Hi Tom
Then I am flummoxed by the line: OCTET = %x00-FF Which appears several lines before the 6.2 in the same RFC2234.
In addition Megaco already has the following definition: nonEscapeChar = ( "}" / %x01-7C / %x7E-FF )
How then these are encoded?
Regards, Sasha
-----Original Message----- From: Tom Taylor [mailto:taylor@nortel.com] Sent: Friday, June 24, 2005 9:30 AM To: Christian Groves Cc: Sasha Ruditsky; itu-sg16@external.cisco.com; Angelo.Contardi@ITALTEL.IT Subject: Re: H.248 and UTF-8 strings.
I'd guess the restriction came from RFC 2234 (ABNF). See paragraph 6.2.
Christian Groves wrote:
Hello Sasha,
You're quite welcome to bring in a contribution to the July Meeting on
this issue (addressed to Q.3- same procedure as any question), although I hope that there will be some agreement on the solution on the Megaco list. Those that can remember that far back know that I wasn't really a proponent of the text encoding so I can't remember why
these "extra chars" were excluded in the first place. I've added Tom to see if he can remember. In terms of solution I would support adding
this to VALUE only as indicated below.
Regards, Christian
Sasha Ruditsky wrote:
Hi Christian
As you correctly stated all the "extra chars" are the region between 0x80 and 0xff (0xf7 to be precise). I am not aware about any special meaning of the characters from this region, so as a result I cannot understand why these "extra chars" need to be escaped or quoted in any way.
The naive question is what is wrong with extending SafeChar to contain this region? I.e. SafeChar = DIGIT / ALPHA / "+" / "-" / "&" / "!" / "_" / "/" / "'" / "?" / "@" / "^" / "`" / "~" / "*" / "$" / "" / "(" / ")" / "%" / "|" / "." / %x80-F7 Or, if for some reason the UTF-8 strings may be used only in VALUE, then:
VALUE = quotedString / 1*(SafeChar / %x80-F7) quotedString = DQUOTE *(SafeChar / %x80-F7 / RestChar /
WSP)
DQUOTE
And...
Assuming that the way to fix this is found, can it be fixed in ver 3? If yes, then what is the procedure? Do you want me to bring relevant contribution to July meeting?
Thanks, Sasha
-----Original Message----- From: Christian Groves [mailto:christian.groves@ericsson.com] Sent: Wednesday, June 22, 2005 8:16 PM To: Sasha Ruditsky Cc: itu-sg16@external.cisco.com; Angelo.Contardi@italtel.it Subject: Re: H.248 and UTF-8 strings.
Hello Sasha,
This problem was raised recently on the Megaco list. I've had some off-line discussion with Angelo (the person who raised the problem) and currently there's 2 proposed solutions (I hope he would sent this to the Megaco list):
- The simple one, Code the UTF-8 string in "Octect Mode". This is a
BAD solution from the efficiency transmission point of view because of it "halve the TX band": to TX one UTF-8 char (max 4 ASCII chars) i
must TX max 2 x 4 = 8 ASCII chars.
- The complicated one, allow the ABNF quoted form of VALUE to TX ALL
ASCII chars 0x01-0xFF, except 0x22, that should be ESCAPED with "", as already done for ABNF Local and Remote Descriptor (see SDP). Note that '\0' (0x00) is NOT ALLOWED in this new quoted string form as in the present one, but this is not a problem because in UTF-8 the char
'\0'
(0x00) is the same as in ASCII (string terminator) and is NOT used to
code "non ASCII" UTF-8 chars, all those chars > 0x7F that require more than one ASCII chars to be encoded (from 2 to 4 ASCII chars). In
fact the "extra chars" needed to code an UTF-8 char are all above 0x7F (have the MSBit = 1).
Regards, Christian
Sasha Ruditsky wrote:
Hi
I'm trying to understand how H.248 supports UTF-8 string properties. According to H.248 the string property is encoded as UTF-8 string.
UTF-8 encoding is defined by the following table:
Scalar Value 1st Byte 2nd Byte 3rd Byte 4th Byte 00000000 0xxxxxxx 0xxxxxxx 00000yyy yyxxxxxx 110yyyyy 10xxxxxx zzzzyyyy yyxxxxxx 1110zzzz 10yyyyyy 10xxxxxx 000uuuuu zzzzyyyy yyxxxxxx 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
I.e. all the character codes between x80 and xf7 need to be
supported.
According to H.248 Annex B.2:
The ABNF in this section uses the VALUE construct (or lists of VALUE constructs) to encode various package element values (properties, signal parameters, etc.).
The VALUE is defined as follows:
VALUE = quotedString / 1*(SafeChar) SafeChar = DIGIT / ALPHA / "+" / "-" / "&" / "!" / "_" / "/" / "'" / "?" / "@" / "^" / "`" / "~" / "*" / "$" / "" / "(" / ")" / "%" / "|" / "." ALPHA = %x41-5A / %x61-7A ; A-Z / a-z DIGIT = %x30-39 ; 0-9 quotedString = DQUOTE *(SafeChar / RestChar/ WSP) DQUOTE RestChar = ";" / "[" / "]" / "{" / "}" / ":" / "," /
"#"
/
"<" / ">" / "="WSP = SP / HTAB ; white space SP = %x20 ; space HTAB = %x09 ; horizontal tab DQUOTE = %x22 ; " (Double Quote)
So I believe this excludes the x80-xff characters.
So the question is how to text encoding defined in Annex B to encode UTF-8 strings?
Thanks, Sasha