1 /* GObject - GLib Type, Object, Parameter and Signal Library
2 * Copyright (C) 1997-1999, 2000-2001 Tim Janik and Red Hat, Inc.
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
14 * You should have received a copy of the GNU Lesser General
15 * Public License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
17 * Boston, MA 02111-1307, USA.
29 #include "gvaluecollector.h"
30 #include "gbsearcharray.h"
31 #include "gobjectalias.h"
35 * SECTION:generic_values
37 * @Short_description: A polymorphic type that can hold values of any
40 * @See_also: The fundamental types which all support #GValue
41 * operations and thus can be used as a type initializer for
42 * g_value_init() are defined by a separate interface. See the <link
43 * linkend="gobject-Standard-Parameter-and-Value-Types">Standard
44 * Values API</link> for details.
46 * @Title: Generic values
48 * The #GValue structure is basically a variable container that consists
49 * of a type identifier and a specific value of that type.
50 * The type identifier within a #GValue structure always determines the
51 * type of the associated value.
52 * To create a undefined #GValue structure, simply create a zero-filled
53 * #GValue structure. To initialize the #GValue, use the g_value_init()
54 * function. A #GValue cannot be used until it is initialized.
55 * The basic type operations (such as freeing and copying) are determined
56 * by the #GTypeValueTable associated with the type ID stored in the #GValue.
57 * Other #GValue operations (such as converting values between types) are
58 * provided by this interface.
62 /* --- typedefs & structures --- */
70 /* --- prototypes --- */
71 static gint transform_entries_cmp (gconstpointer bsearch_node1,
72 gconstpointer bsearch_node2);
75 /* --- variables --- */
76 static GBSearchArray *transform_array = NULL;
77 static GBSearchConfig transform_bconfig = {
78 sizeof (TransformEntry),
79 transform_entries_cmp,
84 /* --- functions --- */
88 transform_array = g_bsearch_array_create (&transform_bconfig);
91 static inline void /* keep this function in sync with gvaluecollector.h and gboxed.c */
92 value_meminit (GValue *value,
95 value->g_type = value_type;
96 memset (value->data, 0, sizeof (value->data));
101 * @value: A zero-filled (uninitialized) #GValue structure.
102 * @g_type: Type the #GValue should hold values of.
104 * Initializes @value with the default value of @type.
106 * Returns: the #GValue structure that has been passed in
109 g_value_init (GValue *value,
112 /* g_return_val_if_fail (G_TYPE_IS_VALUE (g_type), NULL); be more elaborate below */
113 g_return_val_if_fail (value != NULL, NULL);
114 /* g_return_val_if_fail (G_VALUE_TYPE (value) == 0, NULL); be more elaborate below */
116 if (G_TYPE_IS_VALUE (g_type) && G_VALUE_TYPE (value) == 0)
118 GTypeValueTable *value_table = g_type_value_table_peek (g_type);
121 value_meminit (value, g_type);
122 value_table->value_init (value);
124 else if (G_VALUE_TYPE (value))
125 g_warning ("%s: cannot initialize GValue with type `%s', the value has already been initialized as `%s'",
127 g_type_name (g_type),
128 g_type_name (G_VALUE_TYPE (value)));
129 else /* !G_TYPE_IS_VALUE (g_type) */
130 g_warning ("%s: cannot initialize GValue with type `%s', %s",
132 g_type_name (g_type),
133 g_type_value_table_peek (g_type) ?
134 "this type is abstract with regards to GValue use, use a more specific (derived) type" :
135 "this type has no GTypeValueTable implementation");
141 * @src_value: An initialized #GValue structure.
142 * @dest_value: An initialized #GValue structure of the same type as @src_value.
144 * Copies the value of @src_value into @dest_value.
147 g_value_copy (const GValue *src_value,
150 g_return_if_fail (G_IS_VALUE (src_value));
151 g_return_if_fail (G_IS_VALUE (dest_value));
152 g_return_if_fail (g_value_type_compatible (G_VALUE_TYPE (src_value), G_VALUE_TYPE (dest_value)));
154 if (src_value != dest_value)
156 GType dest_type = G_VALUE_TYPE (dest_value);
157 GTypeValueTable *value_table = g_type_value_table_peek (dest_type);
159 /* make sure dest_value's value is free()d */
160 if (value_table->value_free)
161 value_table->value_free (dest_value);
164 value_meminit (dest_value, dest_type);
165 value_table->value_copy (src_value, dest_value);
171 * @value: An initialized #GValue structure.
