representing all your data,
> like utf-8 which can represent anything, the database encoding does
> not matter. And it should not, proper code should work with any
> database encoding. Even more, I can do encode(convert_to(utf8)) in a
> latin1 database conecting with any encoding, then send the hex to
> convert_from(decode(),utf8) to an ebcdic database use another encoding
> ( Of course I may need to transcode the hex, but not to the ebcdic,
> but to the client encoding been used in teh second case ), ant it
> would work as long as all the characters In the source data are
> representable in the destination database ( if they are not you are
> out luck in any scheme you may think off ).
>
> You cannot encode generically an string to hex unless you define an
> encoding. How do you encode '1', "31" or "F1" ? or maybe "0031" or
> "3100"? You can do a quick hack, but normally what you want is first
> to encode a sequence of characters to a sequence of bytes and then
> hex-encode that, as nearly everybody uses the same conversion for
> hex-encoding a byte sequence. This means you can have a '0' in a
> ebcdic database, transform it to to [0x30] byte array, encode this as
> "30" and then transform the later to 00 30 00 10 because you are using
> UTF16-BE wire encoding. Encoding is tricky enough without relying on
> implicit convertion or on a character being the same as a byte.
>
> Francisco Olarte.
>

--
Best regards,
Sincerely yours,
Yuriy Rusinov.