~bzr-pqm/bzr/bzr.dev

/* 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

 */

#ifndef _IMPORT_C_API_H_

#define _IMPORT_C_API_H_

/**

 * Helper functions to eliminate some of the boilerplate when importing a C API

 * from a CPython extension module.

 *

 * For more information see _export_c_api.h

 */

static const char *_C_API_NAME = "_C_API";

/**

 * Import a function from the _C_API_NAME dict that is part of module.

 *

 * @param   module  The Python module we are importing from

 *                  the attribute _C_API_NAME will be used as a dictionary

 *                  containing the function pointer we are looking for.

 * @param   funcname    Name of the function we want to import

 * @param   func    A pointer to the function handle where we will store the

 *                  function.

 * @param   signature   The C signature of the function. This is validated

 *                      against the signature stored in the C api, to make sure

 *                      there is no versioning skew.

 */

static int _import_function(PyObject *module, const char *funcname,

                            void **func, const char *signature)

{

    PyObject *d = NULL;

    PyObject *c_obj = NULL;

    const char *desc = NULL;

    /* (char *) because Python2.4 defines this as (char *) rather than

     * (const char *)

     */

    d = PyObject_GetAttrString(module, (char *)_C_API_NAME);

    if (!d) {

        // PyObject_GetAttrString sets an appropriate exception

        goto bad;

    }

    c_obj = PyDict_GetItemString(d, funcname);

    if (!c_obj) {

        // PyDict_GetItemString does not set an exception

        PyErr_Format(PyExc_AttributeError,

            "Module %s did not export a function named %s\n",

            PyModule_GetName(module), funcname);

        goto bad;

    }

    desc = (char *)PyCObject_GetDesc(c_obj);

    if (!desc || strcmp(desc, signature) != 0) {

        if (desc == NULL) {

            desc = "<null>";

        }

        PyErr_Format(PyExc_TypeError,

            "C function %s.%s has wrong signature (expected %s, got %s)",

                PyModule_GetName(module), funcname, signature, desc);

        goto bad;

    }

    *func = PyCObject_AsVoidPtr(c_obj);

    Py_DECREF(d);

    return 0;

bad:

    Py_XDECREF(d);

    return -1;

}

/**

 * Get a pointer to an exported PyTypeObject.

 *

 * @param   module        The Python module we are importing from

 * @param   class_name    Attribute of the module that should reference the

 *                        Type object. Note that a PyTypeObject is the python

 *                        description of the type, not the raw C structure.

 * @return  A Pointer to the requested type object. On error NULL will be

 *          returned and an exception will be set.

 */

static PyTypeObject *

_import_type(PyObject *module, const char *class_name)

{

    PyObject *type = NULL;

    type = PyObject_GetAttrString(module, (char *)class_name);

    if (!type) {

        goto bad;

    }

    if (!PyType_Check(type)) {

        PyErr_Format(PyExc_TypeError,

            "%s.%s is not a type object",

            PyModule_GetName(module), class_name);

        goto bad;

    }

    return (PyTypeObject *)type;

bad:

    Py_XDECREF(type);

    return NULL;

}

struct function_description

{

    const char *name;

    void **pointer;

    const char *signature;

};

struct type_description

{

    const char *name;

    PyTypeObject **pointer;

};

/**

 * Helper for importing several functions and types in a data-driven manner.

 *

 * @param   module  The name of the module we will be importing

 * @param   functions   A list of function_description objects, describing the

 *                      functions being imported.

 *                      The list should be terminated with {NULL} to indicate

 *                      there are no more functions to import.

 * @param   types       A list of type_description objects describing type

 *                      objects that we want to import. The list should be

 *                      terminated with {NULL} to indicate there are no more

 *                      types to import.

 * @return  0 on success, -1 on error and an exception should be set.

 */

static int

_import_extension_module(const char *module_name,

                         struct function_description *functions,

                         struct type_description *types)

{

    PyObject *module = NULL;

    struct function_description *cur_func;

    struct type_description *cur_type;

    int ret_code;

    module = PyImport_ImportModule((char *)module_name);

    if (!module)

        goto bad;

    if (functions != NULL) {

        cur_func = functions;

        while (cur_func->name != NULL) {

            ret_code = _import_function(module, cur_func->name,

                                        cur_func->pointer,

                                        cur_func->signature);

            if (ret_code < 0)

                goto bad;

            cur_func++;

        }

    }

    if (types != NULL) {

        PyTypeObject *type_p = NULL;

        cur_type = types;

        while (cur_type->name != NULL)  {

            type_p = _import_type(module, cur_type->name);

            if (type_p == NULL)

                goto bad;

            *(cur_type->pointer) = type_p;

            cur_type++;

        }

    }

    Py_XDECREF(module);

    return 0;

bad:

    Py_XDECREF(module);

    return -1;

}

#endif // _IMPORT_C_API_H_