Skip to content
Cannot retrieve contributors at this time
Implementation of compiled C callbacks (@cfunc).
import ctypes
from numba.core import utils, compiler, registry
from numba.core.caching import NullCache, FunctionCache
from numba.core.dispatcher import _FunctionCompiler
from numba.core.typing import signature
from numba.core.typing.ctypes_utils import to_ctypes
from numba.core.compiler_lock import global_compiler_lock
class _CFuncCompiler(_FunctionCompiler):
def _customize_flags(self, flags):
flags.no_cpython_wrapper = True
flags.no_cfunc_wrapper = False
# Disable compilation of the IR module, because we first want to
# add the cfunc wrapper.
flags.no_compile = True
# Object mode is not currently supported in C callbacks
# (no reliable way to get the environment)
flags.enable_pyobject = False
if flags.force_pyobject:
raise NotImplementedError("object mode not allowed in C callbacks")
return flags
class CFunc(object):
A compiled C callback, as created by the @cfunc decorator.
_targetdescr = registry.cpu_target
def __init__(self, pyfunc, sig, locals, options,
args, return_type = sig
if return_type is None:
raise TypeError("C callback needs an explicit return type")
self.__name__ = pyfunc.__name__
self.__qualname__ = getattr(pyfunc, '__qualname__', self.__name__)
self.__wrapped__ = pyfunc
self._pyfunc = pyfunc
self._sig = signature(return_type, *args)
self._compiler = _CFuncCompiler(pyfunc, self._targetdescr,
options, locals,
self._wrapper_name = None
self._wrapper_address = None
self._cache = NullCache()
self._cache_hits = 0
def enable_caching(self):
self._cache = FunctionCache(self._pyfunc)
def compile(self):
# Try to load from cache
cres = self._cache.load_overload(self._sig,
if cres is None:
cres = self._compile_uncached()
self._cache.save_overload(self._sig, cres)
self._cache_hits += 1
self._library = cres.library
self._wrapper_name = cres.fndesc.llvm_cfunc_wrapper_name
self._wrapper_address = self._library.get_pointer_to_function(
def _compile_uncached(self):
sig = self._sig
# Compile native function as well as cfunc wrapper
return self._compiler.compile(sig.args, sig.return_type)
def native_name(self):
The process-wide symbol the C callback is exposed as.
# Note from our point of view, the C callback is the wrapper around
# the native function.
return self._wrapper_name
def address(self):
The address of the C callback.
return self._wrapper_address
def cffi(self):
A cffi function pointer representing the C callback.
import cffi
ffi = cffi.FFI()
# cffi compares types by name, so using precise types would risk
# spurious mismatches (such as "int32_t" vs. "int").
return ffi.cast("void *", self.address)
def ctypes(self):
A ctypes function object representing the C callback.
ctypes_args = [to_ctypes(ty) for ty in self._sig.args]
ctypes_restype = to_ctypes(self._sig.return_type)
functype = ctypes.CFUNCTYPE(ctypes_restype, *ctypes_args)
return functype(self.address)
def inspect_llvm(self):
Return the LLVM IR of the C callback definition.
return self._library.get_llvm_str()
def cache_hits(self):
return self._cache_hits
def __repr__(self):
return "<Numba C callback %r>" % (self.__qualname__,)
def __call__(self, *args, **kwargs):
return self._pyfunc(*args, **kwargs)