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# -*- coding: utf-8 -*-
#
# Copyright 2009-2017 Wander Lairson Costa
# Copyright 2009-2021 PyUSB contributors
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import ctypes
import ctypes.util
import logging
import sys
__all__ = [
'LibraryException',
'LibraryNotFoundException',
'NoLibraryCandidatesException',
'LibraryNotLoadedException',
'LibraryMissingSymbolsException',
'locate_library',
'load_library',
'load_locate_library'
]
_LOGGER = logging.getLogger('usb.libloader')
class LibraryException(OSError):
pass
class LibraryNotFoundException(LibraryException):
pass
class NoLibraryCandidatesException(LibraryNotFoundException):
pass
class LibraryNotLoadedException(LibraryException):
pass
class LibraryMissingSymbolsException(LibraryException):
pass
def locate_library (candidates, find_library=ctypes.util.find_library):
"""Tries to locate a library listed in candidates using the given
find_library() function (or ctypes.util.find_library).
Returns the first library found, which can be the library's name
or the path to the library file, depending on find_library().
Returns None if no library is found.
arguments:
* candidates -- iterable with library names
* find_library -- function that takes one positional arg (candidate)
and returns a non-empty str if a library has been found.
Any "false" value (None,False,empty str) is interpreted
as "library not found".
Defaults to ctypes.util.find_library if not given or
None.
"""
if find_library is None:
find_library = ctypes.util.find_library
use_dll_workaround = (
sys.platform == 'win32' and find_library is ctypes.util.find_library
)
for candidate in candidates:
# Workaround for CPython 3.3 issue#16283 / pyusb #14
if use_dll_workaround:
candidate += '.dll'
libname = find_library(candidate)
if libname:
return libname
# -- end for
return None
def load_library(lib, name=None, lib_cls=None):
"""Loads a library. Catches and logs exceptions.
Returns: the loaded library or None
arguments:
* lib -- path to/name of the library to be loaded
* name -- the library's identifier (for logging)
Defaults to None.
* lib_cls -- library class. Defaults to None (-> ctypes.CDLL).
"""
try:
if lib_cls:
return lib_cls(lib)
else:
return ctypes.CDLL(lib)
except Exception:
if name:
lib_msg = '%s (%s)' % (name, lib)
else:
lib_msg = lib
lib_msg += ' could not be loaded'
if sys.platform == 'cygwin':
lib_msg += ' in cygwin'
_LOGGER.error(lib_msg, exc_info=True)
return None
def load_locate_library(candidates, cygwin_lib, name,
win_cls=None, cygwin_cls=None, others_cls=None,
find_library=None, check_symbols=None):
"""Locates and loads a library.
Returns: the loaded library
arguments:
* candidates -- candidates list for locate_library()
* cygwin_lib -- name of the cygwin library
* name -- lib identifier (for logging). Defaults to None.
* win_cls -- class that is used to instantiate the library on
win32 platforms. Defaults to None (-> ctypes.CDLL).
* cygwin_cls -- library class for cygwin platforms.
Defaults to None (-> ctypes.CDLL).
* others_cls -- library class for all other platforms.
Defaults to None (-> ctypes.CDLL).
* find_library -- see locate_library(). Defaults to None.
* check_symbols -- either None or a list of symbols that the loaded lib
must provide (hasattr(<>)) in order to be considered
valid. LibraryMissingSymbolsException is raised if
any symbol is missing.
raises:
* NoLibraryCandidatesException
* LibraryNotFoundException
* LibraryNotLoadedException
* LibraryMissingSymbolsException
"""
if sys.platform == 'cygwin':
if cygwin_lib:
loaded_lib = load_library(cygwin_lib, name, cygwin_cls)
else:
raise NoLibraryCandidatesException(name)
elif candidates:
lib = locate_library(candidates, find_library)
if lib:
if sys.platform == 'win32':
loaded_lib = load_library(lib, name, win_cls)
else:
loaded_lib = load_library(lib, name, others_cls)
else:
_LOGGER.error('%r could not be found', (name or candidates))
raise LibraryNotFoundException(name)
else:
raise NoLibraryCandidatesException(name)
if loaded_lib is None:
raise LibraryNotLoadedException(name)
elif check_symbols:
symbols_missing = [
s for s in check_symbols if not hasattr(loaded_lib, s)
]
if symbols_missing:
msg = ('%r, missing symbols: %r', lib, symbols_missing )
_LOGGER.error(msg)
raise LibraryMissingSymbolsException(lib)
else:
return loaded_lib
else:
return loaded_lib
|
