summaryrefslogtreecommitdiffstats
path: root/xpcom/glue/nsTHashtable.h
blob: b382da0bcc594eb4936a35702219b45aabdf2b56 (plain)
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
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef nsTHashtable_h__
#define nsTHashtable_h__

#include "PLDHashTable.h"
#include "nsPointerHashKeys.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/fallible.h"
#include "mozilla/MemoryChecking.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Move.h"
#include "mozilla/OperatorNewExtensions.h"
#include "mozilla/PodOperations.h"
#include "mozilla/TypeTraits.h"

#include <new>

/**
 * a base class for templated hashtables.
 *
 * Clients will rarely need to use this class directly. Check the derived
 * classes first, to see if they will meet your needs.
 *
 * @param EntryType  the templated entry-type class that is managed by the
 *   hashtable. <code>EntryType</code> must extend the following declaration,
 *   and <strong>must not declare any virtual functions or derive from classes
 *   with virtual functions.</strong>  Any vtable pointer would break the
 *   PLDHashTable code.
 *<pre>   class EntryType : public PLDHashEntryHdr
 *   {
 *   public: or friend nsTHashtable<EntryType>;
 *     // KeyType is what we use when Get()ing or Put()ing this entry
 *     // this should either be a simple datatype (uint32_t, nsISupports*) or
 *     // a const reference (const nsAString&)
 *     typedef something KeyType;
 *     // KeyTypePointer is the pointer-version of KeyType, because
 *     // PLDHashTable.h requires keys to cast to <code>const void*</code>
 *     typedef const something* KeyTypePointer;
 *
 *     EntryType(KeyTypePointer aKey);
 *
 *     // A copy or C++11 Move constructor must be defined, even if
 *     // AllowMemMove() == true, otherwise you will cause link errors.
 *     EntryType(const EntryType& aEnt);  // Either this...
 *     EntryType(EntryType&& aEnt);       // ...or this
 *
 *     // the destructor must be defined... or you will cause link errors!
 *     ~EntryType();
 *
 *     // KeyEquals(): does this entry match this key?
 *     bool KeyEquals(KeyTypePointer aKey) const;
 *
 *     // KeyToPointer(): Convert KeyType to KeyTypePointer
 *     static KeyTypePointer KeyToPointer(KeyType aKey);
 *
 *     // HashKey(): calculate the hash number
 *     static PLDHashNumber HashKey(KeyTypePointer aKey);
 *
 *     // ALLOW_MEMMOVE can we move this class with memmove(), or do we have
 *     // to use the copy constructor?
 *     enum { ALLOW_MEMMOVE = true/false };
 *   }</pre>
 *
 * @see nsInterfaceHashtable
 * @see nsDataHashtable
 * @see nsClassHashtable
 * @author "Benjamin Smedberg <bsmedberg@covad.net>"
 */

template<class EntryType>
class MOZ_NEEDS_NO_VTABLE_TYPE nsTHashtable
{
  typedef mozilla::fallible_t fallible_t;
  static_assert(mozilla::IsPointer<typename EntryType::KeyTypePointer>::value,
                "KeyTypePointer should be a pointer");

public:
  // Separate constructors instead of default aInitLength parameter since
  // otherwise the default no-arg constructor isn't found.
  nsTHashtable()
    : mTable(Ops(), sizeof(EntryType), PLDHashTable::kDefaultInitialLength)
  {}
  explicit nsTHashtable(uint32_t aInitLength)
    : mTable(Ops(), sizeof(EntryType), aInitLength)
  {}

  /**
   * destructor, cleans up and deallocates
   */
  ~nsTHashtable();

  nsTHashtable(nsTHashtable<EntryType>&& aOther);

  /**
   * Return the generation number for the table. This increments whenever
   * the table data items are moved.
   */
  uint32_t GetGeneration() const { return mTable.Generation(); }

  /**
   * KeyType is typedef'ed for ease of use.
   */
  typedef typename EntryType::KeyType KeyType;

  /**
   * KeyTypePointer is typedef'ed for ease of use.
   */
  typedef typename EntryType::KeyTypePointer KeyTypePointer;

  /**
   * Return the number of entries in the table.
   * @return    number of entries
   */
  uint32_t Count() const { return mTable.EntryCount(); }

  /**
   * Return true if the hashtable is empty.
   */
  bool IsEmpty() const { return Count() == 0; }

  /**
   * Get the entry associated with a key.
   * @param     aKey the key to retrieve
   * @return    pointer to the entry class, if the key exists; nullptr if the
   *            key doesn't exist
   */
  EntryType* GetEntry(KeyType aKey) const
  {
    return static_cast<EntryType*>(
      const_cast<PLDHashTable*>(&mTable)->Search(EntryType::KeyToPointer(aKey)));
  }

