evolution/camel/camel-object.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/* camel-object.c: Base class for Camel */

/*
 * Author:
 *  Dan Winship <danw@helixcode.com>
 *
 * Copyright 2000 Helix Code, Inc. (http://www.helixcode.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 */

#include <config.h>
#include "camel-object.h"

/* I just mashed the keyboard for these... */
#define CAMEL_OBJECT_MAGIC_VALUE           0x77A344EF
#define CAMEL_OBJECT_CLASS_MAGIC_VALUE     0xEE26A990
#define CAMEL_OBJECT_FINALIZED_VALUE       0x84AC3656
#define CAMEL_OBJECT_CLASS_FINALIZED_VALUE 0x7621ABCD

#define DEFAULT_PREALLOCS 8

#define BAST_CASTARD 1		/* Define to return NULL when casts fail */

#define NULL_PREP_VALUE ((gpointer)make_global_classfuncs)	/* See camel_object_class_declare_event */

/* ** Quickie type system ************************************************* */

typedef struct _CamelTypeInfo
{
	CamelType self;
	CamelType parent;
	const gchar *name;

	size_t instance_size;
	GMemChunk *instance_chunk;
	CamelObjectInitFunc instance_init;
	CamelObjectFinalizeFunc instance_finalize;
	GList *free_instances;

	size_t classfuncs_size;
	CamelObjectClassInitFunc class_init;
	CamelObjectClassFinalizeFunc class_finalize;
	CamelObjectClass *global_classfuncs;
}
CamelTypeInfo;

typedef struct _CamelHookPair
{
	CamelObjectEventHookFunc func;
	gpointer user_data;
}
CamelHookPair;

/* ************************************************************************ */

static void camel_type_lock_up (void);
static void camel_type_lock_down (void);

static void obj_init (CamelObject * obj);
static void obj_finalize (CamelObject * obj);
static void obj_class_init (CamelObjectClass * class);
static void obj_class_finalize (CamelObjectClass * class);

static gboolean shared_is_of_type (CamelObjectShared * sh, CamelType ctype,
				   gboolean is_obj);
static void make_global_classfuncs (CamelTypeInfo * type_info);

/* ************************************************************************ */

G_LOCK_DEFINE_STATIC (type_system);
G_LOCK_DEFINE_STATIC (type_system_level);
static GPrivate *type_system_locklevel = NULL;

G_LOCK_DEFINE_STATIC (refcount);

static gboolean type_system_initialized = FALSE;
static GHashTable *ctype_to_typeinfo = NULL;
static const CamelType camel_object_type = 1;
static CamelType cur_max_type = CAMEL_INVALID_TYPE;

/* ************************************************************************ */

#define LOCK_VAL (GPOINTER_TO_INT (g_private_get (type_system_locklevel)))
#define LOCK_SET( val ) g_private_set (type_system_locklevel, GINT_TO_POINTER (val))

static void
camel_type_lock_up (void)
{
	G_LOCK (type_system_level);

	if (type_system_locklevel == NULL)
		type_system_locklevel = g_private_new (GINT_TO_POINTER (0));

	if (LOCK_VAL == 0) {
		G_UNLOCK (type_system_level);
		G_LOCK (type_system);
		G_LOCK (type_system_level);
	}

	LOCK_SET (LOCK_VAL + 1);

	G_UNLOCK (type_system_level);
}

static void
camel_type_lock_down (void)
{
	G_LOCK (type_system_level);

	if (type_system_locklevel == NULL) {
		g_warning
			("camel_type_lock_down: lock down before a lock up?");
		type_system_locklevel = g_private_new (GINT_TO_POINTER (0));
		G_UNLOCK (type_system_level);
		return;
	}

	LOCK_SET (LOCK_VAL - 1);

	if (LOCK_VAL == 0)
		G_UNLOCK (type_system);

