path: root/e-util/e-module.c

/*
 * e-module.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) version 3.
 *
 * 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with the program; if not, see <http://www.gnu.org/licenses/>
 *
 *
 * Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 *
 */

/**
 * SECTION: e-module
 * @short_description: a module loader
 * @include: e-util/e-module.h
 **/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "e-module.h"

#include <glib/gi18n.h>

/* This is the symbol we call when loading a module. */
#define LOAD_SYMBOL "e_module_load"

/* This is the symbol we call when unloading a module. */
#define UNLOAD_SYMBOL   "e_module_unload"

struct _EModulePrivate {
    GModule *module;
    gchar *filename;

    void (*load) (GTypeModule *type_module);
    void (*unload) (GTypeModule *type_module);
};

enum {
    PROP_0,
    PROP_FILENAME
};

G_DEFINE_TYPE (
    EModule,
    e_module,
    G_TYPE_TYPE_MODULE)

static void
module_set_filename (EModule *module,
                     const gchar *filename)
{
    g_return_if_fail (module->priv->filename == NULL);

    module->priv->filename = g_strdup (filename);
}

static void
module_set_property (GObject *object,
                     guint property_id,
                     const GValue *value,
                     GParamSpec *pspec)
{
    switch (property_id) {
        case PROP_FILENAME:
            module_set_filename (
                E_MODULE (object),
                g_value_get_string (value));
            return;
    }

    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
}

static void
module_get_property (GObject *object,
                     guint property_id,
                     GValue *value,
                     GParamSpec *pspec)
{
    switch (property_id) {
        case PROP_FILENAME:
            g_value_set_string (
                value, e_module_get_filename (
                E_MODULE (object)));
            return;
    }

    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
}

static void
module_finalize (GObject *object)
{
    EModulePrivate *priv;

    priv = E_MODULE (object)->priv;

    g_free (priv->filename);

    /* Chain up to parent's finalize() method. */
    G_OBJECT_CLASS (e_module_parent_class)->finalize (object);
}

static gboolean
module_load (GTypeModule *type_module)
{
    EModulePrivate *priv;
    gpointer symbol;

    priv = E_MODULE (type_module)->priv;

    g_return_val_if_fail (priv->filename != NULL, FALSE);
    priv->module = g_module_open (priv->filename, 0);

    if (priv->module == NULL)
        goto fail;

    if (!g_module_symbol (priv->module, LOAD_SYMBOL, &symbol))
        goto fail;

    priv->load = symbol;

    if (!g_module_symbol (priv->module, UNLOAD_SYMBOL, &symbol))
        goto fail;

    priv->unload = symbol;

    priv->load (type_module);

    /* XXX This is a Band-Aid for a design flaw in EExtension.  If the
     *     "extensible_type" member of EExtensionClass is set to a GType
     *     that hasn't already been registered, then when the extension's
     *     module is unloaded the GType registration that was triggered
     *     by setting "extensible_type" will be invalidated and cause
     *     Evolution to malfunction when the module is loaded again.
     *
     *     Extension modules get loaded and unloaded repeatedly by
     *     e_extensible_load_extensions(), which temporarily references
     *     all extension classes and picks out the ones it needs for a
     *     given EExtensible instance based on the "extensible_type"
     *     class member.
     *
     *     Making the module resident prevents the aforementioned GType
     *     registration from being invalidated when the extension class
     *     is unreferenced.
     */
    g_module_make_resident (priv->module);

    return TRUE;

fail:
    g_warning ("%s", g_module_error ());

    if (priv->module != NULL)
        g_module_close (priv->module);

    return FALSE;
}

static void
module_unload (GTypeModule *type_module)
{
    EModulePrivate *priv;

    priv = E_MODULE (type_module)->priv;

    priv->unload (type_module);

    g_module_close (priv->module);
    priv->module = NULL;

    priv->load = NULL;
    priv->unload = NULL;
}

static void
e_module_class_init (EModuleClass *class)
{
    GObjectClass *object_class;
    GTypeModuleClass *type_module_class;

    g_type_class_add_private (class, sizeof (EModulePrivate));

    object_class = G_OBJECT_CLASS (class);
    object_class->set_property = module_set_property;
    object_class->get_property = module_get_property;
    object_class->finalize = module_finalize;

    type_module_class = G_TYPE_MODULE_CLASS (class);
    type_module_class->load = module_load;
    type_module_class->unload = module_unload;

    /**
     * EModule:filename
     *
     * The filename of the module.
     **/
    g_object_class_install_property (
        object_class,
        PROP_FILENAME,
        g_param_spec_string (
            "filename",
            "Filename",
            "The filename of the module",
            NULL,
            G_PARAM_READWRITE |
            G_PARAM_CONSTRUCT_ONLY));
}

static void
e_module_init (EModule *module)
{
    module->priv = G_TYPE_INSTANCE_GET_PRIVATE (
        module, E_TYPE_MODULE, EModulePrivate);
}

/**
 * e_module_new:
 * @filename: filename of the shared library module
 *
 * Creates a new #EModule that will load the specific shared library
 * when in use.
 *
 * Returns: a new #EModule for @filename
 **/
EModule *
e_module_new (const gchar *filename)
{
    g_return_val_if_fail (filename != NULL, NULL);

    return g_object_new (E_TYPE_MODULE, "filename", filename, NULL);
}

/**
 * e_module_get_filename:
 * @module: an #EModule
 *
 * Returns the filename of the shared library for @module.  The
 * string is owned by @module and should not be modified or freed.
 *
 * Returns: the filename for @module
 **/
const gchar *
e_module_get_filename (EModule *module)
{
    g_return_val_if_fail (E_IS_MODULE (module), NULL);

    return module->priv->filename;
}

/**
 * e_module_load_all_in_directory:
 * @dirname: pathname for a directory containing modules to load
 *
 * Loads all the modules in the specified directory into memory.  If
 * you want to unload them (enabling on-demand loading) you must call
 * g_type_module_unuse() on all the modules.  Free the returned list
 * with g_list_free().
 *
 * Returns: a list of #EModules loaded from @dirname
 **/
GList *
e_module_load_all_in_directory (const gchar *dirname)
{
    GDir *dir;
    const gchar *basename;
    GList *loaded_modules = NULL;
    GError *error = NULL;

    g_return_val_if_fail (dirname != NULL, NULL);

    if (!g_module_supported ())
        return NULL;

    dir = g_dir_open (dirname, 0, &error);
    if (dir == NULL) {
        g_warning ("%s", error->message);
        g_error_free (error);
        return NULL;
    }

    while ((basename = g_dir_read_name (dir)) != NULL) {
        EModule *module;
        gchar *filename;

        if (!g_str_has_suffix (basename, "." G_MODULE_SUFFIX))
            continue;

        filename = g_build_filename (dirname, basename, NULL);

        module = e_module_new (filename);

        if (!g_type_module_use (G_TYPE_MODULE (module))) {
            g_printerr ("Failed to load module: %s\n", filename);
            g_object_unref (module);
            g_free (filename);
            continue;
        }

        g_free (filename);

        loaded_modules = g_list_prepend (loaded_modules, module);
    }

    g_dir_close (dir);

    return loaded_modules;
}