On 11/8/22 09:38, Daniel Stenberg via curl-library wrote:
Hello all!
I just want to highlight Stefan Eissing's work in progress that looks
like it might become one of the largest PRs in a long time:
https://github.com/curl/curl/pull/9855
We call the concept "connection filters" and it is a new way for
libcurl internals to handle data over connections. Each filter is a
stage in a data pipeline. TLS handling is a filter, a SOCKS proxy is,
HTTP/2 is and so on.
Coincidence or not, I have a stalled project of the same kind. It was an
idle work and far from mature. I called it "stomhaxx" in reference to
the curl project origin and a mechanism similar to ruminants' digestive
tract :-)
Something I noticed about this concept is that it easily copies data
from a buffer to another if not designed carefully. That is why I
provided two kind of input methods: read() that moves data to a buffer
and get() that keeps data in place and returns a pointer and a length.
The get() method is preferred between the different stomhaxx. Each of
the stomaxx can then transform, insert or delete data in the flow. This
also reduces the buffer allocation needs.
IMO, such an interface should also be made available on the caller's
side: its own stage of stomhaxx can be designed and stacked to its side
of the flow. In addition, providing a way to connect the application to
curl with this feature is much more powerful than our current
memory/file/callback interfaces (those are provided as "mouth"
stomhaxx). Some useful user side stomhaxx can be provided too, like
base64 transform, quoted-printable encoding, line end or tab
transformation, data compression/expansion, etc.
I also dreamed of a mouth stomhaxx that accesses another curl handle...
From what I've seen in Stephan's PR, SSL and proxy are mainly targetted
now. In the future, this feature could also be used to implement SASL
data encryption that we do not support yet or replace mime composing. I
also think of tiny things like the dotted-line transformation in mails.
Although not complete and not yet connected to curl itself, I can send
the stomhaxx code in its current state here if someone is interested in
looking at it.
Patrick
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