glib/gobject/gvalue.c

/* GObject - GLib Type, Object, Parameter and Signal Library
 * Copyright (C) 1997-1999, 2000-2001 Tim Janik and Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/*
 * FIXME: MT-safety
 */

#include <string.h>

#include "gobjectalias.h"
#include "gvalue.h"
#include "gvaluecollector.h"
#include "gbsearcharray.h"


/* --- typedefs & structures --- */
typedef struct {
  GType src_type;
  GType dest_type;
  GValueTransform func;
} TransformEntry;


/* --- prototypes --- */
static gint	transform_entries_cmp	(gconstpointer bsearch_node1,
					 gconstpointer bsearch_node2);


/* --- variables --- */
static GBSearchArray *transform_array = NULL;
static GBSearchConfig transform_bconfig = {
  sizeof (TransformEntry),
  transform_entries_cmp,
  0,
};


/* --- functions --- */
void
g_value_c_init (void)
{
  transform_array = g_bsearch_array_create (&transform_bconfig);
}

static inline void		/* keep this function in sync with gvaluecollector.h and gboxed.c */
value_meminit (GValue *value,
	       GType   value_type)
{
  value->g_type = value_type;
  memset (value->data, 0, sizeof (value->data));
}

GValue*
g_value_init (GValue *value,
	      GType   g_type)
{
  /* g_return_val_if_fail (G_TYPE_IS_VALUE (g_type), NULL);	be more elaborate below */
  g_return_val_if_fail (value != NULL, NULL);
  /* g_return_val_if_fail (G_VALUE_TYPE (value) == 0, NULL);	be more elaborate below */

  if (G_TYPE_IS_VALUE (g_type) && G_VALUE_TYPE (value) == 0)
    {
      GTypeValueTable *value_table = g_type_value_table_peek (g_type);

      /* setup and init */
      value_meminit (value, g_type);
      value_table->value_init (value);
    }
  else if (G_VALUE_TYPE (value))
    g_warning ("%s: cannot initialize GValue with type `%s', the value has already been initialized as `%s'",
	       G_STRLOC,
	       g_type_name (g_type),
	       g_type_name (G_VALUE_TYPE (value)));
  else /* !G_TYPE_IS_VALUE (g_type) */
    g_warning ("%s: cannot initialize GValue with type `%s', %s",
	       G_STRLOC,
	       g_type_name (g_type),
	       g_type_value_table_peek (g_type) ?
	       "this type is abstract with regards to GValue use, use a more specific (derived) type" :
	       "this type has no GTypeValueTable implementation");
  return value;
}

void
g_value_copy (const GValue *src_value,
	      GValue       *dest_value)
{
  g_return_if_fail (G_IS_VALUE (src_value));
  g_return_if_fail (G_IS_VALUE (dest_value));
  g_return_if_fail (g_value_type_compatible (G_VALUE_TYPE (src_value), G_VALUE_TYPE (dest_value)));
  
  if (src_value != dest_value)
    {
      GType dest_type = G_VALUE_TYPE (dest_value);
      GTypeValueTable *value_table = g_type_value_table_peek (dest_type);

      /* make sure dest_value's value is free()d */
      if (value_table->value_free)
	value_table->value_free (dest_value);

      /* setup and copy */
      value_meminit (dest_value, dest_type);
      value_table->value_copy (src_value, dest_value);
    }
}

GValue*
g_value_reset (GValue *value)
{
  GTypeValueTable *value_table;
  GType g_type;
  
  g_return_val_if_fail (G_IS_VALUE (value), NULL);
  
  g_type = G_VALUE_TYPE (value);
  value_table = g_type_value_table_peek (g_type);

  /* make sure value's value is free()d */
  if (value_table->value_free)
    value_table->value_free (value);

  /* setup and init */
  value_meminit (value, g_type);
  value_table->value_init (value);

  return value;
}

void
g_value_unset (GValue *value)
{
  GTypeValueTable *value_table;
  
  g_return_if_fail (G_IS_VALUE (value));

  value_table = g_type_value_table_peek (G_VALUE_TYPE (value));

  if (value_table->value_free)
    value_table->value_free (value);
  memset (value, 0, sizeof (*value));
}

gboolean
g_value_fits_pointer (const GValue *value)
{
  GTypeValueTable *value_table;

  g_return_val_if_fail (G_IS_VALUE (value), FALSE);

  value_table = g_type_value_table_peek (G_VALUE_TYPE (value));

  return value_table->value_peek_pointer != NULL;
}

gpointer
g_value_peek_pointer (const GValue *value)
{
  GTypeValueTable *value_table;

  g_return_val_if_fail (G_IS_VALUE (value), NULL);

  value_table = g_type_value_table_peek (G_VALUE_TYPE (value));
  if (!value_table->value_peek_pointer)
    {
      g_assert (g_value_fits_pointer (value) == TRUE);
      return NULL;
    }

  return value_table->value_peek_pointer (value);
}

void
g_value_set_instance (GValue  *value,
		      gpointer instance)
{
  GType g_type;
  GTypeValueTable *value_table;
  GTypeCValue cvalue;
  gchar *error_msg;
  
  g_return_if_fail (G_IS_VALUE (value));
  if (instance)
    {
      g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
      g_return_if_fail (g_value_type_compatible (G_TYPE_FROM_INSTANCE (instance), G_VALUE_TYPE (value)));
    }
  
  g_type = G_VALUE_TYPE (value);
  value_table = g_type_value_table_peek (g_type);
  
  g_return_if_fail (strcmp (value_table->collect_format, "p") == 0);
  
  memset (&cvalue, 0, sizeof (cvalue));
  cvalue.v_pointer = instance;
  
