create a Header instance. Closes feature request #539481.
Header.__init__(): Allow the initial string to be omitted.
__eq__(), __ne__(): Support rich comparisons for equality of Header
instances withy Header instances or strings.
Also, update a bunch of docstrings.
headers with no charset or 'us-ascii' charsets. Actually this is only
partially true: we know about semicolons (but not true parameters) and
we know about whitespace (but not technically folding whitespace).
Still it should be good enough for all practical purposes.
Other changes include:
__init__(): Add a continuation_ws argument, which defaults to a single
space. Set this to change the whitespace used for continuation lines
when a header must be split. Also, changed the way header line
lengths are calculated, so that they take into account continuation_ws
(when tabs-expanded) and any provided header_name parameter. This
should do much better on returning split headers for which the first
and subsequent lines must fit into a specified width.
guess_maxlinelen(): Removed. I don't think we need this method as
part of the public API.
encode_chunks() -> _encode_chunks(): I don't think we need this one as
part of the public API either.
single byte character sets. Also fixed a semantic problem with the
constructor's default arguments. Specifically,
__init__(): Change the maxlinelen argument default to None instead of
MAXLINELEN. The semantics should have been (and now are) that if
maxlinelen is given it is always honored. If it isn't given, but
header_name is given, then the maximum line length is calculated. If
neither are given then the default 76 characters is used.
_split(): If the character set is a single byte character set then we
can split the line at the maxlinelen because we know that encoding the
header won't increase its length. If the charset isn't a single byte
charset then we use the quicker divide-and-conquer line splitting
algorithm as before.
non-us-ascii character sets in headers and bodies. Some API changes
(with DeprecationWarnings for the old APIs). Better RFC-compliant
implementations of base64 and quoted-printable.
Updated test cases. Documentation updates to follow (after I finish
writing them ;).
Barry Warsaw
Tim Peters