Entity
[Class: Getting and setting entity values.]

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Detailed Description

This file defines an API that adds types to the GUID's. GUID's with types can be used to identify and reference typed entities.

The idea here is that a GUID can be used to uniquely identify some thing. By adding a type, one can then talk about the type of thing identified. By adding a collection, one can then work with a handle to a collection of things of a given type, each uniquely identified by a given ID. QOF Entities can be used independently of any other part of the system. In particular, Entities can be useful even if one is not using the Query ond Object parts of the QOF system.

Identifiers are globally-unique and permanent, i.e., once an entity has been assigned an identifier, it retains that same identifier for its lifetime. Identifiers can be encoded as hex strings.

GUID Identifiers are 'typed' with strings. The native ids used by QOF are defined below.

1. An id with type QOF_ID_NONE does not refer to any entity.
2. An id with type QOF_ID_NULL does not refer to any entity, and will never refer to any entity. =# An identifier with any other type may refer to an actual entity, but that is not guaranteed as that entity does not have to exist within the current book. (See PARTIAL_QOFBOOK). Also, creating a new entity from a data source involves creating a temporary GUID and then setting the value from the data source. If an id does refer to an entity, the type of the entity will match the type of the identifier.

If you have a type name, and you want to have a way of finding a collection that is associated with that type, then you must use Books.

Entities can refer to other entities as well as to the basic QOF types, using the qofclass parameters.

Files
file	qofid.h
	QOF entity type identification system.
Data Structures
struct	QofEntity_s
Collections of Entities
typedef void(*	QofEntityForeachCB )(QofEntity *, gpointer user_data)
QofCollection *	qof_collection_new (QofIdType type)
guint	qof_collection_count (QofCollection *col)
void	qof_collection_destroy (QofCollection *col)
QofIdType	qof_collection_get_type (QofCollection *)
QofEntity *	qof_collection_lookup_entity (QofCollection *, const GUID *)
void	qof_collection_foreach (QofCollection *, QofEntityForeachCB, gpointer user_data)
gpointer	qof_collection_get_data (QofCollection *col)
void	qof_collection_set_data (QofCollection *col, gpointer user_data)
gboolean	qof_collection_is_dirty (QofCollection *col)
QOF Entity Initialization & Shutdown
void	qof_entity_init (QofEntity *, QofIdType, QofCollection *)
void	qof_entity_release (QofEntity *)
QOF_TYPE_COLLECT: Linking one entity to many of one type
Note: These are NOT the same as the main collections in the book. QOF_TYPE_COLLECT is a secondary collection, used to select entities of one object type as references of another entity. See also: QOF_TYPE_CHOICE.
gboolean	qof_collection_add_entity (QofCollection *coll, QofEntity *ent)
	Add an entity to a QOF_TYPE_COLLECT.
gboolean	qof_collection_merge (QofCollection *target, QofCollection *merge)
	Merge two QOF_TYPE_COLLECT of the same type.
gint	qof_collection_compare (QofCollection *target, QofCollection *merge)
	Compare two secondary collections.
QofCollection *	qof_collection_from_glist (QofIdType type, GList *glist)
	Create a secondary collection from a GList.
Defines
#define	QOF_ID_NONE   NULL
#define	QOF_ID_NULL   "null"
#define	QOF_ID_BOOK   "Book"
#define	QOF_ID_SESSION   "Session"
#define	QOF_ENTITY(object)   ((QofEntity *)(object))
#define	QSTRCMP(da, db)
#define	QOF_CHECK_TYPE(obj, type)
#define	QOF_CHECK_CAST(obj, e_type, c_type)
Typedefs
typedef const gchar *	QofIdType
typedef const gchar *	QofIdTypeConst
typedef const gchar *	QofLogModule
typedef struct QofEntity_s	QofEntity
typedef struct QofCollection_s	QofCollection
Functions
const GUID *	qof_entity_get_guid (QofEntity *)

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Define Documentation

#define QOF_CHECK_CAST	(	obj,
		e_type,
		c_type		)

Value:

(                   \
  QOF_CHECK_TYPE((obj),(e_type)) ?                            \
  (c_type *) (obj) :                                          \
  (c_type *) ({                                               \
     g_log (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,               \
       "Error: Bad QofEntity at %s:%d", __FILE__, __LINE__);  \
     (obj);                                                   \
  }))

cast object to the indicated type, print error message if its bad

Definition at line 119 of file qofid.h.

#define QOF_CHECK_TYPE	(	obj,
		type		)

Value:

(((obj) != NULL) && \
  (0 == QSTRCMP((type),(((QofEntity *)(obj))->e_type))))

return TRUE if object is of the given type

Definition at line 114 of file qofid.h.