	G_UNLOCK (type_system_level);
}

void
camel_type_init (void)
{
	CamelTypeInfo *obj_info;

	camel_type_lock_up ();

	if (type_system_initialized) {
		g_warning
			("camel_type_init: type system already initialized.");
		camel_type_lock_down ();
		return;
	}

	type_system_initialized = TRUE;
	ctype_to_typeinfo = g_hash_table_new (g_direct_hash, g_direct_equal);

	obj_info = g_new (CamelTypeInfo, 1);
	obj_info->self = camel_object_type;
	obj_info->parent = CAMEL_INVALID_TYPE;
	obj_info->name = "CamelObject";

	obj_info->instance_size = sizeof (CamelObject);
	obj_info->instance_chunk =
		g_mem_chunk_create (CamelObject, DEFAULT_PREALLOCS,
				    G_ALLOC_ONLY);
	obj_info->instance_init = obj_init;
	obj_info->instance_finalize = obj_finalize;
	obj_info->free_instances = NULL;

	obj_info->classfuncs_size = sizeof (CamelObjectClass);
	obj_info->class_init = obj_class_init;
	obj_info->class_finalize = obj_class_finalize;

	g_hash_table_insert (ctype_to_typeinfo,
			     GINT_TO_POINTER (CAMEL_INVALID_TYPE), NULL);
	g_hash_table_insert (ctype_to_typeinfo,
			     GINT_TO_POINTER (camel_object_type), obj_info);

	/* Sigh. Ugly */
	make_global_classfuncs (obj_info);

	cur_max_type = camel_object_type;

	camel_type_lock_down ();
}

CamelType
camel_type_register (CamelType parent, const gchar * name,
		     size_t instance_size, size_t classfuncs_size,
		     CamelObjectClassInitFunc class_init,
		     CamelObjectClassFinalizeFunc class_finalize,
		     CamelObjectInitFunc instance_init,
		     CamelObjectFinalizeFunc instance_finalize)
{
	CamelTypeInfo *parent_info;
	CamelTypeInfo *obj_info;
	gchar *chunkname;

	g_return_val_if_fail (parent != CAMEL_INVALID_TYPE,
			      CAMEL_INVALID_TYPE);
	g_return_val_if_fail (name, CAMEL_INVALID_TYPE);
	g_return_val_if_fail (instance_size, CAMEL_INVALID_TYPE);
	g_return_val_if_fail (classfuncs_size, CAMEL_INVALID_TYPE);

	camel_type_lock_up ();

	if (type_system_initialized == FALSE) {
		G_UNLOCK (type_system);
		camel_type_init ();
		G_LOCK (type_system);
	}

	parent_info =
		g_hash_table_lookup (ctype_to_typeinfo,
				     GINT_TO_POINTER (parent));

	if (parent_info == NULL) {
		g_warning
			("camel_type_register: no such parent type %d of class `%s'",
			 parent, name);
		camel_type_lock_down ();
		return CAMEL_INVALID_TYPE;
	}

	if (parent_info->instance_size > instance_size) {
		g_warning
			("camel_type_register: instance of class `%s' would be smaller than parent `%s'",
			 name, parent_info->name);
		camel_type_lock_down ();
		return CAMEL_INVALID_TYPE;
	}

	if (parent_info->classfuncs_size > classfuncs_size) {
		g_warning
			("camel_type_register: classfuncs of class `%s' would be smaller than parent `%s'",
			 name, parent_info->name);
		camel_type_lock_down ();
		return CAMEL_INVALID_TYPE;
	}

	cur_max_type++;

	obj_info = g_new (CamelTypeInfo, 1);
	obj_info->self = cur_max_type;
	obj_info->parent = parent;
	obj_info->name = name;

	obj_info->instance_size = instance_size;
	chunkname =
		g_strdup_printf ("chunk for instances of Camel type `%s'",
				 name);
	obj_info->instance_chunk =
		g_mem_chunk_new (chunkname, instance_size,
				 instance_size * DEFAULT_PREALLOCS,
				 G_ALLOC_ONLY);
	g_free (chunkname);
	obj_info->instance_init = instance_init;
	obj_info->instance_finalize = instance_finalize;
	obj_info->free_instances = NULL;

	obj_info->classfuncs_size = classfuncs_size;
	obj_info->class_init = class_init;
	obj_info->class_finalize = class_finalize;

	g_hash_table_insert (ctype_to_typeinfo,
			     GINT_TO_POINTER (obj_info->self), obj_info);

