nsTHashtable.h
/* -*- Mode: C++; tab-width: 2; 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 "nscore.h"
#include "pldhash.h"
#include "nsDebug.h"
#include NEW_H
#include "mozilla/fallible.h"
// helper function for nsTHashtable::Clear()
NS_COM_GLUE PLDHashOperator
PL_DHashStubEnumRemove(PLDHashTable *table,
PLDHashEntryHdr *entry,
uint32_t ordinal,
void *userArg);
/**
* 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 pldhash.h
* // requires keys to cast to <code>const void*</code>
* typedef const something* KeyTypePointer;
*
* EntryType(KeyTypePointer aKey);
*
* // the copy constructor must be defined, even if AllowMemMove() == true
* // or you will cause link errors!
* EntryType(const EntryType& aEnt);
*
* // 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 = PR_(TRUE or FALSE) };
* }</pre>
*
* @see nsInterfaceHashtable
* @see nsDataHashtable
* @see nsClassHashtable
* @author "Benjamin Smedberg <bsmedberg@covad.net>"
*/
template<class EntryType>
class nsTHashtable
{
typedef mozilla::fallible_t fallible_t;
public:
/**
* A dummy constructor; you must call Init() before using this class.
*/
nsTHashtable();
/**
* destructor, cleans up and deallocates
*/
~nsTHashtable();
/**
* Initialize the table. This function must be called before any other
* class operations. This can fail due to OOM conditions.
* @param initSize the initial number of buckets in the hashtable, default 16
* @return true if the class was initialized properly.
*/
void Init(uint32_t initSize = PL_DHASH_MIN_SIZE)
{
if (!Init(initSize, fallible_t()))
NS_RUNTIMEABORT("OOM");
}
bool Init(const fallible_t&) NS_WARN_UNUSED_RESULT
{ return Init(PL_DHASH_MIN_SIZE, fallible_t()); }
bool Init(uint32_t initSize, const fallible_t&) NS_WARN_UNUSED_RESULT;
/**
* Check whether the table has been initialized. This can be useful for static hashtables.
* @return the initialization state of the class.
*/
bool IsInitialized() const { return !!mTable.entrySize; }
/**
* 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; }
/**
* 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
{
NS_ASSERTION(mTable.entrySize, "nsTHashtable was not initialized properly.");
EntryType* entry =
reinterpret_cast<EntryType*>
(PL_DHashTableOperate(
const_cast<PLDHashTable*>(&mTable),
EntryType::KeyToPointer(aKey),
PL_DHASH_LOOKUP));
return PL_DHASH_ENTRY_IS_BUSY(entry) ? entry : nullptr;
}
/**
* 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)
{
EntryType* e = PutEntry(aKey, fallible_t());
if (!e)
NS_RUNTIMEABORT("OOM");
return e;
}
EntryType* PutEntry(KeyType aKey, const fallible_t&) NS_WARN_UNUSED_RESULT
{
NS_ASSERTION(mTable.entrySize, "nsTHashtable was not initialized properly.");
return static_cast<EntryType*>
(PL_DHashTableOperate(
&mTable,
EntryType::KeyToPointer(aKey),
PL_DHASH_ADD));
}
/**
* Remove the entry associated with a key.
* @param aKey of the entry to remove
*/
void RemoveEntry(KeyType aKey)
{
NS_ASSERTION(mTable.entrySize, "nsTHashtable was not initialized properly.");
PL_DHashTableOperate(&mTable,
EntryType::KeyToPointer(aKey),
PL_DHASH_REMOVE);
}
/**
* 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 and you need the extra performance. This method can be used
* during enumeration, while RemoveEntry() cannot.
* @param aEntry the entry-pointer to remove (obtained from GetEntry or
* the enumerator
*/
void RawRemoveEntry(EntryType* aEntry)
{
PL_DHashTableRawRemove(&mTable, aEntry);
}
/**
* client must provide an <code>Enumerator</code> function for
* EnumerateEntries
* @param aEntry the entry being enumerated
* @param userArg passed unchanged from <code>EnumerateEntries</code>
* @return combination of flags
* @link PLDHashOperator::PL_DHASH_NEXT PL_DHASH_NEXT @endlink ,
* @link PLDHashOperator::PL_DHASH_STOP PL_DHASH_STOP @endlink ,
* @link PLDHashOperator::PL_DHASH_REMOVE PL_DHASH_REMOVE @endlink
*/
typedef PLDHashOperator (* Enumerator)(EntryType* aEntry, void* userArg);
/**
* Enumerate all the entries of the function.
