os's Blog
Happy coding
gobject/gstobject的初始化(包括类型，类，实例等的初始化）。
os
posted @ 2013年8月28日 10:47
in GObject
, 3031 阅读
Type，Class, instance 初始化，包括其中函数调用的过程总结：
| 阶段 | 相应API | 作用 | GObject 调用顺序 | GstObject | GstElement |
| 1 | xxx_yyy_get_type() |
创建TypeNode, 并且赋值一些APIs: base_class_init() class_init() instance_init(), 等等 |
|||
| 2 | g_type_class_ref() |
调用base_class_init() 从父-->子， |
g_object_base_class_init() |
1. 父类：g_object_base_class_init() 2. 自己没有base_init() |
1. 爷爷：g_object_base_class_init() 2. 父亲没有base_init() 3. gst_element_base_class_init |
|
调用class_init(), 指定各种APIs 包括class->constructor(), set_property()/get_property() dispose()/finalize() |
g_object_do_class_init() |
gst_object_class_init（） 1. 首选取得GObjectClass 2. 重载一些函数 3. 装载一些自己的signal |
gst_element_class_init（） 1. 首选取得GObjectClass 2. 把GObjectClass的一些函数换成自己的（重载） 3. 装载自己的信号 |
||
| 3 | g_object_new() |
调用class->constructor() --> g_type_create_instance() --> 父类的instance(), 自己的instance() |
g_object_constructor()->g_type_create_instance() -> 1. g_object_init() |
g_object_constructor()->g_type_create_instance() -> 1. 父亲：g_object_init() 2.自己：gst_object_init（） |
g_object_constructor()->g_type_create_instance() -> 1. 爷爷：g_object_init() 2.父亲：gst_object_init（） 3. 自己：gst_element_init（）
|
| set properties |
下面是具体的分析：
g_object_type_init()
1. 这个API完成GObject类型的注册
2. GObject 作为一个基础类型，放入全局数组以及Hash Table中
3. 分配GObject Node的数据，并且把用户指定的一系列函数指针赋值过去
4. 此时还没有真正的GObject对象实例。
void
g_type_init (void)
{
g_type_init_with_debug_flags (0);
}
/* G_TYPE_OBJECT */ g_object_type_init ();
void
g_object_type_init (void)
{
static gboolean initialized = FALSE;
static const GTypeFundamentalInfo finfo = {
G_TYPE_FLAG_CLASSED | G_TYPE_FLAG_INSTANTIATABLE | G_TYPE_FLAG_DERIVABLE | G_TYPE_FLAG_DEEP_DERIVABLE,
};
static GTypeInfo info = {
sizeof (GObjectClass),
(GBaseInitFunc) g_object_base_class_init,
(GBaseFinalizeFunc) g_object_base_class_finalize,
(GClassInitFunc) g_object_do_class_init,
NULL /* class_destroy */,
NULL /* class_data */,
sizeof (GObject),
0 /* n_preallocs */,
(GInstanceInitFunc) g_object_init,
NULL, /* value_table */
};
static const GTypeValueTable value_table = {
g_value_object_init, /* value_init */
g_value_object_free_value, /* value_free */
g_value_object_copy_value, /* value_copy */
g_value_object_peek_pointer, /* value_peek_pointer */
"p", /* collect_format */
g_value_object_collect_value, /* collect_value */
"p", /* lcopy_format */
g_value_object_lcopy_value, /* lcopy_value */
};
GType type;
g_return_if_fail (initialized == FALSE);
initialized = TRUE;
/* G_TYPE_OBJECT
*/
info.value_table = &value_table;
type = g_type_register_fundamental (G_TYPE_OBJECT, g_intern_static_string ("GObject"), &info, &finfo, 0);
g_assert (type == G_TYPE_OBJECT);
g_value_register_transform_func (G_TYPE_OBJECT, G_TYPE_OBJECT, g_value_object_transform_value);
}
这里注册GObject类型：
1. 指定这个类型的标记flag
static const GTypeFundamentalInfo finfo = {
G_TYPE_FLAG_CLASSED | G_TYPE_FLAG_INSTANTIATABLE | G_TYPE_FLAG_DERIVABLE | G_TYPE_FLAG_DEEP_DERIVABLE,
};
2. 注册Class的GTypeInfo. 相关的几个函数指针
3. 注册GObject type的函数表Value Table
问题来了：
g_object_base_class_init、g_object_do_class_init、g_object_init 何时被调用？
有什么严格的顺序吗？
我们先看看GObject的内部注册过程中，干了些什么？然后再看看基于Gobject生成新的object实例时
做了些什么？
GType
g_type_register_fundamental (GType type_id,
const gchar *type_name,
const GTypeInfo *info,
const GTypeFundamentalInfo *finfo,
GTypeFlags flags)
{
TypeNode *node;
G_WRITE_LOCK (&type_rw_lock);
node = type_node_fundamental_new_W (type_id, type_name, finfo->type_flags);
type_add_flags_W (node, flags);
if (check_type_info_I (NULL, NODE_FUNDAMENTAL_TYPE (node), type_name, info))
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 NODE_TYPE (node);
}
其中关系不大的代码去掉了。
因为GObject是基础类型，没有父节点，所以代码中，去掉了部分。
static TypeNode*
type_node_any_new_W (TypeNode *pnode,
GType ftype,
const gchar *name,
GTypePlugin *plugin,
GTypeFundamentalFlags type_flags)
{
guint n_supers;
GType type;
TypeNode *node;
guint i, node_size = 0;
n_supers = pnode ? pnode->n_supers + 1 : 0;
if (!pnode)
