File: item.h

package info (click to toggle)
kdepimlibs 4%3A4.14.10-11
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 35,856 kB
  • sloc: cpp: 269,391; xml: 4,188; ansic: 2,946; yacc: 1,904; perl: 381; ruby: 60; sh: 60; makefile: 13
file content (745 lines) | stat: -rw-r--r-- 24,881 bytes parent folder | download | duplicates (4)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
/*
    Copyright (c) 2006 Volker Krause <vkrause@kde.org>
                  2007 Till Adam <adam@kde.org>

    This library is free software; you can redistribute it and/or modify it
    under the terms of the GNU Library 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 Library General Public
    License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to the
    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301, USA.
*/

#ifndef AKONADI_ITEM_H
#define AKONADI_ITEM_H

#include "akonadi_export.h"

#include <akonadi/entity.h>
#include <akonadi/exception.h>
#include <akonadi/tag.h>
#include <akonadi/collection.h>
#include "itempayloadinternals_p.h"

#include <QtCore/QByteArray>
#include <QtCore/QMetaType>
#include <QtCore/QSet>

#include <boost/static_assert.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <boost/utility/enable_if.hpp>

#include <typeinfo>
#include <memory>

class KUrl;

template <typename T>
class QVector;

namespace Akonadi {

class ItemPrivate;

/**
 * @short Represents a PIM item stored in Akonadi storage.
 *
 * A PIM item consists of one or more parts, allowing a fine-grained access on its
 * content where needed (eg. mail envelope, mail body and attachments).
 *
 * There is also a namespace (prefix) for special parts which are local to Akonadi.
 * These parts, prefixed by "akonadi-", will never be fetched in the resource.
 * They are useful for local extensions like agents which might want to add meta data
 * to items in order to handle them but the meta data should not be stored back to the
 * resource.
 *
 * This class is implicitly shared.
 *
 * <h4>Payload</h4>
 *
 * This class contains, beside some type-agnostic information (flags, revision),
 * zero or more payload objects representing its actual data. Which objects these actually
 * are depends on the mimetype of the item and the corresponding serializer plugin(s).
 *
 * Technically the only restriction on payload objects is that they have to be copyable.
 * For safety reasons, pointer payloads are forbidden as well though, as the
 * ownership would not be clear. In this case, usage of a shared pointer is
 * recommended (such as boost::shared_ptr or QSharedPointer).
 *
 * Using a shared pointer is also required in case the payload is a polymorphic
 * type. For supported shared pointer types implicit casting is provided when possible.
 *
 * When using a value-based class as payload, it is recommended to use one that does
 * support implicit sharing as setting and retrieving a payload as well as copying
 * an Akonadi::Item object imply copying of the payload object.
 *
 * Since KDE 4.6, Item supports multiple payload types per mime type,
 * and will automatically convert between them using the serialiser
 * plugins (which is slow). It also supports mixing shared pointer
 * types, e.g. inserting a boost::shared_ptr<Foo> and extracting a
 * QSharedPointer<Foo>. Since the two shared pointer types cannot
 * share ownership of the same object, the payload class @c T needs to
 * provide a @c clone() method with the usual signature, ie.
 *
 * @code
 * virtual T * T::clone() const
 * @endcode
 *
 * If the class that does not have a @c clone() method, asking for an
 * incompatible shared pointer will throw a PayloadException.
 *
 * Since using different shared pointer types and different payload
 * types for the same mimetype incurs slow conversions (between
 * payload types) and cloning (between shared pointer types), as well
 * as manifold memory usage (results of conversions are cached inside
 * the Item, and only destroyed when a new payload is set by the user
 * of the class), you want to restrict yourself to just one type and
 * one shared pointer type. This mechanism was mainly introduced for
 * backwards compatibility (e.g., putting in a
 * boost::shared_ptr<KCal::Incidence> and extracting a
 * QSharedPointer<KCalCore::Incidence>), so it is not optimized for
 * performance.
 *
 * The availability of a payload of a specific type can be checked using hasPayload(),
 * payloads can be retrieved by using payload() and set by using setPayload(). Refer
 * to the documentation of those methods for more details.
 *
 * @author Volker Krause <vkrause@kde.org>, Till Adam <adam@kde.org>, Marc Mutz <mutz@kde.org>
 */
class AKONADI_EXPORT Item : public Entity
{
public:
    /**
     * Describes a list of items.
     */
    typedef QList<Item> List;

