On Wed, Jun 13, 2012 at 12:59 PM, Charles Mills <charl...@mcn.org> wrote: > I got a response to the PMR. Taking the liberty of paraphrasing a long > reply, the essence of it seemed to be that -- per the CCSID pair lists in > the manual -- they support round trip conversion from 1027 to 1208 but not > from 1208 to 1027. Here is what I wrote back: > What this means is: Roundtrip example: Every defined character in 1027, excluding values that do not have a character defined, exist in 1208, is successfully translated from 1027 to 1208 and back to 1027. All codepoints that do not have a character defined will be translated to (one?) non-valid value.
Non-roundtrip example: Some defined characters in 1208, and all codepoints that do not have a character defined, do not exist in 1027. If you translate text from 1208 to 1027, the characters not defined in 1027, and all undefined codepoints will be translated to (one?) non-valid codepoint. In any translation, a codepoint that does not encode a character will be translated to (one?) non-valid codepoint. If, while the text is in 1208 is changed to add a character not in 1027, upon translation that value will be changed to an invalid value in 1027. > It sounds like you are saying (for the CCSIDs in question) "we support > round trip, but in one direction only." It would be like if I bought a > round trip ticket on Delta between San Francisco and Atlanta, and after > I got to Atlanta, they explained that it was a round trip ticket only > in one direction. > > I would kind of question also whether what you are doing conforms to > your definition of round trip in the Unicode manual glossary: Round > trip. Encoding that occurs when every code point in the source CCSID > maps to a unique code point in the target CCSID. You missed the word defined. If a codepoint does not have a defined character, it is translated to (one?) invalid value. > Using round trip > tables ensure the capability of reversing the conversion, and > recovering the complete original source datastream. > > I would question "every code point in the source CCSID maps to a unique > code point in the target CCSID" when both 3F and 41 map to the same > code point, and I wonder how I would recover the original source > datastream. > Again, you missed the word defined. If a codepoint does not have a defined character, it is translated to (one?) invalid value. > Charles > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
