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RE: %NN encoding, request/response headers, UTF-8 ?

From: Joris Dobbelsteen <joris.dobbelsteen@mail.com>
Date: Mon, 11 Jun 2001 00:21:01 +0200
To: "'Peter W'" <peterw@usa.net>
Cc: "WWW WG (E-mail)" <http-wg@cuckoo.hpl.hp.com>
Message-ID: <000701c0f1fb$a263f900$0d0ba8c0@joris2k.local>
They are still used, I think.... (e.g. IE)

The specification expects ASCII characters, but if UTF-8 is compatible with
ASCII and the spec this can be used.

>-----Original Message-----
>From: Peter W [mailto:peterw@usa.net]
>Sent: Friday, 08 June 2001 1:22
>To: http-wg@cuckoo.hpl.hp.com
>Subject: %NN encoding, request/response headers, UTF-8 ?
>
>
>I'm curious
> - whether Unicode characters with values 0x100 and greater
>are allowed in
>   request headers (especially the request line)

No, solely ASCII, according to the spec. It states ASCII characters, with a
range from 0x00 to 0xFF. Depending on what you are entering, there may be
some more limitations (see spec).

> - if so, if UTF-8 encoding is allowed\

Don't know about UTF-8, I thought IE could use it to encode the URL.

> - how a client indicates to the server that it's using UTF-8
> - how an HTTP server application decides how to interpret
>   hex-encoded information, e.g. is %C3%B1 encoding two characters,
>   or the UTF-8 encoding for the single character ""
> - how/if a server might use UTF-8 in its response headers
>
>It looks like any content that is sent with MIME headers
>(e.g., an object
>sent by the HTTP server) could be announced with a charset
>value indicating
>UTF-8 encoding, but that headers (request or response) are
>only expected to
>contain characters 0x00 -> 0xFF. Yet I don't see this clearly stated.
>
>It seems fairly clear, though, that double-byte character sets
>(e.g., 16
>bits for each character regardless of its value) should not be used in
>either request or response headers. Right?

Seems like it. It might, however, be possible to encode them so they comply
with the spec. Still, I'm not sure about this.

>
>I appreciate any light you may be able to shed on this topic.
>
>-Peter
>http://www.tux.org/~peterw/
>

- Joris
>
Received on Sunday, 10 June 2001 23:20:22 EDT

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