    /**
     * Describes a flag name.
     */
    typedef QByteArray Flag;

    /**
     * Describes a set of flag names.
     */
    typedef QSet<QByteArray> Flags;

    /**
     * Describes the part name that is used to fetch the
     * full payload of an item.
     */
    static const char *FullPayload;

    /**
     * Creates a new item.
     */
    Item();

    /**
     * Creates a new item with the given unique @p id.
     */
    explicit Item(Id id);

    /**
     * Creates a new item with the given mime type.
     *
     * @param mimeType The mime type of the item.
     */
    explicit Item(const QString &mimeType);

    /**
     * Creates a new item from an @p other item.
     */
    Item(const Item &other);

    /**
     * Destroys the item.
     */
    ~Item();

    /**
     * Creates an item from the given @p url.
     */
    static Item fromUrl(const KUrl &url);

    /**
     * Returns all flags of this item.
     */
    Flags flags() const;

    /**
     * Returns the timestamp of the last modification of this item.
     * @since 4.2
     */
    QDateTime modificationTime() const;

    /**
     * Sets the timestamp of the last modification of this item.
     * @param datetime the modification time to set
     * @note Do not modify this value from within an application,
     * it is updated automatically by the revision checking functions.
     * @since 4.2
     */
    void setModificationTime(const QDateTime &datetime);

    /**
     * Returns whether the flag with the given @p name is
     * set in the item.
     */
    bool hasFlag(const QByteArray &name) const;

    /**
     * Sets the flag with the given @p name in the item.
     */
    void setFlag(const QByteArray &name);

    /**
     * Removes the flag with the given @p name from the item.
     */
    void clearFlag(const QByteArray &name);

    /**
     * Overwrites all flags of the item by the given @p flags.
     */
    void setFlags(const Flags &flags);

    /**
     * Removes all flags from the item.
     */
    void clearFlags();

    void setTags(const Tag::List &list);

    void setTag(const Tag &tag);

    Tag::List tags() const;

    bool hasTag(const Tag &tag) const;

    void clearTag(const Tag &tag);

    void clearTags();

    /**
     * Sets the payload based on the canonical representation normally
     * used for data of this mime type.
     *
     * @param data The encoded data.
     * @see fullPayloadData
     */
    void setPayloadFromData(const QByteArray &data);

    /**
     * Returns the full payload in its canonical representation, e.g. the
     * binary or textual format usually used for data with this mime type.
     * This is useful when communicating with non-Akonadi application by
     * e.g. drag&drop, copy&paste or stored files.
     */
    QByteArray payloadData() const;

    /**
     * Returns the list of loaded payload parts. This is not necessarily
     * identical to all parts in the cache or to all available parts on the backend.
     */
    QSet<QByteArray> loadedPayloadParts() const;

    /**
     * Marks that the payload shall be cleared from the cache when this
     * item is passed to an ItemModifyJob the next time.
     * This will trigger a refetch of the payload from the backend when the
     * item is accessed afterwards. Only resources should have a need for
     * this functionality.
     *
     * @since 4.5
     */
    void clearPayload();

    /**
     * Sets the @p revision number of the item.
     * @param revision the revision number to set
     * @note Do not modify this value from within an application,
     * it is updated automatically by the revision checking functions.
     */
    void setRevision(int revision);

    /**
     * Returns the revision number of the item.
     */
    int revision() const;

