BIG encoding and UTF8?

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We have an application that uses UTF8 everywhere to load / save / process
documents.
One of our clients is having a problem with BIG Encoded files being trashed
after running through our app.

Indeed I have verified that if I go to a website in Taiwan and save the file
in BIG5 and then just load / save the file with a UTF8 text reader / write
some bytes are modified.

How can I correct this? It was my understanding the UTF8 was supposed to be
high byte friendly.



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