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2511b2c327
It's an annotation that is used a lot, and should be used even more, so a shorter name is better. MozReview-Commit-ID: 1VS4Dney4WX --HG-- extra : rebase_source : b26919c1b0fcb32e5339adeef5be5becae6032cf
438 lines
13 KiB
C++
438 lines
13 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsTHashtable_h__
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#define nsTHashtable_h__
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#include "PLDHashTable.h"
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#include "mozilla/Assertions.h"
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#include "mozilla/Attributes.h"
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#include "mozilla/fallible.h"
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#include "mozilla/MemoryChecking.h"
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#include "mozilla/MemoryReporting.h"
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#include "mozilla/Move.h"
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#include "mozilla/PodOperations.h"
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#include "mozilla/TypeTraits.h"
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#include <new>
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/**
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* a base class for templated hashtables.
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*
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* Clients will rarely need to use this class directly. Check the derived
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* classes first, to see if they will meet your needs.
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*
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* @param EntryType the templated entry-type class that is managed by the
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* hashtable. <code>EntryType</code> must extend the following declaration,
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* and <strong>must not declare any virtual functions or derive from classes
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* with virtual functions.</strong> Any vtable pointer would break the
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* PLDHashTable code.
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*<pre> class EntryType : public PLDHashEntryHdr
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* {
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* public: or friend nsTHashtable<EntryType>;
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* // KeyType is what we use when Get()ing or Put()ing this entry
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* // this should either be a simple datatype (uint32_t, nsISupports*) or
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* // a const reference (const nsAString&)
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* typedef something KeyType;
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* // KeyTypePointer is the pointer-version of KeyType, because
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* // PLDHashTable.h requires keys to cast to <code>const void*</code>
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* typedef const something* KeyTypePointer;
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*
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* EntryType(KeyTypePointer aKey);
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*
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* // A copy or C++11 Move constructor must be defined, even if
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* // AllowMemMove() == true, otherwise you will cause link errors.
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* EntryType(const EntryType& aEnt); // Either this...
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* EntryType(EntryType&& aEnt); // ...or this
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*
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* // the destructor must be defined... or you will cause link errors!
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* ~EntryType();
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*
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* // KeyEquals(): does this entry match this key?
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* bool KeyEquals(KeyTypePointer aKey) const;
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*
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* // KeyToPointer(): Convert KeyType to KeyTypePointer
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* static KeyTypePointer KeyToPointer(KeyType aKey);
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*
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* // HashKey(): calculate the hash number
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* static PLDHashNumber HashKey(KeyTypePointer aKey);
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*
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* // ALLOW_MEMMOVE can we move this class with memmove(), or do we have
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* // to use the copy constructor?
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* enum { ALLOW_MEMMOVE = true/false };
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* }</pre>
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*
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* @see nsInterfaceHashtable
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* @see nsDataHashtable
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* @see nsClassHashtable
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* @author "Benjamin Smedberg <bsmedberg@covad.net>"
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*/
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template<class EntryType>
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class MOZ_NEEDS_NO_VTABLE_TYPE nsTHashtable
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{
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typedef mozilla::fallible_t fallible_t;
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static_assert(mozilla::IsPointer<typename EntryType::KeyTypePointer>::value,
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"KeyTypePointer should be a pointer");
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public:
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// Separate constructors instead of default aInitLength parameter since
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// otherwise the default no-arg constructor isn't found.
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nsTHashtable()
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: mTable(Ops(), sizeof(EntryType), PLDHashTable::kDefaultInitialLength)
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{}
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explicit nsTHashtable(uint32_t aInitLength)
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: mTable(Ops(), sizeof(EntryType), aInitLength)
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{}
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/**
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* destructor, cleans up and deallocates
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*/
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~nsTHashtable();
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nsTHashtable(nsTHashtable<EntryType>&& aOther);
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/**
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* Return the generation number for the table. This increments whenever
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* the table data items are moved.
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*/
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uint32_t GetGeneration() const { return mTable.Generation(); }
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/**
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* KeyType is typedef'ed for ease of use.
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*/
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typedef typename EntryType::KeyType KeyType;
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/**
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* KeyTypePointer is typedef'ed for ease of use.
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*/
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typedef typename EntryType::KeyTypePointer KeyTypePointer;
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/**
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* Return the number of entries in the table.
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* @return number of entries
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*/
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uint32_t Count() const { return mTable.EntryCount(); }
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/**
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* Return true if the hashtable is empty.
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*/
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bool IsEmpty() const { return Count() == 0; }
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/**
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* Get the entry associated with a key.
