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
36 * @short_description: A polymorphic type that can hold values of any
38 * @see_also: The fundamental types which all support #GValue
39 * operations and thus can be used as a type initializer for
40 * g_value_init() are defined by a separate interface. See the <link
41 * linkend="gobject-Standard-Parameter-and-Value-Types">Standard
42 * Values API</link> for details.
43 * @title: Generic values
45 * The #GValue structure is basically a variable container that consists
46 * of a type identifier and a specific value of that type.
47 * The type identifier within a #GValue structure always determines the
48 * type of the associated value.
49 * To create a undefined #GValue structure, simply create a zero-filled
50 * #GValue structure. To initialize the #GValue, use the g_value_init()
51 * function. A #GValue cannot be used until it is initialized.
52 * The basic type operations (such as freeing and copying) are determined
53 * by the #GTypeValueTable associated with the type ID stored in the #GValue.
54 * Other #GValue operations (such as converting values between types) are
55 * provided by this interface.
59 /* --- typedefs & structures --- */
67 /* --- prototypes --- */
68 static gint transform_entries_cmp (gconstpointer bsearch_node1,
69 gconstpointer bsearch_node2);
72 /* --- variables --- */
73 static GBSearchArray *transform_array = NULL;
74 static GBSearchConfig transform_bconfig = {
75 sizeof (TransformEntry),
76 transform_entries_cmp,
81 /* --- functions --- */
85 transform_array = g_bsearch_array_create (&transform_bconfig);
88 static inline void /* keep this function in sync with gvaluecollector.h and gboxed.c */
89 value_meminit (GValue *value,
92 value->g_type = value_type;
93 memset (value->data, 0, sizeof (value->data));
98 * @value: A zero-filled (uninitialized) #GValue structure.
99 * @g_type: Type the #GValue should hold values of.
101 * Initializes @value with the default value of @type.
103 * Returns: the #GValue structure that has been passed in
106 g_value_init (GValue *value,
109 /* g_return_val_if_fail (G_TYPE_IS_VALUE (g_type), NULL); be more elaborate below */
110 g_return_val_if_fail (value != NULL, NULL);
111 /* g_return_val_if_fail (G_VALUE_TYPE (value) == 0, NULL); be more elaborate below */
113 if (G_TYPE_IS_VALUE (g_type) && G_VALUE_TYPE (value) == 0)
115 GTypeValueTable *value_table = g_type_value_table_peek (g_type);
118 value_meminit (value, g_type);
119 value_table->value_init (value);
121 else if (G_VALUE_TYPE (value))
122 g_warning ("%s: cannot initialize GValue with type `%s', the value has already been initialized as `%s'",
124 g_type_name (g_type),
125 g_type_name (G_VALUE_TYPE (value)));
126 else /* !G_TYPE_IS_VALUE (g_type) */
127 g_warning ("%s: cannot initialize GValue with type `%s', %s",
129 g_type_name (g_type),
130 g_type_value_table_peek (g_type) ?
131 "this type is abstract with regards to GValue use, use a more specific (derived) type" :
132 "this type has no GTypeValueTable implementation");
138 * @src_value: An initialized #GValue structure.
139 * @dest_value: An initialized #GValue structure of the same type as @src_value.
141 * Copies the value of @src_value into @dest_value.
144 g_value_copy (const GValue *src_value,
147 g_return_if_fail (G_IS_VALUE (src_value));
148 g_return_if_fail (G_IS_VALUE (dest_value));
149 g_return_if_fail (g_value_type_compatible (G_VALUE_TYPE (src_value), G_VALUE_TYPE (dest_value)));
151 if (src_value != dest_value)
153 GType dest_type = G_VALUE_TYPE (dest_value);
154 GTypeValueTable *value_table = g_type_value_table_peek (dest_type);
156 /* make sure dest_value's value is free()d */
157 if (value_table->value_free)
158 value_table->value_free (dest_value);
161 value_meminit (dest_value, dest_type);
162 value_table->value_copy (src_value, dest_value);
168 * @value: An initialized #GValue structure.
170 * Clears the current value in @value and resets it to the default value
171 * (as if the value had just been initialized).