  /* make sure value's value is free()d */
  if (value_table->value_free)
    value_table->value_free (value);

  /* setup and collect */
  value_meminit (value, g_type);
  error_msg = value_table->collect_value (value, 1, &cvalue, 0);
  if (error_msg)
    {
      g_warning ("%s: %s", G_STRLOC, error_msg);
      g_free (error_msg);
      
      /* we purposely leak the value here, it might not be
       * in a sane state if an error condition occoured
       */
      value_meminit (value, g_type);
      value_table->value_init (value);
    }
}

static GValueTransform
transform_func_lookup (GType src_type,
		       GType dest_type)
{
  TransformEntry entry;

  entry.src_type = src_type;
  do
    {
      entry.dest_type = dest_type;
      do
	{
	  TransformEntry *e;
	  
	  e = g_bsearch_array_lookup (transform_array, &transform_bconfig, &entry);
	  if (e)
	    {
	      /* need to check that there hasn't been a change in value handling */
	      if (g_type_value_table_peek (entry.dest_type) == g_type_value_table_peek (dest_type) &&
		  g_type_value_table_peek (entry.src_type) == g_type_value_table_peek (src_type))
		return e->func;
	    }
	  entry.dest_type = g_type_parent (entry.dest_type);
	}
      while (entry.dest_type);
      
      entry.src_type = g_type_parent (entry.src_type);
    }
  while (entry.src_type);

  return NULL;
}

static gint
transform_entries_cmp (gconstpointer bsearch_node1,
		       gconstpointer bsearch_node2)
{
  const TransformEntry *e1 = bsearch_node1;
  const TransformEntry *e2 = bsearch_node2;
  gint cmp = G_BSEARCH_ARRAY_CMP (e1->src_type, e2->src_type);

  if (cmp)
    return cmp;
  else
    return G_BSEARCH_ARRAY_CMP (e1->dest_type, e2->dest_type);
}

void
g_value_register_transform_func (GType           src_type,
				 GType           dest_type,
				 GValueTransform transform_func)
{
  TransformEntry entry;

  /* these checks won't pass for dynamic types.
   * g_return_if_fail (G_TYPE_HAS_VALUE_TABLE (src_type));
   * g_return_if_fail (G_TYPE_HAS_VALUE_TABLE (dest_type));
   */
  g_return_if_fail (transform_func != NULL);

  entry.src_type = src_type;
  entry.dest_type = dest_type;

#if 0 /* let transform function replacement be a valid operation */
  if (g_bsearch_array_lookup (transform_array, &transform_bconfig, &entry))
    g_warning ("reregistering value transformation function (%p) for `%s' to `%s'",
	       transform_func,
	       g_type_name (src_type),
	       g_type_name (dest_type));
#endif

  entry.func = transform_func;
  transform_array = g_bsearch_array_replace (transform_array, &transform_bconfig, &entry);
}

gboolean
g_value_type_transformable (GType src_type,
			    GType dest_type)
{
  g_return_val_if_fail (G_TYPE_IS_VALUE (src_type), FALSE);
  g_return_val_if_fail (G_TYPE_IS_VALUE (dest_type), FALSE);

  return (g_value_type_compatible (src_type, dest_type) ||
	  transform_func_lookup (src_type, dest_type) != NULL);
}

gboolean
g_value_type_compatible (GType src_type,
			 GType dest_type)
{
  g_return_val_if_fail (G_TYPE_IS_VALUE (src_type), FALSE);
  g_return_val_if_fail (G_TYPE_IS_VALUE (dest_type), FALSE);

  return (g_type_is_a (src_type, dest_type) &&
	  g_type_value_table_peek (dest_type) == g_type_value_table_peek (src_type));
}

gboolean
g_value_transform (const GValue *src_value,
		   GValue       *dest_value)
{
  GType dest_type;

  g_return_val_if_fail (G_IS_VALUE (src_value), FALSE);
  g_return_val_if_fail (G_IS_VALUE (dest_value), FALSE);

  dest_type = G_VALUE_TYPE (dest_value);
  if (g_value_type_compatible (G_VALUE_TYPE (src_value), dest_type))
    {
      g_value_copy (src_value, dest_value);
      
      return TRUE;
    }
  else
    {
      GValueTransform transform = transform_func_lookup (G_VALUE_TYPE (src_value), dest_type);

      if (transform)
	{
	  g_value_unset (dest_value);
	  
	  /* setup and transform */
	  value_meminit (dest_value, dest_type);
	  transform (src_value, dest_value);
	  
	  return TRUE;
	}
    }
  return FALSE;
}