JezK
Edit File: api.py
import sys, types from .lock import allocate_lock 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 class FFIError(Exception): pass class CDefError(Exception): def __str__(self): try: line = 'line %d: ' % (self.args[1].coord.line,) except (AttributeError, TypeError, IndexError): line = '' return '%s%s' % (line, self.args[0]) 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. """ from . import cparser, model 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__ assert backend.__version__ == __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.) 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 = [] if hasattr(backend, 'set_ffi'): backend.set_ffi(self) for name in backend.__dict__: if name.startswith('RTLD_'): setattr(self, name, getattr(backend, name)) # with self._lock: self.BVoidP = self._get_cached_btype(model.voidp_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() def cdef(self, csource, override=False, packed=False): """Parse the given C source. This registers all declared functions, types, and global variables. The functions and global variables can then be accessed via either 'ffi.dlopen()' or 'ffi.verify()'. The types can be used in 'ffi.new()' and other functions. If 'packed' is specified as True, all structs declared inside this cdef are packed, i.e. laid out without any field alignment at all. """ if not isinstance(csource, str): # unicode, on Python 2 if not isinstance(csource, basestring): raise TypeError("cdef() argument must be a string") csource = csource.encode('ascii') with self._lock: self._parser.parse(csource, override=override, packed=packed) self._cdefsources.append(csource) if override: for cache in self._function_caches: cache.clear() def dlopen(self, name, flags=0): """Load and return a dynamic library identified by 'name'. The standard C library can be loaded by passing None. Note that functions and types declared by 'ffi.cdef()' are not linked to a particular library, just like C headers; in the library we only look for the actual (untyped) symbols. """ assert isinstance(name, basestring) or name is None with self._lock: lib, function_cache = _make_ffi_library(self, name, flags) self._function_caches.append(function_cache) self._libraries.append(lib) return lib def _typeof_locked(self, cdecl): # call me with the lock! key = cdecl if key in self._parsed_types: return self._parsed_types[key] # if not isinstance(cdecl, str): # unicode, on Python 2 cdecl = cdecl.encode('ascii') # type = self._parser.parse_type(cdecl) really_a_function_type = type.is_raw_function if really_a_function_type: type = type.as_function_pointer() btype = self._get_cached_btype(type) result = btype, really_a_function_type self._parsed_types[key] = result return result def _typeof(self, cdecl, consider_function_as_funcptr=False): # string -> ctype object try: result = self._parsed_types[cdecl] except KeyError: with self._lock: result = self._typeof_locked(cdecl) # btype, really_a_function_type = result if really_a_function_type and not consider_function_as_funcptr: raise CDefError("the type %r is a function type, not a " "pointer-to-function type" % (cdecl,)) return btype def typeof(self, cdecl): """Parse the C type given as a string and return the corresponding <ctype> object. It can also be used on 'cdata' instance to get its C type. """ if isinstance(cdecl, basestring): return self._typeof(cdecl) if isinstance(cdecl, self.CData): return self._backend.typeof(cdecl) if isinstance(cdecl, types.BuiltinFunctionType): res = _builtin_function_type(cdecl) if res is not None: return res if (isinstance(cdecl, types.FunctionType) and hasattr(cdecl, '_cffi_base_type')): with self._lock: return self._get_cached_btype(cdecl._cffi_base_type) raise TypeError(type(cdecl)) def sizeof(self, cdecl): """Return the size in bytes of the argument. It can be a string naming a C type, or a 'cdata' instance. """ if isinstance(cdecl, basestring): BType = self._typeof(cdecl) return self._backend.sizeof(BType) else: return self._backend.sizeof(cdecl) def alignof(self, cdecl): """Return the natural alignment size in bytes of the C type given as a string. """ if isinstance(cdecl, basestring): cdecl = self._typeof(cdecl) return self._backend.alignof(cdecl) def offsetof(self, cdecl, fieldname): """Return the offset of the named field inside the given structure, which must be given as a C type name. """ if isinstance(cdecl, basestring): cdecl = self._typeof(cdecl) return self._backend.typeoffsetof(cdecl, fieldname)[1] def new(self, cdecl, init=None): """Allocate an instance according to the specified C type and return a pointer to it. The specified C type must be either a pointer or an array: ``new('X *')`` allocates an X and returns a pointer to it, whereas ``new('X[n]')`` allocates an array of n X'es and returns an array referencing it (which works mostly