node_size += SIZEOF_FUNDAMENTAL_INFO; /* fundamental type info */
node_size += SIZEOF_BASE_TYPE_NODE (); /* TypeNode structure */
node_size += (sizeof (GType) * (1 + n_supers + 1)); /* self + ancestors + (0) for ->supers[] */
node = g_malloc0 (node_size);
if (!pnode) /* offset fundamental types */
{
node = G_STRUCT_MEMBER_P (node, SIZEOF_FUNDAMENTAL_INFO);
static_fundamental_type_nodes[ftype >> G_TYPE_FUNDAMENTAL_SHIFT] = node;
type = ftype;
}
node->n_supers = n_supers;
if (!pnode)
{
node->supers[0] = type;
node->supers[1] = 0;
node->is_classed = (type_flags & G_TYPE_FLAG_CLASSED) != 0;
node->is_instantiatable = (type_flags & G_TYPE_FLAG_INSTANTIATABLE) != 0;
if (NODE_IS_IFACE (node))
{
IFACE_NODE_N_PREREQUISITES (node) = 0;
IFACE_NODE_PREREQUISITES (node) = NULL;
}
else
_g_atomic_array_init (CLASSED_NODE_IFACES_ENTRIES (node));
}
TRACE(GOBJECT_TYPE_NEW(name, node->supers[1], type));
node->plugin = plugin;
node->n_children = 0;
node->children = NULL;
node->data = NULL;
node->qname = g_quark_from_string (name);
node->global_gdata = NULL;
g_hash_table_insert (static_type_nodes_ht,
GUINT_TO_POINTER (node->qname),
(gpointer) type);
return node;
}
上面重要的地方：
static_fundamental_type_nodes[ftype >> G_TYPE_FUNDAMENTAL_SHIFT] = node; //把G_OBJECT_TYPE放入基础类型数组。
node->supers[0] = type; //没有父亲节点
node->supers[1] = 0;
node->is_classed = (type_flags & G_TYPE_FLAG_CLASSED) != 0; //可类化
node->is_instantiatable = (type_flags & G_TYPE_FLAG_INSTANTIATABLE) != 0; //可实例化
下面是把前面设置的GObject的标识：存入node的qdata中，用quark:static_quark_type_flags 来标识。
即：
static void
type_add_flags_W (TypeNode *node,
GTypeFlags flags)
{
guint dflags;
g_return_if_fail ((flags & ~TYPE_FLAG_MASK) == 0);
g_return_if_fail (node != NULL);
if ((flags & TYPE_FLAG_MASK) && node->is_classed && node->data && node->data->class.class)
g_warning ("tagging type `%s' as abstract after class initialization", NODE_NAME (node));
dflags = GPOINTER_TO_UINT (type_get_qdata_L (node, static_quark_type_flags));
dflags |= flags;
type_set_qdata_W (node, static_quark_type_flags, GUINT_TO_POINTER (dflags));
}
重点是下面：
/* --- type info (type node data) --- */
static void
type_data_make_W (TypeNode *node,
const GTypeInfo *info,
const GTypeValueTable *value_table)
{
TypeData *data;
GTypeValueTable *vtable = NULL;
guint vtable_size = 0;
g_assert (node->data == NULL && info != NULL);
if (!value_table)
{
TypeNode *pnode = lookup_type_node_I (NODE_PARENT_TYPE (node));
if (pnode)
vtable = pnode->data->common.value_table;
else
{
static const GTypeValueTable zero_vtable = { NULL, };
value_table = &zero_vtable;
}
}
if (value_table)
{
/* need to setup vtable_size since we have to allocate it with data in one chunk */
vtable_size = sizeof (GTypeValueTable);
if (value_table->collect_format)
vtable_size += strlen (value_table->collect_format);
if (value_table->lcopy_format)
vtable_size += strlen (value_table->lcopy_format);
vtable_size += 2;
}
if (node->is_instantiatable) /* carefull, is_instantiatable is also is_classed */
{
TypeNode *pnode = lookup_type_node_I (NODE_PARENT_TYPE (node));
data = g_malloc0 (sizeof (InstanceData) + vtable_size);
if (vtable_size)
vtable = G_STRUCT_MEMBER_P (data, sizeof (InstanceData));
data->instance.class_size = info->class_size;
data->instance.class_init_base = info->base_init;
data->instance.class_finalize_base = info->base_finalize;
data->instance.class_init = info->class_init;
data->instance.class_finalize = info->class_finalize;
data->instance.class_data = info->class_data;
data->instance.class = NULL;
data->instance.init_state = UNINITIALIZED;
data->instance.instance_size = info->instance_size;
/* We'll set the final value for data->instance.private size
* after the parent class has been initialized
*/
data->instance.private_size = 0;
data->instance.class_private_size = 0;
if (pnode)
data->instance.class_private_size = pnode->data->instance.class_private_size;
#ifdef DISABLE_MEM_POOLS
data->instance.n_preallocs = 0;
#else /* !DISABLE_MEM_POOLS */
data->instance.n_preallocs = MIN (info->n_preallocs, 1024);
#endif /* !DISABLE_MEM_POOLS */
