Python Twisted + sendfile(2)

sendfile.py

# coding: utf-8

import os
import sys

from cffi import FFI

from twisted.internet.defer import Deferred
from twisted.internet import reactor
from twisted.python import log
from twisted.web.server import Site, NOT_DONE_YET
from twisted.web.resource import Resource
from twisted.internet.endpoints import TCP4ServerEndpoint


ffi = FFI()
ffi.cdef("""
    typedef long off_t;
    ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count);
""")
lib = ffi.verify("""
    #include <sys/sendfile.h>
""")


class _Sender(object):
    def __init__(self, consumer, fileobj, size):
        self.consumer = consumer
        self.fileno = fileobj.fileno()
        self.size = size
        self.dfd = Deferred()

    def resumeProducing(self):
        offset = ffi.new('off_t*', 0)
        lib.sendfile(self.consumer.fileno(), self.fileno, offset, self.size)
        self.consumer.unregisterProducer()
        self.dfd.callback(None)

    def stopProducing(self):
        pass


def doSendfile(req, fileobj):
    fileno = fileobj.fileno()
    size = os.fstat(fileno).st_size

    sender = _Sender(req.transport, fileobj, size)

    req.setHeader('content-length', size)

    # kickstart this shit, will call sender.resumeProducing
    req.write('')
    req.transport.producer = sender

    return sender.dfd


class Res(Resource):
    isLeaf = True
    def render_GET(self, req):
        f = open('foo.txt')
        (doSendfile(req, f)
            .addCallback(lambda i: req.finish())
            .addCallback(lambda i: f.close())
        )
        return NOT_DONE_YET


with open('foo.txt', 'w') as f:
    f.write('asdasdasasd\n')

site = Site(Res())
TCP4ServerEndpoint(reactor, 8080).listen(site)
log.startLogging(sys.stderr)
reactor.run()