Direct I/O in Python with Cython

helloworld.pyx

from libc.stdlib cimport malloc, free
from libc.stdio   cimport *
from posix.unistd cimport *
from posix.stdlib cimport *
from posix.fcntl  cimport *

def test_cython(path):
    cdef int ret
    cdef int stdout_save, dev_null
    cdef int O_DIRECT = 040000
    cdef char *buffer = <char *> malloc(512 * sizeof(char))
    cdef char **bb    = &buffer
    posix_memalign(<void **>bb, 512, 512)
    # buffer = *bb
    dev_null = open(path.encode('utf8'), O_DIRECT | O_RDONLY, 0)
    print(lseek(dev_null, 1024*1024+4096, 0))
    print(read(dev_null, <void *> buffer, 512))
    print(buffer)
    ret = close(dev_null)
    print(ret)
    free(buffer)
# print("Hello World")

setup.py

from distutils.core import setup
from Cython.Build import cythonize

setup(
    ext_modules = cythonize("helloworld.pyx")
)