data->instance.instance_init = info->instance_init;
}
else if (node->is_classed) /* only classed */
{
TypeNode *pnode = lookup_type_node_I (NODE_PARENT_TYPE (node));
data = g_malloc0 (sizeof (ClassData) + vtable_size);
if (vtable_size)
vtable = G_STRUCT_MEMBER_P (data, sizeof (ClassData));
data->class.class_size = info->class_size;
data->class.class_init_base = info->base_init;
data->class.class_finalize_base = info->base_finalize;
data->class.class_init = info->class_init;
data->class.class_finalize = info->class_finalize;
data->class.class_data = info->class_data;
data->class.class = NULL;
data->class.class_private_size = 0;
if (pnode)
data->class.class_private_size = pnode->data->class.class_private_size;
data->class.init_state = UNINITIALIZED;
}
else if (NODE_IS_IFACE (node))
{
data = g_malloc0 (sizeof (IFaceData) + vtable_size);
if (vtable_size)
vtable = G_STRUCT_MEMBER_P (data, sizeof (IFaceData));
data->iface.vtable_size = info->class_size;
data->iface.vtable_init_base = info->base_init;
data->iface.vtable_finalize_base = info->base_finalize;
data->iface.dflt_init = info->class_init;
data->iface.dflt_finalize = info->class_finalize;
data->iface.dflt_data = info->class_data;
data->iface.dflt_vtable = NULL;
}
else if (NODE_IS_BOXED (node))
{
data = g_malloc0 (sizeof (BoxedData) + vtable_size);
if (vtable_size)
vtable = G_STRUCT_MEMBER_P (data, sizeof (BoxedData));
}
else
{
data = g_malloc0 (sizeof (CommonData) + vtable_size);
if (vtable_size)
vtable = G_STRUCT_MEMBER_P (data, sizeof (CommonData));
}
node->data = data;
if (vtable_size)
{
gchar *p;
/* we allocate the vtable and its strings together with the type data, so
* children can take over their parent's vtable pointer, and we don't
* need to worry freeing it or not when the child data is destroyed
*/
*vtable = *value_table;
p = G_STRUCT_MEMBER_P (vtable, sizeof (*vtable));
p[0] = 0;
vtable->collect_format = p;
if (value_table->collect_format)
{
strcat (p, value_table->collect_format);
p += strlen (value_table->collect_format);
}
p++;
p[0] = 0;
vtable->lcopy_format = p;
if (value_table->lcopy_format)
strcat (p, value_table->lcopy_format);
}
node->data->common.value_table = vtable;
node->mutatable_check_cache = (node->data->common.value_table->value_init != NULL &&
!((G_TYPE_FLAG_VALUE_ABSTRACT | G_TYPE_FLAG_ABSTRACT) &
GPOINTER_TO_UINT (type_get_qdata_L (node, static_quark_type_flags))));
g_assert (node->data->common.value_table != NULL); /* paranoid */
g_atomic_int_set ((int *) &node->ref_count, 1);
}
这里有个union的变量：node->data: 可选4个类型：BoxedData/IFaceData/ClassData/InsanceData
node->is_instantiatable = 1
所以选择InstanceData
if (node->is_instantiatable) /* carefull, is_instantiatable is also is_classed */
{
TypeNode *pnode = lookup_type_node_I (NODE_PARENT_TYPE (node));
data = g_malloc0 (sizeof (InstanceData) + vtable_size);
if (vtable_size)
vtable = G_STRUCT_MEMBER_P (data, sizeof (InstanceData));
data->instance.class_size = info->class_size;
data->instance.class_init_base = info->base_init;
data->instance.class_finalize_base = info->base_finalize;
data->instance.class_init = info->class_init;
data->instance.class_finalize = info->class_finalize;
data->instance.class_data = info->class_data;
data->instance.class = NULL;
data->instance.init_state = UNINITIALIZED;
data->instance.instance_size = info->instance_size;
/* We'll set the final value for data->instance.private size
* after the parent class has been initialized
*/
data->instance.private_size = 0;
data->instance.class_private_size = 0;
if (pnode)
data->instance.class_private_size = pnode->data->instance.class_private_size;
#ifdef DISABLE_MEM_POOLS
data->instance.n_preallocs = 0;
#else /* !DISABLE_MEM_POOLS */
data->instance.n_preallocs = MIN (info->n_preallocs, 1024);
#endif /* !DISABLE_MEM_POOLS */
data->instance.instance_init = info->instance_init;
}
node->data = data;
把前面class的base/class/instance的APIs, Value Table APIs, 赋值给node->data
g_type_init():
1. ....
2. g_object_type_init()
3. ...
用户如何用呢？
之后应该就是g_object_new?
