[SM-DEVEL] decode 8bit characters in message headers

[Sergey G. <ge...@ws...>]

  Hello, All!

I am downloaded SquirrelMail v.1.4.0.

I need decode 8bit characters in header fields to $default_charset
from charset specified in Content-type header, charset subheader. How can I do it?
What function in which file parses the headers?

For example, in folder can be message with following headers:
From: xxxxxx <us...@do...>
To: xxxxxx <us...@do...>
Subject: xxxxxxx

where "xxxxx" is any 8bit (>=0x080) characters. Also subject can be
encoded by base64 or quoted-printable

Best regards, Sergey