source: vbox/trunk/src/libs/xpcom18a4/python/src/PyGStub.cpp

/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the Python XPCOM language bindings.
 *
 * The Initial Developer of the Original Code is
 * ActiveState Tool Corp.
 * Portions created by the Initial Developer are Copyright (C) 2000
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Mark Hammond <mhammond@skippinet.com.au> (original author)
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

// PyXPTStub - the stub for implementing interfaces.
//
// This code is part of the XPCOM extensions for Python.
//
// Written May 2000 by Mark Hammond.
//
// Based heavily on the Python COM support, which is
// (c) Mark Hammond and Greg Stein.
//
// (c) 2000, ActiveState corp.

#include "PyXPCOM_std.h"
#include <nsIInterfaceInfoManager.h>

void *PyXPCOM_XPTStub::ThisAsIID(const nsIID &iid)
{
        if (iid.Equals(NS_GET_IID(nsISupports)))
            return (nsISupports *)(nsXPTCStubBase *)this;
        else if (iid.Equals(m_iid))
                return (nsISupports *)(nsXPTCStubBase *)this;
        else
                return PyG_Base::ThisAsIID(iid);
}


NS_IMETHODIMP
PyXPCOM_XPTStub::GetInterfaceInfo(nsIInterfaceInfo** info)
{
        NS_PRECONDITION(info, "NULL pointer");
        if (info==nsnull)
                return NS_ERROR_NULL_POINTER;
        // Simply get the XPCOM runtime to provide this
        // (but there must be some reason why they dont get it themselves!?
        // Maybe because they dont know the IID?
        nsCOMPtr<nsIInterfaceInfoManager> iim(do_GetService(
                        NS_INTERFACEINFOMANAGER_SERVICE_CONTRACTID));
        NS_ABORT_IF_FALSE(iim != nsnull, "Cant get interface from IIM!");
        if (iim==nsnull)
                return NS_ERROR_FAILURE;

        return iim->GetInfoForIID( &m_iid, info);
}

// call this method and return result
NS_IMETHODIMP
PyXPCOM_XPTStub::CallMethod(PRUint16 methodIndex,
                          const nsXPTMethodInfo* info,
                          nsXPTCMiniVariant* params)
{
        nsresult rc = NS_ERROR_FAILURE;
        NS_PRECONDITION(info, "NULL methodinfo pointer");
        NS_PRECONDITION(params, "NULL variant pointer");
        CEnterLeavePython _celp;
        PyObject *obParams = NULL;
        PyObject *result = NULL;
        PyObject *obThisObject = NULL;
        PyObject *obMI = PyObject_FromXPTMethodDescriptor(info);
        PyXPCOM_GatewayVariantHelper arg_helper(this, methodIndex, info, params);
        if (obMI==NULL)
                goto done;
        // base object is passed raw.
        obThisObject = PyObject_FromNSInterface((nsXPTCStubBase *)this,
                                                m_iid, PR_FALSE);
        obParams = arg_helper.MakePyArgs();
        if (obParams==NULL)
                goto done;
        result = PyObject_CallMethod(m_pPyObject, 
                                               (char*)"_CallMethod_",
                                               (char*)"OiOO",
                                               obThisObject,
                                               (int)methodIndex,
                                               obMI,
                                               obParams);
        if (result!=NULL) {
                rc = arg_helper.ProcessPythonResult(result);
                // Use an xor to check failure && pyerr, or !failure && !pyerr.
                NS_ABORT_IF_FALSE( ((NS_FAILED(rc)!=0)^(PyErr_Occurred()!=0)) == 0, "We must have failure with a Python error, or success without a Python error.");
        }
done:
        if (PyErr_Occurred()) {
                // The error handling - fairly involved, but worth it as
                // good error reporting is critical for users to know WTF 
                // is going on - especially with TypeErrors etc in their
                // return values (ie, after the Python code has successfully
                // exited, but we encountered errors unpacking the
                // result values for the COM caller - there is literally no 
                // way to catch these exceptions from Python code, as their
                // is no Python function on the call-stack)

                // First line of attack in an error is to call-back on the policy.
                // If the callback of the error handler succeeds and returns an
                // integer (for the nsresult), we take no further action.

                // If this callback fails, we log _2_ exceptions - the error handler
                // error, and the original error.

                PRBool bProcessMainError = PR_TRUE; // set to false if our exception handler does its thing!
                PyObject *exc_typ, *exc_val, *exc_tb;
                PyErr_Fetch(&exc_typ, &exc_val, &exc_tb);
                PyErr_NormalizeException( &exc_typ, &exc_val, &exc_tb);

                PyObject *err_result = PyObject_CallMethod(m_pPyObject, 
                                               (char*)"_CallMethodException_",
                                               (char*)"OiOO(OOO)",
                                               obThisObject,
                                               (int)methodIndex,
                                               obMI,
                                               obParams,
                                               exc_typ ? exc_typ : Py_None, // should never be NULL, but defensive programming...
                                               exc_val ? exc_val : Py_None, // may well be NULL.
                                               exc_tb ? exc_tb : Py_None); // may well be NULL.
                if (err_result == NULL) {
                        PyXPCOM_LogError("The exception handler _CallMethodException_ failed!\n");
                } else if (err_result == Py_None) {
                        // The exception handler has chosen not to do anything with
                        // this error, so we still need to print it!
                        ;
                } else if (PyInt_Check(err_result)) {
                        // The exception handler has given us the nresult.
                        rc = PyInt_AsLong(err_result);
                        bProcessMainError = PR_FALSE;
                } else {
                        // The exception handler succeeded, but returned other than
                        // int or None.
                        PyXPCOM_LogError("The _CallMethodException_ handler returned object of type '%s' - None or an integer expected\n", PyXPCOM_ObTypeName(err_result));
                }
                Py_XDECREF(err_result);
                PyErr_Restore(exc_typ, exc_val, exc_tb);
                if (bProcessMainError) {
                        PyXPCOM_LogError("The function '%s' failed\n", info->GetName());
                        rc = PyXPCOM_SetCOMErrorFromPyException();
                }
                // else everything is already setup,
                // just clear the Python error state.
                PyErr_Clear();
        }

        Py_XDECREF(obMI);
        Py_XDECREF(obParams);
        Py_XDECREF(obThisObject);
        Py_XDECREF(result);
        return rc;
}