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from .lock import allocate_lock
from .error import CDefError
from . import model

try:
    callable
except NameError:
    # Python 3.1
    from collections import Callable
    callable = lambda x: isinstance(x, Callable)

try:
    basestring
except NameError:
    # Python 3.x
    basestring = str

_unspecified = object()


class FFI(object):
    r'''
    The main top-level class that you instantiate once, or once per module.

    Example usage:

        ffi = FFI()
        ffi.cdef("""
            int printf(const char *, ...);
        """)

        C = ffi.dlopen(None)   # standard library
        -or-
        C = ffi.verify()  # use a C compiler: verify the decl above is right

        C.printf("hello, %s!\n", ffi.new("char[]", "world"))
    '''

    def __init__(self, backend=None):
        """Create an FFI instance.  The 'backend' argument is used to
        select a non-default backend, mostly for tests.
        """
        if backend is None:
            # You need PyPy (>= 2.0 beta), or a CPython (>= 2.6) with
            # _cffi_backend.so compiled.
            import _cffi_backend as backend
            from . import __version__
            if backend.__version__ != __version__:
                # bad version!  Try to be as explicit as possible.
                if hasattr(backend, '__file__'):
                    # CPython
                    raise Exception("Version mismatch: this is the 'cffi' package version %s, located in %r.  When we import the top-level '_cffi_backend' extension module, we get version %s, located in %r.  The two versions should be equal; check your installation." % (
                        __version__, __file__,
                        backend.__version__, backend.__file__))
                else:
                    # PyPy
                    raise Exception("Version mismatch: this is the 'cffi' package version %s, located in %r.  This interpreter comes with a built-in '_cffi_backend' module, which is version %s.  The two versions should be equal; check your installation." % (
                        __version__, __file__, backend.__version__))
            # (If you insist you can also try to pass the option
            # 'backend=backend_ctypes.CTypesBackend()', but don't
            # rely on it!  It's probably not going to work well.)

        from . import cparser
        self._backend = backend
        self._lock = allocate_lock()
        self._parser = cparser.Parser()
        self._cached_btypes = {}
        self._parsed_types = types.ModuleType('parsed_types').__dict__
        self._new_types = types.ModuleType('new_types').__dict__
        self._function_caches = []
        self._libraries = []
        self._cdefsources = []
        self._included_ffis = []
        self._windows_unicode = None
        self._init_once_cache = {}
        self._cdef_version = None
        self._embedding = None
        self._typecache = model.get_typecache(backend)
        if hasattr(backend, 'set_ffi'):
            backend.set_ffi(self)
        for name in list(backend.__dict__):
            if name.startswith('RTLD_'):
                setattr(self, name, getattr(backend, name))
        #
        with self._lock:
            self.BVoidP = self._get_cached_btype(model.voidp_type)
            self.BCharA = self._get_cached_btype(model.char_array_type)
        if isinstance(backend, types.ModuleType):
            # _cffi_backend: attach these constants to the class
            if not hasattr(FFI, 'NULL'):
                FFI.NULL = self.cast(self.BVoidP, 0)
                FFI.CData, FFI.CType = backend._get_types()
        else:
            # ctypes backend: attach these constants to the instance
            self.NULL = self.cast(self.BVoidP, 0)
            self.CData, self.CType = backend._get_types()
        self.buffer = backend.buffer

    def cdef(self, csource, override=False, packed=False, pack=None):
        """Parse the given C source.  This registers all declared functions,
        types, and global variables.  The fu