Current File : //lib/python3/dist-packages/pyudev/discover.py
# -*- coding: utf-8 -*-
# Copyright (C) 2015 mulhern <amulhern@redhat.com>
# This library is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation; either version 2.1 of the License, or (at your
# option) any later version.
# This library is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
# for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with this library; if not, write to the Free Software Foundation,
# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
"""
pyudev.discover
===============
Tools to discover a device given limited information.
.. moduleauthor:: mulhern <amulhern@redhat.com>
"""
# isort: STDLIB
import abc
import functools
import os
import re
# isort: LOCAL
from pyudev._errors import DeviceNotFoundError
from pyudev.device import Devices
def wrap_exception(func):
"""
Allow Device discovery methods to return None instead of raising an
exception.
"""
@functools.wraps(func)
def the_func(*args, **kwargs):
"""
Returns result of calling ``func`` on ``args``, ``kwargs``.
Returns None if ``func`` raises :exc:`DeviceNotFoundError`.
"""
try:
return func(*args, **kwargs)
except DeviceNotFoundError:
return None
return the_func
class Hypothesis(object):
"""
Represents a hypothesis about the meaning of the device identifier.
"""
__metaclass__ = abc.ABCMeta
@classmethod
@abc.abstractmethod
def match(cls, value): # pragma: no cover
"""
Match the given string according to the hypothesis.
The purpose of this method is to obtain a value corresponding to
``value`` if that is possible. It may use a regular expression, but
in general it should just return ``value`` and let the lookup method
sort out the rest.
:param str value: the string to inspect
:returns: the matched thing or None if unmatched
:rtype: the type of lookup's key parameter or NoneType
"""
raise NotImplementedError()
@classmethod
@abc.abstractmethod
def lookup(cls, context, key): # pragma: no cover
"""
Lookup the given string according to the hypothesis.
:param Context context: the pyudev context
:param key: a key with which to lookup the device
:type key: the type of match's return value if not None
:returns: a list of Devices obtained
:rtype: frozenset of :class:`Device`
"""
raise NotImplementedError()
@classmethod
def setup(cls, context):
"""
A potentially expensive method that may allow an :class:`Hypothesis`
to find devices more rapidly or to find a device that it would
otherwise miss.
:param Context context: the pyudev context
"""
pass
@classmethod
def get_devices(cls, context, value):
"""
Get any devices that may correspond to the given string.
:param Context context: the pyudev context
:param str value: the value to look for
:returns: a list of devices obtained
:rtype: set of :class:`Device`
"""
key = cls.match(value)
return cls.lookup(context, key) if key is not None else frozenset()
class DeviceNumberHypothesis(Hypothesis):
"""
Represents the hypothesis that the device is a device number.
The device may be separated into major/minor number or a composite number.
"""
@classmethod
def _match_major_minor(cls, value):
"""
Match the number under the assumption that it is a major,minor pair.
:param str value: value to match
:returns: the device number or None
:rtype: int or NoneType
"""
major_minor_re = re.compile(r"^(?P<major>\d+)(\D+)(?P<minor>\d+)$")
match = major_minor_re.match(value)
return match and os.makedev(
int(match.group("major")), int(match.group("minor"))
)
@classmethod
def _match_number(cls, value):
"""
Match the number under the assumption that it is a single number.
:param str value: value to match
:returns: the device number or None
:rtype: int or NoneType
"""
number_re = re.compile(r"^(?P<number>\d+)$")
match = number_re.match(value)
return match and int(match.group("number"))
@classmethod
def match(cls, value):
"""
Match the number under the assumption that it is a device number.
:returns: the device number or None
:rtype: int or NoneType
"""
return cls._match_major_minor(value) or cls._match_number(value)
@classmethod
def find_subsystems(cls, context):
"""
Find subsystems in /sys/dev.
:param Context context: the context
:returns: a lis of available subsystems
:rtype: list of str
"""
sys_path = context.sys_path
return os.listdir(os.path.join(sys_path, "dev"))
@classmethod
def lookup(cls, context, key):
"""
Lookup by the device number.
:param Context context: the context
:param int key: the device number
:returns: a list of matching devices
:rtype: frozenset of :class:`Device`
"""
func = wrap_exception(Devices.from_device_number)
res = (func(context, s, key) for s in cls.find_subsystems(context))
return frozenset(r for r in res if r is not None)
class DevicePathHypothesis(Hypothesis):
"""
Discover the device assuming the identifier is a device path.
