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Diffstat (limited to '')
| -rw-r--r-- | xpcom/ds/nsAtomTable.cpp | 670 |
1 files changed, 670 insertions, 0 deletions
diff --git a/xpcom/ds/nsAtomTable.cpp b/xpcom/ds/nsAtomTable.cpp new file mode 100644 index 0000000000..56618cd46c --- /dev/null +++ b/xpcom/ds/nsAtomTable.cpp @@ -0,0 +1,670 @@ +/* -*- 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/. */ + +#include "mozilla/Assertions.h" +#include "mozilla/Attributes.h" +#include "mozilla/HashFunctions.h" +#include "mozilla/MemoryReporting.h" +#include "mozilla/MruCache.h" +#include "mozilla/Mutex.h" +#include "mozilla/DebugOnly.h" +#include "mozilla/Sprintf.h" +#include "mozilla/TextUtils.h" +#include "mozilla/Unused.h" + +#include "nsAtom.h" +#include "nsAtomTable.h" +#include "nsCRT.h" +#include "nsGkAtoms.h" +#include "nsHashKeys.h" +#include "nsPrintfCString.h" +#include "nsString.h" +#include "nsThreadUtils.h" +#include "nsUnicharUtils.h" +#include "PLDHashTable.h" +#include "prenv.h" + +// There are two kinds of atoms handled by this module. +// +// - Dynamic: the atom itself is heap allocated, as is the char buffer it +// points to. |gAtomTable| holds weak references to dynamic atoms. When the +// refcount of a dynamic atom drops to zero, we increment a static counter. +// When that counter reaches a certain threshold, we iterate over the atom +// table, removing and deleting dynamic atoms with refcount zero. This allows +// us to avoid acquiring the atom table lock during normal refcounting. +// +// - Static: both the atom and its chars are statically allocated and +// immutable, so it ignores all AddRef/Release calls. +// +// Note that gAtomTable is used on multiple threads, and has internal +// synchronization. + +using namespace mozilla; + +//---------------------------------------------------------------------- + +enum class GCKind { + RegularOperation, + Shutdown, +}; + +//---------------------------------------------------------------------- + +// gUnusedAtomCount is incremented when an atom loses its last reference +// (and thus turned into unused state), and decremented when an unused +// atom gets a reference again. The atom table relies on this value to +// schedule GC. This value can temporarily go below zero when multiple +// threads are operating the same atom, so it has to be signed so that +// we wouldn't use overflow value for comparison. +// See nsAtom::AddRef() and nsAtom::Release(). +// This atomic can be accessed during the GC and other places where recorded +// events are not allowed, so its value is not preserved when recording or +// replaying. +Atomic<int32_t, ReleaseAcquire> nsDynamicAtom::gUnusedAtomCount; + +nsDynamicAtom::nsDynamicAtom(const nsAString& aString, uint32_t aHash, + bool aIsAsciiLowercase) + : nsAtom(aString, aHash, aIsAsciiLowercase), mRefCnt(1) {} + +// Returns true if ToLowercaseASCII would return the string unchanged. +static bool IsAsciiLowercase(const char16_t* aString, const uint32_t aLength) { + for (uint32_t i = 0; i < aLength; ++i) { + if (IS_ASCII_UPPER(aString[i])) { + return false; + } + } + + return true; +} + +nsDynamicAtom* nsDynamicAtom::Create(const nsAString& aString, uint32_t aHash) { + // We tack the chars onto the end of the nsDynamicAtom object. + size_t numCharBytes = (aString.Length() + 1) * sizeof(char16_t); + size_t numTotalBytes = sizeof(nsDynamicAtom) + numCharBytes; + + bool isAsciiLower = ::IsAsciiLowercase(aString.Data(), aString.Length()); + + nsDynamicAtom* atom = (nsDynamicAtom*)moz_xmalloc(numTotalBytes); + new (atom) nsDynamicAtom(aString, aHash, isAsciiLower); + memcpy(const_cast<char16_t*>(atom->String()), + PromiseFlatString(aString).get(), numCharBytes); + + MOZ_ASSERT(atom->String()[atom->GetLength()] == char16_t(0)); + MOZ_ASSERT(atom->Equals(aString)); + MOZ_ASSERT(atom->mHash == HashString(atom->String(), atom->GetLength())); + MOZ_ASSERT(atom->mIsAsciiLowercase == isAsciiLower); + + return atom; +} + +void nsDynamicAtom::Destroy(nsDynamicAtom* aAtom) { + aAtom->~nsDynamicAtom(); + free(aAtom); +} + +void nsAtom::ToString(nsAString& aString) const { + // See the comment on |mString|'s declaration. + if (IsStatic()) { + // AssignLiteral() lets us assign without copying. This isn't a string + // literal, but it's a static atom and thus has an unbounded lifetime, + // which is what's important. + aString.AssignLiteral(AsStatic()->String(), mLength); + } else { + aString.Assign(AsDynamic()->String(), mLength); + } +} + +void nsAtom::ToUTF8String(nsACString& aBuf) const { + CopyUTF16toUTF8(nsDependentString(GetUTF16String(), mLength), aBuf); +} + +void nsAtom::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf, + AtomsSizes& aSizes) const { + // Static atoms are in static memory, and so are not measured here. + if (IsDynamic()) { + aSizes.mDynamicAtoms += aMallocSizeOf(this); + } +} + +char16ptr_t nsAtom::GetUTF16String() const { + return IsStatic() ? AsStatic()->String() : AsDynamic()->String(); +} + +//---------------------------------------------------------------------- + +struct AtomTableKey { + explicit AtomTableKey(const nsStaticAtom* aAtom) + : mUTF16String(aAtom->String()), + mUTF8String(nullptr), + mLength(aAtom->GetLength()), + mHash(aAtom->hash()) { + MOZ_ASSERT(HashString(mUTF16String, mLength) == mHash); + } + + AtomTableKey(const char16_t* aUTF16String, uint32_t aLength) + : mUTF16String(aUTF16String), mUTF8String(nullptr), mLength(aLength) { + mHash = HashString(mUTF16String, mLength); + } + + AtomTableKey(const char* aUTF8String, uint32_t aLength, bool* aErr) + : mUTF16String(nullptr), mUTF8String(aUTF8String), mLength(aLength) { + mHash = HashUTF8AsUTF16(mUTF8String, mLength, aErr); + } + + const char16_t* mUTF16String; + const char* mUTF8String; + uint32_t mLength; + uint32_t mHash; +}; + +struct AtomTableEntry : public PLDHashEntryHdr { + // These references are either to dynamic atoms, in which case they are + // non-owning, or they are to static atoms, which aren't really refcounted. + // See the comment at the top of this file for more details. + nsAtom* MOZ_NON_OWNING_REF mAtom; +}; + +struct AtomCache : public MruCache<AtomTableKey, nsAtom*, AtomCache> { + static HashNumber Hash(const AtomTableKey& aKey) { return aKey.mHash; } + static bool Match(const AtomTableKey& aKey, const nsAtom* aVal) { + MOZ_ASSERT(aKey.mUTF16String); + return aVal->Equals(aKey.mUTF16String, aKey.mLength); + } +}; + +static AtomCache sRecentlyUsedMainThreadAtoms; + +// In order to reduce locking contention for concurrent atomization, we segment +// the atom table into N subtables, each with a separate lock. If the hash +// values we use to select the subtable are evenly distributed, this reduces the +// probability of contention by a factor of N. See bug 1440824. +// +// NB: This is somewhat similar to the technique used by Java's +// ConcurrentHashTable. +class nsAtomSubTable { + friend class nsAtomTable; + Mutex mLock; + PLDHashTable