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* @param aKey the key to retrieve
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* @return pointer to the entry class, if the key exists; nullptr if the
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* key doesn't exist
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*/
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EntryType* GetEntry(KeyType aKey) const
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{
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return static_cast<EntryType*>(
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const_cast<PLDHashTable*>(&mTable)->Search(EntryType::KeyToPointer(aKey)));
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}
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/**
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* Return true if an entry for the given key exists, false otherwise.
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* @param aKey the key to retrieve
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* @return true if the key exists, false if the key doesn't exist
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*/
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bool Contains(KeyType aKey) const { return !!GetEntry(aKey); }
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/**
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* Get the entry associated with a key, or create a new entry,
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* @param aKey the key to retrieve
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* @return pointer to the entry class retreived; nullptr only if memory
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can't be allocated
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*/
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EntryType* PutEntry(KeyType aKey)
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{
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// infallible add
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return static_cast<EntryType*>(mTable.Add(EntryType::KeyToPointer(aKey)));
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}
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MOZ_MUST_USE
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EntryType* PutEntry(KeyType aKey, const fallible_t&)
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{
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return static_cast<EntryType*>(mTable.Add(EntryType::KeyToPointer(aKey),
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mozilla::fallible));
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}
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/**
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* Remove the entry associated with a key.
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* @param aKey of the entry to remove
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*/
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void RemoveEntry(KeyType aKey)
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{
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mTable.Remove(EntryType::KeyToPointer(aKey));
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}
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/**
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* Remove the entry associated with a key.
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* @param aEntry the entry-pointer to remove (obtained from GetEntry)
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*/
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void RemoveEntry(EntryType* aEntry)
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{
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mTable.RemoveEntry(aEntry);
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}
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/**
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* Remove the entry associated with a key, but don't resize the hashtable.
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* This is a low-level method, and is not recommended unless you know what
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* you're doing. If you use it, please add a comment explaining why you
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* didn't use RemoveEntry().
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* @param aEntry the entry-pointer to remove (obtained from GetEntry)
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*/
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void RawRemoveEntry(EntryType* aEntry)
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{
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mTable.RawRemove(aEntry);
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}
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// This is an iterator that also allows entry removal. Example usage:
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//
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// for (auto iter = table.Iter(); !iter.Done(); iter.Next()) {
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// Entry* entry = iter.Get();
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// // ... do stuff with |entry| ...
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// // ... possibly call iter.Remove() once ...
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// }
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//
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class Iterator : public PLDHashTable::Iterator
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{
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public:
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typedef PLDHashTable::Iterator Base;
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explicit Iterator(nsTHashtable* aTable) : Base(&aTable->mTable) {}
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Iterator(Iterator&& aOther) : Base(aOther.mTable) {}
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~Iterator() {}
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EntryType* Get() const { return static_cast<EntryType*>(Base::Get()); }
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private:
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Iterator() = delete;
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Iterator(const Iterator&) = delete;
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Iterator& operator=(const Iterator&) = delete;
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Iterator& operator=(const Iterator&&) = delete;
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};
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Iterator Iter() { return Iterator(this); }
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Iterator ConstIter() const
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{
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return Iterator(const_cast<nsTHashtable*>(this));
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}
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/**
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* Remove all entries, return hashtable to "pristine" state. It's
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* conceptually the same as calling the destructor and then re-calling the
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* constructor.
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*/
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void Clear()
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{
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mTable.Clear();
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}
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/**
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* Measure the size of the table's entry storage. Does *not* measure anything
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* hanging off table entries; hence the "Shallow" prefix. To measure that,
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* either use SizeOfExcludingThis() or iterate manually over the entries,
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* calling SizeOfExcludingThis() on each one.
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*
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* @param aMallocSizeOf the function used to measure heap-allocated blocks
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* @return the measured shallow size of the table
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*/
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size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
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{
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return mTable.ShallowSizeOfExcludingThis(aMallocSizeOf);
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}
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/**
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* Like ShallowSizeOfExcludingThis, but includes sizeof(*this).
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*/
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size_t ShallowSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
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{
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return aMallocSizeOf(this) + ShallowSizeOfExcludingThis(aMallocSizeOf);
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}
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/**
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* This is a "deep" measurement of the table. To use it, |EntryType| must
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* define SizeOfExcludingThis, and that method will be called on all live
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* entries.
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*/
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size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
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{
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size_t n = ShallowSizeOfExcludingThis(aMallocSizeOf);
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for (auto iter = ConstIter(); !iter.Done(); iter.Next()) {
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n += (*iter.Get()).SizeOfExcludingThis(aMallocSizeOf);
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}
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return n;
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}
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/**
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* Like SizeOfExcludingThis, but includes sizeof(*this).
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*/
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size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
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{
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return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
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}
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/**
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* Swap the elements in this hashtable with the elements in aOther.