like a pointer, like in C). You can also use ``new('X[]', n)`` to allocate an array of a non-constant length n. The memory is initialized following the rules of declaring a global variable in C: by default it is zero-initialized, but an explicit initializer can be given which can be used to fill all or part of the memory. When the returned <cdata> object goes out of scope, the memory is freed. In other words the returned <cdata> object has ownership of the value of type 'cdecl' that it points to. This means that the raw data can be used as long as this object is kept alive, but must not be used for a longer time. Be careful about that when copying the pointer to the memory somewhere else, e.g. into another structure. """ if isinstance(cdecl, basestring): cdecl = self._typeof(cdecl) return self._backend.newp(cdecl, init) def cast(self, cdecl, source): """Similar to a C cast: returns an instance of the named C type initialized with the given 'source'. The source is casted between integers or pointers of any type. """ if isinstance(cdecl, basestring): cdecl = self._typeof(cdecl) return self._backend.cast(cdecl, source) def string(self, cdata, maxlen=-1): """Return a Python string (or unicode string) from the 'cdata'. If 'cdata' is a pointer or array of characters or bytes, returns the null-terminated string. The returned string extends until the first null character, or at most 'maxlen' characters. If 'cdata' is an array then 'maxlen' defaults to its length. If 'cdata' is a pointer or array of wchar_t, returns a unicode string following the same rules. If 'cdata' is a single character or byte or a wchar_t, returns it as a string or unicode string. If 'cdata' is an enum, returns the value of the enumerator as a string, or 'NUMBER' if the value is out of range. """ return self._backend.string(cdata, maxlen) def buffer(self, cdata, size=-1): """Return a read-write buffer object that references the raw C data pointed to by the given 'cdata'. The 'cdata' must be a pointer or an array. Can be passed to functions expecting a buffer, or directly manipulated with: buf[:] get a copy of it in a regular string, or buf[idx] as a single character buf[:] = ... buf[idx] = ... change the content """ return self._backend.buffer(cdata, size) def callback(self, cdecl, python_callable=None, error=None): """Return a callback object or a decorator making such a callback object. 'cdecl' must name a C function pointer type. The callback invokes the specified 'python_callable' (which may be provided either directly or via a decorator). Important: the callback object must be manually kept alive for as long as the callback may be invoked from the C level. """ def callback_decorator_wrap(python_callable): if not callable(python_callable): raise TypeError("the 'python_callable' argument " "is not callable") return self._backend.callback(cdecl, python_callable, error) if isinstance(cdecl, basestring): cdecl = self._typeof(cdecl, consider_function_as_funcptr=True) if python_callable is None: return callback_decorator_wrap # decorator mode else: return callback_decorator_wrap(python_callable) # direct mode def getctype(self, cdecl, replace_with=''): """Return a string giving the C type 'cdecl', which may be itself a string or a <ctype> object. If 'replace_with' is given, it gives extra text to append (or insert for more complicated C types), like a variable name, or '*' to get actually the C type 'pointer-to-cdecl'. """ if isinstance(cdecl, basestring): cdecl = self._typeof(cdecl) replace_with = replace_with.strip() if (replace_with.startswith('*') and '&[' in self._backend.getcname(cdecl, '&')): replace_with = '(%s)' % replace_with elif replace_with and not replace_with[0] in '[(': replace_with = ' ' + replace_with return self._backend.getcname(cdecl, replace_with) def gc(self, cdata, destructor): """Return a new cdata object that points to the same data. Later, when this new cdata object is garbage-collected, 'destructor(old_cdata_object)' will be called. """ with self._lock: try: gc_weakrefs = self.gc_weakrefs except AttributeError: from .gc_weakref import GcWeakrefs gc_weakrefs = self.gc_weakrefs = GcWeakrefs(self) return gc_weakrefs.build(cdata, destructor) def _get_cached_btype(self, type): assert self._lock.acquire(False) is False # call me with the lock! try: BType = self._cached_btypes[type] except KeyError: finishlist = [] BType = type.get_cached_btype(self, finishlist) for type in finishlist: type.finish_backend_type(self, finishlist) return BType def verify(self, source='', tmpdir=None, **kwargs): """Verify that the current ffi signatures compile on this machine, and return a dynamic library object. The dynamic library can be used to call functions and access global variables declared in this 'ffi'. The library is compiled by the C compiler: it gives you C-level API compatibility (including