Add CDataType to return a C pointer.

theano/gof/type.py

@@ -2,6 +2,8 @@
 
 __docformat__ = "restructuredtext en"
 
+from theano.compat import PY3
+
 from theano.gof import utils
 from theano.gof.utils import MethodNotDefined, object2
 from theano.gof import graph
@@ -470,3 +472,85 @@ class Generic(SingletonType):
         return self.__class__.__name__
 
 generic = Generic()
+
+
+class CDataType(Type):
+    """
+    Represents opaque C data to be passed around.
+    """
+    def __init__(self, ctype, freefunc=None):
+        self.ctype = ctype
+        self.freefunc = freefunc
+
+    def __eq__(self, other):
+        return (type(self) == type(other) and
+                self.ctype == other.ctype,
+                self.freefunc == other.freefunc)
+
+    def __hash__(self):
+        return hash((type(self), self.ctype, self.freefunc))
+
+    def filter(self, data, strict=False, allow_downcast=None):
+        if data is not None:
+            raise TypeError("only None is valid")
+
+    def is_valid_value(self, a):
+        return a is None
+
+    def c_declare(self, name, sub, check_input=True):
+        return """
+        %(ctype)s %(name)s;
+        """ % dict(ctype=self.ctype, name=name)
+
+    def c_init(self, name, sub):
+        return "%(name)s = NULL;" % dict(name=name)
+
+    def c_extract(self, name, sub, check_input=True):
+        if PY3:
+            s = """
+  %(name)s = (%(ctype)s)PyCapsule_GetPointer(py_%(name)s, NULL);
+  if (%(name)s == NULL) %(fail)s
+"""
+        else:
+            s = """
+  %(name)s = (%(ctype)s)PyCObject_AsVoidPtr(py_%(name)s);
+"""
+        return s % dict(name=name, ctype=self.ctype, fail=sub['fail'])
+
+    def c_cleanup(self, name, sub):
+        if self.freefunc is not None:
+            return "%(freefunc)s(%(name)s);" % dict(freefunc=self.freefunc,
+                                                    name=name)
+        else:
+            return ""
+
+    def c_sync(self, name, sub):
+        freefunc = self.freefunc
+        if freefunc is None:
+            freefunc = "NULL"
+        s = """
+Py_XDECREF(py_%(name)s);
+if (%(name)s == NULL) {
+  py_%(name)s = Py_None;
+  Py_INCREF(py_%(name)s);
+} else """
+        if PY3:
+            s += """{
+  py_%(name)s = PyCapsule_New((void *)%(name)s, NULL,
+                              (void (*)(void *))%(freefunc)s);
+}"""
+        else:
+            s += """{
+py_%(name)s = PyCObject_FromVoidPtr((void *)%(name)s,
+                                    (void (*)(void *))%(freefunc)s);
+}"""
+        s += """
+if (py_%(name)s != NULL) { %(name)s = NULL; }
+"""
+        return s % dict(name=name, freefunc=freefunc)
+
+    def c_code_cache_version(self):
+        return (0,)
+
+    def __str__(self):
+        return self.__class__.__name__