Kenichi Handa <[EMAIL PROTECTED]> writes: > In article <[EMAIL PROTECTED]>, Stefan Monnier <[EMAIL PROTECTED]> writes: > >>> I'd like to know whether coding systems in general are supposed to be >>> robust, meaning that decoding some random byte string into the coding >>> system and reencoding it is guaranteed to deliver the same byte string >>> again? > >> AFAIK, (encode-coding-string (decode-coding-string STR 'foo) 'foo) >> should always return STR, otherwise it's a bug. >> With the introduction of eight-bit-*, this should be true of "all" >> coding-systems in Emacs-21, > > No. Redundant escape sequences in iso-2022 based coding > systems are just ignored. For instance, > > (decode-coding-string "\e(J" 'iso-2022-jp) => "" > > And we can't recover "\e(J" on encoding.
Ok, making the problem somewhat more confined: if I have a file that is written _by_ _Emacs_ in some coding system, and then externally I chop parts of it into pieces (not dropping material) not taking into account multibyte boundaries, convert these pieces with interspersed ASCII) into the original decoding, encode it again to a unibyte string, properly replace the ASCII-fied pieces with the original material and decode to the original decoding (phew), I am pretty sure that I have round-trip behavior, right? Well, almost. On escape-based coding systems I don't see in the first place that one can encode/decode string parts in isolation, so I am afraid that it is not really feasible to promise anything. Do the escapes at least start fresh every line? I am just being curious here, there is no actual chance that I am going to support such a coding system, and I don't see how I sensibly could. -- David Kastrup, Kriemhildstr. 15, 44793 Bochum _______________________________________________ Emacs-devel mailing list Emacs-devel@gnu.org http://lists.gnu.org/mailman/listinfo/emacs-devel