* @param enumFunc the <code>Enumerator</code> function to call
* @param userArg a pointer to pass to the
* <code>Enumerator</code> function
* @return the number of entries actually enumerated
*/
uint32_t EnumerateEntries(Enumerator enumFunc, void* userArg)
{
NS_ASSERTION(mTable.entrySize, "nsTHashtable was not initialized properly.");
s_EnumArgs args = { enumFunc, userArg };
return PL_DHashTableEnumerate(&mTable, s_EnumStub, &args);
}
/**
* remove all entries, return hashtable to "pristine" state ;)
*/
void Clear()
{
NS_ASSERTION(mTable.entrySize, "nsTHashtable was not initialized properly.");
PL_DHashTableEnumerate(&mTable, PL_DHashStubEnumRemove, nullptr);
}
/**
* client must provide a <code>SizeOfEntryExcludingThisFun</code> function for
* SizeOfExcludingThis.
* @param aEntry the entry being enumerated
* @param mallocSizeOf the function used to measure heap-allocated blocks
* @param arg passed unchanged from <code>SizeOf{In,Ex}cludingThis</code>
* @return summed size of the things pointed to by the entries
*/
typedef size_t (* SizeOfEntryExcludingThisFun)(EntryType* aEntry,
nsMallocSizeOfFun mallocSizeOf,
void *arg);
/**
* Measure the size of the table's entry storage, and if
* |sizeOfEntryExcludingThis| is non-NULL, measure the size of things pointed
* to by entries.
*
* @param sizeOfEntryExcludingThis the
* <code>SizeOfEntryExcludingThisFun</code> function to call
* @param mallocSizeOf the function used to measure heap-allocated blocks
* @param userArg a pointer to pass to the
* <code>SizeOfEntryExcludingThisFun</code> function
* @return the summed size of all the entries
*/
size_t SizeOfExcludingThis(SizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
nsMallocSizeOfFun mallocSizeOf, void *userArg = NULL) const
{
if (!IsInitialized()) {
return 0;
}
if (sizeOfEntryExcludingThis) {
s_SizeOfArgs args = { sizeOfEntryExcludingThis, userArg };
return PL_DHashTableSizeOfExcludingThis(&mTable, s_SizeOfStub, mallocSizeOf, &args);
}
return PL_DHashTableSizeOfExcludingThis(&mTable, NULL, mallocSizeOf);
}
#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()
{
NS_ASSERTION(mTable.entrySize, "nsTHashtable was not initialized properly.");
PL_DHashMarkTableImmutable(&mTable);
}
#endif
protected:
PLDHashTable mTable;
static const void* s_GetKey(PLDHashTable *table,
PLDHashEntryHdr *entry);
static PLDHashNumber s_HashKey(PLDHashTable *table,
const void *key);
static bool s_MatchEntry(PLDHashTable *table,
const PLDHashEntryHdr *entry,
const void *key);
static void s_CopyEntry(PLDHashTable *table,
const PLDHashEntryHdr *from,
PLDHashEntryHdr *to);
static void s_ClearEntry(PLDHashTable *table,
PLDHashEntryHdr *entry);
static bool s_InitEntry(PLDHashTable *table,
PLDHashEntryHdr *entry,
const void *key);
/**
* passed internally during enumeration. Allocated on the stack.
*
* @param userFunc the Enumerator function passed to
* EnumerateEntries by the client
* @param userArg the userArg passed unaltered
*/
struct s_EnumArgs
{
Enumerator userFunc;
void* userArg;
};
static PLDHashOperator s_EnumStub(PLDHashTable *table,
PLDHashEntryHdr *entry,
uint32_t number,
void *arg);
/**
* passed internally during sizeOf counting. Allocated on the stack.
