> 3. If the language string is an overloaded text/bytes type, as is > regrettably quite common, what do we do then? > > The current answer to this question is "send it as vbin". That's very > safe, insofar as it won't throw any sort of encoding exception. It > does not, however, always honor what I think is the user's more > typical intention: produce an ascii string at the other end.
I guess the problem is between dynamically and statically typed languages, if you stay with the same language you don't notice anything, but this slightly defeats the object of AMQP! > So for 3, I'd like to consider the possibility of, by default, sending > ambiguous language strings as ascii rendered to amqp str16. This > requires an encoding step that may produce errors. And maybe that's > just too obnoxious! That's what I'd like to know. I'm not convinced, but I'm prepared to be convinced. If I put a binary value in a map and encoded it some of the time it might be valid utf8, other times not. Could this lead to a class of subtle bugs where a receiver written in a statically typed language will work most of the time when the value appears as a vbin, but not other times when it "accidentally" appears a a str16? > In summary, if we have a way to determine what the user wanted (text > or bytes), we should try to carry that through on the wire. At the > following URL I've tried to map out what type information we can get > for each language. Please update it as you please. > > > https://cwiki.apache.org/confluence/display/qpid/Language+support+for+unambiguous+text+string+and+byte+array+types I've just signed up, but don't seem to be able to edit the page? I'll add the stuff about utf8::upgrade when I can edit. > On Wed, Aug 21, 2013 at 8:44 AM, Jimmy Jones <jimmyjon...@gmx.co.uk> wrote: >>> > AFAIK in perl, if you include unicode characters in a string it'll >>> > set the utf8 flag. If you don't include any unicode characters (eg. 7 >>> > bit ascii, or raw bytes) the flag won't be set. So given a perl >>> > scalar that doesn't contain any utf8 characters, you don't know if >>> > its a textual string (str16) or a binary string (vbin). There is a >>> > is_utf8_string function, but that'll only tell you if the string >>> > would be valid utf8, but it could be a binary string that happens to >>> > be valid utf8, so that's not really safe. >>> >>> You can explicitly mark it as utf8 using utf8::upgrade() though, right? >>> Certainly I tried that in a simple test and the property in question was >>> then sent as str16. >> >> Yes, if I as a user had a string that was textual, I could call >> utf8::upgrade() to ensure it got sent as str16. I guess this is similar in >> concept to calling setEncoding in C++, although maybe less natural in a >> dynamically typed language. > > It would be more reasonable to treat perl scalars as textual for our > API if perl offered a good way to explicitly handle byte arrays. My > (certainly insufficient) web browsing suggested that wasn't really > available, or not in a form recommended for use. Any candidates for a > serviceable explicitly-arbitrary-bytes-and-not-text-at-all "type" in > perl? Sorry, I don't know of any, althogh I'm no perl guru! I'll have another look though. --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@qpid.apache.org For additional commands, e-mail: dev-h...@qpid.apache.org