173 * Clears the current value in @value and resets it to the default value
174 * (as if the value had just been initialized).
176 * Returns: the #GValue structure that has been passed in
179 g_value_reset (GValue *value)
181 GTypeValueTable *value_table;
184 g_return_val_if_fail (G_IS_VALUE (value), NULL);
186 g_type = G_VALUE_TYPE (value);
187 value_table = g_type_value_table_peek (g_type);
189 /* make sure value's value is free()d */
190 if (value_table->value_free)
191 value_table->value_free (value);
194 value_meminit (value, g_type);
195 value_table->value_init (value);
202 * @value: An initialized #GValue structure.
204 * Clears the current value in @value and "unsets" the type,
205 * this releases all resources associated with this GValue.
206 * An unset value is the same as an uninitialized (zero-filled)
210 g_value_unset (GValue *value)
212 GTypeValueTable *value_table;
214 g_return_if_fail (G_IS_VALUE (value));
216 value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
218 if (value_table->value_free)
219 value_table->value_free (value);
220 memset (value, 0, sizeof (*value));
224 * g_value_fits_pointer:
225 * @value: An initialized #GValue structure.
227 * Determines if @value will fit inside the size of a pointer value.
228 * This is an internal function introduced mainly for C marshallers.
230 * Returns: %TRUE if @value will fit inside a pointer value.
233 g_value_fits_pointer (const GValue *value)
235 GTypeValueTable *value_table;
237 g_return_val_if_fail (G_IS_VALUE (value), FALSE);
239 value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
241 return value_table->value_peek_pointer != NULL;
245 * g_value_peek_pointer:
246 * @value: An initialized #GValue structure.
248 * Return the value contents as pointer. This function asserts that
249 * g_value_fits_pointer() returned %TRUE for the passed in value.
250 * This is an internal function introduced mainly for C marshallers.
252 * Returns: %TRUE if @value will fit inside a pointer value.
255 g_value_peek_pointer (const GValue *value)
257 GTypeValueTable *value_table;
259 g_return_val_if_fail (G_IS_VALUE (value), NULL);
261 value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
262 if (!value_table->value_peek_pointer)
264 g_return_val_if_fail (g_value_fits_pointer (value) == TRUE, NULL);
268 return value_table->value_peek_pointer (value);
272 * g_value_set_instance:
273 * @value: An initialized #GValue structure.
274 * @instance: the instance
276 * Sets @value from an instantiatable type via the
277 * value_table's collect_value() function.
280 g_value_set_instance (GValue *value,
284 GTypeValueTable *value_table;
288 g_return_if_fail (G_IS_VALUE (value));
291 g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
292 g_return_if_fail (g_value_type_compatible (G_TYPE_FROM_INSTANCE (instance), G_VALUE_TYPE (value)));
295 g_type = G_VALUE_TYPE (value);
296 value_table = g_type_value_table_peek (g_type);
298 g_return_if_fail (strcmp (value_table->collect_format, "p") == 0);
300 memset (&cvalue, 0, sizeof (cvalue));
301 cvalue.v_pointer = instance;
303 /* make sure value's value is free()d */
304 if (value_table->value_free)
305 value_table->value_free (value);
307 /* setup and collect */
308 value_meminit (value, g_type);
309 error_msg = value_table->collect_value (value, 1, &cvalue, 0);
312 g_warning ("%s: %s", G_STRLOC, error_msg);
315 /* we purposely leak the value here, it might not be
316 * in a sane state if an error condition occoured
318 value_meminit (value, g_type);
319 value_table->value_init (value);
323 static GValueTransform
324 transform_func_lookup (GType src_type,
327 TransformEntry entry;
329 entry.src_type = src_type;
332 entry.dest_type = dest_type;
337 e = g_bsearch_array_lookup (transform_array, &transform_bconfig, &entry);
340 /* need to check that there hasn't been a change in value handling */
341 if (g_type_value_table_peek (entry.dest_type) == g_type_value_table_peek (dest_type) &&
342 g_type_value_table_peek (entry.src_type) == g_type_value_table_peek (src_type))
345 entry.dest_type = g_type_parent (entry.dest_type);
347 while (entry.dest_type);
349 entry.src_type = g_type_parent (entry.src_type);
351 while (entry.src_type);
357 transform_entries_cmp (gconstpointer bsearch_node1,
358 gconstpointer bsearch_node2)
360 const TransformEntry *e1 = bsearch_node1;
361 const TransformEntry *e2 = bsearch_node2;
362 gint cmp = G_BSEARCH_ARRAY_CMP (e1->src_type, e2->src_type);
367 return G_BSEARCH_ARRAY_CMP (e1->dest_type, e2->dest_type);
371 * g_value_register_transform_func:
372 * @src_type: Source type.
