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pyudev
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_libudev.py
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# -*- coding: utf-8 -*- # Copyright (C) 2010, 2011, 2012 Sebastian Wiesner <lunaryorn@gmail.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 """ _libudev ======== Wrapper types for libudev. Use ``libudev`` attribute to access libudev functions. .. moduleauthor:: Sebastian Wiesner <lunaryorn@gmail.com> """ from __future__ import (print_function, division, unicode_literals, absolute_import) import os import errno from ctypes import (CDLL, Structure, POINTER, get_errno, c_char, c_char_p, c_int, c_ulonglong) from ctypes.util import find_library class udev(Structure): """ Dummy for ``udev`` structure. """ pass udev_p = POINTER(udev) class udev_enumerate(Structure): """ Dummy for ``udev_enumerate`` structure. """ udev_enumerate_p = POINTER(udev_enumerate) class udev_list_entry(Structure): """ Dummy for ``udev_list_entry`` structure. """ udev_list_entry_p = POINTER(udev_list_entry) class udev_device(Structure): """ Dummy for ``udev_device`` structure. """ udev_device_p = POINTER(udev_device) class udev_monitor(Structure): """ Dummy for ``udev_device`` structure. """ udev_monitor_p = POINTER(udev_monitor) dev_t = c_ulonglong SIGNATURES = { # context 'udev': dict( new=([], udev_p), unref=([udev_p], None), ref=([udev_p], udev_p), get_sys_path=([udev_p], c_char_p), get_dev_path=([udev_p], c_char_p), get_run_path=([udev_p], c_char_p), get_log_priority=([udev_p], c_int), set_log_priority=([udev_p, c_int], None)), # enumeration 'udev_enumerate': dict( new=([udev_p], udev_enumerate_p), ref=([udev_enumerate_p], udev_enumerate_p), unref=([udev_enumerate_p], None), add_match_subsystem=([udev_enumerate_p, c_char_p], c_int), add_nomatch_subsystem=([udev_enumerate_p, c_char_p], c_int), add_match_property=([udev_enumerate_p, c_char_p, c_char_p], c_int), add_match_sysattr=([udev_enumerate_p, c_char_p, c_char_p], c_int), add_nomatch_sysattr=([udev_enumerate_p, c_char_p, c_char_p], c_int), add_match_tag=([udev_enumerate_p, c_char_p], c_int), add_match_sysname=([udev_enumerate_p, c_char_p], c_int), add_match_parent=([udev_enumerate_p, udev_device_p], c_int), add_match_is_initialized=([udev_enumerate_p], c_int), scan_devices=([udev_enumerate_p], c_int), get_list_entry=([udev_enumerate_p], udev_list_entry_p)), # list entries 'udev_list_entry': dict( get_next=([udev_list_entry_p], udev_list_entry_p), get_name=([udev_list_entry_p], c_char_p), get_value=([udev_list_entry_p], c_char_p)), # devices 'udev_device': dict( ref=([udev_device_p], udev_device_p), unref=([udev_device_p], None), new_from_syspath=([udev_p, c_char_p], udev_device_p), new_from_subsystem_sysname=([udev_p, c_char_p, c_char_p], udev_device_p), new_from_devnum=([udev_p, c_char, dev_t], udev_device_p), new_from_environment=([udev_p], udev_device_p), get_parent=([udev_device_p], udev_device_p), get_parent_with_subsystem_devtype=([udev_device_p, c_char_p, c_char_p], udev_device_p), get_devpath=([udev_device_p], c_char_p), get_subsystem=([udev_device_p], c_char_p), get_syspath=([udev_device_p], c_char_p), get_sysnum=([udev_device_p], c_char_p), get_sysname=([udev_device_p], c_char_p), get_driver=([udev_device_p], c_char_p), get_devtype=([udev_device_p], c_char_p), get_devnode=([udev_device_p], c_char_p), get_property_value=([udev_device_p, c_char_p], c_char_p), get_sysattr_value=([udev_device_p, c_char_p], c_char_p), get_devnum=([udev_device_p], dev_t), get_action=([udev_device_p], c_char_p), get_seqnum=([udev_device_p], c_ulonglong), get_is_initialized=([udev_device_p], c_int), get_usec_since_initialized=([udev_device_p], c_ulonglong), get_devlinks_list_entry=([udev_device_p], udev_list_entry_p), get_tags_list_entry=([udev_device_p], udev_list_entry_p), get_properties_list_entry=([udev_device_p], udev_list_entry_p), get_sysattr_list_entry=([udev_device_p], udev_list_entry_p), has_tag=([udev_device_p, c_char_p], c_int)), # monitoring 