Keyed Data Lists

Keyed Data Lists — lists of data elements which are accessible by a string or GQuark identifier

Synopsis

#include <glib.h>

                    GData;
void                g_datalist_init                     (GData **datalist);

#define             g_datalist_id_set_data              (dl,
                                                         q,
                                                         d)
void                g_datalist_id_set_data_full         (GData **datalist,
                                                         GQuark key_id,
                                                         gpointer data,
                                                         GDestroyNotify destroy_func);
gpointer            g_datalist_id_get_data              (GData **datalist,
                                                         GQuark key_id);
#define             g_datalist_id_remove_data           (dl,
                                                         q)
gpointer            g_datalist_id_remove_no_notify      (GData **datalist,
                                                         GQuark key_id);
gpointer            (*GDuplicateFunc)                   (gpointer data,
                                                         gpointer user_data);
gpointer            g_datalist_id_dup_data              (GData **datalist,
                                                         GQuark key_id,
                                                         GDuplicateFunc dup_func,
                                                         gpointer user_data);
gboolean            g_datalist_id_replace_data          (GData **datalist,
                                                         GQuark key_id,
                                                         gpointer oldval,
                                                         gpointer newval,
                                                         GDestroyNotify destroy,
                                                         GDestroyNotify *old_destroy);

#define             g_datalist_set_data                 (dl,
                                                         k,
                                                         d)
#define             g_datalist_set_data_full            (dl,
                                                         k,
                                                         d,
                                                         f)
gpointer            g_datalist_get_data                 (GData **datalist,
                                                         const gchar *key);
#define             g_datalist_remove_data              (dl,
                                                         k)
#define             g_datalist_remove_no_notify         (dl,
                                                         k)

void                g_datalist_foreach                  (GData **datalist,
                                                         GDataForeachFunc func,
                                                         gpointer user_data);
void                g_datalist_clear                    (GData **datalist);
void                g_datalist_set_flags                (GData **datalist,
                                                         guint flags);
void                g_datalist_unset_flags              (GData **datalist,
                                                         guint flags);
guint               g_datalist_get_flags                (GData **datalist);
#define             G_DATALIST_FLAGS_MASK

Description

Keyed data lists provide lists of arbitrary data elements which can be accessed either with a string or with a GQuark corresponding to the string.

The GQuark methods are quicker, since the strings have to be converted to GQuarks anyway.

Data lists are used for associating arbitrary data with GObjects, using g_object_set_data() and related functions.

To create a datalist, use g_datalist_init().

To add data elements to a datalist use g_datalist_id_set_data(), g_datalist_id_set_data_full(), g_datalist_set_data() and g_datalist_set_data_full().

To get data elements from a datalist use g_datalist_id_get_data() and g_datalist_get_data().

To iterate over all data elements in a datalist use g_datalist_foreach() (not thread-safe).

To remove data elements from a datalist use g_datalist_id_remove_data() and g_datalist_remove_data().

To remove all data elements from a datalist, use g_datalist_clear().

Details

GData

typedef struct _GData GData;

The GData struct is an opaque data structure to represent a Keyed Data List. It should only be accessed via the following functions.

g_datalist_init ()

void                g_datalist_init                     (GData **datalist);

Resets the datalist to NULL. It does not free any memory or call any destroy functions.

datalist :

 a pointer to a pointer to a datalist.

g_datalist_id_set_data()

#define             g_datalist_id_set_data(dl, q, d)

Sets the data corresponding to the given GQuark id. Any previous data with the same key is removed, and its destroy function is called.

dl :

 a datalist.

q :

 the GQuark to identify the data element.

d :

 the data element, or NULL to remove any previous element corresponding to q. [allow-none]

g_datalist_id_set_data_full ()

void                g_datalist_id_set_data_full         (GData **datalist,
                                                         GQuark key_id,
                                                         gpointer data,
                                                         GDestroyNotify destroy_func);

Sets the data corresponding to the given GQuark id, and the function to be called when the element is removed from the datalist. Any previous data with the same key is removed, and its destroy function is called.

datalist :

 a datalist.

key_id :

 the GQuark to identify the data element.

data :

 the data element or NULL to remove any previous element corresponding to key_id. [allow-none]

destroy_func :

 the function to call when the data element is removed. This function will be called with the data element and can be used to free any memory allocated for it. If data is NULL, then destroy_func must also be NULL.

g_datalist_id_get_data ()

gpointer            g_datalist_id_get_data              (GData **datalist,
                                                         GQuark key_id);

Retrieves the data element corresponding to key_id.

datalist :

 a datalist.

key_id :

 the GQuark identifying a data element.

Returns :

 the data element, or NULL if it is not found.

g_datalist_id_remove_data()

#define             g_datalist_id_remove_data(dl, q)

Removes an element, using its GQuark identifier.

dl :

 a datalist.

q :

 the GQuark identifying the data element.

g_datalist_id_remove_no_notify ()

gpointer            g_datalist_id_remove_no_notify      (GData **datalist,
                                                         GQuark key_id);

Removes an element, without calling its destroy notification function.

datalist :

 a datalist.

key_id :

 the GQuark identifying a data element.

Returns :

 the data previously stored at key_id, or NULL if none.

GDuplicateFunc ()

gpointer            (*GDuplicateFunc)                   (gpointer data,
                                                         gpointer user_data);

The type of functions that are used to 'duplicate' an object. What this means depends on the context, it could just be incrementing the reference count, if data is a ref-counted object.

data :

 the data to duplicate

user_data :

 user data that was specified in g_datalist_id_dup_data()

Returns :

 a duplicate of data

g_datalist_id_dup_data ()

gpointer            g_datalist_id_dup_data              (GData **datalist,
                                                         GQuark key_id,
                                                         GDuplicateFunc dup_func,
                                                         gpointer user_data);

This is a variant of g_datalist_id_get_data() which returns a 'duplicate' of the value. dup_func defines the meaning of 'duplicate' in this context, it could e.g. take a reference on a ref-counted object.

