gst init.

os posted @ 2013年8月10日 17:20 in GStreamer , 5568 阅读

Gstreamer学习list.

 

gobject.c中:

static GType gst_signal_object_get_type (void);

其实还有一个宏:

G_DEFINE_ABSTRACT_TYPE (GstObject,gst_object, G_TYPE_OBJECT);

这个宏定义:gtype.h

#define G_DEFINE_ABSTRACT_TYPE(TN, t_n, T_P) G_DEFINE_TYPE_EXTENDED (TN, t_n, T_P, G_TYPE_FLAG_ABSTRACT, {})

#define G_DEFINE_TYPE_EXTENDED(TN, t_n, T_P, _f_, _C_) _G_DEFINE_TYPE_EXTENDED_BEGIN (TN, t_n, T_P, _f_) {_C_;} _G_DEFINE_TYPE_EXTENDED_END()

把宏展开:

#define _G_DEFINE_TYPE_EXTENDED_BEGIN(GstObject, gst_object, G_TYPE_OBJECT, flags) \

\

static void gst_object_init (GstObject *self); \

static void gst_object_class_init (GstObjectClass *klass); \

static gpointer gst_object _parent_class = NULL; \

static void gst_object_class_intern_init (gpointer klass) \

{ \

gst_object_parent_class = g_type_class_peek_parent (klass); \

gst_object_class_init ((GstObject Class*) klass); \

} \

\

GType \

gst_object_get_type (void) \

{ \

static volatile gsize g_define_type_id__volatile = 0; \

if (g_once_init_enter (&g_define_type_id__volatile)) \

{ \

GType g_define_type_id = \

g_type_register_static_simple (G_TYPE_OBJECT, \

g_intern_static_string (“GstObject”), \

sizeof (GstObjectClass), \

(GClassInitFunc)gst_object_class_intern_init, \

sizeof (GstObject), \

(GInstanceInitFunc)gst_object_init, \

(GTypeFlags) flags); \

{ /* custom code follows */

#define _G_DEFINE_TYPE_EXTENDED_END() \

/* following custom code */ \

} \

g_once_init_leave (&g_define_type_id__volatile, g_define_type_id); \

} \

return g_define_type_id__volatile; \

} /* closes gst_object_get_type() */

Gst.c中:

static gboolean

init_post (GOptionContext * context, GOptionGroup * group, gpointer data,

GError ** error)

{

//….

g_type_class_ref (gst_object_get_type ()); //这个是非常重要的,里面执行和很多的东西

这个函数会调用前面定义的函数。

gst_object_get_type()会首先调用:

GType

g_type_register_static_simple (GType parent_type,

const gchar *type_name,

guint class_size,

GClassInitFunc class_init,

guint instance_size,

GInstanceInitFunc instance_init,

GTypeFlags flags)

{

GTypeInfo info;

 

/* Instances are not allowed to be larger than this. If you have a big

* fixed-length array or something, point to it instead.

*/

g_return_val_if_fail (class_size <= G_MAXUINT16, G_TYPE_INVALID);

g_return_val_if_fail (instance_size <= G_MAXUINT16, G_TYPE_INVALID);

 

info.class_size = class_size;

info.base_init = NULL;

info.base_finalize = NULL;

info.class_init = class_init;

info.class_finalize = NULL;

info.class_data = NULL;

info.instance_size = instance_size;

info.n_preallocs = 0;

info.instance_init = instance_init;

info.value_table = NULL;

 

return g_type_register_static (parent_type, type_name, &info, flags);

}

 

//给新类型,分配一块内存;

//和父亲建立联系;

//把定义的新类型的类函数/实例化函数,等都复制过去

GType

g_type_register_static (GType parent_type,

const gchar *type_name,

const GTypeInfo *info,

GTypeFlags flags)

{

TypeNode *pnode, *node;

GType type = 0;

 

g_return_val_if_type_system_uninitialized (0);

g_return_val_if_fail (parent_type > 0, 0);

g_return_val_if_fail (type_name != NULL, 0);

g_return_val_if_fail (info != NULL, 0);

 

if (!check_type_name_I (type_name) ||

!check_derivation_I (parent_type, type_name))

return 0;

if (info->class_finalize)

{

g_warning ("class finalizer specified for static type `%s'",

type_name);

return 0;

}

 

pnode = lookup_type_node_I (parent_type);

G_WRITE_LOCK (&type_rw_lock);

type_data_ref_Wm (pnode);

if (check_type_info_I (pnode, NODE_FUNDAMENTAL_TYPE (pnode), type_name, info))

{

node = type_node_new_W (pnode, type_name, NULL);

type_add_flags_W (node, flags);

type = NODE_TYPE (node);

type_data_make_W (node, info,

check_value_table_I (type_name, info->value_table) ? info->value_table : NULL);

}

G_WRITE_UNLOCK (&type_rw_lock);

 

return type;

}

所以gst_object_get_type(),就是获取一个新类型,并且把定义的一些函数指针赋值过去。

下面看另外一个重要的函数:

g_type_class_ref

gpointer

g_type_class_ref (GType type)

{

TypeNode *node;

GType ptype;

gboolean holds_ref;

GTypeClass *pclass;

 

/* optimize for common code path */

node = lookup_type_node_I (type);

if (!node || !node->is_classed)

{

g_warning ("cannot retrieve class for invalid (unclassed) type `%s'",

type_descriptive_name_I (type));

return NULL;

}

 

if (G_LIKELY (type_data_ref_U (node)))

{

if (G_LIKELY (g_atomic_int_get (&node->data->class.init_state) == INITIALIZED))

return node->data->class.class;

holds_ref = TRUE;

}

else

holds_ref = FALSE;

 

/* here, we either have node->data->class.class == NULL, or a recursive

* call to g_type_class_ref() with a partly initialized class, or

* node->data->class.init_state == INITIALIZED, because any

* concurrently running initialization was guarded by class_init_rec_mutex.

*/

g_rec_mutex_lock (&class_init_rec_mutex); /* required locking order: 1) class_init_rec_mutex, 2) type_rw_lock */

 

/* we need an initialized parent class for initializing derived classes */

ptype = NODE_PARENT_TYPE (node);

pclass = ptype ? g_type_class_ref (ptype) : NULL;//如果父亲的类没有初始化,先递归处理父亲,祖父等的事情

 

G_WRITE_LOCK (&type_rw_lock);

 

if (!holds_ref)

type_data_ref_Wm (node);

 

if (!node->data->class.class) /* class uninitialized */

type_class_init_Wm (node, pclass);//这个地方会调用gst_object_class_init,包括可能递归调用父类的类初始化函数

 

G_WRITE_UNLOCK (&type_rw_lock);

 

if (pclass)

g_type_class_unref (pclass);

 

g_rec_mutex_unlock (&class_init_rec_mutex);

 

return node->data->class.class;

}

 


登录 *


loading captcha image...
(输入验证码)
or Ctrl+Enter