'udev_monitor': dict( ref=([udev_monitor_p], udev_monitor_p), unref=([udev_monitor_p], None), new_from_netlink=([udev_p, c_char_p], udev_monitor_p), enable_receiving=([udev_monitor_p], c_int), set_receive_buffer_size=([udev_monitor_p, c_int], c_int), get_fd=([udev_monitor_p], c_int), receive_device=([udev_monitor_p], udev_device_p), filter_add_match_subsystem_devtype=( [udev_monitor_p, c_char_p, c_char_p], c_int), filter_add_match_tag=([udev_monitor_p, c_char_p], c_int), filter_update=([udev_monitor_p], c_int), filter_remove=([udev_monitor_p], c_int)) } ERRNO_EXCEPTIONS = { errno.ENOMEM: MemoryError, errno.EOVERFLOW: OverflowError, errno.EINVAL: ValueError } def exception_from_errno(errno): """ Create an exception from ``errno``. ``errno`` is an integral error number. Return an exception object appropriate to ``errno``. """ exception = ERRNO_EXCEPTIONS.get(errno) if exception is not None: return exception() else: return EnvironmentError(errno, os.strerror(errno)) def check_negative_errorcode(result, func, *args): """ Error checker for udev funtions, which return negative error codes. If ``result`` is smaller than ``0``, it is interpreted as negative error code, and an appropriate exception is raised: - ``-ENOMEM`` raises a :exc:`~exceptions.MemoryError` - ``-EOVERFLOW`` raises a :exc:`~exceptions.OverflowError` - all other error codes raise :exc:`~exceptions.EnvironmentError` If result is greater or equal to ``0``, it is returned unchanged. """ if result < 0: # udev returns the *negative* errno code at this point errno = -result raise exception_from_errno(errno) else: return result def check_errno(result, func, *args): """ Error checker to check the system ``errno`` as returned by :func:`ctypes.get_errno()`. If ``result`` is not ``0``, an exception according to this errno is raised. Otherwise nothing happens. """ if result != 0: errno = get_errno() if errno != 0: raise exception_from_errno(errno) return result def check_errno_on_null_pointer(result, func, *args): """ Error checker to check the system ``errno`` as returned by :func:`ctypes.get_errno()`. If ``result`` is a null pointer, an exception according to this errno is raised. Otherwise nothing happens. """ if not result: errno = get_errno() if errno != 0: raise exception_from_errno(errno) return result ERROR_CHECKERS = dict( udev_enumerate_add_match_parent=check_negative_errorcode, udev_enumerate_add_match_subsystem=check_negative_errorcode, udev_enumerate_add_nomatch_subsystem=check_negative_errorcode, udev_enumerate_add_match_property=check_negative_errorcode, udev_enumerate_add_match_sysattr=check_negative_errorcode, udev_enumerate_add_nomatch_sysattr=check_negative_errorcode, udev_enumerate_add_match_tag=check_negative_errorcode, udev_enumerate_add_match_sysname=check_negative_errorcode, udev_enumerate_add_match_is_initialized=check_negative_errorcode, udev_monitor_set_receive_buffer_size=check_errno, # libudev doc says, enable_receiving returns a negative errno, but tests # show that this is not reliable, so query the real error code udev_monitor_enable_receiving=check_errno, udev_monitor_receive_device=check_errno_on_null_pointer, udev_monitor_filter_add_match_subsystem_devtype=check_negative_errorcode, udev_monitor_filter_add_match_tag=check_negative_errorcode, udev_monitor_filter_update=check_errno, udev_monitor_filter_remove=check_errno, ) def load_udev_library(): """ Load the ``udev`` library and return a :class:`ctypes.CDLL` object for it. The library has errno handling enabled. Important functions are given proper signatures and return types to support type checking and argument conversion. Raise :exc:`~exceptions.ImportError`, if the udev library was not found. """ libudev = CDLL('libudev.so.1', use_errno=True) # context function signature for namespace, members in SIGNATURES.items(): for funcname in members: fullname = '{0}_{1}'.format(namespace, funcname) func = getattr(libudev, fullname, None) if func: argtypes, restype = members[funcname] func.argtypes = argtypes func.restype = restype errorchecker = ERROR_CHECKERS.get(fullname) if errorchecker: func.errcheck = errorchecker return libudev libudev = load_udev_library()