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  :   ˆl–Ü4ý( ©–Ú”Ònã,ÜjbÑ¿Í„Ì…¿a–äY>”ËmJqAàY¸'”Å£Ë ?÷     # Copyright (C) 2003-2007, 2009-2011 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""Talk to a DNS server."""

from __future__ import generators

import errno
import select
import socket
import struct
import sys
import time

import dns.exception
import dns.inet
import dns.name
import dns.message
import dns.rdataclass
import dns.rdatatype

class UnexpectedSource(dns.exception.DNSException):
    """Raised if a query response comes from an unexpected address or port."""
    pass

class BadResponse(dns.exception.FormError):
    """Raised if a query response does not respond to the question asked."""
    pass

def _compute_expiration(timeout):
    if timeout is None:
        return None
    else:
        return time.time() + timeout

def _poll_for(fd, readable, writable, error, timeout):
    """Poll polling backend.
    @param fd: File descriptor
    @type fd: int
    @param readable: Whether to wait for readability
    @type readable: bool
    @param writable: Whether to wait for writability
    @type writable: bool
    @param timeout: Deadline timeout (expiration time, in seconds)
    @type timeout: float
    @return True on success, False on timeout
    """
    event_mask = 0
    if readable:
        event_mask |= select.POLLIN
    if writable:
        event_mask |= select.POLLOUT
    if error:
        event_mask |= select.POLLERR

    pollable = select.poll()
    pollable.register(fd, event_mask)

    if timeout:
        event_list = pollable.poll(long(timeout * 1000))
    else:
        event_list = pollable.poll()

    return bool(event_list)

def _select_for(fd, readable, writable, error, timeout):
    """Select polling backend.
    @param fd: File descriptor
    @type fd: int
    @param readable: Whether to wait for readability
    @type readable: bool
    @param writable: Whether to wait for writability
    @type writable: bool
    @param timeout: Deadline timeout (expiration time, in seconds)
    @type timeout: float
    @return True on success, False on timeout
    """
    rset, wset, xset = [], [], []

    if readable:
        rset = [fd]
    if writable:
        wset = [fd]
    if error:
        xset = [fd]

    if timeout is None:
        (rcount, wcount, xcount) = select.select(rset, wset, xset)
    else:
        (rcount, wcount, xcount) = select.select(rset, wset, xset, timeout)

    return bool((rcount or wcount or xcount))

def _wait_for(fd, readable, writable, error, expiration):
    done = False
    while not done:
        if expiration is None:
            timeout = None
        else:
            timeout = expiration - time.time()
            if timeout <= 0.0:
                raise dns.exception.Timeout
        try:
            if not _polling_backend(fd, readable, writable, error, timeout):
                raise dns.exception.Timeout
        except select.error, e:
            if e.args[0] != errno.EINTR:
                raise e
        done = True

def _set_polling_backend(fn):
    """
    Internal API. Do not use.
    """
    global _polling_backend

    _polling_backend = fn

if hasattr(select, 'poll'):
    # Prefer poll() on platforms that support it because it has no
    # limits on the maximum value of a file descriptor (plus it will
    # be more efficient for high values).
    _polling_backend = _poll_for
else:
    _polling_back