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gecko/xpcom/ds/nsAtomTable.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
// vim:cindent:ts=2:et:sw=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/. */
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/MemoryReporting.h"
#include "nsAtomTable.h"
#include "nsStaticAtom.h"
#include "nsString.h"
#include "nsCRT.h"
#include "pldhash.h"
#include "prenv.h"
#include "nsThreadUtils.h"
#include "nsDataHashtable.h"
#include "nsHashKeys.h"
#include "nsAutoPtr.h"
#include "nsUnicharUtils.h"
using namespace mozilla;
/**
* The shared hash table for atom lookups.
*
* XXX This should be manipulated in a threadsafe way or we should make
* sure it's only manipulated from the main thread. Probably the latter
* is better, since the former would hurt performance.
*
* If |gAtomTable.ops| is 0, then the table is uninitialized.
*/
static PLDHashTable gAtomTable;
/**
* A hashtable of static atoms that existed at app startup. This hashtable helps
* nsHtml5AtomTable.
*/
static nsDataHashtable<nsStringHashKey, nsIAtom*>* gStaticAtomTable = 0;
/**
* Whether it is still OK to add atoms to gStaticAtomTable.
*/
static bool gStaticAtomTableSealed = false;
//----------------------------------------------------------------------
/**
* Note that AtomImpl objects are sometimes converted into PermanentAtomImpl
* objects using placement new and just overwriting the vtable pointer.
*/
class AtomImpl : public nsIAtom {
public:
AtomImpl(const nsAString& aString, PLDHashNumber aKeyHash);
// This is currently only used during startup when creating a permanent atom
// from NS_RegisterStaticAtoms
AtomImpl(nsStringBuffer* aData, uint32_t aLength, PLDHashNumber aKeyHash);
protected:
// This is only intended to be used when a normal atom is turned into a
// permanent one.
AtomImpl() {
// We can't really assert that mString is a valid nsStringBuffer string,
// so do the best we can do and check for some consistencies.
NS_ASSERTION((mLength + 1) * sizeof(PRUnichar) <=
nsStringBuffer::FromData(mString)->StorageSize() &&
mString[mLength] == 0,
"Not initialized atom");
}
// We don't need a virtual destructor here because PermanentAtomImpl
// deletions aren't handled through Release().
~AtomImpl();
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIATOM
enum { REFCNT_PERMANENT_SENTINEL = UINT32_MAX };
virtual bool IsPermanent();
// We can't use the virtual function in the base class destructor.
bool IsPermanentInDestructor() {
return mRefCnt == REFCNT_PERMANENT_SENTINEL;
}
// for |#ifdef NS_BUILD_REFCNT_LOGGING| access to reference count
nsrefcnt GetRefCount() { return mRefCnt; }
size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const;
};
/**
* A non-refcounted implementation of nsIAtom.
*/
class PermanentAtomImpl MOZ_FINAL : public AtomImpl {
public:
PermanentAtomImpl(const nsAString& aString, PLDHashNumber aKeyHash)
: AtomImpl(aString, aKeyHash)
{}
PermanentAtomImpl(nsStringBuffer* aData, uint32_t aLength,
PLDHashNumber aKeyHash)
: AtomImpl(aData, aLength, aKeyHash)
{}
PermanentAtomImpl()
{}
~PermanentAtomImpl();
NS_IMETHOD_(nsrefcnt) AddRef();
NS_IMETHOD_(nsrefcnt) Release();
virtual bool IsPermanent();
// SizeOfIncludingThis() isn't needed -- the one inherited from AtomImpl is
// good enough, because PermanentAtomImpl doesn't add any new data members.