我们找个例子看看：
GObject
`|_____ GstObject
在gstobject.c:
G_DEFINE_ABSTRACT_TYPE (GstObject, gst_object, G_TYPE_OBJECT);
先比较一下gobject.c/gstobject.c提供的一些API:
| 父 | Me (当前) | 儿子 | 孙子 | 重孙子 |
| GObject | GstObject | GstElement | GstBin | GstPipeline |
| g_object_base_class_init() | gst_element_base_class_init | gst_bin_base_init | gst_pipeline_base_init | |
| g_object_do_class_init() | gst_object_class_init() | gst_element_class_init | gst_bin_class_init | gst_pipeline_class_init |
| g_object_init() | gst_object_init() | gst_element_init | gst_bin_init | gst_pipeline_init |
把宏展开，看到上面gstobject提供的两个API，绑定了：
#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 ((GstObjectlass*) 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 (CGstObjectClass), \
(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() */
首先取得父类的class数据:
gpointer
g_type_class_peek_parent (gpointer g_class)
{
TypeNode *node;
gpointer class = NULL;
g_return_val_if_fail (g_class != NULL, NULL);
node = lookup_type_node_I (G_TYPE_FROM_CLASS (g_class));
/* We used to acquire a read lock here. That is not necessary, since
* parent->data->class.class is constant as long as the derived class
* exists.
*/
if (node && node->is_classed && node->data && NODE_PARENT_TYPE (node))
{
node = lookup_type_node_I (NODE_PARENT_TYPE (node));
class = node->data->class.class;
}
else if (NODE_PARENT_TYPE (node))
g_warning (G_STRLOC ": invalid class pointer `%p'", g_class);
return class;
}
class = node->data->class.class;
然后真正开始Init:
gst.c中：
g_type_class_ref (gst_object_get_type ());
首先会调用：
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;
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);
}
然后指定自己的class_init/Instance_init函数，就开始创建这个TypeNode.
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;
}
1. type_data_ref_Wm (pnode); //给父节点增加一个引用计数
2. node = type_node_new_W (pnode, type_name, NULL); //从父节点拷贝出一份内存，并且建立父子关系；
并且把新创建的“子节点” 保存在父节点的数组中：pnode->children[i] = type;
3. type_data_make_W, 就是用户指定的各种APIs, Value Table APIs, 指定给这个新建的Type Node, 这里是给GstObject
g_type_class_ref(GstObject);
好戏都在g_type_class_ref
这个函数是个循环嵌套函数！
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);
/* we need an initialized parent class for initializing derived classes */
ptype = NODE_PARENT_TYPE (node);
pclass = ptype ? g_type_class_ref (ptype) : NULL;
它会顺藤摸瓜！找到最上面的祖先：
这里它会找到GObject （GstObject的父类），GObject已经是最顶层了。
好，接着往下:
if (!holds_ref)
type_data_ref_Wm (node);
if (!node->data->class.class) /* class uninitialized */
type_class_init_Wm (node, pclass);
最关键的地方：如果当前class并没有被初始化，则进行初始化。
先初始化GObject, 然后轮到其儿子:GstObject.
对某个typeclass进行下面的顺序进行初始化：
BASE_CLASS_INIT
BASE_IFACE_INIT
CLASS_INIT
IFACE_INIT
INITIALIZED
对GObject的初始化：
1. BASE_CLASS_INIT
/* stack all base class initialization functions, so we
* call them in ascending order.
*/
for (bnode = node; bnode; bnode = lookup_type_node_I (NODE_PARENT_TYPE (bnode)))
{
if (bnode->data->class.class_init_base)
init_slist = g_slist_prepend (init_slist, (gpointer) bnode->data->class.class_init_base);
}
for (slist = init_slist; slist; slist = slist->next)
{
GBaseInitFunc class_init_base = (GBaseInitFunc) slist->data;
class_init_base (class);
}
for (bnode = node; bnode; bnode = lookup_type_nodeI (NODE_PARENT_TYPE (bnode)))
是从最底层往上层循环（孙子 --> 儿子--> 爷爷）
init_slist, 是反过来弄的：
爷爷->儿子-->孙子，这么一个顺序，进行class_init_base()
后面会印证。
2. CLASS_INIT
g_atomic_int_set (&node->data->class.init_state, CLASS_INIT);
G_WRITE_UNLOCK (&type_rw_lock);
if (node->data->class.class_init)
node->data->class.class_init (class, (gpointer) node->data->class.class_data);
此时执行：g_object_do_class_init()
父类初始化完成后，嵌套退回一层，开始自行GstObjec的初始化：
也是按照那个顺序，有的成员是NULL, 就跳过去：
3. GstObject的CLASS_INIT
g_atomic_int_set (&node->data->class.init_state, CLASS_INIT);
G_WRITE_UNLOCK (&type_rw_lock);
if (node->data->class.class_init)
node->data->class.class_init (class, (gpointer) node->data->class.class_data);
此时执行：gst_object_class_init()
注意，此时：gobject/gstobject的实例instance对象还没有建立！
static void
g_object_base_class_init (GObjectClass *class)
{
GObjectClass *pclass = g_type_class_peek_parent (class);
/* Don't inherit HAS_DERIVED_CLASS flag from parent class */
class->flags &= ~CLASS_HAS_DERIVED_CLASS_FLAG;
if (pclass)
pclass->flags |= CLASS_HAS_DERIVED_CLASS_FLAG;
/* reset instance specific fields and methods that don't get inherited */
class->construct_properties = pclass ? g_slist_copy (pclass->construct_properties) : NULL;
class->get_property = NULL;
class->set_property = NULL;
}
static void
g_object_do_class_init (GObjectClass *class)
{
/* read the comment about typedef struct CArray; on why not to change this quark */
quark_closure_array = g_quark_from_static_string ("GObject-closure-array");
quark_weak_refs = g_quark_from_static_string ("GObject-weak-references");
quark_toggle_refs = g_quark_from_static_string ("GObject-toggle-references");
pspec_pool = g_param_spec_pool_new (TRUE);
property_notify_context.quark_notify_queue = g_quark_from_static_string ("GObject-notify-queue");
property_notify_context.dispatcher = g_object_notify_dispatcher;
class->constructor = g_object_constructor;
class->constructed = g_object_constructed;
class->set_property = g_object_do_set_property;
class->get_property = g_object_do_get_property;
class->dispose = g_object_real_dispose;
class->finalize = g_object_finalize;
class->dispatch_properties_changed = g_object_dispatch_properties_changed;
class->notify = NULL;
/**
* GObject::notify:
* @gobject: the object which received the signal.