mTable; + nsAtomSubTable(); + void GCLocked(GCKind aKind) MOZ_REQUIRES(mLock); + void AddSizeOfExcludingThisLocked(MallocSizeOf aMallocSizeOf, + AtomsSizes& aSizes) MOZ_REQUIRES(mLock); + + AtomTableEntry* Search(AtomTableKey& aKey) const MOZ_REQUIRES(mLock) { + mLock.AssertCurrentThreadOwns(); + return static_cast<AtomTableEntry*>(mTable.Search(&aKey)); + } + + AtomTableEntry* Add(AtomTableKey& aKey) MOZ_REQUIRES(mLock) { + mLock.AssertCurrentThreadOwns(); + return static_cast<AtomTableEntry*>(mTable.Add(&aKey)); // Infallible + } +}; + +// The outer atom table, which coordinates access to the inner array of +// subtables. +class nsAtomTable { + public: + nsAtomSubTable& SelectSubTable(AtomTableKey& aKey); + void AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf, AtomsSizes& aSizes); + void GC(GCKind aKind); + already_AddRefed<nsAtom> Atomize(const nsAString& aUTF16String); + already_AddRefed<nsAtom> Atomize(const nsACString& aUTF8String); + already_AddRefed<nsAtom> AtomizeMainThread(const nsAString& aUTF16String); + nsStaticAtom* GetStaticAtom(const nsAString& aUTF16String); + void RegisterStaticAtoms(const nsStaticAtom* aAtoms, size_t aAtomsLen); + + // The result of this function may be imprecise if other threads are operating + // on atoms concurrently. It's also slow, since it triggers a GC before + // counting. + size_t RacySlowCount(); + + // This hash table op is a static member of this class so that it can take + // advantage of |friend| declarations. + static void AtomTableClearEntry(PLDHashTable* aTable, + PLDHashEntryHdr* aEntry); + + // We achieve measurable reduction in locking contention in parallel CSS + // parsing by increasing the number of subtables up to 128. This has been + // measured to have neglible impact on the performance of initialization, GC, + // and shutdown. + // + // Another important consideration is memory, since we're adding fixed + // overhead per content process, which we try to avoid. Measuring a + // mostly-empty page [1] with various numbers of subtables, we get the + // following deep sizes for the atom table: + // 1 subtable: 278K + // 8 subtables: 279K + // 16 subtables: 282K + // 64 subtables: 286K + // 128 subtables: 290K + // + // So 128 subtables costs us 12K relative to a single table, and 4K relative + // to 64 subtables. Conversely, measuring parallel (6 thread) CSS parsing on + // tp6-facebook, a single table provides ~150ms of locking overhead per + // thread, 64 subtables provides ~2-3ms of overhead, and 128 subtables + // provides <1ms. And so while either 64 or 128 subtables would probably be + // acceptable, achieving a measurable reduction in contention for 4k of fixed + // memory overhead is probably worth it. + // + // [1] The numbers will look different for content processes with complex + // pages loaded, but in those cases the actual atoms will dominate memory + // usage and the overhead of extra tables will be negligible. We're mostly + // interested in the fixed cost for nearly-empty content processes. + const static size_t kNumSubTables = 128; // Must be power of two. + + private: + nsAtomSubTable mSubTables[kNumSubTables]; +}; + +// Static singleton instance for the atom table. +static nsAtomTable* gAtomTable; + +static PLDHashNumber AtomTableGetHash(const void* aKey) { + const AtomTableKey* k = static_cast<const AtomTableKey*>(aKey); + return k->mHash; +} + +static bool AtomTableMatchKey(const PLDHashEntryHdr* aEntry, const void* aKey) { + const