calling macros). This is unlike 'ffi.dlopen()', which requires binary compatibility in the signatures. """ from .verifier import Verifier, _caller_dir_pycache tmpdir = tmpdir or _caller_dir_pycache() self.verifier = Verifier(self, source, tmpdir, **kwargs) lib = self.verifier.load_library() self._libraries.append(lib) return lib def _get_errno(self): return self._backend.get_errno() def _set_errno(self, errno): self._backend.set_errno(errno) errno = property(_get_errno, _set_errno, None, "the value of 'errno' from/to the C calls") def getwinerror(self, code=-1): return self._backend.getwinerror(code) def _pointer_to(self, ctype): from . import model with self._lock: return model.pointer_cache(self, ctype) def addressof(self, cdata, field=None): """Return the address of a <cdata 'struct-or-union'>. If 'field' is specified, return the address of this field. """ ctype = self._backend.typeof(cdata) ctype, offset = self._backend.typeoffsetof(ctype, field) ctypeptr = self._pointer_to(ctype) return self._backend.rawaddressof(ctypeptr, cdata, offset) def include(self, ffi_to_include): """Includes the typedefs, structs, unions and enums defined in another FFI instance. Usage is similar to a #include in C, where a part of the program might include types defined in another part for its own usage. Note that the include() method has no effect on functions, constants and global variables, which must anyway be accessed directly from the lib object returned by the original FFI instance. """ with ffi_to_include._lock: with self._lock: self._parser.include(ffi_to_include._parser) self._cdefsources.append('[') self._cdefsources.extend(ffi_to_include._cdefsources) self._cdefsources.append(']') def new_handle(self, x): return self._backend.newp_handle(self.BVoidP, x) def from_handle(self, x): return self._backend.from_handle(x) def _load_backend_lib(backend, name, flags): if name is None: if sys.platform != "win32": return backend.load_library(None, flags) name = "c" # Windows: load_library(None) fails, but this works # (backward compatibility hack only) try: if '.' not in name and '/' not in name: raise OSError("library not found: %r" % (name,)) return backend.load_library(name, flags) except OSError: import ctypes.util path = ctypes.util.find_library(name) if path is None: raise # propagate the original OSError return backend.load_library(path, flags) def _make_ffi_library(ffi, libname, flags): import os backend = ffi._backend backendlib = _load_backend_lib(backend, libname, flags) copied_enums = [] # def make_accessor_locked(name): key = 'function ' + name if key in ffi._parser._declarations: tp = ffi._parser._declarations[key] BType = ffi._get_cached_btype(tp) try: value = backendlib.load_function(BType, name) except KeyError as e: raise AttributeError('%s: %s' % (name, e)) library.__dict__[name] = value return # key = 'variable ' + name if key in ffi._parser._declarations: tp = ffi._parser._declarations[key] BType = ffi._get_cached_btype(tp) read_variable = backendlib.read_variable write_variable = backendlib.write_variable setattr(FFILibrary, name, property( lambda self: read_variable(BType, name), lambda self, value: write_variable(BType, name, value))) return # if not copied_enums: from . import model for key, tp in ffi._parser._declarations.items(): if not isinstance(tp, model.EnumType): continue for enumname, enumval in zip(tp.enumerators, tp.enumvalues): if enumname not in library.__dict__: library.__dict__[enumname] = enumval for key, val in ffi._parser._int_constants.items(): if key not in library.__dict__: library.__dict__[key] = val copied_enums.append(True) if name in library.__dict__: return # raise AttributeError(name) # def make_accessor(name): with ffi._lock: if name in library.__dict__ or name in FFILibrary.__dict__: return # added by another thread while waiting for the lock make_accessor_locked(name) # class FFILibrary(object): def __getattr__(self, name): make_accessor(name) return getattr(self, name) def __setattr__(self, name, value): try: property = getattr(self.__class__, name) except AttributeError: make_accessor(name) setattr(self, name, value) else: property.__set__(self, value) # if libname is not None: try: if not isinstance(libname, str): # unicode, on Python 2 libname = libname.encode('utf-8') FFILibrary.__name__ = 'FFILibrary_%s' % libname except UnicodeError: pass library = FFILibrary() return library, library.__dict__ def _builtin_function_type(func): # a hack to make at least ffi.typeof(builtin_function) work, # if the builtin function was obtained by 'vengine_cpy'. import sys try: module = sys.modules[func.__module__] ffi = module._cffi_original_ffi types_of_builtin_funcs = module._cffi_types_of_builtin_funcs tp = types_of_builtin_funcs[func] except (KeyError, AttributeError, TypeError): return None else: with ffi._lock: return ffi._get_cached_btype(tp)