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Happy coding
gobject中比较常用，但是又比较生疏的数据类型quark/dataset。
glib中除了提供
1. array/byte array/pointer array
2. SList/List
3. Hash Table
4. Queue
5. String
6. Tree
之外，还有quark/dataset, 这是gobject中用的非常多的。要理解它。
GQuark:
quark其实就是个数字，用来和字符串进行匹配。
只有一个gquark.h, 没有gquark.c
typedef guint32 GQuark;
实现文件在gdataset.c
static GHashTable *g_quark_ht = NULL; static gchar **g_quarks = NULL; static GQuark g_quark_seq_id = 0;
上面定义了一个hash table：g_quark_ht和一个全局的指针数组：g_quarks。
从下面的new中，我们可以很清楚的看到，string如何和数字对应的：
/* HOLDS: g_quark_global_lock */
static inline GQuark
g_quark_new (gchar *string)
{
GQuark quark;
if (g_quark_seq_id % G_QUARK_BLOCK_SIZE == 0)
g_quarks = g_renew (gchar*, g_quarks, g_quark_seq_id + G_QUARK_BLOCK_SIZE);
if (!g_quark_ht)
{
g_assert (g_quark_seq_id == 0);
g_quark_ht = g_hash_table_new (g_str_hash, g_str_equal);
g_quarks[g_quark_seq_id++] = NULL;
}
quark = g_quark_seq_id++;
g_quarks[quark] = string;
g_hash_table_insert (g_quark_ht, string, GUINT_TO_POINTER (quark));
return quark;
}
会创建一个全局的Hash Table: g_quark_ht, 用来保持string/quark
同时把string放入数组中：g_quarks[quark] = string.
如果一个进程中有很多string, 那个这个指针数组是否很大？占用的内存如何？能否优化一些不用的？
GData
有了gquark后，就可以有GData了，这是和
gquark关联的一个数据元链表。
struct _GData
{
GData *next;
GQuark id;
gpointer data;
GDestroyNotify destroy_func;
};
这个data list, 并没有一个明显的全局变量来保持它。
1. 用时分配内存
2. 存放在一个全局的Hash Table中
3. 用完释放掉
GDataset:
struct _GDataset
{
gconstpointer location;
GData *datalist;
};
Datalist的作用主要是：
给GObject关联任意数据。
Data lists are used for associating arbitrary data with #GObjects
定义了一个全局的Hash Table来保存，新生成的datalist
static GHashTable *g_dataset_location_ht = NULL; static GDataset *g_dataset_cached = NULL; /* should this be threadspecific? */
static void
g_data_initialize (void)
{
g_return_if_fail (g_dataset_location_ht == NULL);
g_dataset_location_ht = g_hash_table_new (g_direct_hash, NULL);
g_dataset_cached = NULL;
}
下面2个函数会把new的数据，放到hash table中：
void g_dataset_id_set_data_full (gconstpointer dataset_location, GQuark key_id, gpointer data, GDestroyNotify destroy_func)
void g_datalist_id_set_data_full (GData **datalist, GQuark key_id, gpointer data, GDestroyNotify destroy_func)
再仔细看下这个函数：
void
g_dataset_id_set_data_full (gconstpointer dataset_location,
GQuark key_id,
gpointer data,
GDestroyNotify destroy_func)
{
register GDataset *dataset;
g_return_if_fail (dataset_location != NULL);
if (!data)
g_return_if_fail (destroy_func == NULL);
if (!key_id)
{
if (data)
g_return_if_fail (key_id > 0);
else
return;
}
G_LOCK (g_dataset_global);
if (!g_dataset_location_ht)
g_data_initialize ();
dataset = g_dataset_lookup (dataset_location);
if (!dataset)
{
dataset = g_slice_new (GDataset);
dataset->location = dataset_location;
g_datalist_init (&dataset->datalist);
g_hash_table_insert (g_dataset_location_ht,
(gpointer) dataset->location,
dataset);
}
g_data_set_internal (&dataset->datalist, key_id, data, destroy_func, dataset);
G_UNLOCK (g_dataset_global);
}
0. 先根据hash table的key查询一下，是否已经存在与之关联的dataset
如果没有，则新分配；如果有，则把相关的数据(data)放到这个data_list中
1. 上面是给GDataset分配一块内存
2. 把新的dataset插入到hash table中
3. 把用户想携带的data/destroy_func放到data_list中
实际使用：
在实际使用中g_dataset_xxx用的并不多，
而是g_datalist_xxx用的多：
#define g_datalist_id_set_data(dl, q, d) \
g_datalist_id_set_data_full ((dl), (q), (d), NULL)
实际使用中，GObject主要用了这个函数：g_datalist_id_set_data
void
g_datalist_id_set_data_full (GData **datalist,
GQuark key_id,
gpointer data,
GDestroyNotify destroy_func)
{
g_return_if_fail (datalist != NULL);
if (!data)
g_return_if_fail (destroy_func == NULL);
if (!key_id)
{
if (data)
g_return_if_fail (key_id > 0);
else
return;
}
G_LOCK (g_dataset_global);
if (!g_dataset_location_ht)
g_data_initialize ();
g_data_set_internal (datalist, key_id, data, destroy_func, NULL);
G_UNLOCK (g_dataset_global);
}
查询一下：
