Encoding convertions... optimized two-stage table?

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ThunderMusic - 01 Feb 2007 22:13 GMT

Hi,
I want to convert UTF-16 (or unicode) to ISO-8859-1... The .Net
encoding does a pretty code job, but some characters are not converted, like
"O" that becomes "?"... I want it to become "oe"... So, what I want to know
is the method used by the .NET encoders to convert from one encoding to the
other... is it using an optimized two-stage table or a multistate table or
other method?

As I know the first 256 characters are the same, it's easy to convert those
256, but for the others, we have to make a correspondance, would an
optimized two-stage table be the best way to go? Does somebody know where I
could get such a table so I don't have to type it all myself?

thanks

ThunderMusic

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Jon Skeet [C# MVP] - 01 Feb 2007 22:23 GMT

> I want to convert UTF-16 (or unicode) to ISO-8859-1... The .Net
> encoding does a pretty code job, but some characters are not converted, like
> "O" that becomes "?"... I want it to become "oe"... So, what I want to know
> is the method used by the .NET encoders to convert from one encoding to the
> other... is it using an optimized two-stage table or a multistate table or
> other method?

Converting from one encoding to another is just a matter of decoding
from a byte array to the Unicode (.NET's "native" UTF-16 format), then
encoding from the Unicode to a byte array.

> As I know the first 256 characters are the same, it's easy to convert those
> 256, but for the others, we have to make a correspondance, would an
> optimized two-stage table be the best way to go? Does somebody know where I
> could get such a table so I don't have to type it all myself?

The process that .NET encodings are using won't help you much,
unfortunately. It sounds like the conversion you need is entirely
within text form - from the combined character to the multi-character
version.

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Jon Skeet - <skeet@pobox.com>
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Mihai N. - 01 Feb 2007 23:23 GMT

> I want to convert UTF-16 (or unicode) to ISO-8859-1... The .Net
> encoding does a pretty code job, but some characters are not converted,
[quoted text clipped - 3 lines]
> other... is it using an optimized two-stage table or a multistate table or
> other method?

The real solution is to move everything to Unicode, not trying to "squize"
the whole Unicode thru some code page hole with a non-standard,
patchy conversion.

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Mihai Nita [Microsoft MVP, Windows - SDK]
http://www.mihai-nita.net
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ThunderMusic - 02 Feb 2007 13:26 GMT

actually, I just seen that the "O" character went wrong in the post (it must
be plain US ASCII), what I wanted to post is the one character "oe"... and
you just seen that the conversion is not perfect because only the "O" went
through... Well, I'll try my best anyway...

thanks everyone...

ThunderMusic

>> I want to convert UTF-16 (or unicode) to ISO-8859-1... The .Net
>> encoding does a pretty code job, but some characters are not converted,
[quoted text clipped - 9 lines]
> the whole Unicode thru some code page hole with a non-standard,
> patchy conversion.

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Encoding convertions... optimized two-stage table?

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