AtomTableEntry* he = static_cast<const AtomTableEntry*>(aEntry); + const AtomTableKey* k = static_cast<const AtomTableKey*>(aKey); + + if (k->mUTF8String) { + bool err = false; + return (CompareUTF8toUTF16(nsDependentCSubstring( + k->mUTF8String, k->mUTF8String + k->mLength), + nsDependentAtomString(he->mAtom), &err) == 0) && + !err; + } + + return he->mAtom->Equals(k->mUTF16String, k->mLength); +} + +void nsAtomTable::AtomTableClearEntry(PLDHashTable* aTable, + PLDHashEntryHdr* aEntry) { + auto entry = static_cast<AtomTableEntry*>(aEntry); + entry->mAtom = nullptr; +} + +static void AtomTableInitEntry(PLDHashEntryHdr* aEntry, const void* aKey) { + static_cast<AtomTableEntry*>(aEntry)->mAtom = nullptr; +} + +static const PLDHashTableOps AtomTableOps = { + AtomTableGetHash, AtomTableMatchKey, PLDHashTable::MoveEntryStub, + nsAtomTable::AtomTableClearEntry, AtomTableInitEntry}; + +// The atom table very quickly gets 10,000+ entries in it (or even 100,000+). +// But choosing the best initial subtable length has some subtleties: we add +// ~2700 static atoms at start-up, and then we start adding and removing +// dynamic atoms. If we make the tables too big to start with, when the first +// dynamic atom gets removed from a given table the load factor will be < 25% +// and we will shrink it. +// +// So we first make the simplifying assumption that the atoms are more or less +// evenly-distributed across the subtables (which is the case empirically). +// Then, we take the total atom count when the first dynamic atom is removed +// (~2700), divide that across the N subtables, and the largest capacity that +// will allow each subtable to be > 25% full with that count. +// +// So want an initial subtable capacity less than (2700 / N) * 4 = 10800 / N. +// Rounding down to the nearest power of two gives us 8192 / N. Since the +// capacity is double the initial length, we end up with (4096 / N) per +// subtable. +#define INITIAL_SUBTABLE_LENGTH (4096 / nsAtomTable::kNumSubTables) + +nsAtomSubTable& nsAtomTable::SelectSubTable(AtomTableKey& aKey) { + // There are a few considerations around how we select subtables. + // + // First, we want entries to be evenly distributed across the subtables. This + // can be achieved by using any bits in the hash key, assuming the key itself + // is evenly-distributed. Empirical measurements indicate that this method + // produces a roughly-even distribution across subtables. + // + // Second, we want to use the hash bits that are least likely to influence an + // entry's position within the subtable. If we used the exact same bits used + // by the subtables, then each subtable would compute the same position for + // every entry it observes, leading to pessimal performance. In this case, + // we're using PLDHashTable, whose primary hash function uses the N leftmost + // bits of the hash value (where N is the log2 capacity of the table). This + // means we should prefer the rightmost bits here. + // + // Note that the below is equivalent to mHash % kNumSubTables, a replacement + // which an optimizing compiler should make, but let's avoid any doubt. + static_assert((kNumSubTables & (kNumSubTables - 1)) == 0, + "must be power of two"); + return mSubTables[aKey.mHash & (kNumSubTables - 1)]; +} + +void nsAtomTable::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf, + AtomsSizes& aSizes) { + MOZ_ASSERT(NS_IsMainThread()); + aSizes.mTable += aMallocSizeOf(this); + for (auto& table : mSubTables) { + MutexAutoLock