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_closure_array, NULL); Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_weak_refs, NULL); Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_closure_array, NULL); Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_weak_refs, NULL); Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark, data); Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, g_quark_from_string (key), data); Gobjectnotifyqueue.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, context->quark_notify_queue, NULL); Gparam.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&pspec->qdata, quark, data); Gstobject.c (\gstreamer-0.10.36\gst): g_datalist_id_set_data (&object_name_counts, q, GINT_TO_POINTER (count + 1));
GObject中的qdata:
1. 内部使用的
2. 进一步封装，提供给调用者使用的APIs
在GObject自己内部用了3个quark来标识与之关联的data(任何数据）
static GQuark quark_closure_array = 0; static GQuark quark_weak_refs = 0; static GQuark quark_toggle_refs = 0;
再复杂的data, 用这个quark/datalist, 都可以绑定/提取，这样看来datalist还是很强大滴~
Gobject.c (\glib-2.28.6\gobject):static GQuark quark_closure_array = 0;
Gobject.c (\glib-2.28.6\gobject): quark_closure_array = g_quark_from_static_string ("GObject-closure-array");
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_closure_array, NULL);
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_closure_array, NULL);
Gobject.c (\glib-2.28.6\gobject): carray = g_object_get_qdata (object, quark_closure_array);
Gobject.c (\glib-2.28.6\gobject): * letting it fiddle with quark_closure_array which is empty anyways
Gobject.c (\glib-2.28.6\gobject): carray = g_datalist_id_remove_no_notify (&object->qdata, quark_closure_array);
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data_full (&object->qdata, quark_closure_array, carray, destroy_closure_array);
---- quark_weak_refs Matches (7 in 1 files) ----
Gobject.c (\glib-2.28.6\gobject):static GQuark quark_weak_refs = 0;
Gobject.c (\glib-2.28.6\gobject): quark_weak_refs = g_quark_from_static_string ("GObject-weak-references");
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_weak_refs, NULL);
Gobject.c (\glib-2.28.6\gobject): wstack = g_datalist_id_remove_no_notify (&object->qdata, quark_weak_refs);
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data_full (&object->qdata, quark_weak_refs, wstack, weak_refs_notify);
Gobject.c (\glib-2.28.6\gobject): wstack = g_datalist_id_get_data (&object->qdata, quark_weak_refs);
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data (&object->qdata, quark_weak_refs, NULL);
---- quark_toggle_refs Matches (6 in 1 files) ----
Gobject.c (\glib-2.28.6\gobject):static GQuark quark_toggle_refs = 0;
Gobject.c (\glib-2.28.6\gobject): quark_toggle_refs = g_quark_from_static_string ("GObject-toggle-references");
Gobject.c (\glib-2.28.6\gobject): tstackptr = g_datalist_id_get_data (&object->qdata, quark_toggle_refs);
Gobject.c (\glib-2.28.6\gobject): tstack = g_datalist_id_remove_no_notify (&object->qdata, quark_toggle_refs);
Gobject.c (\glib-2.28.6\gobject): g_datalist_id_set_data_full (&object->qdata, quark_toggle_refs, tstack,
Gobject.c (\glib-2.28.6\gobject): tstack = g_datalist_id_get_data (&object->qdata, quark_toggle_refs);
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");
上面这3个quark来标识GObject的3种重要数据：
1）GObject的Closure Array
2) Weak Reference
3) Toggle reference
Closure Array用quark来存取：
void
g_object_watch_closure (GObject *object,
GClosure *closure)
{
CArray *carray;
guint i;
g_return_if_fail (G_IS_OBJECT (object));
g_return_if_fail (closure != NULL);
g_return_if_fail (closure->is_invalid == FALSE);
g_return_if_fail (closure->in_marshal == FALSE);
g_return_if_fail (object->ref_count > 0); /* this doesn't work on finalizing objects */
g_closure_add_invalidate_notifier (closure, object, object_remove_closure);
g_closure_add_marshal_guards (closure,
object, (GClosureNotify) g_object_ref,
object, (GClosureNotify) g_object_unref);
G_LOCK (closure_array_mutex);
carray = g_datalist_id_remove_no_notify (&object->qdata, quark_closure_array);
if (!carray)
{
carray = g_renew (CArray, NULL, 1);
carray->object = object;
carray->n_closures = 1;
i = 0;
}
else
{
i = carray->n_closures++;
carray = g_realloc (carray, sizeof (*carray) + sizeof (carray->closures[0]) * i);
}