373 * @dest_type: Target type.
374 * @transform_func: a function which transforms values of type @src_type
375 * into value of type @dest_type
377 * Registers a value transformation function for use in g_value_transform().
378 * A previously registered transformation function for @src_type and @dest_type
382 g_value_register_transform_func (GType src_type,
384 GValueTransform transform_func)
386 TransformEntry entry;
388 /* these checks won't pass for dynamic types.
389 * g_return_if_fail (G_TYPE_HAS_VALUE_TABLE (src_type));
390 * g_return_if_fail (G_TYPE_HAS_VALUE_TABLE (dest_type));
392 g_return_if_fail (transform_func != NULL);
394 entry.src_type = src_type;
395 entry.dest_type = dest_type;
397 #if 0 /* let transform function replacement be a valid operation */
398 if (g_bsearch_array_lookup (transform_array, &transform_bconfig, &entry))
399 g_warning ("reregistering value transformation function (%p) for `%s' to `%s'",
401 g_type_name (src_type),
402 g_type_name (dest_type));
405 entry.func = transform_func;
406 transform_array = g_bsearch_array_replace (transform_array, &transform_bconfig, &entry);
410 * g_value_type_transformable:
411 * @src_type: Source type.
412 * @dest_type: Target type.
414 * Check whether g_value_transform() is able to transform values
415 * of type @src_type into values of type @dest_type.
417 * Returns: %TRUE if the transformation is possible, %FALSE otherwise.
420 g_value_type_transformable (GType src_type,
423 g_return_val_if_fail (G_TYPE_IS_VALUE (src_type), FALSE);
424 g_return_val_if_fail (G_TYPE_IS_VALUE (dest_type), FALSE);
426 return (g_value_type_compatible (src_type, dest_type) ||
427 transform_func_lookup (src_type, dest_type) != NULL);
431 * g_value_type_compatible:
432 * @src_type: source type to be copied.
433 * @dest_type: destination type for copying.
435 * Returns whether a #GValue of type @src_type can be copied into
436 * a #GValue of type @dest_type.
438 * Returns: %TRUE if g_value_copy() is possible with @src_type and @dest_type.
441 g_value_type_compatible (GType src_type,
444 g_return_val_if_fail (G_TYPE_IS_VALUE (src_type), FALSE);
445 g_return_val_if_fail (G_TYPE_IS_VALUE (dest_type), FALSE);
447 return (g_type_is_a (src_type, dest_type) &&
448 g_type_value_table_peek (dest_type) == g_type_value_table_peek (src_type));
453 * @src_value: Source value.
454 * @dest_value: Target value.
456 * Tries to cast the contents of @src_value into a type appropriate
457 * to store in @dest_value, e.g. to transform a %G_TYPE_INT value
458 * into a %G_TYPE_FLOAT value. Performing transformations between
459 * value types might incur precision lossage. Especially
460 * transformations into strings might reveal seemingly arbitrary
461 * results and shouldn't be relied upon for production code (such
462 * as rcfile value or object property serialization).
464 * Returns: Whether a transformation rule was found and could be applied.
465 * Upon failing transformations, @dest_value is left untouched.
468 g_value_transform (const GValue *src_value,
473 g_return_val_if_fail (G_IS_VALUE (src_value), FALSE);
474 g_return_val_if_fail (G_IS_VALUE (dest_value), FALSE);
476 dest_type = G_VALUE_TYPE (dest_value);
477 if (g_value_type_compatible (G_VALUE_TYPE (src_value), dest_type))
479 g_value_copy (src_value, dest_value);
485 GValueTransform transform = transform_func_lookup (G_VALUE_TYPE (src_value), dest_type);
489 g_value_unset (dest_value);
491 /* setup and transform */
492 value_meminit (dest_value, dest_type);
493 transform (src_value, dest_value);
501 #define __G_VALUE_C__
502 #include "gobjectaliasdef.c"