lock(table.mLock); + table.AddSizeOfExcludingThisLocked(aMallocSizeOf, aSizes); + } +} + +void nsAtomTable::GC(GCKind aKind) { + MOZ_ASSERT(NS_IsMainThread()); + sRecentlyUsedMainThreadAtoms.Clear(); + + // Note that this is effectively an incremental GC, since only one subtable + // is locked at a time. + for (auto& table : mSubTables) { + MutexAutoLock lock(table.mLock); + table.GCLocked(aKind); + } + + // We would like to assert that gUnusedAtomCount matches the number of atoms + // we found in the table which we removed. However, there are two problems + // with this: + // * We have multiple subtables, each with their own lock. For optimal + // performance we only want to hold one lock at a time, but this means + // that atoms can be added and removed between GC slices. + // * Even if we held all the locks and performed all GC slices atomically, + // the locks are not acquired for AddRef() and Release() calls. This means + // we might see a gUnusedAtomCount value in between, say, AddRef() + // incrementing mRefCnt and it decrementing gUnusedAtomCount. + // + // So, we don't bother asserting that there are no unused atoms at the end of + // a regular GC. But we can (and do) assert this just after the last GC at + // shutdown. + // + // Note that, barring refcounting bugs, an atom can only go from a zero + // refcount to a non-zero refcount while the atom table lock is held, so + // so we won't try to resurrect a zero refcount atom while trying to delete + // it. + + MOZ_ASSERT_IF(aKind == GCKind::Shutdown, + nsDynamicAtom::gUnusedAtomCount == 0); +} + +size_t nsAtomTable::RacySlowCount() { + // Trigger a GC so that the result is deterministic modulo other threads. + GC(GCKind::RegularOperation); + size_t count = 0; + for (auto& table : mSubTables) { + MutexAutoLock lock(table.mLock); + count += table.mTable.EntryCount(); + } + + return count; +} + +nsAtomSubTable::nsAtomSubTable() + : mLock("Atom Sub-Table Lock"), + mTable(&AtomTableOps, sizeof(AtomTableEntry), INITIAL_SUBTABLE_LENGTH) {} + +void nsAtomSubTable::GCLocked(GCKind aKind) { + MOZ_ASSERT(NS_IsMainThread()); + mLock.AssertCurrentThreadOwns(); + + int32_t removedCount = 0; // A non-atomic temporary for cheaper increments. + nsAutoCString nonZeroRefcountAtoms; + uint32_t nonZeroRefcountAtomsCount = 0; + for (auto i = mTable.Iter(); !i.Done(); i.Next()) { + auto entry = static_cast<AtomTableEntry*>(i.Get()); + if (entry->mAtom->IsStatic()) { + continue; + } + + nsAtom* atom = entry->mAtom; + if (atom->IsDynamic() && atom->AsDynamic()->mRefCnt == 0) { + i.Remove(); + nsDynamicAtom::Destroy(atom->AsDynamic()); + ++removedCount; + } +#ifdef NS_FREE_PERMANENT_DATA + else if (aKind == GCKind::Shutdown && PR_GetEnv("XPCOM_MEM_BLOAT_LOG")) { + // Only report leaking atoms in leak-checking builds in a run where we + // are checking for leaks, during shutdown. If something is anomalous, + // then we'll assert later in this function. + nsAutoCString name; + atom->ToUTF8String(name); + if (nonZeroRefcountAtomsCount == 0) { + nonZeroRefcountAtoms = name; + } else if (nonZeroRefcountAtomsCount < 20) { + nonZeroRefcountAtoms += ","_ns + name; + } else if (nonZeroRefcountAtomsCount == 20) { + nonZeroRefcountAtoms += ",..."