Efficient way to ASCII encode UTF-8

Posted by Andreas Gohr on Stack Overflow See other posts from Stack Overflow or by Andreas Gohr
Published on 2010-04-02T14:59:00Z Indexed on 2010/04/02 15:03 UTC
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utf-8

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punycode

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encoding

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ascii

I'm looking for a simple and efficient way to store UTF-8 strings in ASCII-7. With efficient I mean the following:

all ASCII chars in the input should stay ASCII chars in the output
the resulting string should be as short as possible
the operation needs to be reversable without any data loss
there should be no restriction on the input length
the whole UTF-8 range should be allowed

My first idea was to use Punycode (IDNA) as it fits the first three requirements, but it fails at the last two.

Can anyone recommend an alternative encoding scheme? Even better if there's some code available to look at.

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