void* operator new(size_t size, AtomImpl* aAtom) CPP_THROW_NEW;
void* operator new(size_t size) CPP_THROW_NEW
{
return ::operator new(size);
}
};
//----------------------------------------------------------------------
struct AtomTableEntry : public PLDHashEntryHdr {
AtomImpl* mAtom;
};
struct AtomTableKey
{
AtomTableKey(const PRUnichar* aUTF16String, uint32_t aLength)
: mUTF16String(aUTF16String),
mUTF8String(nullptr),
mLength(aLength)
{
}
AtomTableKey(const char* aUTF8String, uint32_t aLength)
: mUTF16String(nullptr),
mUTF8String(aUTF8String),
mLength(aLength)
{
}
const PRUnichar* mUTF16String;
const char* mUTF8String;
uint32_t mLength;
};
static PLDHashNumber
AtomTableGetHash(PLDHashTable *table, const void *key)
{
const AtomTableKey *k = static_cast<const AtomTableKey*>(key);
if (k->mUTF8String) {
bool err;
uint32_t hash = HashUTF8AsUTF16(k->mUTF8String, k->mLength, &err);
if (err) {
AtomTableKey* mutableKey = const_cast<AtomTableKey*>(k);
mutableKey->mUTF8String = nullptr;
mutableKey->mLength = 0;
hash = 0;
}
return hash;
}
return HashString(k->mUTF16String, k->mLength);
}
static bool
AtomTableMatchKey(PLDHashTable *table, const PLDHashEntryHdr *entry,
const void *key)
{
const AtomTableEntry *he = static_cast<const AtomTableEntry*>(entry);
const AtomTableKey *k = static_cast<const AtomTableKey*>(key);
if (k->mUTF8String) {
return
CompareUTF8toUTF16(nsDependentCSubstring(k->mUTF8String,
k->mUTF8String + k->mLength),
nsDependentAtomString(he->mAtom)) == 0;
}
uint32_t length = he->mAtom->GetLength();
if (length != k->mLength) {
return false;
}
return memcmp(he->mAtom->GetUTF16String(),
k->mUTF16String, length * sizeof(PRUnichar)) == 0;
}
static void
AtomTableClearEntry(PLDHashTable *table, PLDHashEntryHdr *entry)
{
// Normal |AtomImpl| atoms are deleted when their refcount hits 0, and
// they then remove themselves from the table. In other words, they
// are owned by the callers who own references to them.
// |PermanentAtomImpl| permanent atoms ignore their refcount and are
// deleted when they are removed from the table at table destruction.
// In other words, they are owned by the atom table.
AtomImpl *atom = static_cast<AtomTableEntry*>(entry)->mAtom;
if (atom->IsPermanent()) {
// Note that the cast here is important since AtomImpls doesn't have a
// virtual dtor.
delete static_cast<PermanentAtomImpl*>(atom);
}
}
static bool
AtomTableInitEntry(PLDHashTable *table, PLDHashEntryHdr *entry,
const void *key)
{
static_cast<AtomTableEntry*>(entry)->mAtom = nullptr;
return true;
}
static const PLDHashTableOps AtomTableOps = {
PL_DHashAllocTable,
PL_DHashFreeTable,
AtomTableGetHash,
AtomTableMatchKey,
PL_DHashMoveEntryStub,
AtomTableClearEntry,
PL_DHashFinalizeStub,
AtomTableInitEntry
};
#ifdef DEBUG
static PLDHashOperator
DumpAtomLeaks(PLDHashTable *table, PLDHashEntryHdr *he,
uint32_t index, void *arg)
{
AtomTableEntry *entry = static_cast<AtomTableEntry*>(he);
AtomImpl* atom = entry->mAtom;
if (!atom->IsPermanent()) {
++*static_cast<uint32_t*>(arg);
nsAutoCString str;
atom->ToUTF8String(str);
fputs(str.get(), stdout);
fputs("\n", stdout);
}
return PL_DHASH_NEXT;
}
#endif
static inline
void PromoteToPermanent(AtomImpl* aAtom)
{
#ifdef NS_BUILD_REFCNT_LOGGING
{
nsrefcnt refcount = aAtom->GetRefCount();
do {
NS_LOG_RELEASE(aAtom, --refcount, "AtomImpl");
} while (refcount);
}
#endif
aAtom = new (aAtom) PermanentAtomImpl();