* @pspec: the #GParamSpec of the property which changed.
*
* The notify signal is emitted on an object when one of its
* properties has been changed. Note that getting this signal
* doesn't guarantee that the value of the property has actually
* changed, it may also be emitted when the setter for the property
* is called to reinstate the previous value.
*
* This signal is typically used to obtain change notification for a
* single property, by specifying the property name as a detail in the
* g_signal_connect() call, like this:
* |[
* g_signal_connect (text_view->buffer, "notify::paste-target-list",
* G_CALLBACK (gtk_text_view_target_list_notify),
* text_view)
* ]|
* It is important to note that you must use
* <link linkend="canonical-parameter-name">canonical</link> parameter names as
* detail strings for the notify signal.
*/
gobject_signals[NOTIFY] =
g_signal_new (g_intern_static_string ("notify"),
G_TYPE_FROM_CLASS (class),
G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE | G_SIGNAL_DETAILED | G_SIGNAL_NO_HOOKS | G_SIGNAL_ACTION,
G_STRUCT_OFFSET (GObjectClass, notify),
NULL, NULL,
g_cclosure_marshal_VOID__PARAM,
G_TYPE_NONE,
1, G_TYPE_PARAM);
/* Install a check function that we'll use to verify that classes that
* implement an interface implement all properties for that interface
*/
g_type_add_interface_check (NULL, object_interface_check_properties);
}
static void
gst_object_class_init (GstObjectClass * klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
parent_class = g_type_class_peek_parent (klass);
#ifndef GST_DISABLE_TRACE
_gst_object_trace = gst_alloc_trace_register (g_type_name (GST_TYPE_OBJECT));
#endif
gobject_class->set_property = gst_object_set_property;
gobject_class->get_property = gst_object_get_property;
g_object_class_install_property (gobject_class, ARG_NAME,
g_param_spec_string ("name", "Name", "The name of the object",
NULL,
G_PARAM_READWRITE | G_PARAM_CONSTRUCT | G_PARAM_STATIC_STRINGS));
/**
* GstObject::parent-set:
* @gstobject: a #GstObject
* @parent: the new parent
*
* Emitted when the parent of an object is set.
*/
gst_object_signals[PARENT_SET] =
g_signal_new ("parent-set", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
G_STRUCT_OFFSET (GstObjectClass, parent_set), NULL, NULL,
g_cclosure_marshal_VOID__OBJECT, G_TYPE_NONE, 1, GST_TYPE_OBJECT);
/**
* GstObject::parent-unset:
* @gstobject: a #GstObject
* @parent: the old parent
*
* Emitted when the parent of an object is unset.
*/
gst_object_signals[PARENT_UNSET] =
g_signal_new ("parent-unset", G_TYPE_FROM_CLASS (klass),
G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstObjectClass, parent_unset), NULL,
NULL, g_cclosure_marshal_VOID__OBJECT, G_TYPE_NONE, 1, GST_TYPE_OBJECT);
#if !defined(GST_DISABLE_LOADSAVE) && !defined(GST_REMOVE_DEPRECATED)
/**
* GstObject::object-saved:
* @gstobject: a #GstObject
* @xml_node: the xmlNodePtr of the parent node
*
* Trigered whenever a new object is saved to XML. You can connect to this
* signal to insert custom XML tags into the core XML.
