Kiril Avdeiv wrote:
>
> Hi everybody!
>
> I'm writing a sort of parser, and would like to do replacement of certain character sequences in underflow. I have derived a class from std::filebuf, called parsing_filebuf. And in the parsing_filebuf::underflow I first call filebuf::underflow to do the actual work and set gptr(), egptr(), and eback(). In case everything goes well, I then call an algorithm that does the replacement. The replacement is always done in such a way that the resulting sequence is shorter than the one that filebuf_underflow returned in [eback(), egptr()). So, at the end of my overrider, I myself shorten the pending sequence by modifying the end pointer egptr() with a call to streambuf::setg.
>
> I find the above approach pretty elegant, and it's been working for me. I only wonder how portable what I'm doing is according to the standard.
>
> The implementation that I've looked at RogueWave does seem to be gratious enough to allow for such a technique to work.
>
> Would be helpful to any constructive recommendation or advice.

This approach should work, although for sequence conversion I would recommend
writing your own codecvt-derived facet. Doing so is considerably less involved
than implementing your own {over,under}flow() and will let you use it with any
stream or stream buffer object.

Regards
Martin

>
> With best regards.
> Kiril.
>
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Hi everybody!

I'm writing a sort of parser, and would like to do replacement of certain character sequences in underflow. I have derived a class from std::filebuf, called parsing_filebuf. And in the parsing_filebuf::underflow I first call filebuf::underflow to do the actual work and set gptr(), egptr(), and eback(). In case everything goes well, I then call an algorithm that does the replacement. The replacement is always done in such a way that the resulting sequence is shorter than the one that filebuf_underflow returned in [eback(), egptr()). So, at the end of my overrider, I myself shorten the pending sequence by modifying the end pointer egptr() with a call to streambuf::setg.

I find the above approach pretty elegant, and it's been working for me. I only wonder how portable what I'm doing is according to the standard.

The implementation that I've looked at RogueWave does seem to be gratious enough to allow for such a technique to work.

Would be helpful to any constructive recommendation or advice.

With best regards.
Kiril.

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Posted from [213.17.94.30] by way of mx5.port.ru [194.67.23.40]
via Mailgate.ORG Server - http://www.Mailgate.ORG

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