}
void
NS_PurgeAtomTable()
{
delete gStaticAtomTable;
if (gAtomTable.ops) {
#ifdef DEBUG
const char *dumpAtomLeaks = PR_GetEnv("MOZ_DUMP_ATOM_LEAKS");
if (dumpAtomLeaks && *dumpAtomLeaks) {
uint32_t leaked = 0;
printf("*** %d atoms still exist (including permanent):\n",
gAtomTable.entryCount);
PL_DHashTableEnumerate(&gAtomTable, DumpAtomLeaks, &leaked);
printf("*** %u non-permanent atoms leaked\n", leaked);
}
#endif
PL_DHashTableFinish(&gAtomTable);
gAtomTable.entryCount = 0;
gAtomTable.ops = nullptr;
}
}
AtomImpl::AtomImpl(const nsAString& aString, PLDHashNumber aKeyHash)
{
mLength = aString.Length();
nsRefPtr<nsStringBuffer> buf = nsStringBuffer::FromString(aString);
if (buf) {
mString = static_cast<PRUnichar*>(buf->Data());
} else {
buf = nsStringBuffer::Alloc((mLength + 1) * sizeof(PRUnichar));
mString = static_cast<PRUnichar*>(buf->Data());
CopyUnicodeTo(aString, 0, mString, mLength);
mString[mLength] = PRUnichar(0);
}
// The low bit of aKeyHash is generally useless, so shift it out
MOZ_ASSERT(sizeof(mHash) == sizeof(PLDHashNumber));
mHash = aKeyHash >> 1;
NS_ASSERTION(mString[mLength] == PRUnichar(0), "null terminated");
NS_ASSERTION(buf && buf->StorageSize() >= (mLength+1) * sizeof(PRUnichar),
"enough storage");
NS_ASSERTION(Equals(aString), "correct data");
// Take ownership of buffer
buf.forget();
}
AtomImpl::AtomImpl(nsStringBuffer* aStringBuffer, uint32_t aLength,
PLDHashNumber aKeyHash)
{
mLength = aLength;
mString = static_cast<PRUnichar*>(aStringBuffer->Data());
// Technically we could currently avoid doing this addref by instead making
// the static atom buffers have an initial refcount of 2.
aStringBuffer->AddRef();
// The low bit of aKeyHash is generally useless, so shift it out
MOZ_ASSERT(sizeof(mHash) == sizeof(PLDHashNumber));
mHash = aKeyHash >> 1;
NS_ASSERTION(mString[mLength] == PRUnichar(0), "null terminated");
NS_ASSERTION(aStringBuffer &&
aStringBuffer->StorageSize() == (mLength+1) * sizeof(PRUnichar),
"correct storage");
}
AtomImpl::~AtomImpl()
{
NS_PRECONDITION(gAtomTable.ops, "uninitialized atom hashtable");
// Permanent atoms are removed from the hashtable at shutdown, and we
// don't want to remove them twice. See comment above in
// |AtomTableClearEntry|.
if (!IsPermanentInDestructor()) {
AtomTableKey key(mString, mLength);
PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_REMOVE);
if (gAtomTable.entryCount == 0) {
PL_DHashTableFinish(&gAtomTable);
NS_ASSERTION(gAtomTable.entryCount == 0,
"PL_DHashTableFinish changed the entry count");
}
}
nsStringBuffer::FromData(mString)->Release();
}
NS_IMPL_ISUPPORTS1(AtomImpl, nsIAtom)
PermanentAtomImpl::~PermanentAtomImpl()
{
// So we can tell if we were permanent while running the base class dtor.
mRefCnt = REFCNT_PERMANENT_SENTINEL;
}
NS_IMETHODIMP_(nsrefcnt) PermanentAtomImpl::AddRef()
{
MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
return 2;
}
NS_IMETHODIMP_(nsrefcnt) PermanentAtomImpl::Release()
{
MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
return 1;
}
/* virtual */ bool
AtomImpl::IsPermanent()
{
return false;
}
/* virtual */ bool
PermanentAtomImpl::IsPermanent()
{
return true;
}
void* PermanentAtomImpl::operator new ( size_t size, AtomImpl* aAtom ) CPP_THROW_NEW {
MOZ_ASSERT(!aAtom->IsPermanent(),
"converting atom that's already permanent");
// Just let the constructor overwrite the vtable pointer.
