method
charset
charset()
public
returns a charset parameter in Content-Type field. It is downcased for canonicalization.
If charset parameter is not given but a block is given, the block is called and its result is returned. It can be used to guess charset.
If charset parameter and block is not given, nil is returned except text type in HTTP. In that case, “iso-8859-1” is returned as defined by RFC2616 3.7.1.