~bzr-pqm/bzr/bzr.dev : contents of bzrlib/_export_c

~bzr-pqm/bzr/bzr.dev : (revision 6228.3.4)

/* Copyright (C) 2009 Canonical Ltd
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */


/* This file contains helper functions for exporting a C API for a CPython
 * extension module.
 */

#ifndef _EXPORT_C_API_H_
#define _EXPORT_C_API_H_

static const char *_C_API_NAME = "_C_API";

/**
 * Add a C function to the modules _C_API
 * This wraps the function in a PyCObject, and inserts that into a dict.
 * The key of the dict is the function name, and the description is the
 * signature of the function.
 * This is generally called during a modules init_MODULE function.
 *
 * @param   module  A Python module (the one being initialized)
 * @param   funcname The name of the function being exported
 * @param   func    A pointer to the function
 * @param   signature The C signature of the function
 * @return  0 if everything is successful, -1 if there is a problem. An
 *          exception should also be set
 */
static int
_export_function(PyObject *module, char *funcname, void *func, char *signature)
{
    PyObject *d = NULL;
    PyObject *c_obj = NULL;

    /* (char *) is because python2.4 declares this api as 'char *' rather than
     * const char* which it really is.
     */
    d = PyObject_GetAttrString(module, (char *)_C_API_NAME);
    if (!d) {
        PyErr_Clear();
        d = PyDict_New();
        if (!d)
            goto bad;
        Py_INCREF(d);
        if (PyModule_AddObject(module, (char *)_C_API_NAME, d) < 0)
            goto bad;
    }
    c_obj = PyCObject_FromVoidPtrAndDesc(func, signature, 0);
    if (!c_obj)
        goto bad;
    if (PyDict_SetItemString(d, funcname, c_obj) < 0)
        goto bad;
    Py_DECREF(d);
    return 0;
bad:
    Py_XDECREF(c_obj);
    Py_XDECREF(d);
    return -1;
}

/* Note:
 *  It feels like more could be done here. Specifically, if you look at
 *  _static_tuple_c.h you can see some boilerplate where we have:
 * #ifdef STATIC_TUPLE_MODULE  // are we exporting or importing
 * static RETVAL FUNCNAME PROTO;
 * #else
 * static RETVAL (*FUNCNAME) PROTO;
 * #endif
 * 
 * And then in _static_tuple_c.c we have
 * int setup_c_api()
 * {
 *   _export_function(module, #FUNCNAME, FUNCNAME, #PROTO);
 * }
 *
 * And then in _static_tuple_c.h import_##MODULE
 * struct function_definition functions[] = {
 *   {#FUNCNAME, (void **)&FUNCNAME, #RETVAL #PROTO},
 *   ...
 *   {NULL}};
 *
 * And some similar stuff for types. However, this would mean that we would
 * need a way for the C preprocessor to build up a list of definitions to be
 * generated, and then expand that list at the appropriate time.
 * I would guess there would be a way to do this, but probably not without a
 * lot of magic, and the end result probably wouldn't be very pretty to
 * maintain. Perhaps python's dynamic nature has left me jaded about writing
 * boilerplate....
 */