    /**
     * Returns the unique identifier of the collection this item is stored in. There is only
     * a single such collection, although the item can be linked into arbitrary many
     * virtual collections.
     * Calling this method makes sense only after running an ItemFetchJob on the item.
     * @returns the collection ID if it is known, -1 otherwise.
     * @since 4.3
     */
    Entity::Id storageCollectionId() const;

    /**
     * Set the size of the item in bytes.
     * @param size the size of the item in bytes
     * @since 4.2
     */
    void setSize(qint64 size);

    /**
     * Returns the size of the items in bytes.
     *
     * @since 4.2
     */
    qint64 size() const;

    /**
     * Sets the mime type of the item to @p mimeType.
     */
    void setMimeType(const QString &mimeType);

    /**
     * Returns the mime type of the item.
     */
    QString mimeType() const;

    /**
     * Sets the @p gid of the entity.
     *
     * @since 4.12
     */
    void setGid(const QString &gid);

    /**
     * Returns the gid of the entity.
     *
     * @since 4.12
     */
    QString gid() const;

    /**
     * Sets the virtual @p collections that this item is linked into.
     *
     * @note Note that changing this value makes no effect on what collections
     * this item is linked to. To link or unlink an item to/from a virtual
     * collection, use LinkJob and UnlinkJob.
     *
     * @since 4.14
     */
    void setVirtualReferences(const Collection::List &collections);

    /**
     * Lists virtual collections that this item is linked to.
     *
     * @note This value is populated only when this item was retrieved by
     * ItemFetchJob with fetchVirtualReferences set to true in ItemFetchScope,
     * otherwise this list is always empty.
     *
     * @since 4.14
     */
    Collection::List virtualReferences() const;

    /**
     * Returns a list of metatype-ids, describing the different
     * variants of payload that are currently contained in this item.
     *
     * The result is always sorted (increasing ids).
     */
    QVector<int> availablePayloadMetaTypeIds() const;

    /**
     * Sets the payload object of this PIM item.
     *
     * @param p The payload object. Must be copyable and must not be a pointer,
     * will cause a compilation failure otherwise. Using a type that can be copied
     * fast (such as implicitly shared classes) is recommended.
     * If the payload type is polymorphic and you intend to set and retrieve payload
     * objects with mismatching but castable types, make sure to use a supported
     * shared pointer implementation (currently boost::shared_ptr and QSharedPointer)
     * and make sure there is a specialization of Akonadi::super_trait for your class.
     */
    template <typename T> void setPayload(const T &p);
    //@cond PRIVATE
    template <typename T> void setPayload(T *p);
    template <typename T> void setPayload(std::auto_ptr<T> p);
    //@endcond

    /**
     * Returns the payload object of this PIM item. This method will only succeed if either
     * you requested the exact same payload type that was put in or the payload uses a
     * supported shared pointer type (currently boost::shared_ptr and QSharedPointer), and
     * is castable to the requested type. For this to work there needs to be a specialization
     * of Akonadi::super_trait of the used classes.
     *
     * If a mismatching or non-castable payload type is requested, an Akonadi::PayloadException
     * is thrown. Therefore it is generally recommended to guard calls to payload() with a
     * corresponding hasPayload() call.
     *
     * Trying to retrieve a pointer type will fail to compile.
     */
    template <typename T> T payload() const;

    /**
     * Returns whether the item has a payload object.
     */
    bool hasPayload() const;

    /**
     * Returns whether the item has a payload of type @c T.
     * This method will only return @c true if either you requested the exact same payload type
     * that was put in or the payload uses a supported shared pointer type (currently boost::shared_ptr
     * and QSharedPointer), and is castable to the requested type. For this to work there needs
     * to be a specialization of Akonadi::super_trait of the used classes.
     *
     * Trying to retrieve a pointer type will fail to compile.
     */
    template <typename T> bool hasPayload() const;

    /**
     * Describes the type of url which is returned in url().
     */
    enum UrlType {
        UrlShort = 0,         ///< A short url which contains the identifier only (default)
        UrlWithMimeType = 1   ///< A url with identifier and mimetype
    };

