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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /xpcom/glue/nsTHashtable.h
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Add m-esr52 at 52.6.0
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diff --git a/xpcom/glue/nsTHashtable.h b/xpcom/glue/nsTHashtable.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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<const KeyTypePointer>(aKey));
+}
+
+template<class EntryType>
+bool
+nsTHashtable<EntryType>::s_MatchEntry(const PLDHashEntryHdr* aEntry,
+ const void* aKey)
+{
+ return ((const EntryType*)aEntry)->KeyEquals(
+ static_cast<const 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__