  /**
   * Return true if an entry for the given key exists, false otherwise.
   * @param     aKey the key to retrieve
   * @return    true if the key exists, false if the key doesn't exist
   */
  bool Contains(KeyType aKey) const { return !!GetEntry(aKey); }

  /**
   * Get the entry associated with a key, or create a new entry,
   * @param     aKey the key to retrieve
   * @return    pointer to the entry class retreived; nullptr only if memory
                can't be allocated
   */
  EntryType* PutEntry(KeyType aKey)
  {
    // infallible add
    return static_cast<EntryType*>(mTable.Add(EntryType::KeyToPointer(aKey)));
  }

  MOZ_MUST_USE
  EntryType* PutEntry(KeyType aKey, const fallible_t&)
  {
    return static_cast<EntryType*>(mTable.Add(EntryType::KeyToPointer(aKey),
                                              mozilla::fallible));
  }

  /**
   * Remove the entry associated with a key.
   * @param     aKey of the entry to remove
   */
  void RemoveEntry(KeyType aKey)
  {
    mTable.Remove(EntryType::KeyToPointer(aKey));
  }

  /**
   * Remove the entry associated with a key.
   * @param aEntry   the entry-pointer to remove (obtained from GetEntry)
   */
  void RemoveEntry(EntryType* aEntry)
  {
    mTable.RemoveEntry(aEntry);
  }

  /**
   * Remove the entry associated with a key, but don't resize the hashtable.
   * This is a low-level method, and is not recommended unless you know what
   * you're doing. If you use it, please add a comment explaining why you
   * didn't use RemoveEntry().
   * @param aEntry   the entry-pointer to remove (obtained from GetEntry)
   */
  void RawRemoveEntry(EntryType* aEntry)
  {
    mTable.RawRemove(aEntry);
  }

  // This is an iterator that also allows entry removal. Example usage:
  //
  //   for (auto iter = table.Iter(); !iter.Done(); iter.Next()) {
  //     Entry* entry = iter.Get();
  //     // ... do stuff with |entry| ...
  //     // ... possibly call iter.Remove() once ...
  //   }
  //
  class Iterator : public PLDHashTable::Iterator
  {
  public:
    typedef PLDHashTable::Iterator Base;

    explicit Iterator(nsTHashtable* aTable) : Base(&aTable->mTable) {}
    Iterator(Iterator&& aOther) : Base(aOther.mTable) {}
    ~Iterator() {}

    EntryType* Get() const { return static_cast<EntryType*>(Base::Get()); }

  private:
    Iterator() = delete;
    Iterator(const Iterator&) = delete;
    Iterator& operator=(const Iterator&) = delete;
    Iterator& operator=(const Iterator&&) = delete;
  };

  Iterator Iter() { return Iterator(this); }

  Iterator ConstIter() const
  {
    return Iterator(const_cast<nsTHashtable*>(this));
  }

  /**
   * Remove all entries, return hashtable to "pristine" state. It's
   * conceptually the same as calling the destructor and then re-calling the
   * constructor.
   */
  void Clear()
  {
    mTable.Clear();
  }

  /**
   * Measure the size of the table's entry storage. Does *not* measure anything
   * hanging off table entries; hence the "Shallow" prefix. To measure that,
   * either use SizeOfExcludingThis() or iterate manually over the entries,
   * calling SizeOfExcludingThis() on each one.
   *
   * @param     aMallocSizeOf the function used to measure heap-allocated blocks
   * @return    the measured shallow size of the table
   */
  size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
  {
    return mTable.ShallowSizeOfExcludingThis(aMallocSizeOf);
  }

  /**
   * Like ShallowSizeOfExcludingThis, but includes sizeof(*this).
   */
  size_t ShallowSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
  {
    return aMallocSizeOf(this) + ShallowSizeOfExcludingThis(aMallocSizeOf);
  }

  /**
   * This is a "deep" measurement of the table. To use it, |EntryType| must
   * define SizeOfExcludingThis, and that method will be called on all live
   * entries.
   */
  size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
  {
    size_t n = ShallowSizeOfExcludingThis(aMallocSizeOf);
    for (auto iter = ConstIter(); !iter.Done(); iter.Next()) {
      n += (*iter.Get()).SizeOfExcludingThis(aMallocSizeOf);
    }
    return n;
  }

  /**
   * Like SizeOfExcludingThis, but includes sizeof(*this).
   */
  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
  {
    return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
  }