	/* Sigh. Ugly. */
	make_global_classfuncs (obj_info);

	camel_type_lock_down ();
	return obj_info->self;
}

CamelObjectClass *
camel_type_get_global_classfuncs (CamelType type)
{
	CamelTypeInfo *type_info;

	g_return_val_if_fail (type != CAMEL_INVALID_TYPE, NULL);

	camel_type_lock_up ();
	type_info =
		g_hash_table_lookup (ctype_to_typeinfo,
				     GINT_TO_POINTER (type));
	camel_type_lock_down ();

	g_return_val_if_fail (type_info != NULL, NULL);

	return type_info->global_classfuncs;
}

const gchar *
camel_type_to_name (CamelType type)
{
	CamelTypeInfo *type_info;

	g_return_val_if_fail (type != CAMEL_INVALID_TYPE,
			      "(the invalid type)");

	camel_type_lock_up ();
	type_info =
		g_hash_table_lookup (ctype_to_typeinfo,
				     GINT_TO_POINTER (type));
	camel_type_lock_down ();

	g_return_val_if_fail (type_info != NULL,
			      "(a bad type parameter was specified)");

	return type_info->name;
}

/* ** The CamelObject ***************************************************** */

static void
obj_init (CamelObject * obj)
{
	obj->s.magic = CAMEL_OBJECT_MAGIC_VALUE;
	obj->ref_count = 1;
	obj->event_to_hooklist = NULL;
	obj->in_event = 0;
}

static void
obj_finalize (CamelObject * obj)
{
	g_return_if_fail (obj->s.magic == CAMEL_OBJECT_MAGIC_VALUE);
	g_return_if_fail (obj->ref_count == 0);
	g_return_if_fail (obj->in_event == 0);

	obj->s.magic = CAMEL_OBJECT_FINALIZED_VALUE;

	if (obj->event_to_hooklist) {
		g_hash_table_foreach (obj->event_to_hooklist, (GHFunc) g_free,
				      NULL);
		g_hash_table_destroy (obj->event_to_hooklist);
		obj->event_to_hooklist = NULL;
	}
}

static void
obj_class_init (CamelObjectClass * class)
{
	class->s.magic = CAMEL_OBJECT_CLASS_MAGIC_VALUE;

	camel_object_class_declare_event (class, "finalize", NULL);
}

static void
obj_class_finalize (CamelObjectClass * class)
{
	g_return_if_fail (class->s.magic == CAMEL_OBJECT_CLASS_MAGIC_VALUE);

	class->s.magic = CAMEL_OBJECT_CLASS_FINALIZED_VALUE;

	if (class->event_to_preplist) {
		g_hash_table_foreach (class->event_to_preplist,
				      (GHFunc) g_free, NULL);
		g_hash_table_destroy (class->event_to_preplist);
		class->event_to_preplist = NULL;
	}
}

CamelType
camel_object_get_type (void)
{
	if (type_system_initialized == FALSE)
		camel_type_init ();

	return camel_object_type;
}

CamelObject *
camel_object_new (CamelType type)
{
	CamelTypeInfo *type_info;
	GSList *parents = NULL;
	GSList *head = NULL;
	CamelObject *instance;

	g_return_val_if_fail (type != CAMEL_INVALID_TYPE, NULL);

	/* Look up the type */

	camel_type_lock_up ();

	type_info =
		g_hash_table_lookup (ctype_to_typeinfo,
				     GINT_TO_POINTER (type));

	if (type_info == NULL) {
		g_warning
			("camel_object_new: trying to create object of invalid type %d",
			 type);
		camel_type_lock_down ();
		return NULL;
	}

	/* Grab an instance out of the freed ones if possible, alloc otherwise */

	if (type_info->free_instances) {
		GList *first;

		first = g_list_first (type_info->free_instances);
		instance = first->data;
		type_info->free_instances =
			g_list_remove_link (type_info->free_instances, first);
		g_list_free_1 (first);
	} else {
		instance = g_mem_chunk_alloc0 (type_info->instance_chunk);
	}

	/* Init the instance and classfuncs a bit */

	instance->s.type = type;
	instance->classfuncs = type_info->global_classfuncs;

	/* Loop through the parents in simplest -> most complex order, initing the class and instance.