    /**
     * Returns the url of the item.
     */
    KUrl url(UrlType type = UrlShort) const;

    /**
     * Returns the parts available for this item.
     *
     * The returned set refers to parts available on the akonadi server or remotely,
     * but does not include the loadedPayloadParts() of this item.
     *
     * @since 4.4
     */
    QSet<QByteArray> availablePayloadParts() const;

    /**
     * Returns the parts available for this item in the cache. The list might be a subset
     * of the actual parts in cache, as it contains only the requested parts. See @see ItemFetchJob and
     * @see ItemFetchScope
     *
     * The returned set refers to parts available on the akonadi server.
     *
     * @since 4.11
     */
    QSet<QByteArray> cachedPayloadParts() const;

    /**
     * Applies the parts of Item @p other to this item.
     * Any parts or attributes available in other, will be applied to this item,
     * and the payload parts of other will be inserted into this item, overwriting
     * any existing parts with the same part name.
     *
     * If there is an ItemSerialzerPluginV2 for the type, the merge method in that plugin is
     * used to perform the merge. If only an ItemSerialzerPlugin class is found, or the merge
     * method of the -V2 plugin is not implemented, the merge is performed with multiple deserializations
     * of the payload.
     * @param other the item to get values from
     * @since 4.4
     */
    void apply(const Item &other);

    /**
     * Registers \a T as a legacy type for mime type \a mimeType.
     *
     * This is required information for Item to return the correct
     * type from payload() when clients have not been recompiled to
     * use the new code.
     * @param mimeType the mimeType to register
     * @since 4.6
     */
    template <typename T> static void addToLegacyMapping(const QString &mimeType);
    void setCachedPayloadParts(const QSet<QByteArray> &cachedParts);

private:
    //@cond PRIVATE
    friend class ItemCreateJob;
    friend class ItemModifyJob;
    friend class ItemModifyJobPrivate;
    friend class ItemSync;
    friend class ProtocolHelper;
    PayloadBase *payloadBase() const;
    void setPayloadBase(PayloadBase *p);
    PayloadBase *payloadBaseV2(int sharedPointerId, int metaTypeId) const;
    //std::auto_ptr<PayloadBase> takePayloadBase( int sharedPointerId, int metaTypeId );
    void setPayloadBaseV2(int sharedPointerId, int metaTypeId, std::auto_ptr<PayloadBase> p);
    void addPayloadBaseVariant(int sharedPointerId, int metaTypeId, std::auto_ptr<PayloadBase> p) const;
    static void addToLegacyMappingImpl(const QString &mimeType, int sharedPointerId, int metaTypeId, std::auto_ptr<PayloadBase> p);

    /**
     * Try to ensure that we have a variant of the payload for metatype id @a mtid.
     * @return @c true if a type exists or could be created through conversion, @c false otherwise.
     */
    bool ensureMetaTypeId(int mtid) const;

    template <typename T>
    typename boost::enable_if_c<Internal::PayloadTrait<T>::isPolymorphic, void>::type
    setPayloadImpl(const T &p, const int * /*disambiguate*/ = 0);
    template <typename T>
    typename boost::disable_if_c<Internal::PayloadTrait<T>::isPolymorphic, void>::type
    setPayloadImpl(const T &p);

    template <typename T>
    typename boost::enable_if_c<Internal::PayloadTrait<T>::isPolymorphic, T>::type
    payloadImpl(const int * /*disambiguate*/ = 0) const;
    template <typename T>
    typename boost::disable_if_c<Internal::PayloadTrait<T>::isPolymorphic, T>::type
    payloadImpl() const;

    template <typename T>
    typename boost::enable_if_c<Internal::PayloadTrait<T>::isPolymorphic, bool>::type
    hasPayloadImpl(const int * /*disambiguate*/ = 0) const;
    template <typename T>
    typename boost::disable_if_c<Internal::PayloadTrait<T>::isPolymorphic, bool>::type
    hasPayloadImpl() const;

    template <typename T>
    typename boost::enable_if<Internal::is_shared_pointer<T>, bool>::type
    tryToClone(T *ret, const int * /*disambiguate*/ = 0) const;
    template <typename T>
    typename boost::disable_if<Internal::is_shared_pointer<T>, bool>::type
    tryToClone(T *) const;

