[phobos] Transcoded text stdio

[Andrei Alexandrescu]

We definitely need to keep an eye on this issue while the new stream 
design is in flux. Transcoding Windows I/O is a major application.

Andrei

On 9/17/10 12:04 PM, Shin Fujishiro wrote:
> Thank you for picking up the topic!
>
> Andrei Alexandrescu<andrei at erdani.com>  wrote:
>> Regarding transcoding output, please let me know I understand the
>> problem correctly: under Windows (and possibly under other OSs under
>> certain configurations) the console is not UTF and cannot be reasonably
>> forced to be UTF.
>
> Yes.  Neither input or output isn't UTF under Windows.
>
>> I think for such situations, the classic Decorator-based design with
>> stacked interfaces works well: you have a TranscodingStream wrapping a
>> NativeStream or a UTFStream or whatever.
>>
>> The streaming interface question comes again, i.e. what is the interface
>> that allows such stacking with minimal cost in efficiency?
>
> The cost is minimal when the transcoder has direct access to both I/O
> device and buffer.  I mean, there would be no redundant copy involved:
>
>      ubyte[N] tmp = void;
>      convert(buffer, tmp);
>      device_write(tmp);
>
> So, the best layer for doing converted (or filtered) I/O is the stream
> buffer.  But I feels like it's not quite right... buffering layer might
> be too 'low level' for character code conversion.
>
>
> Shin
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