If the key_id is not set in the datalist then dup_func will be called with a NULL argument.

Note that dup_func is called while the datalist is locked, so it is not allowed to read or modify the datalist.

This function can be useful to avoid races when multiple threads are using the same datalist and the same key.

datalist :

 location of a datalist

key_id :

 the GQuark identifying a data element

dup_func :

 function to duplicate the old value. [allow-none]

user_data :

 passed as user_data to dup_func. [allow-none]

Returns :

 the result of calling dup_func on the value associated with key_id in datalist, or NULL if not set. If dup_func is NULL, the value is returned unmodified.

Since 2.34

g_datalist_id_replace_data ()

gboolean            g_datalist_id_replace_data          (GData **datalist,
                                                         GQuark key_id,
                                                         gpointer oldval,
                                                         gpointer newval,
                                                         GDestroyNotify destroy,
                                                         GDestroyNotify *old_destroy);

Compares the member that is associated with key_id in datalist to oldval, and if they are the same, replace oldval with newval.

This is like a typical atomic compare-and-exchange operation, for a member of datalist.

If the previous value was replaced then ownership of the old value (oldval) is passed to the caller, including the registred destroy notify for it (passed out in old_destroy). Its up to the caller to free this as he wishes, which may or may not include using old_destroy as sometimes replacement should not destroy the object in the normal way.

Return: TRUE if the existing value for key_id was replaced by newval, FALSE otherwise.

datalist :

 location of a datalist

key_id :

 the GQuark identifying a data element

oldval :

 the old value to compare against. [allow-none]

newval :

 the new value to replace it with. [allow-none]

destroy :

 destroy notify for the new value. [allow-none]

old_destroy :

 destroy notify for the existing value. [allow-none]

Since 2.34

g_datalist_set_data()

#define             g_datalist_set_data(dl, k, d)

Sets the data element corresponding to the given string identifier.

dl :

 a datalist.

k :

 the string to identify the data element.

d :

 the data element, or NULL to remove any previous element corresponding to k. [allow-none]

g_datalist_set_data_full()

#define             g_datalist_set_data_full(dl, k, d, f)

Sets the data element corresponding to the given string identifier, and the function to be called when the data element is removed.

dl :

 a datalist.

k :

 the string to identify the data element.

d :

 the data element, or NULL to remove any previous element corresponding to k. [allow-none]

f :

 the function to call when the data element is removed. This function will be called with the data element and can be used to free any memory allocated for it. If d is NULL, then f must also be NULL.

g_datalist_get_data ()

gpointer            g_datalist_get_data                 (GData **datalist,
                                                         const gchar *key);

Gets a data element, using its string identifier. This is slower than g_datalist_id_get_data() because it compares strings.

datalist :

 a datalist.

key :

 the string identifying a data element.

Returns :

 the data element, or NULL if it is not found.

g_datalist_remove_data()

#define             g_datalist_remove_data(dl, k)

Removes an element using its string identifier. The data element's destroy function is called if it has been set.

dl :

 a datalist.

k :

 the string identifying the data element.

g_datalist_remove_no_notify()

#define             g_datalist_remove_no_notify(dl, k)

Removes an element, without calling its destroy notifier.

dl :

 a datalist.

k :

 the string identifying the data element.

g_datalist_foreach ()

void                g_datalist_foreach                  (GData **datalist,
                                                         GDataForeachFunc func,
                                                         gpointer user_data);

Calls the given function for each data element of the datalist. The function is called with each data element's GQuark id and data, together with the given user_data parameter. Note that this function is NOT thread-safe. So unless datalist can be protected from any modifications during invocation of this function, it should not be called.

datalist :

 a datalist.

func :

 the function to call for each data element.

user_data :

 user data to pass to the function.

g_datalist_clear ()

void                g_datalist_clear                    (GData **datalist);

Frees all the data elements of the datalist. The data elements' destroy functions are called if they have been set.

datalist :

 a datalist.

g_datalist_set_flags ()

void                g_datalist_set_flags                (GData **datalist,
                                                         guint flags);

Turns on flag values for a data list. This function is used to keep a small number of boolean flags in an object with a data list without using any additional space. It is not generally useful except in circumstances where space is very tight. (It is used in the base GObject type, for example.)

datalist :

 pointer to the location that holds a list

flags :

 the flags to turn on. The values of the flags are restricted by G_DATALIST_FLAGS_MASK (currently 3; giving two possible boolean flags). A value for flags that doesn't fit within the mask is an error.

Since 2.8

g_datalist_unset_flags ()

void                g_datalist_unset_flags              (GData **datalist,
                                                         guint flags);

Turns off flag values for a data list. See g_datalist_unset_flags()

datalist :

 pointer to the location that holds a list

flags :

 the flags to turn off. The values of the flags are restricted by G_DATALIST_FLAGS_MASK (currently 3: giving two possible boolean flags). A value for flags that doesn't fit within the mask is an error.

Since 2.8

g_datalist_get_flags ()

guint               g_datalist_get_flags                (GData **datalist);

Gets flags values packed in together with the datalist. See g_datalist_set_flags().

datalist :

 pointer to the location that holds a list

Returns :

 the flags of the datalist

Since 2.8

G_DATALIST_FLAGS_MASK

#define G_DATALIST_FLAGS_MASK 0x3

A bitmask that restricts the possible flags passed to g_datalist_set_flags(). Passing a flags value where flags & ~G_DATALIST_FLAGS_MASK != 0 is an error.

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