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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import, division, print_function
import binascii
import sys
import threading
from cffi import FFI
from cffi.verifier import Verifier
class LazyLibrary(object):
def __init__(self, ffi):
self._ffi = ffi
self._lib = None
self._lock = threading.Lock()
def __getattr__(self, name):
if self._lib is None:
with self._lock:
if self._lib is None:
self._lib = self._ffi.verifier.load_library()
return getattr(self._lib, name)
def load_library_for_binding(ffi, module_prefix, modules):
lib = ffi.verifier.load_library()
for name in modules:
module_name = module_prefix + name
module = sys.modules[module_name]
for condition, names in module.CONDITIONAL_NAMES.items():
if not getattr(lib, condition):
for name in names:
delattr(lib, name)
return lib
def build_ffi_for_binding(module_prefix, modules, pre_include="",
post_include="", libraries=[], extra_compile_args=[],
extra_link_args=[]):
"""
Modules listed in ``modules`` should have the following attributes:
* ``INCLUDES``: A string containing C includes.
* ``TYPES``: A string containing C declarations for types.
* ``FUNCTIONS``: A string containing C declarations for functions.
* ``MACROS``: A string containing C declarations for any macros.
* ``CUSTOMIZATIONS``: A string containing arbitrary top-level C code, this
can be used to do things like test for a define and provide an
alternate implementation based on that.
* ``CONDITIONAL_NAMES``: A dict mapping strings of condition names from the
library to a list of names which will not be present without the
condition.
"""
types = []
includes = []
functions = []
macros = []
customizations = []
for name in modules:
module_name = module_prefix + name
__import__(module_name)
module = sys.modules[module_name]
types.append(module.TYPES)
macros.append(module.MACROS)
functions.append(module.FUNCTIONS)
includes.append(module.INCLUDES)
customizations.append(module.CUSTOMIZATIONS)
# We include functions here so that if we got any of their definitions
# wrong, the underlying C compiler will explode. In C you are allowed
# to re-declare a function if it has the same signature. That is:
# int foo(int);
# int foo(int);
# is legal, but the following will fail to compile:
# int foo(int);
# int foo(short);
verify_source = "\n".join(
[pre_include] +
includes +
[post_include] +
functions +
customizations
)
ffi = build_ffi(
cdef_source="\n".join(types + functions + macros),
verify_source=verify_source,
libraries=libraries,
extra_compile_args=extra_compile_args,
extra_link_args=extra_link_args,
)
return ffi
def build_ffi(cdef_source, verify_source, libraries=[], extra_compile_args=[],
extra_link_args=[]):
ffi = FFI()
ffi.cdef(cdef_source)
ffi.verifier = Verifier(
ffi,
verify_source,
tmpdir='',
modulename=_create_modulename(cdef_source, verify_source, sys.version),
libraries=libraries,
ext_package="cryptography",
extra_compile_args=extra_compile_args,
extra_link_args=extra_link_args,
)
return ffi
def _create_modulename(cdef_sources, source, sys_version):
"""
cffi creates a modulename internally that incorporates the cffi version.
This will cause cryptography's wheels to break when the version of cffi
the user has does not match what was used when building the wheel. To
resolve this we build our own modulename that uses most of the same code
from cffi but elides the version key.
"""
key = '\x00'.join([sys_version[:3], source, cdef_sources])
key = key.encode('utf-8')
k1 = hex(binascii.crc32(key[0::2]) & 0xffffffff)
k1 = k1.lstrip('0x').rstrip('L')
k2 = hex(binascii.crc32(key[1::2]) & 0xffffffff)
k2 = k2.lstrip('0').rstrip('L')
return '_Cryptography_cffi_{0}{1}'.format(k1, k2)
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