gistfile1.txt

import ctypes
from ctypes import cdll, util
import os

libc = cdll.LoadLibrary(util.find_library('c'))

_get_errno_loc = libc.__errno_location
_get_errno_loc.restype = ctypes.POINTER(ctypes.c_int)
def get_errno():
    return _get_errno_loc().contents.value

def errcheck(ret, func, args):
    if ret == -1:
        e = get_errno()
        msg = os.strerror(e)
        raise OSError(e, msg)
    return ret

_pwrite = libc.pwrite
_pwrite.argtypes = [ctypes.c_int, ctypes.c_void_p, ctypes.c_size_t,
                    ctypes.c_uint64]
_pwrite.errcheck = errcheck

_pread = libc.pread
_pread.argtypes = [ctypes.c_int, ctypes.c_void_p, ctypes.c_size_t,
                   ctypes.c_uint64]
_pwrite.errcheck = errcheck


def pwrite(fd, buff, count=None, offset=0):
    if count is None:
        count = len(buff)
    _pwrite(fd, buff, count, offset)


def pread(fd, count, offset=0):
    buff = ctypes.create_string_buffer(count)
    _bytes_read = _pread(fd, buff, count, offset)
    return buff.value

class DirectFile(file):

    def pwrite(self, buff, count=None, offset=0):
        pwrite(self.fileno(), buff, count, offset)

    def pread(self, count, offset=0):
        return pread(self.fileno(), count, offset)