Re: Register EBCDIC Character Set "OSD_EBCDIC_DF04_1"

[jean-frederic clere <jfrederic.clere@fujitsu-siemens.com>]

Markus Scherer wrote:
> jean-frederic clere wrote:
> 
>> For OSD_EBCDIC_DF04_1 and OSD_EBCDIC_DF04_15 that is a 8 bits 
>> roundtrip mapping but for 2 bytes mapping, undefined characters are 
>> mapped as '?' 0x6F.
> 
> 
> Ok, so the substitution character for these tables is 0x6F.
> 
> On the question of roundtrips, I think we are not communicating properly 
> due to a mismatch in terminology.
> 
> I believe what you are saying is that these _tables_ as a whole perform 
> a roundtrip of their repertoire between a BS2000-EBCDIC codepage and the 
> Unicode portion corresponding to the equivalent ISO 8859 codepage. In 
> other words, the tables map between exactly N codes on the EBCDIC-based 
> and N Unicode code points. (N being the same on both sides, N=256 for 
> SBCS and N=128 for IRV.) Is this correct?

Yes.

> 
> Then, for every Unicode character _outside_ of this repertoire, there is 
> no mapping, and the default behavior is to use 0x6F as the substitution 
> character.

Yes.

> 
> What I was trying to ask was whether the individual _mappings_ in the 
> tables (each line in the text table listing) were roundtrip mappings. 
> This means that when you write something like
> 0xFC    0x00DC  #LATIN CAPITAL LETTER U WITH DIAERESIS
> that means that you map Unicode U+00DC to 0xFC while converting from 
> Unicode to this charset, and you map 0xFC to Unicode U+00DC while 
> converting from the charset to Unicode. Fallback mappings only go one 
> way. Since many conversion implementations have fallback mappings in 
> addition to roundtrip mappings, they should be published, and should be 
> marked properly. See Unicode TR 22 for details.
> 
> If the tables in your registration requests are pure remappings as 
> described above, then of course each mapping is a roundtrip mapping
> 
> Is this how the converter implementation works on BS2000? Is it true 
> that BS2000 converters do not perform any fallback (one-way) mappings?

Ok, the 3 mappings submitted are roundtrip mappings.

> 
> Best regards,
> markus
> 
> 

Thanks for the comments

Jean-Frederic