#define QOF_ENTITY

(

object

)

((QofEntity *)(object))

simple,cheesy cast but holds water for now

Definition at line 94 of file qofid.h.

#define QSTRCMP	(	da,
		db		)

Value:

({                \
  gint val = 0;                          \
  if ((da) && (db)) {                    \
    if ((da) != (db)) {                  \
      val = strcmp ((da), (db));         \
    }                                    \
  } else                                 \
  if ((!(da)) && (db)) {                 \
    val = -1;                            \
  } else                                 \
  if ((da) && (!(db))) {                 \
    val = 1;                             \
  }                                      \
  val; /* block assumes value of last statment */  \
})

Inline string comparision; compiler will optimize away most of this

Definition at line 97 of file qofid.h.

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Typedef Documentation

typedef struct QofCollection_s QofCollection

QofCollection declaration

Parameters:

	e_type	QofIdType
	is_dirty	gboolean
	hash_of_entities	GHashTable
	data	gpointer, place where object class can hang arbitrary data

Definition at line 138 of file qofid.h.

typedef struct QofEntity_s QofEntity

QofEntity declaration

Definition at line 129 of file qofid.h.

typedef void(* QofEntityForeachCB)(QofEntity *, gpointer user_data)

Callback type for qof_entity_foreach

Definition at line 187 of file qofid.h.

typedef const gchar* QofIdType

QofIdType declaration

Definition at line 81 of file qofid.h.

typedef const gchar* QofIdTypeConst

QofIdTypeConst declaration

Definition at line 83 of file qofid.h.

typedef const gchar* QofLogModule

QofLogModule declaration

Definition at line 85 of file qofid.h.

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Function Documentation

gboolean qof_collection_add_entity	(	QofCollection *	coll,
		QofEntity *	ent
	)

Add an entity to a QOF_TYPE_COLLECT.

Note:

These are NOT the same as the main collections in the book.

Entities can be freely added and merged across these secondary collections, they will not be removed from the original collection as they would by using qof_entity_insert_entity or qof_entity_remove_entity.

Definition at line 211 of file qofid.c.

{
    QofEntity *e;

    e = NULL;
    if (!coll || !ent)
    {
        return FALSE;
    }
    if (guid_equal (&ent->guid, guid_null ()))
    {
        return FALSE;
    }
    g_return_val_if_fail (coll->e_type == ent->e_type, FALSE);
    e = qof_collection_lookup_entity (coll, &ent->guid);
    if (e != NULL)
    {
        return FALSE;
    }
    g_hash_table_insert (coll->hash_of_entities, &ent->guid, ent);
    qof_collection_mark_dirty (coll);
    return TRUE;
}

gint qof_collection_compare	(	QofCollection *	target,
		QofCollection *	merge
	)

Compare two secondary collections.

Performs a deep comparision of the collections. Each QofEntity in each collection is looked up in the other collection, via the GUID.

Returns:

0 if the collections are identical or both are NULL otherwise -1 if target is NULL or either collection contains an entity with an invalid GUID or if the types of the two collections do not match, or +1 if merge is NULL or if any entity exists in one collection but not in the other.

Definition at line 293 of file qofid.c.

{
    gint value;

    value = 0;
    if (!target && !merge)
        return 0;
    if (target == merge)
        return 0;
    if (!target && merge)
        return -1;
    if (target && !merge)
        return 1;
    if (target->e_type != merge->e_type)
        return -1;
    qof_collection_set_data (target, &value);
    qof_collection_foreach (merge, collection_compare_cb, target);
    value = *(gint *) qof_collection_get_data (target);
    if (value == 0)
    {
        qof_collection_set_data (merge, &value);
        qof_collection_foreach (target, collection_compare_cb, merge);
        value = *(gint *) qof_collection_get_data (merge);
    }
    return value;
}

guint qof_collection_count

(

QofCollection *

col

)

return the number of entities in the collection.

Definition at line 351 of file qofid.c.

{
    guint c;

    c = g_hash_table_size (col->hash_of_entities);
    return c;
}

void qof_collection_destroy

(

QofCollection *

col

)

destroy the collection

XXX there should be a destroy notifier for this

Definition at line 161 of file qofid.c.

{
    CACHE_REMOVE (col->e_type);
    g_hash_table_destroy (col->hash_of_entities);
    col->e_type = NULL;
    col->hash_of_entities = NULL;
    col->data = NULL; 
    g_free (col);
}

void qof_collection_foreach	(	QofCollection *	,
		QofEntityForeachCB	,
		gpointer	user_data
	)

Call the callback for each entity in the collection.

Definition at line 421 of file qofid.c.

