Merged revisions 63988,63991 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r63988 | thomas.heller | 2008-06-06 20:37:55 +0200 (Fr, 06 Jun 2008) | 3 lines

  Performance improvement: Use PyDict_Get/SetItem instead of
  PyDict_Get/SetItemString.
........
  r63991 | thomas.heller | 2008-06-06 22:05:15 +0200 (Fr, 06 Jun 2008) | 5 lines

  Document the new ctypes features.

  It would be great if someone could review both sematics, markup, and
  spelling, and correct the versionadded and versionchanges markers.
........

Doc/library/ctypes.rst

@@ -1335,14 +1335,14 @@ There are several ways to loaded shared libraries into the Python process.  One
 way is to instantiate one of the following classes:
 
 
-.. class:: CDLL(name, mode=DEFAULT_MODE, handle=None)
+.. class:: CDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False)
 
    Instances of this class represent loaded shared libraries. Functions in these
    libraries use the standard C calling convention, and are assumed to return
    ``int``.
 
 
-.. class:: OleDLL(name, mode=DEFAULT_MODE, handle=None)
+.. class:: OleDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False)
 
    Windows only: Instances of this class represent loaded shared libraries,
    functions in these libraries use the ``stdcall`` calling convention, and are
@@ -1352,7 +1352,7 @@ way is to instantiate one of the following classes:
    failure, an :class:`WindowsError` is automatically raised.
 
 
-.. class:: WinDLL(name, mode=DEFAULT_MODE, handle=None)
+.. class:: WinDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False)
 
    Windows only: Instances of this class represent loaded shared libraries,
    functions in these libraries use the ``stdcall`` calling convention, and are
@@ -1385,6 +1385,29 @@ it.
 The *mode* parameter can be used to specify how the library is loaded.  For
 details, consult the ``dlopen(3)`` manpage, on Windows, *mode* is ignored.
 
+The *use_errno* parameter, when set to True, enables a ctypes
+mechanism that allows to access the system `errno` error number in a
+safe way.  `ctypes` maintains a thread-local copy of the systems
+`errno` variable; if you call foreign functions created with
+`use_errno=True` then the `errno` value before the function call is
+swapped with the ctypes private copy, the same happens immediately
+after the function call.
+
+The function `ctypes.get_errno()` returns the value of the ctypes
+private copy, and the function `ctypes.set_errno(value)` changes the
+ctypes private copy to `value` and returns the former value.
+
+The *use_last_error* parameter, when set to True, enables the same
+mechanism for the Windows error code which is managed by the
+GetLastError() and SetLastError() Windows api functions;
+`ctypes.get_last_error()` and `ctypes.set_last_error(value)` are used
+to request and change the ctypes private copy of the windows error
+code.
+
+.. versionchanged:: 2.6
+
+The `use_errno` and `use_last_error` parameters were added in Python
+2.6.
 
 .. data:: RTLD_GLOBAL
    :noindex:
@@ -1583,18 +1606,26 @@ implementation.  The factory functions must be called with the desired result
 type and the argument types of the function.
 
 
-.. function:: CFUNCTYPE(restype, *argtypes)
+.. function:: CFUNCTYPE(restype, *argtypes, use_errno=False, use_last_error=False)
 
    The returned function prototype creates functions that use the standard C
    calling convention.  The function will release the GIL during the call.
+   If `use_errno` is set to True, the ctypes private copy of the system `errno`
+   variable is exchanged with the real `errno` value bafore and after the call;
+   `use_last_error` does the same for the Windows error code.
+
+   .. versionchanged:: 2.6
 
+   The optional `use_errno` and `use_last_error` parameters were added
+   in Python 2.6.
 
-.. function:: WINFUNCTYPE(restype, *argtypes)
+
+.. function:: WINFUNCTYPE(restype, *argtypes, use_errno=False, use_last_error=False)
 
    Windows only: The returned function prototype creates functions that use the
    ``stdcall`` calling convention, except on Windows CE where :func:`WINFUNCTYPE`
    is the same as :func:`CFUNCTYPE`.  The function will release the GIL during the
-   call.
+   call. `use_errno` and `use_last_error` have the same meaning as above.
 
 
 .. function:: PYFUNCTYPE(restype, *argtypes)
@@ -1846,7 +1877,22 @@ Utility functions
 .. function:: GetLastError()
 
    Windows only: Returns the last error code set by Windows in the calling thread.
+   This function calls the Windows `GetLastError()` function directly,
+   it does not return the ctypes-private copy of the error code.
+
+.. function:: get_errno()
+
+   Returns the current value of the ctypes-private copy of the system
+   `errno` variable in the calling thread.
+
+   .. versionadded:: 2.6
 
+.. function:: get_last_error()
+
+   Windows only: returns the current value of the ctypes-private copy of the system
+   `LastError` variable in the calling thread.
+
+   .. versionadded:: 2.6
 
 .. function:: memmove(dst, src, count)
 
@@ -1899,6 +1945,22 @@ Utility functions
    other systems ``('ascii', 'strict')``.
 
 
+.. function:: set_errno(value)
+
+   Set the  current value of the ctypes-private copy of the system
+   `errno` variable in the calling thread to `value` and return the
+   previous value.
+
+   .. versionadded:: 2.6
+
+.. function:: set_last_error(value)
+
+   Windows only: set the current value of the ctypes-private copy of
+   the system `LastError` variable in the calling thread to `value`
+   and return the previous value.
+
+   .. versionadded:: 2.6
+
 .. function:: sizeof(obj_or_type)
 
    Returns the size in bytes of a ctypes type or instance memory buffer. Does the

Modules/_ctypes/callproc.c

@@ -117,12 +117,18 @@ get_error_object(int **pspace)
 {
 	PyObject *dict = PyThreadState_GetDict();
 	PyObject *errobj;
+	static PyObject *error_object_name;
 	if (dict == 0) {
 		PyErr_SetString(PyExc_RuntimeError,
 				"cannot get thread state");
 		return NULL;
 	}
-	errobj = PyDict_GetItemString(dict, "ctypes.error_object");
+	if (error_object_name == NULL) {
+		error_object_name = PyString_InternFromString("ctypes.error_object");
+		if (error_object_name == NULL)
+			return NULL;
+	}
+	errobj = PyDict_GetItem(dict, error_object_name);
 	if (errobj)
 		Py_INCREF(errobj);
 	else {
@@ -133,8 +139,8 @@ get_error_object(int **pspace)
 		errobj = PyCObject_FromVoidPtr(space, PyMem_Free);
 		if (errobj == NULL)
 			return NULL;
-		if (-1 == PyDict_SetItemString(dict, "ctypes.error_object",
-					       errobj)) {
+		if (-1 == PyDict_SetItem(dict, error_object_name,
+					 errobj)) {
 			Py_DECREF(errobj);
 			return NULL;
 		}