*
* @param userFunc the SizeOfEntryExcludingThisFun passed to
* SizeOf{In,Ex}cludingThis by the client
* @param userArg the userArg passed unaltered
*/
struct s_SizeOfArgs
{
SizeOfEntryExcludingThisFun userFunc;
void* userArg;
};
static size_t s_SizeOfStub(PLDHashEntryHdr *entry,
nsMallocSizeOfFun mallocSizeOf,
void *arg);
private:
// copy constructor, not implemented
nsTHashtable(nsTHashtable<EntryType>& toCopy);
// assignment operator, not implemented
nsTHashtable<EntryType>& operator= (nsTHashtable<EntryType>& toEqual);
};
//
// template definitions
//
template<class EntryType>
nsTHashtable<EntryType>::nsTHashtable()
{
// entrySize is our "I'm initialized" indicator
mTable.entrySize = 0;
}
template<class EntryType>
nsTHashtable<EntryType>::~nsTHashtable()
{
if (mTable.entrySize)
PL_DHashTableFinish(&mTable);
}
template<class EntryType>
bool
nsTHashtable<EntryType>::Init(uint32_t initSize, const fallible_t&)
{
if (mTable.entrySize)
{
NS_ERROR("nsTHashtable::Init() should not be called twice.");
return true;
}
static PLDHashTableOps sOps =
{
::PL_DHashAllocTable,
::PL_DHashFreeTable,
s_HashKey,
s_MatchEntry,
::PL_DHashMoveEntryStub,
s_ClearEntry,
::PL_DHashFinalizeStub,
s_InitEntry
};
if (!EntryType::ALLOW_MEMMOVE)
{
sOps.moveEntry = s_CopyEntry;
}
if (!PL_DHashTableInit(&mTable, &sOps, nullptr, sizeof(EntryType), initSize))
{
// if failed, reset "flag"
mTable.entrySize = 0;
return false;
}
return true;
}
// static definitions
template<class EntryType>
PLDHashNumber
nsTHashtable<EntryType>::s_HashKey(PLDHashTable *table,
const void *key)
{
return EntryType::HashKey(reinterpret_cast<const KeyTypePointer>(key));
}
template<class EntryType>
bool
nsTHashtable<EntryType>::s_MatchEntry(PLDHashTable *table,
const PLDHashEntryHdr *entry,
const void *key)
{
return ((const EntryType*) entry)->KeyEquals(
reinterpret_cast<const KeyTypePointer>(key));
}
template<class EntryType>
void
nsTHashtable<EntryType>::s_CopyEntry(PLDHashTable *table,
const PLDHashEntryHdr *from,
PLDHashEntryHdr *to)
{
EntryType* fromEntry =
const_cast<EntryType*>(reinterpret_cast<const EntryType*>(from));
new(to) EntryType(*fromEntry);
fromEntry->~EntryType();
}
template<class EntryType>
void
nsTHashtable<EntryType>::s_ClearEntry(PLDHashTable *table,
PLDHashEntryHdr *entry)
{
reinterpret_cast<EntryType*>(entry)->~EntryType();
}
template<class EntryType>
bool
nsTHashtable<EntryType>::s_InitEntry(PLDHashTable *table,
PLDHashEntryHdr *entry,
const void *key)
{
new(entry) EntryType(reinterpret_cast<KeyTypePointer>(key));
return true;
}
template<class EntryType>
PLDHashOperator
nsTHashtable<EntryType>::s_EnumStub(PLDHashTable *table,
PLDHashEntryHdr *entry,
uint32_t number,
void *arg)
{
// dereferences the function-pointer to the user's enumeration function
return (* reinterpret_cast<s_EnumArgs*>(arg)->userFunc)(
reinterpret_cast<EntryType*>(entry),
reinterpret_cast<s_EnumArgs*>(arg)->userArg);
}
template<class EntryType>
size_t
nsTHashtable<EntryType>::s_SizeOfStub(PLDHashEntryHdr *entry,
nsMallocSizeOfFun mallocSizeOf,
void *arg)
{
// dereferences the function-pointer to the user's enumeration function
return (* reinterpret_cast<s_SizeOfArgs*>(arg)->userFunc)(
reinterpret_cast<EntryType*>(entry),
mallocSizeOf,
reinterpret_cast<s_SizeOfArgs*>(arg)->userArg);
}
#endif // nsTHashtable_h__
