def custom_feeder(input, coro=None):
    def write_proc(fin, pipe, coro=None):
        while True:
            data = yield os.read(fin.fileno(), 8*1024)
            if not data:
                break
            n = yield pipe.write(data, full=True)
            assert n == len(data)
        fin.close()
        pipe.stdin.close()

    def read_proc(pipe, coro=None):
        # output from sha1sum is small, so read until EOF
        data = yield pipe.stdout.read()
        pipe.stdout.close()
        raise StopIteration(data)

    if platform.system() == 'Windows':
        # asyncfile.Popen must be used instead of subprocess.Popen
        pipe = asyncoro.asyncfile.Popen([r'\cygwin64\bin\sha1sum.exe'],
                                        stdin=subprocess.PIPE, stdout=subprocess.PIPE)
    else:
        pipe = subprocess.Popen(['sha1sum'], stdin=subprocess.PIPE, stdout=subprocess.PIPE)

    async_pipe = asyncoro.asyncfile.AsyncPipe(pipe)
    reader = asyncoro.Coro(read_proc, async_pipe)
    writer = asyncoro.Coro(write_proc, open(input), async_pipe)
    stdout = yield reader.finish()
    print('     feeder sha1sum: %s' % stdout)

# asyncoro.logger.setLevel(logging.DEBUG)

# simpler version using 'communicate'
dataset/ETHPy150Open pgiri/asyncoro/examples/pipe_csum.py/custom_feeder/original