*/
/* FIXME This should be the GType of xmlNodePtr instead of G_TYPE_POINTER
* (if libxml would use GObject)
*/
gst_object_signals[OBJECT_SAVED] =
g_signal_new ("object-saved", G_TYPE_FROM_CLASS (klass),
G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstObjectClass, object_saved), NULL,
NULL, g_cclosure_marshal_VOID__POINTER, G_TYPE_NONE, 1, G_TYPE_POINTER);
klass->restore_thyself =
((void (*)(GstObject * object,
gpointer self)) *gst_object_real_restore_thyself);
#endif
/**
* GstObject::deep-notify:
* @gstobject: a #GstObject
* @prop_object: the object that originated the signal
* @prop: the property that changed
*
* The deep notify signal is used to be notified of property changes. It is
* typically attached to the toplevel bin to receive notifications from all
* the elements contained in that bin.
*/
gst_object_signals[DEEP_NOTIFY] =
g_signal_new ("deep-notify", G_TYPE_FROM_CLASS (klass),
G_SIGNAL_RUN_FIRST | G_SIGNAL_NO_RECURSE | G_SIGNAL_DETAILED |
G_SIGNAL_NO_HOOKS, G_STRUCT_OFFSET (GstObjectClass, deep_notify), NULL,
NULL, gst_marshal_VOID__OBJECT_PARAM, G_TYPE_NONE, 2, GST_TYPE_OBJECT,
G_TYPE_PARAM);
klass->path_string_separator = "/";
/* FIXME 0.11: Store this directly in the class struct */
klass->lock = g_slice_new (GStaticRecMutex);
g_static_rec_mutex_init (klass->lock);
klass->signal_object = g_object_newv (gst_signal_object_get_type (), 0, NULL);
/* see the comments at gst_object_dispatch_properties_changed */
gobject_class->dispatch_properties_changed
= GST_DEBUG_FUNCPTR (gst_object_dispatch_properties_changed);
gobject_class->dispose = gst_object_dispose;
gobject_class->finalize = gst_object_finalize;
}
Testing:
1. g_type_class_ref(G_TYPE_OBJECT)
g_type_init(); g_type_class_ref(G_TYPE_OBJECT);
result:
Entering g_type_class_ref Type:GObject +Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() -Leaving type_class_init_Wm Leaving g_type_class_ref
2.
g_type_init(); g_type_class_ref(G_TYPE_OBJECT); g_type_class_ref(GST_TYPE_OBJECT);
Entering g_type_class_ref Type:GObject +Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() -Leaving type_class_init_Wm Leaving g_type_class_ref Entering g_type_class_ref Type:GstObject +Entering g_type_class_ref Type:GObject -Leaving g_type_class_ref +Entering type_class_init_Wm Call GObject.class_init_base() Call GstObject.class_init() ++Entering g_type_class_ref Type:GParamString +++Entering g_type_class_ref Type:GParam ++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParam.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamString.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject +++Entering g_type_class_ref Type:GObject ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GObject.class_init_base() Call GstSignalObject.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject --Leaving g_type_class_ref -Leaving type_class_init_Wm Leaving g_type_class_ref
3.
g_type_init(); g_type_class_ref(GST_TYPE_OBJECT);
Entering g_type_class_ref Type:GstObject +Entering g_type_class_ref Type:GObject ++Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() --Leaving type_class_init_Wm -Leaving g_type_class_ref +Entering type_class_init_Wm Call GObject.class_init_base() Call GstObject.class_init() ++Entering g_type_class_ref Type:GParamString +++Entering g_type_class_ref Type:GParam ++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParam.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamString.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject +++Entering g_type_class_ref Type:GObject ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GObject.class_init_base() Call GstSignalObject.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject --Leaving g_type_class_ref -Leaving type_class_init_Wm Leaving g_type_class_ref
4.
g_type_init(); g_type_class_ref(G_TYPE_OBJECT); g_type_class_ref(GST_TYPE_OBJECT); g_type_class_ref(GST_TYPE_ELEMENT);
============================= Entering g_type_class_ref Type:GObject +Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() -Leaving type_class_init_Wm Leaving g_type_class_ref ============================= Entering g_type_class_ref Type:GstObject +Entering g_type_class_ref Type:GObject -Leaving g_type_class_ref +Entering type_class_init_Wm Call GObject.class_init_base() Call GstObject.class_init() ++Entering g_type_class_ref Type:GParamString +++Entering g_type_class_ref Type:GParam ++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParam.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamString.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject +++Entering g_type_class_ref Type:GObject ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GObject.class_init_base() Call GstSignalObject.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject --Leaving g_type_class_ref -Leaving type_class_init_Wm Leaving g_type_class_ref ============================= Entering g_type_class_ref Type:GstElement +Entering g_type_class_ref Type:GstObject -Leaving g_type_class_ref +Entering type_class_init_Wm Call GstElement.class_init_base() Call GObject.class_init_base() Call GstElement.class_init() -Leaving type_class_init_Wm Leaving g_type_class_ref
5.