173 * Returns: the #GValue structure that has been passed in
176 g_value_reset (GValue *value)
178 GTypeValueTable *value_table;
181 g_return_val_if_fail (G_IS_VALUE (value), NULL);
183 g_type = G_VALUE_TYPE (value);
184 value_table = g_type_value_table_peek (g_type);
186 /* make sure value's value is free()d */
187 if (value_table->value_free)
188 value_table->value_free (value);
191 value_meminit (value, g_type);
192 value_table->value_init (value);
199 * @value: An initialized #GValue structure.
201 * Clears the current value in @value and "unsets" the type,
202 * this releases all resources associated with this GValue.
203 * An unset value is the same as an uninitialized (zero-filled)
207 g_value_unset (GValue *value)
209 GTypeValueTable *value_table;
211 g_return_if_fail (G_IS_VALUE (value));
213 value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
215 if (value_table->value_free)
216 value_table->value_free (value);
217 memset (value, 0, sizeof (*value));
221 * g_value_fits_pointer:
222 * @value: An initialized #GValue structure.
224 * Determines if @value will fit inside the size of a pointer value.
225 * This is an internal function introduced mainly for C marshallers.
227 * Returns: %TRUE if @value will fit inside a pointer value.
230 g_value_fits_pointer (const GValue *value)
232 GTypeValueTable *value_table;
234 g_return_val_if_fail (G_IS_VALUE (value), FALSE);
236 value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
238 return value_table->value_peek_pointer != NULL;
242 * g_value_peek_pointer:
243 * @value: An initialized #GValue structure.
245 * Return the value contents as pointer. This function asserts that
246 * g_value_fits_pointer() returned %TRUE for the passed in value.
247 * This is an internal function introduced mainly for C marshallers.
249 * Returns: %TRUE if @value will fit inside a pointer value.
252 g_value_peek_pointer (const GValue *value)
254 GTypeValueTable *value_table;
256 g_return_val_if_fail (G_IS_VALUE (value), NULL);
258 value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
259 if (!value_table->value_peek_pointer)
261 g_return_val_if_fail (g_value_fits_pointer (value) == TRUE, NULL);
265 return value_table->value_peek_pointer (value);
269 * g_value_set_instance:
270 * @value: An initialized #GValue structure.
271 * @instance: the instance
273 * Sets @value from an instantiatable type via the
274 * value_table's collect_value() function.
277 g_value_set_instance (GValue *value,
281 GTypeValueTable *value_table;
285 g_return_if_fail (G_IS_VALUE (value));
288 g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
289 g_return_if_fail (g_value_type_compatible (G_TYPE_FROM_INSTANCE (instance), G_VALUE_TYPE (value)));
292 g_type = G_VALUE_TYPE (value);
293 value_table = g_type_value_table_peek (g_type);
295 g_return_if_fail (strcmp (value_table->collect_format, "p") == 0);
297 memset (&cvalue, 0, sizeof (cvalue));
298 cvalue.v_pointer = instance;
300 /* make sure value's value is free()d */
301 if (value_table->value_free)
302 value_table->value_free (value);
304 /* setup and collect */
305 value_meminit (value, g_type);
306 error_msg = value_table->collect_value (value, 1, &cvalue, 0);
309 g_warning ("%s: %s", G_STRLOC, error_msg);
312 /* we purposely leak the value here, it might not be
313 * in a sane state if an error condition occoured
315 value_meminit (value, g_type);
316 value_table->value_init (value);
320 static GValueTransform
321 transform_func_lookup (GType src_type,
324 TransformEntry entry;
326 entry.src_type = src_type;
329 entry.dest_type = dest_type;
334 e = g_bsearch_array_lookup (transform_array, &transform_bconfig, &entry);
337 /* need to check that there hasn't been a change in value handling */
338 if (g_type_value_table_peek (entry.dest_type) == g_type_value_table_peek (dest_type) &&
339 g_type_value_table_peek (entry.src_type) == g_type_value_table_peek (src_type))
342 entry.dest_type = g_type_parent (entry.dest_type);
344 while (entry.dest_type);
346 entry.src_type = g_type_parent (entry.src_type);
348 while (entry.src_type);
354 transform_entries_cmp (gconstpointer bsearch_node1,
355 gconstpointer bsearch_node2)
357 const TransformEntry *e1 = bsearch_node1;
358 const TransformEntry *e2 = bsearch_node2;
359 gint cmp = G_BSEARCH_ARRAY_CMP (e1->src_type, e2->src_type);
364 return G_BSEARCH_ARRAY_CMP (e1->dest_type, e2->dest_type);
368 * g_value_register_transform_func:
369 * @src_type: Source type.