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*/
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void SwapElements(nsTHashtable<EntryType>& aOther)
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{
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MOZ_ASSERT_IF(this->mTable.Ops() && aOther.mTable.Ops(),
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this->mTable.Ops() == aOther.mTable.Ops());
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mozilla::Swap(this->mTable, aOther.mTable);
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}
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#ifdef DEBUG
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/**
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* Mark the table as constant after initialization.
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*
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* This will prevent assertions when a read-only hash is accessed on multiple
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* threads without synchronization.
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*/
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void MarkImmutable()
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{
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mTable.MarkImmutable();
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}
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#endif
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protected:
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PLDHashTable mTable;
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static PLDHashNumber s_HashKey(const void* aKey);
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static bool s_MatchEntry(const PLDHashEntryHdr* aEntry,
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const void* aKey);
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static void s_CopyEntry(PLDHashTable* aTable, const PLDHashEntryHdr* aFrom,
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PLDHashEntryHdr* aTo);
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static void s_ClearEntry(PLDHashTable* aTable, PLDHashEntryHdr* aEntry);
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static void s_InitEntry(PLDHashEntryHdr* aEntry, const void* aKey);
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private:
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// copy constructor, not implemented
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nsTHashtable(nsTHashtable<EntryType>& aToCopy) = delete;
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/**
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* Gets the table's ops.
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*/
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static const PLDHashTableOps* Ops();
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// assignment operator, not implemented
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nsTHashtable<EntryType>& operator=(nsTHashtable<EntryType>& aToEqual) = delete;
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};
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//
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// template definitions
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//
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template<class EntryType>
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nsTHashtable<EntryType>::nsTHashtable(nsTHashtable<EntryType>&& aOther)
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: mTable(mozilla::Move(aOther.mTable))
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{
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// aOther shouldn't touch mTable after this, because we've stolen the table's
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// pointers but not overwitten them.
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MOZ_MAKE_MEM_UNDEFINED(&aOther.mTable, sizeof(aOther.mTable));
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}
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template<class EntryType>
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nsTHashtable<EntryType>::~nsTHashtable()
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{
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}
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template<class EntryType>
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/* static */ const PLDHashTableOps*
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nsTHashtable<EntryType>::Ops()
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{
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// If this variable is a global variable, we get strange start-up failures on
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// WindowsCrtPatch.h (see bug 1166598 comment 20). But putting it inside a
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// function avoids that problem.
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static const PLDHashTableOps sOps =
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{
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s_HashKey,
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s_MatchEntry,
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EntryType::ALLOW_MEMMOVE ? PLDHashTable::MoveEntryStub : s_CopyEntry,
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s_ClearEntry,
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s_InitEntry
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};
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return &sOps;
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}
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// static definitions
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template<class EntryType>
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PLDHashNumber
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nsTHashtable<EntryType>::s_HashKey(const void* aKey)
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{
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return EntryType::HashKey(static_cast<const KeyTypePointer>(aKey));
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}
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template<class EntryType>
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bool
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nsTHashtable<EntryType>::s_MatchEntry(const PLDHashEntryHdr* aEntry,
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const void* aKey)
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{
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return ((const EntryType*)aEntry)->KeyEquals(
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static_cast<const KeyTypePointer>(aKey));
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}
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template<class EntryType>
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void
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nsTHashtable<EntryType>::s_CopyEntry(PLDHashTable* aTable,
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const PLDHashEntryHdr* aFrom,
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PLDHashEntryHdr* aTo)
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{
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EntryType* fromEntry =
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const_cast<EntryType*>(static_cast<const EntryType*>(aFrom));
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new (aTo) EntryType(mozilla::Move(*fromEntry));
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fromEntry->~EntryType();
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}
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template<class EntryType>
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void
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nsTHashtable<EntryType>::s_ClearEntry(PLDHashTable* aTable,
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PLDHashEntryHdr* aEntry)
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{
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static_cast<EntryType*>(aEntry)->~EntryType();
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}
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template<class EntryType>
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void
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nsTHashtable<EntryType>::s_InitEntry(PLDHashEntryHdr* aEntry,
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const void* aKey)
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{
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new (aEntry) EntryType(static_cast<KeyTypePointer>(aKey));
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}
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class nsCycleCollectionTraversalCallback;
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template<class EntryType>
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inline void
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ImplCycleCollectionUnlink(nsTHashtable<EntryType>& aField)
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{
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aField.Clear();
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}
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template<class EntryType>
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inline void
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ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
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nsTHashtable<EntryType>& aField,
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const char* aName,
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uint32_t aFlags = 0)
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{
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for (auto iter = aField.Iter(); !iter.Done(); iter.Next()) {
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EntryType* entry = iter.Get();
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ImplCycleCollectionTraverse(aCallback, *entry, aName, aFlags);
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}
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}
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#endif // nsTHashtable_h__
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