It allows to temporarily disable Websocket compression
when it was negotiated. It's ignored otherwise. This
can be used as fine-grained control when some frames
do not compress well.
They allow the server to configure what it is willing to accept
for both the negotiated configuration (takeover and window bits)
and the other zlib options (level, mem_level and strategy).
This can be used to reduce the memory and/or CPU footprint of
the compressed data, which comes with a cost in compression ratio.
Returning the atom auto instead of a callback informs Cowboy
that it needs to handle range requests automatically. This
changes the behavior so that the ProvideCallback function
is called and then Cowboy splits the data on its own and
sends the response without any other user involvement other
than defining the ranges_provided/2 callback.
This is a quick and dirty way to add range request support
to resources, and will be good enough for many cases including
for cowboy_static as it also works when the normal response
body is a sendfile tuple.
It is now possible to stream one or more sendfile tuples.
A simple example of what can now be done would be for
example to build a tar file on the fly using the sendfile
syscall for sending the files, or to support Range requests
with more than one range with the sendfile syscall.
When using cowboy_compress_h unfortunately we have to read
the file in order to send it. More options will be added
at a later time to make sure users don't read too much
into memory. This is a new feature however so existing
code is not affected.
Also rework cowboy_http's data sending to be flatter.
Fix cases where the q-value is 0 and where a wildcard
was sent in the accept-charset header.
Also don't send a charset in the content-type of the
response if the media type is not text.
Thanks to Philip Witty for help figuring this out.
Currently the compression threshold is set to 300 and hardcoded in the
codebase. There are cases where it make sense to allow this to be
configured, for instance when you want to enforce all responses to be
compressed regarldess of their size.