g_type_init(); g_type_class_ref(GST_TYPE_ELEMENT);
Entering g_type_class_ref Type:GstElement +Entering g_type_class_ref Type:GstObject ++Entering g_type_class_ref Type:GObject +++Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering type_class_init_Wm Call GObject.class_init_base() Call GstObject.class_init() +++Entering g_type_class_ref Type:GParamString ++++Entering g_type_class_ref Type:GParam +++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParam.class_init() -----Leaving type_class_init_Wm ----Leaving g_type_class_ref ++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamString.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering g_type_class_ref Type:GstSignalObject ++++Entering g_type_class_ref Type:GObject ----Leaving g_type_class_ref ++++Entering type_class_init_Wm Call GObject.class_init_base() Call GstSignalObject.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering g_type_class_ref Type:GstSignalObject ---Leaving g_type_class_ref --Leaving type_class_init_Wm -Leaving g_type_class_ref +Entering type_class_init_Wm Call GstElement.class_init_base() Call GObject.class_init_base() Call GstElement.class_init() -Leaving type_class_init_Wm Leaving g_type_class_ref
6.
g_type_init(); g_type_class_ref(GST_TYPE_PIPELINE);
Entering g_type_class_ref Type:GstPipeline +Entering g_type_class_ref Type:GstBin ++Entering g_type_class_ref Type:GstElement +++Entering g_type_class_ref Type:GstObject ++++Entering g_type_class_ref Type:GObject +++++Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() -----Leaving type_class_init_Wm ----Leaving g_type_class_ref ++++Entering type_class_init_Wm Call GObject.class_init_base() Call GstObject.class_init() +++++Entering g_type_class_ref Type:GParamString ++++++Entering g_type_class_ref Type:GParam +++++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParam.class_init() -------Leaving type_class_init_Wm ------Leaving g_type_class_ref ++++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamString.class_init() ------Leaving type_class_init_Wm -----Leaving g_type_class_ref +++++Entering g_type_class_ref Type:GstSignalObject ++++++Entering g_type_class_ref Type:GObject ------Leaving g_type_class_ref ++++++Entering type_class_init_Wm Call GObject.class_init_base() Call GstSignalObject.class_init() ------Leaving type_class_init_Wm -----Leaving g_type_class_ref +++++Entering g_type_class_ref Type:GstSignalObject -----Leaving g_type_class_ref ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GstElement.class_init_base() Call GObject.class_init_base() Call GstElement.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering type_class_init_Wm Call GstBin.class_init_base() Call GstElement.class_init_base() Call GObject.class_init_base() Call GstBin.class_init() +++Entering g_type_class_ref Type:GParamBoolean ++++Entering g_type_class_ref Type:GParam ----Leaving g_type_class_ref ++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamBoolean.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering g_type_class_ref Type:GParamBoolean ---Leaving g_type_class_ref +++Entering g_type_class_ref Type:GstBin ++++Entering g_type_class_ref Type:GstElement ----Leaving g_type_class_ref ---Leaving g_type_class_ref --Leaving type_class_init_Wm -Leaving g_type_class_ref +Entering type_class_init_Wm Call GstPipeline.class_init_base() Call GstBin.class_init_base() Call GstElement.class_init_base() Call GObject.class_init_base() Call GstPipeline.class_init() ++Entering g_type_class_ref Type:GParamUInt64 +++Entering g_type_class_ref Type:GParam ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamUInt64.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GParamBoolean --Leaving g_type_class_ref -Leaving type_class_init_Wm Leaving g_type_class_ref
上面的base调用打印应该是反的
Call GstPipeline.class_init_base()
Call GstBin.class_init_base()
Call GstElement.class_init_base()
Call GObject.class_init_base()
实际是：
GObject.class_init_base()
GstElement.class_init_base()
GstBin.class_init_base()
GstPipeline.class_init_base()
先父亲后儿子的顺序，调用base_init():
| 父 | Me (当前) | 儿子 | 孙子 | 重孙子 |
| GObject | GstObject | GstElement | GstBin | GstPipeline |
| g_object_base_class_init() | gst_element_base_class_init | gst_bin_base_init | gst_pipeline_base_init | |
| g_object_do_class_init() | gst_object_class_init() | gst_element_class_init | gst_bin_class_init | gst_pipeline_class_init |
| g_object_init() | gst_object_init() | gst_element_init | gst_bin_init | gst_pipeline_init |
小结一下：
xxx_yyy_get_type(), 是创建type node, 并且，绑定自己定义的一些APIs;
g_type_class_ref(), 是调用用户的一些class: APIs,
先调用base_init() [老子--> 儿子-->当前],
在调用class_init()
这个时候，对象实例依然没有创建。
下面就要看g_object_newv的实力了！
examples:
1.
g_object_new(G_TYPE_OBJECT, NULL);
GEnum->is_classed = 1 GFlags->is_classed = 1 GParam->is_instantiatable = 1 GObject->is_instantiatable = 1 GParamChar->is_instantiatable = 1 GParamUChar->is_instantiatable = 1 GParamBoolean->is_instantiatable = 1 GParamInt->is_instantiatable = 1 GParamUInt->is_instantiatable = 1 GParamLong->is_instantiatable = 1 GParamULong->is_instantiatable = 1 GParamInt64->is_instantiatable = 1 GParamUInt64->is_instantiatable = 1 GParamUnichar->is_instantiatable = 1 GParamEnum->is_instantiatable = 1 GParamFlags->is_instantiatable = 1 GParamFloat->is_instantiatable = 1 GParamDouble->is_instantiatable = 1 GParamString->is_instantiatable = 1 GParamParam->is_instantiatable = 1 GParamBoxed->is_instantiatable = 1 GParamPointer->is_instantiatable = 1 GParamValueArray->is_instantiatable = 1 GParamObject->is_instantiatable = 1 GParamOverride->is_instantiatable = 1 GParamGType->is_instantiatable = 1 GParamVariant->is_instantiatable = 1 ============================= Entering g_type_class_ref Type:GObject +Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() -Leaving type_class_init_Wm Leaving g_type_class_ref Entering g_type_class_ref Type:GObject Leaving g_type_class_ref Call GObject.instance_init()
2.