    /**
     * Set the collection ID to where the item is stored in. Should be set only by the ItemFetchJob.
     * @param collectionId the unique identifier of the collection where this item is stored in.
     * @since 4.3
     */
    void setStorageCollectionId(Entity::Id collectionId);

#if 0
    /**
     * Helper function for non-template throwing of PayloadException.
     */
    QString payloadExceptionText(int spid, int mtid) const;

    /**
     * Non-template throwing of PayloadException.
     * Needs to be inline, otherwise catch (Akonadi::PayloadException)
     * won't work (only catch (Akonadi::Exception))
     */
    inline void throwPayloadException(int spid, int mtid) const {
        throw PayloadException(payloadExceptionText(spid, mtid));
    }
#else
    void throwPayloadException(int spid, int mtid) const;
#endif
    //@endcond

    AKONADI_DECLARE_PRIVATE(Item)
};

template <typename T>
T Item::payload() const
{
    BOOST_STATIC_ASSERT(!boost::is_pointer<T>::value);

    if (!hasPayload()) {
        throwPayloadException(-1, -1);
    }

    return payloadImpl<T>();
}

template <typename T>
typename boost::enable_if_c<Internal::PayloadTrait<T>::isPolymorphic, T>::type
Item::payloadImpl(const int *) const
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((PayloadType::isPolymorphic));

    typedef typename Internal::get_hierarchy_root<T>::type Root_T;
    typedef Internal::PayloadTrait<Root_T> RootType;
    BOOST_STATIC_ASSERT((!RootType::isPolymorphic));   // prevent endless recursion

    return PayloadType::castFrom(payloadImpl<Root_T>());
}

template <typename T>
typename boost::disable_if_c<Internal::PayloadTrait<T>::isPolymorphic, T>::type
Item::payloadImpl() const
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((!PayloadType::isPolymorphic));

    const int metaTypeId = PayloadType::elementMetaTypeId();

    // make sure that we have a payload format represented by 'metaTypeId':
    if (!ensureMetaTypeId(metaTypeId)) {
        throwPayloadException(PayloadType::sharedPointerId, metaTypeId);
    }

    // Check whether we have the exact payload
    // (metatype id and shared pointer type match)
    if (const Payload<T> *const p = Internal::payload_cast<T>(payloadBaseV2(PayloadType::sharedPointerId, metaTypeId))) {
        return p->payload;
    }

    T ret;
    if (!tryToClone<T>(&ret)) {
        throwPayloadException(PayloadType::sharedPointerId, metaTypeId);
    }
    return ret;
}

template <typename T>
typename boost::enable_if<Internal::is_shared_pointer<T>, bool>::type
Item::tryToClone(T *ret, const int *) const
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((!PayloadType::isPolymorphic));

    const int metaTypeId = PayloadType::elementMetaTypeId();

    // Check whether we have the same payload in 'the other
    // shared pointer' (### make it recurse, trying to find one, but
    // don't introduce infinite recursion):
    typedef typename Internal::shared_pointer_traits<T>::next_shared_ptr NewT;
    typedef Internal::PayloadTrait<NewT> NewPayloadType;

    if (const Payload<NewT> *const p = Internal::payload_cast<NewT>(payloadBaseV2(NewPayloadType::sharedPointerId, metaTypeId))) {
        // If found, attempt to make a clone (required the payload to provide virtual T * T::clone() const)
        const T nt = PayloadType::clone(p->payload);
        if (!PayloadType::isNull(nt)) {
            // if clone succeeded, add the clone to the Item:
            std::auto_ptr<PayloadBase> npb(new Payload<T>(nt));
            addPayloadBaseVariant(PayloadType::sharedPointerId, metaTypeId, npb);
            // and return it
            if (ret) {
                *ret = nt;
            }
            return true;
        }
    }