_ns; + } + nonZeroRefcountAtomsCount++; + } +#endif + } + if (nonZeroRefcountAtomsCount) { + nsPrintfCString msg("%d dynamic atom(s) with non-zero refcount: %s", + nonZeroRefcountAtomsCount, nonZeroRefcountAtoms.get()); + NS_ASSERTION(nonZeroRefcountAtomsCount == 0, msg.get()); + } + + nsDynamicAtom::gUnusedAtomCount -= removedCount; +} + +void nsDynamicAtom::GCAtomTable() { + MOZ_ASSERT(gAtomTable); + if (NS_IsMainThread()) { + gAtomTable->GC(GCKind::RegularOperation); + } +} + +//---------------------------------------------------------------------- + +// Have the static atoms been inserted into the table? +static bool gStaticAtomsDone = false; + +void NS_InitAtomTable() { + MOZ_ASSERT(NS_IsMainThread()); + MOZ_ASSERT(!gAtomTable); + + // We register static atoms immediately so they're available for use as early + // as possible. + gAtomTable = new nsAtomTable(); + gAtomTable->RegisterStaticAtoms(nsGkAtoms::sAtoms, nsGkAtoms::sAtomsLen); + gStaticAtomsDone = true; +} + +void NS_ShutdownAtomTable() { + MOZ_ASSERT(NS_IsMainThread()); + MOZ_ASSERT(gAtomTable); + +#ifdef NS_FREE_PERMANENT_DATA + // Do a final GC to satisfy leak checking. We skip this step in release + // builds. + gAtomTable->GC(GCKind::Shutdown); +#endif + + delete gAtomTable; + gAtomTable = nullptr; +} + +void NS_AddSizeOfAtoms(MallocSizeOf aMallocSizeOf, AtomsSizes& aSizes) { + MOZ_ASSERT(NS_IsMainThread()); + MOZ_ASSERT(gAtomTable); + return gAtomTable->AddSizeOfIncludingThis(aMallocSizeOf, aSizes); +} + +void nsAtomSubTable::AddSizeOfExcludingThisLocked(MallocSizeOf aMallocSizeOf, + AtomsSizes& aSizes) { + mLock.AssertCurrentThreadOwns(); + aSizes.mTable += mTable.ShallowSizeOfExcludingThis(aMallocSizeOf); + for (auto iter = mTable.Iter(); !iter.Done(); iter.Next()) { + auto entry = static_cast<AtomTableEntry*>(iter.Get()); + entry->mAtom->AddSizeOfIncludingThis(aMallocSizeOf, aSizes); + } +} + +void nsAtomTable::RegisterStaticAtoms(const nsStaticAtom* aAtoms, + size_t aAtomsLen) { + MOZ_ASSERT(NS_IsMainThread()); + MOZ_RELEASE_ASSERT(!gStaticAtomsDone, "Static atom insertion is finished!"); + + for (uint32_t i = 0; i < aAtomsLen; ++i) { + const nsStaticAtom* atom = &aAtoms[i]; + MOZ_ASSERT(IsAsciiNullTerminated(atom->String())); + MOZ_ASSERT(NS_strlen(atom->String()) == atom->GetLength()); + MOZ_ASSERT(atom->IsAsciiLowercase() == + ::IsAsciiLowercase(atom->String(), atom->GetLength())); + + // This assertion ensures the static atom's precomputed hash value matches + // what would be computed by mozilla::HashString(aStr), which is what we use + // when atomizing strings. We compute this hash in Atom.py. + MOZ_ASSERT(HashString(atom->String()) == atom->hash()); + + AtomTableKey key(atom); + nsAtomSubTable& table = SelectSubTable(key); + MutexAutoLock lock(table.mLock); + AtomTableEntry* he = table.Add(key); + + if (he->mAtom) { + // There are two ways we could get here. + // - Register two static atoms with the same string. + // - Create a dynamic atom and then register a static atom with the same + // string while the dynamic atom is alive. + // Both cases can cause subtle bugs, and are disallowed. We're + // programming in C++ here, not Smalltalk. + nsAutoCString name; + he->mAtom->ToUTF8String(name); + MOZ_CRASH_UNSAFE_PRINTF("Atom for '%s' already exists", name.get()); + } + he->mAtom = const_cast<nsStaticAtom*>(atom); + } +} + +already_AddRefed<nsAtom> NS_Atomize(const char* aUTF8String) { + MOZ_ASSERT(gAtomTable); + return gAtomTable->Atomize(nsDependentCString(aUTF8String)); +} + +already_AddRefed<nsAtom> nsAtomTable::Atomize(const nsACString& aUTF8String) { + bool err; + AtomTableKey key(aUTF8String.Data(), aUTF8String.Length(), &err); + if (MOZ_UNLIKELY(err)) { + MOZ_ASSERT_UNREACHABLE("Tried