g_object_new(GST_TYPE_OBJECT,NULL);
GEnum->is_classed = 1 GFlags->is_classed = 1 GParam->is_instantiatable = 1 GObject->is_instantiatable = 1 GParamChar->is_instantiatable = 1 GParamUChar->is_instantiatable = 1 GParamBoolean->is_instantiatable = 1 GParamInt->is_instantiatable = 1 GParamUInt->is_instantiatable = 1 GParamLong->is_instantiatable = 1 GParamULong->is_instantiatable = 1 GParamInt64->is_instantiatable = 1 GParamUInt64->is_instantiatable = 1 GParamUnichar->is_instantiatable = 1 GParamEnum->is_instantiatable = 1 GParamFlags->is_instantiatable = 1 GParamFloat->is_instantiatable = 1 GParamDouble->is_instantiatable = 1 GParamString->is_instantiatable = 1 GParamParam->is_instantiatable = 1 GParamBoxed->is_instantiatable = 1 GParamPointer->is_instantiatable = 1 GParamValueArray->is_instantiatable = 1 GParamObject->is_instantiatable = 1 GParamOverride->is_instantiatable = 1 GParamGType->is_instantiatable = 1 GParamVariant->is_instantiatable = 1 ============================= GstObject->is_instantiatable = 1 Entering g_type_class_ref Type:GstObject +Entering g_type_class_ref Type:GObject ++Entering type_class_init_Wm Call GObject.class_init_base() Call GObject.class_init() --Leaving type_class_init_Wm -Leaving g_type_class_ref +Entering type_class_init_Wm Call GObject.class_init_base() Call GstObject.class_init() ++Entering g_type_class_ref Type:GParamString +++Entering g_type_class_ref Type:GParam ++++Entering type_class_init_Wm Call GParam.class_init_base() Call GParam.class_init() ----Leaving type_class_init_Wm ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GParam.class_init_base() Call GParamString.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref Call GParam.instance_init() Call GParamString.instance_init() GstSignalObject->is_instantiatable = 1 ++Entering g_type_class_ref Type:GstSignalObject +++Entering g_type_class_ref Type:GObject ---Leaving g_type_class_ref +++Entering type_class_init_Wm Call GObject.class_init_base() Call GstSignalObject.class_init() ---Leaving type_class_init_Wm --Leaving g_type_class_ref ++Entering g_type_class_ref Type:GstSignalObject --Leaving g_type_class_ref Call GObject.instance_init() Call GstSignalObject.instance_init() -Leaving type_class_init_Wm Leaving g_type_class_ref GLib-GObject-WARNING **: cannot create instance of abstract (non-instantiatable) type `GstObject' aborting...
小结：
| 阶段 | 相应API | 作用 | GObject 调用顺序 | GstObject | GstElement |
| 1 | xxx_yyy_get_type() |
创建TypeNode, 并且赋值一些APIs: base_class_init() class_init() instance_init(), 等等 |
|||
| 2 | g_type_class_ref() |
调用base_class_init() 从父-->子， |
g_object_base_class_init() |
1. 父类：g_object_base_class_init() 2. 自己没有base_init() |
1. 爷爷：g_object_base_class_init() 2. 父亲没有base_init() 3. gst_element_base_class_init |
|
调用class_init(), 指定各种APIs 包括class->constructor(), set_property()/get_property() dispose()/finalize() |
g_object_do_class_init() |
gst_object_class_init（） 1. 首选取得GObjectClass 2. 重载一些函数 3. 装载一些自己的signal |
gst_element_class_init（） 1. 首选取得GObjectClass 2. 把GObjectClass的一些函数换成自己的（重载） 3. 装载自己的信号 |
||
| 3 | g_object_new() |
调用class->constructor() --> g_type_create_instance() --> 父类的instance(), 自己的instance() |
g_object_constructor()->g_type_create_instance() -> 1. g_object_init() |
g_object_constructor()->g_type_create_instance() -> 1. 父亲：g_object_init() 2.自己：gst_object_init（） |
g_object_constructor()->g_type_create_instance() -> 1. 爷爷：g_object_init() 2.父亲：gst_object_init（） 3. 自己：gst_element_init（）
|
| set properties |
疑问：在同一进程内，如果同时注册N个话，如果管理？
“用时”注册，会浪费时间吗？
2024年2月21日 21:17
Awesome article, it was exceptionally helpful! I simply began in this and I'm becoming more acquainted with it better. The post is written in very a good manner and it contains many useful information for me. Thank you very much and will look for more postings from you.