{
    struct _iterate qiter;

    g_return_if_fail (col);
    g_return_if_fail (cb_func);

    qiter.fcn = cb_func;
    qiter.data = user_data;

    g_hash_table_foreach (col->hash_of_entities, foreach_cb, &qiter);
}

QofCollection* qof_collection_from_glist	(	QofIdType	type,
		GList *	glist
	)

Create a secondary collection from a GList.

Parameters:

	type	The QofIdType of the QofCollection and of all entities in the GList.
	glist	GList of entities of the same QofIdType.

Returns:

NULL if any of the entities fail to match the QofCollection type, else a pointer to the collection on success.

Definition at line 332 of file qofid.c.

{
    QofCollection *coll;
    QofEntity *ent;
    GList *list;

    coll = qof_collection_new (type);
    for (list = glist; list != NULL; list = list->next)
    {
        ent = (QofEntity *) list->data;
        if (FALSE == qof_collection_add_entity (coll, ent))
        {
            return NULL;
        }
    }
    return coll;
}

gpointer qof_collection_get_data

(

QofCollection *

col

)

Store arbitrary object-defined data

XXX We need to add a callback for when the collection is being destroyed, so that the user has a chance to clean up anything that was put in the 'data' member here.

Definition at line 388 of file qofid.c.

{
    return col ? col->data : NULL;
}

QofIdType qof_collection_get_type

(

QofCollection *

)

return the type that the collection stores

Definition at line 175 of file qofid.c.

{
    return col->e_type;
}

gboolean qof_collection_is_dirty

(

QofCollection *

col

)

Return value of 'dirty' flag on collection

Definition at line 362 of file qofid.c.

{
    return col ? col->is_dirty : FALSE;
}

QofEntity* qof_collection_lookup_entity	(	QofCollection *	,
		const GUID *
	)

Find the entity going only from its guid

Definition at line 321 of file qofid.c.

{
    QofEntity *ent;
    g_return_val_if_fail (col, NULL);
    if (guid == NULL)
        return NULL;
    ent = g_hash_table_lookup (col->hash_of_entities, guid);
    return ent;
}

gboolean qof_collection_merge	(	QofCollection *	target,
		QofCollection *	merge
	)

Merge two QOF_TYPE_COLLECT of the same type.

Note:

NOT the same as the main collections in the book.

QOF_TYPE_COLLECT uses a secondary collection, independent of those in the book. Entities will not be removed from the original collection as when using qof_entity_insert_entity or qof_entity_remove_entity.

Definition at line 245 of file qofid.c.

{
    if (!target || !merge)
    {
        return FALSE;
    }
    g_return_val_if_fail (target->e_type == merge->e_type, FALSE);
    qof_collection_foreach (merge, collection_merge_cb, target);
    return TRUE;
}

QofCollection* qof_collection_new

(

QofIdType

type

)

create a new collection of entities of type

Definition at line 150 of file qofid.c.

{
    QofCollection *col;
    col = g_new0 (QofCollection, 1);
    col->e_type = CACHE_INSERT (type);
    col->hash_of_entities = g_hash_table_new (id_hash, id_compare);
    col->data = NULL;
    return col;
}

void qof_collection_set_data	(	QofCollection *	col,
		gpointer	user_data
	)

Retrieve arbitrary object-defined data

Definition at line 394 of file qofid.c.

{
    if (col)
    {
        col->data = user_data;
    }
}

const GUID* qof_entity_get_guid

(

QofEntity *

)

Return the GUID of this entity

Definition at line 105 of file qofid.c.

{
    if (!ent)
        return guid_null ();
    return &ent->guid;
}

void qof_entity_init	(	QofEntity *	,
		QofIdType	,
		QofCollection *
	)

Initialise the memory associated with an entity

Definition at line 49 of file qofid.c.

{
    g_return_if_fail (NULL != tab);

    /* XXX We passed redundant info to this routine ... but I think that's
     * OK, it might eliminate programming errors. */
    if (safe_strcmp (tab->e_type, type))
    {
        PERR ("attempt to insert \"%s\" into \"%s\"", type, tab->e_type);
        return;
    }
    ent->e_type = CACHE_INSERT (type);

    do
    {
        guid_new (&ent->guid);

        if (NULL == qof_collection_lookup_entity (tab, &ent->guid))
            break;

        PWARN ("duplicate id created, trying again");
    }
    while (1);

    ent->collection = tab;

    qof_collection_insert_entity (tab, ent);
}

void qof_entity_release

(

QofEntity *

)

Release the data associated with this entity. Dont actually free the memory associated with the instance.

Definition at line 79 of file qofid.c.

{
    if (!ent->collection)
        return;
    qof_collection_remove_entity (ent);
    CACHE_REMOVE (ent->e_type);
    ent->e_type = NULL;
}

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