	 * When parent = CAMEL_INVALID_TYPE and we're at the end of the line, _lookup returns NULL
	 * because we inserted it as corresponding to CAMEL_INVALID_TYPE. Clever, eh?
	 */

	while (type_info) {
		parents = g_slist_prepend (parents, type_info);
		type_info =
			g_hash_table_lookup (ctype_to_typeinfo,
					     GINT_TO_POINTER (type_info->
							      parent));
	}

	head = parents;

	for (; parents && parents->data; parents = parents->next) {
		CamelTypeInfo *thisinfo;

		thisinfo = parents->data;
		if (thisinfo->instance_init)
			(thisinfo->instance_init) (instance);
	}

	g_slist_free (head);

	camel_type_lock_down ();
	return instance;
}

void
camel_object_ref (CamelObject * obj)
{
	g_return_if_fail (CAMEL_IS_OBJECT (obj));

	G_LOCK (refcount);
	obj->ref_count++;
	G_UNLOCK (refcount);
}

void
camel_object_unref (CamelObject * obj)
{
	CamelTypeInfo *type_info;
	CamelTypeInfo *iter;
	GSList *parents = NULL;
	GSList *head = NULL;

	g_return_if_fail (CAMEL_IS_OBJECT (obj));

	G_LOCK (refcount);
	obj->ref_count--;

	if (obj->ref_count > 0) {
		G_UNLOCK (refcount);
		return;
	}

	G_UNLOCK (refcount);

	/* Oh no! We want to emit a "finalized" event, but that function refs the object
	 * because it's not supposed to get finalized in an event, but it is being finalized
	 * right now, and AAUGH AAUGH AUGH AUGH!
	 *
	 * So we don't call camel_object_trigger_event. We do it ourselves. We even know
	 * that CamelObject doesn't provide a prep for the finalized event, so we plunge
	 * right in and call our hooks.
	 *
	 * And there was much rejoicing.
	 */

#define hooklist parents	/*cough */

	if (obj->event_to_hooklist) {
		CamelHookPair *pair;

		hooklist =
			g_hash_table_lookup (obj->event_to_hooklist,
					     "finalize");

		while (hooklist && hooklist->data) {
			pair = hooklist->data;
			(pair->func) (obj, NULL, pair->user_data);
			hooklist = hooklist->next;
		}
	}

	hooklist = NULL;	/* Don't mess with this line */

#undef hooklist

	/* Destroy it! hahaha! */

	camel_type_lock_up ();

	type_info =
		g_hash_table_lookup (ctype_to_typeinfo,
				     GINT_TO_POINTER (obj->s.type));

	if (type_info == NULL) {
		g_warning
			("camel_object_unref: seemingly valid object has a bad type %d",
			 obj->s.type);
		camel_type_lock_down ();
		return;
	}

	/* Loop through the parents in most complex -> simplest order, finalizing the class 
	 * and instance.
	 *
	 * When parent = CAMEL_INVALID_TYPE and we're at the end of the line, _lookup returns NULL
	 * because we inserted it as corresponding to CAMEL_INVALID_TYPE. Clever, eh?
	 *
	 * Use iter to preserve type_info for free_{instance,classfunc}s
	 */

	iter = type_info;

	while (iter) {
		parents = g_slist_prepend (parents, iter);
		iter =
			g_hash_table_lookup (ctype_to_typeinfo,
					     GINT_TO_POINTER (iter->parent));
	}

	parents = g_slist_reverse (parents);
	head = parents;

	for (; parents && parents->data; parents = parents->next) {
		CamelTypeInfo *thisinfo;

		thisinfo = parents->data;
		if (thisinfo->instance_finalize)
			(thisinfo->instance_finalize) (obj);
	}

	g_slist_free (head);

	/* A little bit of cleaning up.

