Implement asyncstreams

[termermc]

Implements:

• Async streaming I/O when httpxUseStreams is true
• Exposes request ID
• Exposes parsed request content length

TODO In another PR:

• Limit request header sizes to 8kib
• Write documentation for streams mode

[ringabout]

Tested with Prologue, it passes as well.

[bung87]

how's the performance change?

[termermc]

@bung87 Really bad. That's part of why I never finished it. You can checkout the branch and try it for yourself.

[bung87]

I've heard of the low performance when nim std provide stream api, because it uses dynamic dispatch functions.

[termermc]

I don't think mine uses dynamic dispatch, but there are problems with how httpx/httpbeast read sockets which makes the problem worse.

You can see my implementation here:

https://github.com/ringabout/httpx/blob/83f6a1a839ba0c322859f876938a8881100df4ec/src/httpx/asyncstream.nim

And its tests:

https://github.com/ringabout/httpx/blob/83f6a1a839ba0c322859f876938a8881100df4ec/tests/t_streams.nim

[bung87]

these functions associate with stream object are dynamic dispatch, no ?

result.readCbs = initDeque[AsyncStreamCb](1)
result.writeCbs = initDeque[AsyncStreamCb](1)
result.afterReadCb = afterReadCb
result.afterWriteCb = afterWriteCb

[termermc]

@bung87 AsyncStreamCb just a typedesc, not a method. It won't use dynamic dispatch vtables, but it does run a proc via its pointer. Not sure if that counts.

[atlas-pouriya]

Any progress on this one?

[termermc]

@atlas-pouriya I've abandoned it, the architecture is just too different to support it without breaking everything or making a compiletime switch that requires a lot of conditional code which is hard to test.

I'll close it now.