370 * @dest_type: Target type.
371 * @transform_func: a function which transforms values of type @src_type
372 * into value of type @dest_type
374 * Registers a value transformation function for use in g_value_transform().
375 * A previously registered transformation function for @src_type and @dest_type
379 g_value_register_transform_func (GType src_type,
381 GValueTransform transform_func)
383 TransformEntry entry;
385 /* these checks won't pass for dynamic types.
386 * g_return_if_fail (G_TYPE_HAS_VALUE_TABLE (src_type));
387 * g_return_if_fail (G_TYPE_HAS_VALUE_TABLE (dest_type));
389 g_return_if_fail (transform_func != NULL);
391 entry.src_type = src_type;
392 entry.dest_type = dest_type;
394 #if 0 /* let transform function replacement be a valid operation */
395 if (g_bsearch_array_lookup (transform_array, &transform_bconfig, &entry))
396 g_warning ("reregistering value transformation function (%p) for `%s' to `%s'",
398 g_type_name (src_type),
399 g_type_name (dest_type));
402 entry.func = transform_func;
403 transform_array = g_bsearch_array_replace (transform_array, &transform_bconfig, &entry);
407 * g_value_type_transformable:
408 * @src_type: Source type.
409 * @dest_type: Target type.
411 * Check whether g_value_transform() is able to transform values
412 * of type @src_type into values of type @dest_type.
414 * Returns: %TRUE if the transformation is possible, %FALSE otherwise.
417 g_value_type_transformable (GType src_type,
420 g_return_val_if_fail (G_TYPE_IS_VALUE (src_type), FALSE);
421 g_return_val_if_fail (G_TYPE_IS_VALUE (dest_type), FALSE);
423 return (g_value_type_compatible (src_type, dest_type) ||
424 transform_func_lookup (src_type, dest_type) != NULL);
428 * g_value_type_compatible:
429 * @src_type: source type to be copied.
430 * @dest_type: destination type for copying.
432 * Returns whether a #GValue of type @src_type can be copied into
433 * a #GValue of type @dest_type.
435 * Returns: %TRUE if g_value_copy() is possible with @src_type and @dest_type.
438 g_value_type_compatible (GType src_type,
441 g_return_val_if_fail (G_TYPE_IS_VALUE (src_type), FALSE);
442 g_return_val_if_fail (G_TYPE_IS_VALUE (dest_type), FALSE);
444 return (g_type_is_a (src_type, dest_type) &&
445 g_type_value_table_peek (dest_type) == g_type_value_table_peek (src_type));
450 * @src_value: Source value.
451 * @dest_value: Target value.
453 * Tries to cast the contents of @src_value into a type appropriate
454 * to store in @dest_value, e.g. to transform a %G_TYPE_INT value
455 * into a %G_TYPE_FLOAT value. Performing transformations between
456 * value types might incur precision lossage. Especially
457 * transformations into strings might reveal seemingly arbitrary
458 * results and shouldn't be relied upon for production code (such
459 * as rcfile value or object property serialization).
461 * Returns: Whether a transformation rule was found and could be applied.
462 * Upon failing transformations, @dest_value is left untouched.
465 g_value_transform (const GValue *src_value,
470 g_return_val_if_fail (G_IS_VALUE (src_value), FALSE);
471 g_return_val_if_fail (G_IS_VALUE (dest_value), FALSE);
473 dest_type = G_VALUE_TYPE (dest_value);
474 if (g_value_type_compatible (G_VALUE_TYPE (src_value), dest_type))
476 g_value_copy (src_value, dest_value);
482 GValueTransform transform = transform_func_lookup (G_VALUE_TYPE (src_value), dest_type);
486 g_value_unset (dest_value);
488 /* setup and transform */
489 value_meminit (dest_value, dest_type);
490 transform (src_value, dest_value);
498 #define __G_VALUE_C__
499 #include "gobjectaliasdef.c"