	 * Don't erase the type, so we can peek at it if a finalized object
	 * is check_cast'ed somewhere.
	 */

	memset (obj, 0, type_info->instance_size);
	obj->s.type = type_info->self;
	obj->s.magic = CAMEL_OBJECT_FINALIZED_VALUE;

	/* Tuck away the pointer for use in a new object */

	type_info->free_instances =
		g_list_prepend (type_info->free_instances, obj);

	camel_type_lock_down ();
}

gboolean
camel_object_is_of_type (CamelObject * obj, CamelType ctype)
{
	return shared_is_of_type ((CamelObjectShared *) obj, ctype, TRUE);
}

gboolean
camel_object_class_is_of_type (CamelObjectClass * class, CamelType ctype)
{
	return shared_is_of_type ((CamelObjectShared *) class, ctype, FALSE);
}

#ifdef BAST_CASTARD
#define ERRVAL NULL
#else
#define ERRVAL obj
#endif

CamelObject *
camel_object_check_cast (CamelObject * obj, CamelType ctype)
{
	if (shared_is_of_type ((CamelObjectShared *) obj, ctype, TRUE))
		return obj;
	return ERRVAL;
}

CamelObjectClass *
camel_object_class_check_cast (CamelObjectClass * class, CamelType ctype)
{
	if (shared_is_of_type ((CamelObjectShared *) class, ctype, FALSE))
		return class;
	return ERRVAL;
}

#undef ERRVAL

gchar *
camel_object_describe (CamelObject * obj)
{
	if (obj == NULL)
		return g_strdup ("a NULL pointer");

	if (obj->s.magic == CAMEL_OBJECT_MAGIC_VALUE) {
		return g_strdup_printf ("an instance of `%s' at %p",
					camel_type_to_name (obj->s.type),
					obj);
	} else if (obj->s.magic == CAMEL_OBJECT_FINALIZED_VALUE) {
		return g_strdup_printf ("a finalized instance of `%s' at %p",
					camel_type_to_name (obj->s.type),
					obj);
	} else if (obj->s.magic == CAMEL_OBJECT_CLASS_MAGIC_VALUE) {
		return g_strdup_printf ("the classfuncs of `%s' at %p",
					camel_type_to_name (obj->s.type),
					obj);
	} else if (obj->s.magic == CAMEL_OBJECT_CLASS_FINALIZED_VALUE) {
		return
			g_strdup_printf
			("the finalized classfuncs of `%s' at %p",
			 camel_type_to_name (obj->s.type), obj);
	}

	return g_strdup ("not a CamelObject");
}

/* This is likely to be called in the class_init callback,
 * and the type will likely be somewhat uninitialized. 
 * Is this a problem? We'll see....
 */
void
camel_object_class_declare_event (CamelObjectClass * class,
				  const gchar * name,
				  CamelObjectEventPrepFunc prep)
{
	g_return_if_fail (CAMEL_IS_OBJECT_CLASS (class));
	g_return_if_fail (name);

	if (class->event_to_preplist == NULL)
		class->event_to_preplist =
			g_hash_table_new (g_str_hash, g_str_equal);
	else if (g_hash_table_lookup (class->event_to_preplist, name) != NULL) {
		g_warning
			("camel_object_class_declare_event: event `%s' already declared for `%s'",
			 name, camel_type_to_name (class->s.type));
		return;
	}

	/* AIEEEEEEEEEEEEEEEEEEEEEE

	 * I feel so naughty. Since it's valid to declare an event and not
	 * provide a hook, it should be valid to insert a NULL value into
	 * the table. However, then our lookup in trigger_event would be
	 * ambiguous, not telling us whether the event is undefined or whether
	 * it merely has no hook.
	 *
	 * So we create an 'NULL prep' value that != NULL... specifically, it
	 * equals the address of one of our static functions , because that
	 * can't possibly be your hook.
	 *
	 * Just don't forget to check for the 'evil value' and it'll work,
	 * I promise.
	 */

	if (prep == NULL)
		prep = NULL_PREP_VALUE;

	g_hash_table_insert (class->event_to_preplist, g_strdup (name), prep);
}

void
camel_object_hook_event (CamelObject * obj, const gchar * name,
			 CamelObjectEventHookFunc hook, gpointer user_data)
{
	GSList *hooklist;
	CamelHookPair *pair;

	g_return_if_fail (CAMEL_IS_OBJECT (obj));
	g_return_if_fail (name);
	g_return_if_fail (hook);