return aAtom;
}
NS_IMETHODIMP
AtomImpl::ScriptableToString(nsAString& aBuf)
{
nsStringBuffer::FromData(mString)->ToString(mLength, aBuf);
return NS_OK;
}
NS_IMETHODIMP
AtomImpl::ToUTF8String(nsACString& aBuf)
{
CopyUTF16toUTF8(nsDependentString(mString, mLength), aBuf);
return NS_OK;
}
NS_IMETHODIMP_(bool)
AtomImpl::EqualsUTF8(const nsACString& aString)
{
return CompareUTF8toUTF16(aString,
nsDependentString(mString, mLength)) == 0;
}
NS_IMETHODIMP
AtomImpl::ScriptableEquals(const nsAString& aString, bool* aResult)
{
*aResult = aString.Equals(nsDependentString(mString, mLength));
return NS_OK;
}
NS_IMETHODIMP_(bool)
AtomImpl::IsStaticAtom()
{
return IsPermanent();
}
size_t
AtomImpl::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
{
return aMallocSizeOf(this) +
nsStringBuffer::FromData(mString)->
SizeOfIncludingThisIfUnshared(aMallocSizeOf);
}
//----------------------------------------------------------------------
static size_t
SizeOfAtomTableEntryExcludingThis(PLDHashEntryHdr *aHdr,
MallocSizeOf aMallocSizeOf,
void *aArg)
{
AtomTableEntry* entry = static_cast<AtomTableEntry*>(aHdr);
return entry->mAtom->SizeOfIncludingThis(aMallocSizeOf);
}
static size_t
SizeOfStaticAtomTableEntryExcludingThis(const nsAString& aKey,
nsIAtom* const& aData,
MallocSizeOf aMallocSizeOf,
void* aArg)
{
return aKey.SizeOfExcludingThisIfUnshared(aMallocSizeOf);
}
size_t
NS_SizeOfAtomTablesIncludingThis(MallocSizeOf aMallocSizeOf) {
size_t n = 0;
if (gAtomTable.ops) {
n += PL_DHashTableSizeOfExcludingThis(&gAtomTable,
SizeOfAtomTableEntryExcludingThis,
aMallocSizeOf);
}
if (gStaticAtomTable) {
n += gStaticAtomTable->SizeOfIncludingThis(SizeOfStaticAtomTableEntryExcludingThis,
aMallocSizeOf);
}
return n;
}
#define ATOM_HASHTABLE_INITIAL_SIZE 4096
static void HandleOOM()
{
fputs("Out of memory allocating atom hashtable.\n", stderr);
MOZ_CRASH();
}
static inline void
EnsureTableExists()
{
if (!gAtomTable.ops &&
!PL_DHashTableInit(&gAtomTable, &AtomTableOps, 0,
sizeof(AtomTableEntry), ATOM_HASHTABLE_INITIAL_SIZE)) {
// Initialization failed.
HandleOOM();
}
}
static inline AtomTableEntry*
GetAtomHashEntry(const char* aString, uint32_t aLength)
{
MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
EnsureTableExists();
AtomTableKey key(aString, aLength);
AtomTableEntry* e =
static_cast<AtomTableEntry*>
(PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
if (!e) {
HandleOOM();
}
return e;
}
static inline AtomTableEntry*
GetAtomHashEntry(const PRUnichar* aString, uint32_t aLength)
{
MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
EnsureTableExists();
AtomTableKey key(aString, aLength);
AtomTableEntry* e =
static_cast<AtomTableEntry*>
(PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
if (!e) {
HandleOOM();
}
return e;
}
class CheckStaticAtomSizes
{
CheckStaticAtomSizes() {
static_assert((sizeof(nsFakeStringBuffer<1>().mRefCnt) ==
sizeof(nsStringBuffer().mRefCount)) &&
(sizeof(nsFakeStringBuffer<1>().mSize) ==
sizeof(nsStringBuffer().mStorageSize)) &&
(offsetof(nsFakeStringBuffer<1>, mRefCnt) ==
offsetof(nsStringBuffer, mRefCount)) &&
(offsetof(nsFakeStringBuffer<1>, mSize) ==
offsetof(nsStringBuffer, mStorageSize)) &&
(offsetof(nsFakeStringBuffer<1>, mStringData) ==
sizeof(nsStringBuffer)),
"mocked-up strings' representations should be compatible");
}
};
nsresult