  /**
   * Swap the elements in this hashtable with the elements in aOther.
   */
  void SwapElements(nsTHashtable<EntryType>& aOther)
  {
    MOZ_ASSERT_IF(this->mTable.Ops() && aOther.mTable.Ops(),
                  this->mTable.Ops() == aOther.mTable.Ops());
    mozilla::Swap(this->mTable, aOther.mTable);
  }

#ifdef DEBUG
  /**
   * Mark the table as constant after initialization.
   *
   * This will prevent assertions when a read-only hash is accessed on multiple
   * threads without synchronization.
   */
  void MarkImmutable()
  {
    mTable.MarkImmutable();
  }
#endif

protected:
  PLDHashTable mTable;

  static PLDHashNumber s_HashKey(const void* aKey);

  static bool s_MatchEntry(const PLDHashEntryHdr* aEntry,
                           const void* aKey);

  static void s_CopyEntry(PLDHashTable* aTable, const PLDHashEntryHdr* aFrom,
                          PLDHashEntryHdr* aTo);

  static void s_ClearEntry(PLDHashTable* aTable, PLDHashEntryHdr* aEntry);

  static void s_InitEntry(PLDHashEntryHdr* aEntry, const void* aKey);

private:
  // copy constructor, not implemented
  nsTHashtable(nsTHashtable<EntryType>& aToCopy) = delete;

  /**
   * Gets the table's ops.
   */
  static const PLDHashTableOps* Ops();

  // assignment operator, not implemented
  nsTHashtable<EntryType>& operator=(nsTHashtable<EntryType>& aToEqual) = delete;
};

//
// template definitions
//

template<class EntryType>
nsTHashtable<EntryType>::nsTHashtable(nsTHashtable<EntryType>&& aOther)
  : mTable(mozilla::Move(aOther.mTable))
{
  // aOther shouldn't touch mTable after this, because we've stolen the table's
  // pointers but not overwitten them.
  MOZ_MAKE_MEM_UNDEFINED(&aOther.mTable, sizeof(aOther.mTable));
}

template<class EntryType>
nsTHashtable<EntryType>::~nsTHashtable()
{
}

template<class EntryType>
/* static */ const PLDHashTableOps*
nsTHashtable<EntryType>::Ops()
{
  // If this variable is a global variable, we get strange start-up failures on
  // WindowsCrtPatch.h (see bug 1166598 comment 20). But putting it inside a
  // function avoids that problem.
  static const PLDHashTableOps sOps =
  {
    s_HashKey,
    s_MatchEntry,
    EntryType::ALLOW_MEMMOVE ? PLDHashTable::MoveEntryStub : s_CopyEntry,
    s_ClearEntry,
    s_InitEntry
  };
  return &sOps;
}

// static definitions

template<class EntryType>
PLDHashNumber
nsTHashtable<EntryType>::s_HashKey(const void* aKey)
{
  return EntryType::HashKey(static_cast<KeyTypePointer>(aKey));
}

template<class EntryType>
bool
nsTHashtable<EntryType>::s_MatchEntry(const PLDHashEntryHdr* aEntry,
                                      const void* aKey)
{
  return ((const EntryType*)aEntry)->KeyEquals(
    static_cast<KeyTypePointer>(aKey));
}

template<class EntryType>
void
nsTHashtable<EntryType>::s_CopyEntry(PLDHashTable* aTable,
                                     const PLDHashEntryHdr* aFrom,
                                     PLDHashEntryHdr* aTo)
{
  EntryType* fromEntry =
    const_cast<EntryType*>(static_cast<const EntryType*>(aFrom));

  new (mozilla::KnownNotNull, aTo) EntryType(mozilla::Move(*fromEntry));

  fromEntry->~EntryType();
}

template<class EntryType>
void
nsTHashtable<EntryType>::s_ClearEntry(PLDHashTable* aTable,
                                      PLDHashEntryHdr* aEntry)
{
  static_cast<EntryType*>(aEntry)->~EntryType();
}

template<class EntryType>
void
nsTHashtable<EntryType>::s_InitEntry(PLDHashEntryHdr* aEntry,
                                     const void* aKey)
{
  new (mozilla::KnownNotNull, aEntry) EntryType(static_cast<KeyTypePointer>(aKey));
}

class nsCycleCollectionTraversalCallback;

template<class EntryType>
inline void
ImplCycleCollectionUnlink(nsTHashtable<EntryType>& aField)
{
  aField.Clear();
}

template<class EntryType>
inline void
ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
                            nsTHashtable<EntryType>& aField,
                            const char* aName,
                            uint32_t aFlags = 0)
{
  for (auto iter = aField.Iter(); !iter.Done(); iter.Next()) {
    EntryType* entry = iter.Get();
    ImplCycleCollectionTraverse(aCallback, *entry, aName, aFlags);
  }
}