	if (obj->event_to_hooklist == NULL)
		obj->event_to_hooklist =
			g_hash_table_new (g_str_hash, g_str_equal);

	pair = g_new (CamelHookPair, 1);
	pair->func = hook;
	pair->user_data = user_data;

	hooklist = g_hash_table_lookup (obj->event_to_hooklist, name);
	hooklist = g_slist_prepend (hooklist, pair);
	g_hash_table_insert (obj->event_to_hooklist, g_strdup (name),
			     hooklist);
}

void
camel_object_unhook_event (CamelObject * obj, const gchar * name,
			   CamelObjectEventHookFunc hook, gpointer user_data)
{
	GSList *hooklist;
	GSList *head;

	g_return_if_fail (CAMEL_IS_OBJECT (obj));
	g_return_if_fail (name);
	g_return_if_fail (hook);

	if (obj->event_to_hooklist == NULL) {
		g_warning
			("camel_object_unhook_event: trying to unhook `%s' from an instance "
			 "of `%s' with no hooks attached", name,
			 camel_type_to_name (obj->s.type));
		return;
	}

	hooklist = g_hash_table_lookup (obj->event_to_hooklist, name);

	if (hooklist == NULL) {
		g_warning
			("camel_object_unhook_event: trying to unhook `%s' from an instance "
			 "of `%s' with no hooks attached to that event.",
			 name, camel_type_to_name (obj->s.type));
		return;
	}

	head = hooklist;

	while (hooklist) {
		CamelHookPair *pair = (CamelHookPair *) hooklist->data;

		if (pair->func == hook && pair->user_data == user_data) {
			g_free (hooklist->data);
			head = g_slist_remove_link (head, hooklist);
			g_slist_free_1 (hooklist);
			g_hash_table_insert (obj->event_to_hooklist, (char *) name,
					     head);
			return;
		}

		hooklist = hooklist->next;
	}

	g_warning
		("camel_object_unhook_event: cannot find hook/data pair %p/%p in an "
		 "instance of `%s' attached to `%s'", hook, user_data,
		 camel_type_to_name (obj->s.type), name);
}

void
camel_object_trigger_event (CamelObject * obj, const gchar * name,
			    gpointer event_data)
{
	GSList *hooklist;
	CamelHookPair *pair;
	CamelObjectEventPrepFunc prep;

	g_return_if_fail (CAMEL_IS_OBJECT (obj));
	g_return_if_fail (name);

	if (obj->in_event) {
		g_warning
			("camel_object_trigger_event: trying to trigger `%s' in class "
			 "`%s' while already triggering another event", name,
			 camel_type_to_name (obj->s.type));
		return;
	}

	if (obj->classfuncs->event_to_preplist == NULL) {
		g_warning
			("camel_object_trigger_event: trying to trigger `%s' in class "
			 "`%s' with no defined events.", name,
			 camel_type_to_name (obj->s.type));
		return;
	}

	prep = g_hash_table_lookup (obj->classfuncs->event_to_preplist, name);

	if (prep == NULL) {
		g_warning
			("camel_object_trigger_event: trying to trigger undefined "
			 "event `%s' in class `%s'.", name,
			 camel_type_to_name (obj->s.type));
		return;
	}

	/* Ref so that it can't get destroyed in the event, which would
	 * be Bad. And it's a valid ref anyway...
	 */

	camel_object_ref (obj);
	obj->in_event = 1;

	if ((prep != NULL_PREP_VALUE && !prep (obj, event_data))
	    || obj->event_to_hooklist == NULL) {
		obj->in_event = 0;
		camel_object_unref (obj);
		return;
	}

	hooklist = g_hash_table_lookup (obj->event_to_hooklist, name);

	while (hooklist && hooklist->data) {
		pair = hooklist->data;
		(pair->func) (obj, event_data, pair->user_data);
		hooklist = hooklist->next;
	}

	obj->in_event = 0;
	camel_object_unref (obj);
}

/* ** Static helpers ****************************************************** */

static gboolean
shared_is_of_type (CamelObjectShared * sh, CamelType ctype, gboolean is_obj)
{
	CamelTypeInfo *type_info;
	gchar *targtype;

	if (is_obj)
		targtype = "instance";
	else
		targtype = "classdata";