#endif // _EXPORT_C_API_H_

4679.3.54 by John Arbash Meinel Factor out some of the C API code into some helper headers.	1	/* Copyright (C) 2009 Canonical Ltd
	2	*
	3	* This program is free software; you can redistribute it and/or modify
	4	* it under the terms of the GNU General Public License as published by
	5	* the Free Software Foundation; either version 2 of the License, or
	6	* (at your option) any later version.
	7	*
	8	* This program is distributed in the hope that it will be useful,
	9	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	11	* GNU General Public License for more details.
	12	*
	13	* You should have received a copy of the GNU General Public License
	14	* along with this program; if not, write to the Free Software
	15	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	16	*/
	17
	18
	19	/* This file contains helper functions for exporting a C API for a CPython
	20	* extension module.
	21	*/
	22
	23	#ifndef _EXPORT_C_API_H_
	24	#define _EXPORT_C_API_H_
	25
	26	static const char *_C_API_NAME = "_C_API";
	27
	28	/**
	29	* Add a C function to the modules _C_API
	30	* This wraps the function in a PyCObject, and inserts that into a dict.
	31	* The key of the dict is the function name, and the description is the
	32	* signature of the function.
	33	* This is generally called during a modules init_MODULE function.
	34	*
	35	* @param module A Python module (the one being initialized)
	36	* @param funcname The name of the function being exported
	37	* @param func A pointer to the function
	38	* @param signature The C signature of the function
	39	* @return 0 if everything is successful, -1 if there is a problem. An
	40	* exception should also be set
	41	*/
	42	static int
	43	_export_function(PyObject module, char funcname, void func, char signature)
	44	{
	45	PyObject *d = NULL;
	46	PyObject *c_obj = NULL;
	47
4736.1.1 by John Arbash Meinel Py_ssize_t and its associated function typedefs are not available w/ python 2.4	48	/* (char ) is because python2.4 declares this api as 'char ' rather than
	49	* const char* which it really is.
	50	*/
	51	d = PyObject_GetAttrString(module, (char *)_C_API_NAME);
4679.3.54 by John Arbash Meinel Factor out some of the C API code into some helper headers.	52	if (!d) {
	53	PyErr_Clear();
	54	d = PyDict_New();
	55	if (!d)
	56	goto bad;
	57	Py_INCREF(d);
4736.1.1 by John Arbash Meinel Py_ssize_t and its associated function typedefs are not available w/ python 2.4	58	if (PyModule_AddObject(module, (char *)_C_API_NAME, d) < 0)
4679.3.54 by John Arbash Meinel Factor out some of the C API code into some helper headers.	59	goto bad;
	60	}
	61	c_obj = PyCObject_FromVoidPtrAndDesc(func, signature, 0);
	62	if (!c_obj)
	63	goto bad;
	64	if (PyDict_SetItemString(d, funcname, c_obj) < 0)
	65	goto bad;
	66	Py_DECREF(d);
	67	return 0;
	68	bad:
	69	Py_XDECREF(c_obj);
	70	Py_XDECREF(d);
	71	return -1;
	72	}
	73
4679.3.55 by John Arbash Meinel A quick note about how I'd like to do things.	74	/* Note:
	75	* It feels like more could be done here. Specifically, if you look at
	76	* _static_tuple_c.h you can see some boilerplate where we have:
	77	* #ifdef STATIC_TUPLE_MODULE // are we exporting or importing
	78	* static RETVAL FUNCNAME PROTO;
	79	* #else
	80	* static RETVAL (*FUNCNAME) PROTO;
	81	* #endif
	82	*
	83	* And then in _static_tuple_c.c we have
	84	* int setup_c_api()
	85	* {
	86	* _export_function(module, #FUNCNAME, FUNCNAME, #PROTO);
	87	* }
	88	*
	89	* And then in _static_tuple_c.h import_##MODULE
	90	* struct function_definition functions[] = {
	91	* {#FUNCNAME, (void **)&FUNCNAME, #RETVAL #PROTO},
	92	* ...
	93	* {NULL}};
	94	*
	95	* And some similar stuff for types. However, this would mean that we would
	96	* need a way for the C preprocessor to build up a list of definitions to be
	97	* generated, and then expand that list at the appropriate time.
	98	* I would guess there would be a way to do this, but probably not without a
	99	* lot of magic, and the end result probably wouldn't be very pretty to
	100	* maintain. Perhaps python's dynamic nature has left me jaded about writing
	101	* boilerplate....
	102	*/
	103
4679.3.54 by John Arbash Meinel Factor out some of the C API code into some helper headers.	104	#endif // _EXPORT_C_API_H_