carray->closures[i] = closure;
g_datalist_id_set_data_full (&object->qdata, quark_closure_array, carray, destroy_closure_array);
G_UNLOCK (closure_array_mutex);
}
g_datalist_id_set_data_full (&object->qdata, quark_closure_array, carray, destroy_closure_array);
这是把Closure Array用quark标识后，并且放入data list中
在g_object_unref()中：
g_datalist_id_set_data (&object->qdata, quark_closure_array, NULL);
g_datalist_id_set_data (&object->qdata, quark_weak_refs, NULL);
在dispose时也搞：
static void
g_object_real_dispose (GObject *object)
{
g_signal_handlers_destroy (object);
g_datalist_id_set_data (&object->qdata, quark_closure_array, NULL);
g_datalist_id_set_data (&object->qdata, quark_weak_refs, NULL);
}
Weak Reference用quark来存取：
void
g_object_weak_ref (GObject *object,
GWeakNotify notify,
gpointer data)
{
WeakRefStack *wstack;
guint i;
g_return_if_fail (G_IS_OBJECT (object));
g_return_if_fail (notify != NULL);
g_return_if_fail (object->ref_count >= 1);
G_LOCK (weak_refs_mutex);
wstack = g_datalist_id_remove_no_notify (&object->qdata, quark_weak_refs);
if (wstack)
{
i = wstack->n_weak_refs++;
wstack = g_realloc (wstack, sizeof (*wstack) + sizeof (wstack->weak_refs[0]) * i);
}
else
{
wstack = g_renew (WeakRefStack, NULL, 1);
wstack->object = object;
wstack->n_weak_refs = 1;
i = 0;
}
wstack->weak_refs[i].notify = notify;
wstack->weak_refs[i].data = data;
g_datalist_id_set_data_full (&object->qdata, quark_weak_refs, wstack, weak_refs_notify);
G_UNLOCK (weak_refs_mutex);
}
Toggle Reference用quark来存取：
void
g_object_add_toggle_ref (GObject *object,
GToggleNotify notify,
gpointer data)
{
ToggleRefStack *tstack;
guint i;
g_return_if_fail (G_IS_OBJECT (object));
g_return_if_fail (notify != NULL);
g_return_if_fail (object->ref_count >= 1);
g_object_ref (object);
G_LOCK (toggle_refs_mutex);
tstack = g_datalist_id_remove_no_notify (&object->qdata, quark_toggle_refs);
if (tstack)
{
i = tstack->n_toggle_refs++;
/* allocate i = tstate->n_toggle_refs - 1 positions beyond the 1 declared
* in tstate->toggle_refs */
tstack = g_realloc (tstack, sizeof (*tstack) + sizeof (tstack->toggle_refs[0]) * i);
}
else
{
tstack = g_renew (ToggleRefStack, NULL, 1);
tstack->object = object;
tstack->n_toggle_refs = 1;
i = 0;
}
/* Set a flag for fast lookup after adding the first toggle reference */
if (tstack->n_toggle_refs == 1)
g_datalist_set_flags (&object->qdata, OBJECT_HAS_TOGGLE_REF_FLAG);
tstack->toggle_refs[i].notify = notify;
tstack->toggle_refs[i].data = data;
g_datalist_id_set_data_full (&object->qdata, quark_toggle_refs, tstack,
(GDestroyNotify)g_free);
G_UNLOCK (toggle_refs_mutex);
}
Gobject除了自己内部用的3个quark外，
还封装了一组API给外部调用：调用者可以自己定义自己的quark, 并且可以给object绑定/提取自己关系的数据：
gpointer g_object_get_qdata (GObject *object, GQuark quark); void g_object_set_qdata (GObject *object, GQuark quark, gpointer data); void g_object_set_qdata_full (GObject *object, GQuark quark, gpointer data, GDestroyNotify destroy); gpointer g_object_steal_qdata (GObject *object, GQuark quark); gpointer g_object_get_data (GObject *object, const gchar *key); void g_object_set_data (GObject *object, const gchar *key, gpointer data); void g_object_set_data_full (GObject *object, const gchar *key, gpointer data, GDestroyNotify destroy); gpointer g_object_steal_data (GObject *object, const gchar *key);
这一组首先是定义一个quark,
然后用quark来标识data, 并且进行绑定/提取操作：
gpointer g_object_get_qdata (GObject *object,
GQuark quark);
void g_object_set_qdata (GObject *object,
GQuark quark,
gpointer data);
void g_object_set_qdata_full (GObject *object,
GQuark quark,
gpointer data,
GDestroyNotify destroy);
gpointer g_object_steal_qdata (GObject *object,
GQuark quark);
下面这一组，不仅仅是quark, 可以用字符串来标识。
gpointer g_object_get_data (GObject *object,
const gchar *key);
void g_object_set_data (GObject *object,
const gchar *key,
gpointer data);
void g_object_set_data_full (GObject *object,
const gchar *key,
gpointer data,
GDestroyNotify destroy);
gpointer g_object_steal_data (GObject *object,
const gchar *key);
用的地方很多，非常多~
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