/**
 * For nsTHashtable with pointer entries, we can have a template specialization
 * that layers a typed T* interface on top of a common implementation that
 * works internally with void pointers.  This arrangement saves code size and
 * might slightly improve performance as well.
 */

/**
 * We need a separate entry type class for the inheritance structure of the
 * nsTHashtable specialization below; nsVoidPtrHashKey is simply typedefed to a
 * specialization of nsPtrHashKey, and the formulation:
 *
 * class nsTHashtable<nsPtrHashKey<T>> : protected nsTHashtable<nsPtrHashKey<const void>
 *
 * is not going to turn out very well, since we'd wind up with an nsTHashtable
 * instantiation that is its own base class.
 */
namespace detail {

class VoidPtrHashKey : public nsPtrHashKey<const void>
{
  typedef nsPtrHashKey<const void> Base;

public:
  explicit VoidPtrHashKey(const void* aKey) : Base(aKey) {}
};

} // namespace detail

/**
 * See the main nsTHashtable documentation for descriptions of this class's
 * methods.
 */
template<typename T>
class nsTHashtable<nsPtrHashKey<T>> : protected nsTHashtable<::detail::VoidPtrHashKey>
{
  typedef nsTHashtable<::detail::VoidPtrHashKey> Base;
  typedef nsPtrHashKey<T> EntryType;

  // We play games with reinterpret_cast'ing between these two classes, so
  // try to ensure that playing said games is reasonable.
  static_assert(sizeof(nsPtrHashKey<T>) == sizeof(::detail::VoidPtrHashKey),
                "hash keys must be the same size");

  nsTHashtable(const nsTHashtable& aOther) = delete;
  nsTHashtable& operator=(const nsTHashtable& aOther) = delete;

public:
  nsTHashtable() = default;
  explicit nsTHashtable(uint32_t aInitLength)
    : Base(aInitLength)
  {}

  ~nsTHashtable() = default;

  nsTHashtable(nsTHashtable&&) = default;

  /* Wrapper functions */
  using Base::GetGeneration;
  using Base::Count;
  using Base::IsEmpty;
  using Base::Clear;

  using Base::ShallowSizeOfExcludingThis;
  using Base::ShallowSizeOfIncludingThis;

#ifdef DEBUG
  using Base::MarkImmutable;
#endif

  EntryType* GetEntry(T* aKey) const
  {
    return reinterpret_cast<EntryType*>(Base::GetEntry(aKey));
  }

  bool Contains(T* aKey) const
  {
    return Base::Contains(aKey);
  }

  EntryType* PutEntry(T* aKey)
  {
    return reinterpret_cast<EntryType*>(Base::PutEntry(aKey));
  }

  MOZ_MUST_USE
  EntryType* PutEntry(T* aKey, const mozilla::fallible_t&)
  {
    return reinterpret_cast<EntryType*>(
      Base::PutEntry(aKey, mozilla::fallible));
  }

  void RemoveEntry(T* aKey)
  {
    Base::RemoveEntry(aKey);
  }

  void RemoveEntry(EntryType* aEntry)
  {
    Base::RemoveEntry(reinterpret_cast<::detail::VoidPtrHashKey*>(aEntry));
  }

  void RawRemoveEntry(EntryType* aEntry)
  {
    Base::RawRemoveEntry(reinterpret_cast<::detail::VoidPtrHashKey*>(aEntry));
  }

  class Iterator : public Base::Iterator
  {
  public:
    typedef nsTHashtable::Base::Iterator Base;

    explicit Iterator(nsTHashtable* aTable) : Base(aTable) {}
    Iterator(Iterator&& aOther) : Base(mozilla::Move(aOther)) {}
    ~Iterator() = default;

    EntryType* Get() const { return reinterpret_cast<EntryType*>(Base::Get()); }

  private:
    Iterator() = delete;
    Iterator(const Iterator&) = delete;
    Iterator& operator=(const Iterator&) = delete;
    Iterator& operator=(Iterator&&) = delete;
  };

  Iterator Iter() { return Iterator(this); }

  Iterator ConstIter() const
  {
    return Iterator(const_cast<nsTHashtable*>(this));
  }

  void SwapElements(nsTHashtable& aOther)
  {
    Base::SwapElements(aOther);
  }
};

#endif // nsTHashtable_h__