    return false;
}

template <typename T>
typename boost::disable_if<Internal::is_shared_pointer<T>, bool>::type
Item::tryToClone(T *) const
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((!PayloadType::isPolymorphic));

    return false;
}

template <typename T>
bool Item::hasPayload() const
{
    BOOST_STATIC_ASSERT(!boost::is_pointer<T>::value);
    return hasPayload() && hasPayloadImpl<T>();
}

template <typename T>
typename boost::enable_if_c<Internal::PayloadTrait<T>::isPolymorphic, bool>::type
Item::hasPayloadImpl(const int *) const
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((PayloadType::isPolymorphic));

    typedef typename Internal::get_hierarchy_root<T>::type Root_T;
    typedef Internal::PayloadTrait<Root_T> RootType;
    BOOST_STATIC_ASSERT((!RootType::isPolymorphic));   // prevent endless recursion

    try {
        return hasPayloadImpl<Root_T>()
               && PayloadType::canCastFrom(payload<Root_T>());
    } catch (const Akonadi::PayloadException &) {
        return false;
    }
}

template <typename T>
typename boost::disable_if_c<Internal::PayloadTrait<T>::isPolymorphic, bool>::type
Item::hasPayloadImpl() const
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((!PayloadType::isPolymorphic));

    const int metaTypeId = PayloadType::elementMetaTypeId();

    // make sure that we have a payload format represented by 'metaTypeId':
    if (!ensureMetaTypeId(metaTypeId)) {
        return false;
    }

    // Check whether we have the exact payload
    // (metatype id and shared pointer type match)
    if (const Payload<T> *const p = Internal::payload_cast<T>(payloadBaseV2(PayloadType::sharedPointerId, metaTypeId))) {
        return true;
    }

    return tryToClone<T>(0);
}

template <typename T>
void Item::setPayload(const T &p)
{
    BOOST_STATIC_ASSERT((!boost::is_pointer<T>::value));
    setPayloadImpl(p);
}

template <typename T>
typename boost::enable_if_c<Internal::PayloadTrait<T>::isPolymorphic>::type
Item::setPayloadImpl(const T &p, const int *)
{
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((PayloadType::isPolymorphic));

    typedef typename Internal::get_hierarchy_root<T>::type Root_T;
    typedef Internal::PayloadTrait<Root_T> RootType;
    BOOST_STATIC_ASSERT((!RootType::isPolymorphic));   // prevent endless recursion

    setPayloadImpl<Root_T>(p);
}

template <typename T>
typename boost::disable_if_c<Internal::PayloadTrait<T>::isPolymorphic>::type
Item::setPayloadImpl(const T &p)
{
    typedef Internal::PayloadTrait<T> PayloadType;
    std::auto_ptr<PayloadBase> pb(new Payload<T>(p));
    setPayloadBaseV2(PayloadType::sharedPointerId,
                     PayloadType::elementMetaTypeId(),
                     pb);
}

template <typename T>
void Item::setPayload(T *p)
{
    p->You_MUST_NOT_use_a_pointer_as_payload;
}

template <typename T>
void Item::setPayload(std::auto_ptr<T> p)
{
    p.Nice_try_but_a_std_auto_ptr_is_not_allowed_as_payload_either;
}

template <typename T>
void Item::addToLegacyMapping(const QString &mimeType) {
    typedef Internal::PayloadTrait<T> PayloadType;
    BOOST_STATIC_ASSERT((!PayloadType::isPolymorphic));
    std::auto_ptr<PayloadBase> p(new Payload<T>);
    addToLegacyMappingImpl(mimeType, PayloadType::sharedPointerId, PayloadType::elementMetaTypeId(), p);
}

}

Q_DECLARE_METATYPE(Akonadi::Item)
Q_DECLARE_METATYPE(Akonadi::Item::List)

#endif