/* -*- 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/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); }
/**
* Infallibly get the entry associated with a key, or create a new entry,
* @param aKey the key to retrieve
* @return pointer to the entry retrieved; never nullptr
*/
EntryType* PutEntry(KeyType aKey) {
// infallible add
return static_cast<EntryType*>(mTable.Add(EntryType::KeyToPointer(aKey)));
}
/**
* Fallibly get the entry associated with a key, or create a new entry,
* @param aKey the key to retrieve
* @return pointer to the entry retrieved; nullptr only if memory can't
* be allocated
*/
MOZ_MUST_USE
EntryType* PutEntry(KeyType aKey, const fallible_t&) {
return static_cast<EntryType*>(
mTable.Add(EntryType::KeyToPointer(aKey), mozilla::fallible));
}
/**
* Get the entry associated with a key, or create a new entry using infallible
* allocation and insert that.
* @param aKey the key to retrieve
* @param aEntry will be assigned (if non-null) to the entry that was
* found or created
* @return true if a new entry was created, or false if an existing entry
* was found
*/
MOZ_MUST_USE
bool EnsureInserted(KeyType aKey, EntryType** aEntry = nullptr) {
auto oldCount = Count();
EntryType* entry = PutEntry(aKey);
if (aEntry) {
*aEntry = entry;
}
return oldCount != Count();
}
/**
* Remove the entry associated with a key.
* @param aKey of the entry to remove
*/
void RemoveEntry(KeyType aKey) {
mTable.Remove(EntryType::KeyToPointer(aKey));
}
/**
* Lookup the entry associated with aKey and remove it if found, otherwise
* do nothing.
* @param aKey of the entry to remove
* @return true if an entry was found and removed, or false if no entry
* was found for aKey
*/
bool EnsureRemoved(KeyType aKey) {
auto* entry = GetEntry(aKey);
if (entry) {
RemoveEntry(entry);
return true;
}
return false;
}
/**
* 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;
};
namespace mozilla {
namespace detail {
// Like PLDHashTable::MoveEntryStub, but specialized for fixed N (i.e. the size
// of the entries in the hashtable). Saves a memory read to figure out the size
// from the table and gives the compiler the opportunity to inline the memcpy.
//
// We define this outside of nsTHashtable so only one copy exists for every N,
// rather than separate copies for every EntryType used with nsTHashtable.
template <size_t N>
static void FixedSizeEntryMover(PLDHashTable*, const PLDHashEntryHdr* aFrom,
PLDHashEntryHdr* aTo) {
memcpy(aTo, aFrom, N);
}
} // namespace detail
} // namespace mozilla
//
// template definitions
//
template <class EntryType>
nsTHashtable<EntryType>::nsTHashtable(nsTHashtable<EntryType>&& aOther)
: mTable(mozilla::Move(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
? mozilla::detail::FixedSizeEntryMover<sizeof(EntryType)>
: 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;
using Base::Clear;
using Base::Count;
using Base::GetGeneration;
using Base::IsEmpty;
using Base::ShallowSizeOfExcludingThis;
using Base::ShallowSizeOfIncludingThis;
#ifdef DEBUG
using Base::MarkImmutable;
#endif
/* Wrapper functions */
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));
}
MOZ_MUST_USE
bool EnsureInserted(T* aKey, EntryType** aEntry = nullptr) {
return Base::EnsureInserted(
aKey, reinterpret_cast<::detail::VoidPtrHashKey**>(aEntry));
}
void RemoveEntry(T* aKey) { Base::RemoveEntry(aKey); }
bool EnsureRemoved(T* aKey) { return Base::EnsureRemoved(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__