RegisterStaticAtoms(const nsStaticAtom* aAtoms, uint32_t aAtomCount)
{
// this does three things:
// 1) wraps each static atom in a wrapper, if necessary
// 2) initializes the address pointed to by each mBits slot
// 3) puts the atom into the static atom table as well
if (!gStaticAtomTable && !gStaticAtomTableSealed) {
gStaticAtomTable = new nsDataHashtable<nsStringHashKey, nsIAtom*>();
}
for (uint32_t i=0; i<aAtomCount; i++) {
NS_ASSERTION(nsCRT::IsAscii((PRUnichar*)aAtoms[i].mStringBuffer->Data()),
"Static atoms must be ASCII!");
uint32_t stringLen =
aAtoms[i].mStringBuffer->StorageSize() / sizeof(PRUnichar) - 1;
AtomTableEntry *he =
GetAtomHashEntry((PRUnichar*)aAtoms[i].mStringBuffer->Data(),
stringLen);
if (he->mAtom) {
// there already is an atom with this name in the table.. but we
// still have to update mBits
if (!he->mAtom->IsPermanent()) {
// since we wanted to create a static atom but there is
// already one there, we convert it to a non-refcounting
// permanent atom
PromoteToPermanent(he->mAtom);
}
*aAtoms[i].mAtom = he->mAtom;
}
else {
AtomImpl* atom = new PermanentAtomImpl(aAtoms[i].mStringBuffer,
stringLen,
he->keyHash);
he->mAtom = atom;
*aAtoms[i].mAtom = atom;
if (!gStaticAtomTableSealed) {
gStaticAtomTable->Put(nsAtomString(atom), atom);
}
}
}
return NS_OK;
}
already_AddRefed<nsIAtom>
NS_NewAtom(const char* aUTF8String)
{
return NS_NewAtom(nsDependentCString(aUTF8String));
}
already_AddRefed<nsIAtom>
NS_NewAtom(const nsACString& aUTF8String)
{
AtomTableEntry *he = GetAtomHashEntry(aUTF8String.Data(),
aUTF8String.Length());
if (he->mAtom) {
nsCOMPtr<nsIAtom> atom = he->mAtom;
return atom.forget();
}
// This results in an extra addref/release of the nsStringBuffer.
// Unfortunately there doesn't seem to be any APIs to avoid that.
// Actually, now there is, sort of: ForgetSharedBuffer.
nsString str;
CopyUTF8toUTF16(aUTF8String, str);
nsRefPtr<AtomImpl> atom = new AtomImpl(str, he->keyHash);
he->mAtom = atom;
return atom.forget();
}
already_AddRefed<nsIAtom>
NS_NewAtom(const PRUnichar* aUTF16String)
{
return NS_NewAtom(nsDependentString(aUTF16String));
}
already_AddRefed<nsIAtom>
NS_NewAtom(const nsAString& aUTF16String)
{
AtomTableEntry *he = GetAtomHashEntry(aUTF16String.Data(),
aUTF16String.Length());
if (he->mAtom) {
nsCOMPtr<nsIAtom> atom = he->mAtom;
return atom.forget();
}
nsRefPtr<AtomImpl> atom = new AtomImpl(aUTF16String, he->keyHash);
he->mAtom = atom;
return atom.forget();
}
nsIAtom*
NS_NewPermanentAtom(const nsAString& aUTF16String)
{
AtomTableEntry *he = GetAtomHashEntry(aUTF16String.Data(),
aUTF16String.Length());
AtomImpl* atom = he->mAtom;
if (atom) {
if (!atom->IsPermanent()) {
PromoteToPermanent(atom);
}
}
else {
atom = new PermanentAtomImpl(aUTF16String, he->keyHash);
he->mAtom = atom;
}
// No need to addref since permanent atoms aren't refcounted anyway
return atom;
}
nsrefcnt
NS_GetNumberOfAtoms(void)
{
return gAtomTable.entryCount;
}
nsIAtom*
NS_GetStaticAtom(const nsAString& aUTF16String)
{
NS_PRECONDITION(gStaticAtomTable, "Static atom table not created yet.");
NS_PRECONDITION(gStaticAtomTableSealed, "Static atom table not sealed yet.");
nsIAtom* atom;
if (!gStaticAtomTable->Get(aUTF16String, &atom)) {
atom = nullptr;
}
return atom;
}
void
NS_SealStaticAtomTable()
{
gStaticAtomTableSealed = true;
}
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