gecko-dev/xpcom/ds/nsBaseHashtable.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 nsBaseHashtable_h__
#define nsBaseHashtable_h__
#include "mozilla/MemoryReporting.h"
#include "mozilla/Move.h"
#include "nsTHashtable.h"
#include "nsDebug.h"
template<class KeyClass, class DataType, class UserDataType>
class nsBaseHashtable; // forward declaration
/**
* the private nsTHashtable::EntryType class used by nsBaseHashtable
* @see nsTHashtable for the specification of this class
* @see nsBaseHashtable for template parameters
*/
template<class KeyClass, class DataType>
class nsBaseHashtableET : public KeyClass
{
public:
DataType mData;
friend class nsTHashtable<nsBaseHashtableET<KeyClass, DataType>>;
private:
typedef typename KeyClass::KeyType KeyType;
typedef typename KeyClass::KeyTypePointer KeyTypePointer;
explicit nsBaseHashtableET(KeyTypePointer aKey);
nsBaseHashtableET(nsBaseHashtableET<KeyClass, DataType>&& aToMove);
~nsBaseHashtableET();
};
/**
* templated hashtable for simple data types
* This class manages simple data types that do not need construction or
* destruction.
*
* @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
* for a complete specification.
* @param DataType the datatype stored in the hashtable,
* for example, uint32_t or nsCOMPtr. If UserDataType is not the same,
* DataType must implicitly cast to UserDataType
* @param UserDataType the user sees, for example uint32_t or nsISupports*
*/
template<class KeyClass, class DataType, class UserDataType>
class nsBaseHashtable
: protected nsTHashtable<nsBaseHashtableET<KeyClass, DataType>>
{
typedef mozilla::fallible_t fallible_t;
public:
typedef typename KeyClass::KeyType KeyType;
typedef nsBaseHashtableET<KeyClass, DataType> EntryType;
using nsTHashtable<EntryType>::Contains;
nsBaseHashtable() {}
explicit nsBaseHashtable(uint32_t aInitLength)
: nsTHashtable<EntryType>(aInitLength)
{
}
/**
* Return the number of entries in the table.
* @return number of entries
*/
uint32_t Count() const { return nsTHashtable<EntryType>::Count(); }
/**
* retrieve the value for a key.
* @param aKey the key to retreive
* @param aData data associated with this key will be placed at this
* pointer. If you only need to check if the key exists, aData
* may be null.
* @return true if the key exists. If key does not exist, aData is not
* modified.
*/
bool Get(KeyType aKey, UserDataType* aData) const
{
EntryType* ent = this->GetEntry(aKey);
if (!ent) {
return false;
}
if (aData) {
*aData = ent->mData;
}
return true;
}
/**
* Get the value, returning a zero-initialized POD or a default-initialized
* object if the entry is not present in the table.
*
* @param aKey the key to retrieve
* @return The found value, or UserDataType{} if no entry was found with the
* given key.
* @note If zero/default-initialized values are stored in the table, it is
* not possible to distinguish between such a value and a missing entry.
*/
UserDataType Get(KeyType aKey) const
{
EntryType* ent = this->GetEntry(aKey);
if (!ent) {
return UserDataType{};
}
return ent->mData;
}
/**
* Add key to the table if not already present, and return a reference to its
* value. If key is not already in the table then the value is default
* constructed.
*/
DataType& GetOrInsert(const KeyType& aKey)
{
EntryType* ent = this->GetEntry(aKey);
if (ent) {
return ent->mData;
}
ent = this->PutEntry(aKey);
return ent->mData;
}
/**
* put a new value for the associated key
* @param aKey the key to put
* @param aData the new data
* @return always true, unless memory allocation failed
*/
void Put(KeyType aKey, const UserDataType& aData)
{
if (!Put(aKey, aData, mozilla::fallible)) {
NS_ABORT_OOM(this->mTable.EntrySize() * this->mTable.EntryCount());
}
}
MOZ_MUST_USE bool Put(KeyType aKey, const UserDataType& aData,
const fallible_t&)
{
EntryType* ent = this->PutEntry(aKey, mozilla::fallible);
if (!ent) {
return false;
}
ent->mData = aData;
return true;
}
/**
* remove the data for the associated key
* @param aKey the key to remove from the hashtable
*/
void Remove(KeyType aKey) { this->RemoveEntry(aKey); }
// This is an iterator that also allows entry removal. Example usage:
//
// for (auto iter = table.Iter(); !iter.Done(); iter.Next()) {
// const KeyType key = iter.Key();
// const UserDataType data = iter.UserData();
// // or
// const DataType& data = iter.Data();
// // ... do stuff with |key| and/or |data| ...
// // ... possibly call iter.Remove() once ...
// }
//
class Iterator : public PLDHashTable::Iterator
{
public:
typedef PLDHashTable::Iterator Base;
explicit Iterator(nsBaseHashtable* aTable) : Base(&aTable->mTable) {}
Iterator(Iterator&& aOther) : Base(aOther.mTable) {}
~Iterator() {}
KeyType Key() const { return static_cast<EntryType*>(Get())->GetKey(); }
UserDataType UserData() const
{
return static_cast<EntryType*>(Get())->mData;
}
DataType& Data() const { return static_cast<EntryType*>(Get())->mData; }
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<nsBaseHashtable*>(this));
}
/**
* reset the hashtable, removing all entries
*/
void Clear() { nsTHashtable<EntryType>::Clear(); }
/**
* Measure the size of the table's entry storage. The size of things pointed
* to by entries must be measured separately; hence the "Shallow" prefix.
*
* @param aMallocSizeOf the function used to measure heap-allocated blocks
* @return the summed size of the table's storage
*/
size_t ShallowSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
{
return this->mTable.ShallowSizeOfExcludingThis(aMallocSizeOf);
}
/**
* Like ShallowSizeOfExcludingThis, but includes sizeof(*this).
*/
size_t ShallowSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
{
return aMallocSizeOf(this) + ShallowSizeOfExcludingThis(aMallocSizeOf);
}
/**
* Swap the elements in this hashtable with the elements in aOther.
*/
void SwapElements(nsBaseHashtable& aOther)
{
nsTHashtable<EntryType>::SwapElements(aOther);
}
#ifdef DEBUG
using nsTHashtable<EntryType>::MarkImmutable;
#endif
};
//
// nsBaseHashtableET definitions
//
template<class KeyClass, class DataType>
nsBaseHashtableET<KeyClass, DataType>::nsBaseHashtableET(KeyTypePointer aKey)
: KeyClass(aKey)
, mData()
{
}
template<class KeyClass, class DataType>
nsBaseHashtableET<KeyClass, DataType>::nsBaseHashtableET(
nsBaseHashtableET<KeyClass, DataType>&& aToMove)
: KeyClass(mozilla::Move(aToMove))
, mData(mozilla::Move(aToMove.mData))
{
}
template<class KeyClass, class DataType>
nsBaseHashtableET<KeyClass, DataType>::~nsBaseHashtableET()
{
}
#endif // nsBaseHashtable_h__