[ctypes-commit] ctypes/source cfield.c,1.80,1.81

[Thomas H. <th...@us...>]

Update of /cvsroot/ctypes/ctypes/source
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv23557

Modified Files:
	cfield.c 
Log Message:
It is now (in principle) possible to customize getting structure
fields by implementing a __from_field__ classmethod on the structure
field type.  CField_FromDesc() checks if a __from_field__ attribute
exists on the type, and if so installs  _overloaded_field_getfunc()
in the CFieldObject's getfunc slot.

The __from__field__ method receives an int/long representing the field
address.

The source changes are #ifdef'd out currently.


Index: cfield.c
===================================================================
RCS file: /cvsroot/ctypes/ctypes/source/cfield.c,v
retrieving revision 1.80
retrieving revision 1.81
diff -C2 -d -r1.80 -r1.81
*** cfield.c	23 Mar 2005 18:38:14 -0000	1.80
--- cfield.c	23 Mar 2005 20:25:50 -0000	1.81
***************
*** 32,35 ****
--- 32,55 ----
  }
  
+ #ifdef EXPERIMENTAL
+ /* getfunc overloaded by a __from_field__ callable on the fieldtype */
+ static PyObject *
+ _overloaded_field_getfunc(void *ptr, unsigned size,
+ 			  PyObject *fieldtype, CDataObject *src,
+ 			  int index)
+ {
+ 	PyObject *result;
+ 	PyObject *arg;
+ 	PyObject *func = PyObject_GetAttrString(fieldtype, "__from_field__");
+ 	if (func == NULL)
+ 		return NULL;
+ 	result = PyObject_CallFunctionObjArgs(func,
+ 					      PyLong_FromVoidPtr(ptr), NULL);
+ 	Py_DECREF(func);
+ 	return result;
+ }
+ #endif
+ 
+ 
  /*
   * Expects the size, index and offset for the current field in *psize and
***************
*** 107,111 ****
--- 127,138 ----
  	length = dict->length;
  
+ #ifdef EXPERIMENTAL
+ 	if (PyObject_HasAttrString(desc, "__from_field__"))
+ 		getfunc = _overloaded_field_getfunc;
+ 	else
+ 		getfunc = dict->getfunc ? dict->getfunc : _generic_field_getfunc;
+ #else
  	getfunc = dict->getfunc ? dict->getfunc : _generic_field_getfunc;
+ #endif
  
  	/* Currently, dict->getfunc is only != NULL for SimpleCData types.