"""
@classmethod
def match(cls, value):
"""
Match ``value`` under the assumption that it is a device path.
:returns: the device path or None
:rtype: str or NoneType
"""
return value
@classmethod
def lookup(cls, context, key):
"""
Lookup by the path.
:param Context context: the context
:param str key: the device path
:returns: a list of matching devices
:rtype: frozenset of :class:`Device`
"""
res = wrap_exception(Devices.from_path)(context, key)
return frozenset((res,)) if res is not None else frozenset()
class DeviceNameHypothesis(Hypothesis):
"""
Discover the device assuming the input is a device name.
Try every available subsystem.
"""
@classmethod
def find_subsystems(cls, context):
"""
Find all subsystems in sysfs.
:param Context context: the context
:rtype: frozenset
:returns: subsystems in sysfs
"""
sys_path = context.sys_path
dirnames = ("bus", "class", "subsystem")
absnames = (os.path.join(sys_path, name) for name in dirnames)
realnames = (d for d in absnames if os.path.isdir(d))
return frozenset(n for d in realnames for n in os.listdir(d))
@classmethod
def match(cls, value):
"""
Match ``value`` under the assumption that it is a device name.
:returns: the device path or None
:rtype: str or NoneType
"""
return value
@classmethod
def lookup(cls, context, key):
"""
Lookup by the path.
:param Context context: the context
:param str key: the device path
:returns: a list of matching devices
:rtype: frozenset of :class:`Device`
"""
func = wrap_exception(Devices.from_name)
res = (func(context, s, key) for s in cls.find_subsystems(context))
return frozenset(r for r in res if r is not None)
class DeviceFileHypothesis(Hypothesis):
"""
Discover the device assuming the value is some portion of a device file.
The device file may be a link to a device node.
"""
_LINK_DIRS = [
"/dev",
"/dev/disk/by-id",
"/dev/disk/by-label",
"/dev/disk/by-partlabel",
"/dev/disk/by-partuuid",
"/dev/disk/by-path",
"/dev/disk/by-uuid",
"/dev/input/by-path",
"/dev/mapper",
"/dev/md",
"/dev/vg",
]
@classmethod
def get_link_dirs(cls, context):
"""
Get all directories that may contain links to device nodes.
This method checks the device links of every device, so it is very
expensive.
:param Context context: the context
:returns: a sorted list of directories that contain device links
:rtype: list
"""
devices = context.list_devices()
devices_with_links = (d for d in devices if list(d.device_links))
links = (l for d in devices_with_links for l in d.device_links)
return sorted(set(os.path.dirname(l) for l in links))
@classmethod
def setup(cls, context):
"""
Set the link directories to be used when discovering by file.
Uses `get_link_dirs`, so is as expensive as it is.
:param Context context: the context
"""
cls._LINK_DIRS = cls.get_link_dirs(context)
@classmethod
def match(cls, value):
return value
@classmethod
def lookup(cls, context, key):
"""
Lookup the device under the assumption that the key is part of
the name of a device file.
:param Context context: the context
:param str key: a portion of the device file name
It is assumed that either it is the whole name of the device file
or it is the basename.
A device file may be a device node or a device link.
"""
func = wrap_exception(Devices.from_device_file)
if "/" in key:
device = func(context, key)
return frozenset((device,)) if device is not None else frozenset()
files = (os.path.join(ld, key) for ld in cls._LINK_DIRS)
devices = (func(context, f) for f in files)
return frozenset(d for d in devices if d is not None)
class Discovery(object):
# pylint: disable=too-few-public-methods
"""
Provides discovery methods for devices.
"""
_HYPOTHESES = [
DeviceFileHypothesis,
DeviceNameHypothesis,
DeviceNumberHypothesis,
DevicePathHypothesis,
]
def __init__(self):
self._hypotheses = self._HYPOTHESES
def setup(self, context):
"""
Set up individual hypotheses.
May be an expensive call.
:param Context context: the context
"""
for hyp in self._hypotheses:
hyp.setup(context)
def get_devices(self, context, value):
"""
Get the devices corresponding to value.
:param Context context: the context
:param str value: some identifier of the device
:returns: a list of corresponding devices
:rtype: frozenset of :class:`Device`
"""
return frozenset(
d for h in self._hypotheses for d in h.get_devices(context, value)
)
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