	if (ctype == CAMEL_INVALID_TYPE) {
		g_warning
			("shared_is_of_type: trying to cast to CAMEL_INVALID_TYPE");
		return FALSE;
	}

	if (sh == NULL) {
		g_warning
			("shared_is_of_type: trying to cast NULL to %s of `%s'",
			 targtype, camel_type_to_name (ctype));
		return FALSE;
	}

	if (sh->magic == CAMEL_OBJECT_FINALIZED_VALUE) {
		g_warning
			("shared_is_of_type: trying to cast finalized instance "
			 "of `%s' into %s of `%s'",
			 camel_type_to_name (sh->type), targtype,
			 camel_type_to_name (ctype));
		return FALSE;
	}

	if (sh->magic == CAMEL_OBJECT_CLASS_FINALIZED_VALUE) {
		g_warning
			("shared_is_of_type: trying to cast finalized classdata "
			 "of `%s' into %s of `%s'",
			 camel_type_to_name (sh->type), targtype,
			 camel_type_to_name (ctype));
		return FALSE;
	}

	if (is_obj) {
		if (sh->magic == CAMEL_OBJECT_CLASS_MAGIC_VALUE) {
			g_warning
				("shared_is_of_type: trying to cast classdata "
				 "of `%s' into instance of `%s'",
				 camel_type_to_name (sh->type),
				 camel_type_to_name (ctype));
			return FALSE;
		}

		if (sh->magic != CAMEL_OBJECT_MAGIC_VALUE) {
			g_warning
				("shared_is_of_type: trying to cast junk data "
				 "into instance of `%s'",
				 camel_type_to_name (ctype));
			return FALSE;
		}
	} else {
		if (sh->magic == CAMEL_OBJECT_MAGIC_VALUE) {
			g_warning
				("shared_is_of_type: trying to cast instance "
				 "of `%s' into classdata of `%s'",
				 camel_type_to_name (sh->type),
				 camel_type_to_name (ctype));
			return FALSE;
		}

		if (sh->magic != CAMEL_OBJECT_CLASS_MAGIC_VALUE) {
			g_warning
				("shared_is_of_type: trying to cast junk data "
				 "into classdata of `%s'",
				 camel_type_to_name (ctype));
			return FALSE;
		}
	}

	camel_type_lock_up ();

	type_info =
		g_hash_table_lookup (ctype_to_typeinfo,
				     GINT_TO_POINTER (sh->type));

	if (type_info == NULL) {
		g_warning ("shared_is_of_type: seemingly valid %s has "
			   "bad type %d.", targtype, sh->type);
		camel_type_lock_down ();
		return FALSE;
	}

	while (type_info) {
		if (type_info->self == ctype) {
			camel_type_lock_down ();
			return TRUE;
		}

		type_info =
			g_hash_table_lookup (ctype_to_typeinfo,
					     GINT_TO_POINTER (type_info->
							      parent));
	}

	/* this isn't an error, e.g. CAMEL_IS_FOLDER(folder), its upto  the
	   caller to handle the false case */
	/*g_warning
		("shared_is_of_type: %s of `%s' (@%p) is not also %s of `%s'",
		 targtype, camel_type_to_name (sh->type), sh, targtype,
		 camel_type_to_name (ctype));*/

	camel_type_lock_down ();
	return FALSE;
}

static void
make_global_classfuncs (CamelTypeInfo * type_info)
{
	CamelObjectClass *funcs;
	GSList *parents;
	GSList *head;

	g_assert (type_info);

	funcs = g_malloc0 (type_info->classfuncs_size);
	funcs->s.type = type_info->self;

	type_info->global_classfuncs = funcs;

	parents = NULL;
	while (type_info) {
		parents = g_slist_prepend (parents, type_info);
		type_info =
			g_hash_table_lookup (ctype_to_typeinfo,
					     GINT_TO_POINTER (type_info->
							      parent));
	}

	head = parents;

	for (; parents && parents->data; parents = parents->next) {
		CamelTypeInfo *thisinfo;

		thisinfo = parents->data;
		if (thisinfo->class_init)
			(thisinfo->class_init) (funcs);
	}

	g_slist_free (head);
}