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Name	Size	Permission	Date
__pycache__	[ DIR ]	drwxr-xr-x	2025-08-15 18:09
dnssecalgs	[ DIR ]	drwxr-xr-x	2025-08-15 18:09
quic	[ DIR ]	drwxr-xr-x	2025-08-15 18:09
rdtypes	[ DIR ]	drwxr-xr-x	2025-08-15 18:09
__init__.py	1.62 KB	-rw-r--r--	2024-02-18 18:35
_asyncbackend.py	2.3 KB	-rw-r--r--	2024-02-18 18:35
_asyncio_backend.py	8.76 KB	-rw-r--r--	2024-02-18 18:35
_ddr.py	5.12 KB	-rw-r--r--	2024-02-18 18:35
_features.py	2.33 KB	-rw-r--r--	2024-02-18 18:35
_immutable_ctx.py	2.4 KB	-rw-r--r--	2024-02-18 18:35
asyncbackend.py	2.73 KB	-rw-r--r--	2024-02-18 18:35
asyncquery.py	26.22 KB	-rw-r--r--	2024-02-18 18:35
asyncresolver.py	17.43 KB	-rw-r--r--	2024-02-18 18:35
dnssec.py	39.74 KB	-rw-r--r--	2024-02-18 18:35
dnssectypes.py	1.76 KB	-rw-r--r--	2024-02-18 18:35
e164.py	3.88 KB	-rw-r--r--	2024-02-18 18:35
edns.py	14.91 KB	-rw-r--r--	2024-02-18 18:35
entropy.py	4.14 KB	-rw-r--r--	2024-02-18 18:35
enum.py	3.6 KB	-rw-r--r--	2024-02-18 18:35
exception.py	5.82 KB	-rw-r--r--	2024-02-18 18:35
flags.py	2.69 KB	-rw-r--r--	2024-02-18 18:35
grange.py	2.1 KB	-rw-r--r--	2024-02-18 18:35
immutable.py	1.97 KB	-rw-r--r--	2024-02-18 18:35
inet.py	5.64 KB	-rw-r--r--	2024-02-18 18:35
ipv4.py	2.49 KB	-rw-r--r--	2024-02-18 18:35
ipv6.py	6.45 KB	-rw-r--r--	2024-02-18 18:35
message.py	64.45 KB	-rw-r--r--	2024-02-18 18:35
name.py	41.67 KB	-rw-r--r--	2024-02-18 18:35
namedict.py	3.91 KB	-rw-r--r--	2024-02-18 18:35
nameserver.py	9.68 KB	-rw-r--r--	2024-02-18 18:35
node.py	12.37 KB	-rw-r--r--	2024-02-18 18:35
opcode.py	2.67 KB	-rw-r--r--	2024-02-18 18:35
query.py	53.55 KB	-rw-r--r--	2024-02-18 18:35
rcode.py	4.06 KB	-rw-r--r--	2024-02-18 18:35
rdata.py	28.77 KB	-rw-r--r--	2024-02-18 18:35
rdataclass.py	2.91 KB	-rw-r--r--	2024-02-18 18:35
rdataset.py	16.36 KB	-rw-r--r--	2024-02-18 18:35
rdatatype.py	7.17 KB	-rw-r--r--	2024-02-18 18:35
renderer.py	10.99 KB	-rw-r--r--	2024-02-18 18:35
resolver.py	71.83 KB	-rw-r--r--	2024-02-18 18:35
reversename.py	3.74 KB	-rw-r--r--	2024-02-18 18:35
rrset.py	8.96 KB	-rw-r--r--	2024-02-18 18:35
serial.py	3.52 KB	-rw-r--r--	2024-02-18 18:35
set.py	8.88 KB	-rw-r--r--	2024-02-18 18:35
tokenizer.py	23.03 KB	-rw-r--r--	2024-02-18 18:35
transaction.py	22.11 KB	-rw-r--r--	2024-02-18 18:35
tsig.py	11.15 KB	-rw-r--r--	2024-02-18 18:35
tsigkeyring.py	2.57 KB	-rw-r--r--	2024-02-18 18:35
ttl.py	2.91 KB	-rw-r--r--	2024-02-18 18:35
update.py	11.96 KB	-rw-r--r--	2024-02-18 18:35
version.py	1.88 KB	-rw-r--r--	2024-02-18 18:35
versioned.py	11.49 KB	-rw-r--r--	2024-02-18 18:35
win32util.py	8.89 KB	-rw-r--r--	2024-02-18 18:35
wire.py	2.76 KB	-rw-r--r--	2024-02-18 18:35
xfr.py	12.96 KB	-rw-r--r--	2024-02-18 18:35
zone.py	50.87 KB	-rw-r--r--	2024-02-18 18:35
zonefile.py	27.27 KB	-rw-r--r--	2024-02-18 18:35
zonetypes.py	690 B	-rw-r--r--	2024-02-18 18:35

Rename

# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license

from typing import Dict

import dns.exception

# pylint: disable=unused-import
from dns._asyncbackend import (  # noqa: F401  lgtm[py/unused-import]
    Backend,
    DatagramSocket,
    Socket,
    StreamSocket,
)

# pylint: enable=unused-import

_default_backend = None

_backends: Dict[str, Backend] = {}

# Allow sniffio import to be disabled for testing purposes
_no_sniffio = False

class AsyncLibraryNotFoundError(dns.exception.DNSException):
    pass

def get_backend(name: str) -> Backend:
    """Get the specified asynchronous backend.

*name*, a ``str``, the name of the backend.  Currently the "trio"
    and "asyncio" backends are available.

Raises NotImplementedError if an unknown backend name is specified.
    """
    # pylint: disable=import-outside-toplevel,redefined-outer-name
    backend = _backends.get(name)
    if backend:
        return backend
    if name == "trio":
        import dns._trio_backend

backend = dns._trio_backend.Backend()
    elif name == "asyncio":
        import dns._asyncio_backend

backend = dns._asyncio_backend.Backend()
    else:
        raise NotImplementedError(f"unimplemented async backend {name}")
    _backends[name] = backend
    return backend

def sniff() -> str:
    """Attempt to determine the in-use asynchronous I/O library by using
    the ``sniffio`` module if it is available.

Returns the name of the library, or raises AsyncLibraryNotFoundError
    if the library cannot be determined.
    """
    # pylint: disable=import-outside-toplevel
    try:
        if _no_sniffio:
            raise ImportError
        import sniffio

try:
            return sniffio.current_async_library()
        except sniffio.AsyncLibraryNotFoundError:
            raise AsyncLibraryNotFoundError("sniffio cannot determine async library")
    except ImportError:
        import asyncio

try:
            asyncio.get_running_loop()
            return "asyncio"
        except RuntimeError:
            raise AsyncLibraryNotFoundError("no async library detected")

def get_default_backend() -> Backend:
    """Get the default backend, initializing it if necessary."""
    if _default_backend:
        return _default_backend

return set_default_backend(sniff())

def set_default_backend(name: str) -> Backend:
    """Set the default backend.

It's not normally necessary to call this method, as
    ``get_default_backend()`` will initialize the backend
    appropriately in many cases.  If ``sniffio`` is not installed, or
    in testing situations, this function allows the backend to be set
    explicitly.
    """
    global _default_backend
    _default_backend = get_backend(name)
    return _default_backend