to atomize invalid UTF-8."); + // The input was invalid UTF-8. Let's replace the errors with U+FFFD + // and atomize the result. + nsString str; + CopyUTF8toUTF16(aUTF8String, str); + return Atomize(str); + } + nsAtomSubTable& table = SelectSubTable(key); + MutexAutoLock lock(table.mLock); + AtomTableEntry* he = table.Add(key); + + if (he->mAtom) { + RefPtr<nsAtom> atom = he->mAtom; + return atom.forget(); + } + + nsString str; + CopyUTF8toUTF16(aUTF8String, str); + RefPtr<nsAtom> atom = dont_AddRef(nsDynamicAtom::Create(str, key.mHash)); + + he->mAtom = atom; + + return atom.forget(); +} + +already_AddRefed<nsAtom> NS_Atomize(const nsACString& aUTF8String) { + MOZ_ASSERT(gAtomTable); + return gAtomTable->Atomize(aUTF8String); +} + +already_AddRefed<nsAtom> NS_Atomize(const char16_t* aUTF16String) { + MOZ_ASSERT(gAtomTable); + return gAtomTable->Atomize(nsDependentString(aUTF16String)); +} + +already_AddRefed<nsAtom> nsAtomTable::Atomize(const nsAString& aUTF16String) { + AtomTableKey key(aUTF16String.Data(), aUTF16String.Length()); + nsAtomSubTable& table = SelectSubTable(key); + MutexAutoLock lock(table.mLock); + AtomTableEntry* he = table.Add(key); + + if (he->mAtom) { + RefPtr<nsAtom> atom = he->mAtom; + return atom.forget(); + } + + RefPtr<nsAtom> atom = + dont_AddRef(nsDynamicAtom::Create(aUTF16String, key.mHash)); + he->mAtom = atom; + + return atom.forget(); +} + +already_AddRefed<nsAtom> NS_Atomize(const nsAString& aUTF16String) { + MOZ_ASSERT(gAtomTable); + return gAtomTable->Atomize(aUTF16String); +} + +already_AddRefed<nsAtom> nsAtomTable::AtomizeMainThread( + const nsAString& aUTF16String) { + MOZ_ASSERT(NS_IsMainThread()); + RefPtr<nsAtom> retVal; + AtomTableKey key(aUTF16String.Data(), aUTF16String.Length()); + auto p = sRecentlyUsedMainThreadAtoms.Lookup(key); + if (p) { + retVal = p.Data(); + return retVal.forget(); + } + + nsAtomSubTable& table = SelectSubTable(key); + MutexAutoLock lock(table.mLock); + AtomTableEntry* he = table.Add(key); + + if (he->mAtom) { + retVal = he->mAtom; + } else { + RefPtr<nsAtom> newAtom = + dont_AddRef(nsDynamicAtom::Create(aUTF16String, key.mHash)); + he->mAtom = newAtom; + retVal = std::move(newAtom); + } + + p.Set(retVal); + return retVal.forget(); +} + +already_AddRefed<nsAtom> NS_AtomizeMainThread(const nsAString& aUTF16String) { + MOZ_ASSERT(gAtomTable); + return gAtomTable->AtomizeMainThread(aUTF16String); +} + +nsrefcnt NS_GetNumberOfAtoms(void) { + MOZ_ASSERT(gAtomTable); + return gAtomTable->RacySlowCount(); +} + +int32_t NS_GetUnusedAtomCount(void) { return nsDynamicAtom::gUnusedAtomCount; } + +nsStaticAtom* NS_GetStaticAtom(const nsAString& aUTF16String) { + MOZ_ASSERT(gStaticAtomsDone, "Static atom setup not yet done."); + MOZ_ASSERT(gAtomTable); + return gAtomTable->GetStaticAtom(aUTF16String); +} + +nsStaticAtom* nsAtomTable::GetStaticAtom(const nsAString& aUTF16String) { + AtomTableKey key(aUTF16String.Data(), aUTF16String.Length()); + nsAtomSubTable& table = SelectSubTable(key); + MutexAutoLock lock(table.mLock); + AtomTableEntry* he = table.Search(key); + return he && he->mAtom->IsStatic() ? static_cast<nsStaticAtom*>(he->mAtom) + : nullptr; +} + +void ToLowerCaseASCII(RefPtr<nsAtom>& aAtom) { + // Assume the common case is that the atom is already ASCII lowercase. + if (aAtom->IsAsciiLowercase()) { + return; + } + + nsAutoString lowercased; + ToLowerCaseASCII(nsDependentAtomString(aAtom), lowercased); + aAtom = NS_Atomize(lowercased); +} |