The Tor Browser: xpcom/ds/nsAtomTable.cpp@b8a032363ba2 (annotated)

xpcom/ds/nsAtomTable.cpp@b8a032363ba2 (annotated)

xpcom/ds/nsAtomTable.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- 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/Compiler.h"
 #include "mozilla/HashFunctions.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/DebugOnly.h"
 #include "mozilla/unused.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;
 #if defined(__clang__)
 #  pragma GCC diagnostic ignored "-Wdelete-non-virtual-dtor"
 #elif MOZ_IS_GCC
 #  if MOZ_GCC_VERSION_AT_LEAST(4, 7, 0)
 #    pragma GCC diagnostic ignored "-Wdelete-non-virtual-dtor"
 #  endif
 #endif
 /**
  * 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, uint32_t aHash);
   // This is currently only used during startup when creating a permanent atom
   // from NS_RegisterStaticAtoms
   AtomImpl(nsStringBuffer* aData, uint32_t aLength, uint32_t aHash);
 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(char16_t) <=
                  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_(MozExternalRefCountType) AddRef();
   NS_IMETHOD_(MozExternalRefCountType) 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 char16_t* aUTF16String, uint32_t aLength,
                /*inout*/ uint32_t& aHash)
     : mUTF16String(aUTF16String),
       mUTF8String(nullptr),
       mLength(aLength)
   {
     if (aHash) {
       MOZ_ASSERT(aHash == HashString(mUTF16String, mLength));
       mHash = aHash;
     } else {
       UpdateHashKey();
       aHash = mHash;
     }
   }
   AtomTableKey(const char* aUTF8String, uint32_t aLength,
                /*inout*/ uint32_t& aHash)
     : mUTF16String(nullptr),
       mUTF8String(aUTF8String),
       mLength(aLength)
   {
     if (aHash) {
       mozilla::DebugOnly<bool> err;
       MOZ_ASSERT(aHash == HashUTF8AsUTF16(mUTF8String, mLength, &err));
       mHash = aHash;
     } else {
       UpdateHashKey();
       aHash = mHash;
     }
   }
   const char16_t* mUTF16String;
   const char* mUTF8String;
   uint32_t mLength;
   uint32_t mHash;
   void UpdateHashKey()
   {
     if (mUTF8String) {
       bool err;
       mHash = HashUTF8AsUTF16(mUTF8String, mLength, &err);
       if (err) {
         mUTF8String = nullptr;
         mLength = 0;
         mHash = 0;
       }
     } else {
       mHash = HashString(mUTF16String, mLength);
     }
   }
 };
 static PLDHashNumber
 AtomTableGetHash(PLDHashTable *table, const void *key)
 {
   const AtomTableKey *k = static_cast<const AtomTableKey*>(key);
   return k->mHash;
 }
 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(char16_t)) == 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, uint32_t aHash)
 {
   mLength = aString.Length();
   nsRefPtr<nsStringBuffer> buf = nsStringBuffer::FromString(aString);
   if (buf) {
     mString = static_cast<char16_t*>(buf->Data());
   } else {
     buf = nsStringBuffer::Alloc((mLength + 1) * sizeof(char16_t));
     mString = static_cast<char16_t*>(buf->Data());
     CopyUnicodeTo(aString, 0, mString, mLength);
     mString[mLength] = char16_t(0);
   }
   mHash = aHash;
   MOZ_ASSERT(mHash == HashString(mString, mLength));
   NS_ASSERTION(mString[mLength] == char16_t(0), "null terminated");
   NS_ASSERTION(buf && buf->StorageSize() >= (mLength+1) * sizeof(char16_t),
                "enough storage");
   NS_ASSERTION(Equals(aString), "correct data");
   // Take ownership of buffer
   mozilla::unused << buf.forget();
 }
 AtomImpl::AtomImpl(nsStringBuffer* aStringBuffer, uint32_t aLength,
                    uint32_t aHash)
 {
   mLength = aLength;
   mString = static_cast<char16_t*>(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();
   mHash = aHash;
   MOZ_ASSERT(mHash == HashString(mString, mLength));
   NS_ASSERTION(mString[mLength] == char16_t(0), "null terminated");
   NS_ASSERTION(aStringBuffer &&
                aStringBuffer->StorageSize() == (mLength+1) * sizeof(char16_t),
                "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, mHash);
     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_ISUPPORTS(AtomImpl, nsIAtom)
 PermanentAtomImpl::~PermanentAtomImpl()
 {
   // So we can tell if we were permanent while running the base class dtor.
   mRefCnt = REFCNT_PERMANENT_SENTINEL;
 }
 NS_IMETHODIMP_(MozExternalRefCountType) PermanentAtomImpl::AddRef()
 {
   MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
   return 2;
 }
 NS_IMETHODIMP_(MozExternalRefCountType) 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 inline void
 EnsureTableExists()
 {
   if (!gAtomTable.ops) {
     PL_DHashTableInit(&gAtomTable, &AtomTableOps, 0,
                       sizeof(AtomTableEntry), ATOM_HASHTABLE_INITIAL_SIZE);
   }
 }
 static inline AtomTableEntry*
 GetAtomHashEntry(const char* aString, uint32_t aLength, uint32_t& aHash)
 {
   MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
   EnsureTableExists();
   AtomTableKey key(aString, aLength, aHash);
   AtomTableEntry* e =
     static_cast<AtomTableEntry*>
                (PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
   if (!e) {
     NS_ABORT_OOM(gAtomTable.entryCount * gAtomTable.entrySize);
   }
   return e;
 }
 static inline AtomTableEntry*
 GetAtomHashEntry(const char16_t* aString, uint32_t aLength, uint32_t& aHash)
 {
   MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
   EnsureTableExists();
   AtomTableKey key(aString, aLength, aHash);
   AtomTableEntry* e =
     static_cast<AtomTableEntry*>
                (PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
   if (!e) {
     NS_ABORT_OOM(gAtomTable.entryCount * gAtomTable.entrySize);
   }
   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((char16_t*)aAtoms[i].mStringBuffer->Data()),
                  "Static atoms must be ASCII!");
     uint32_t stringLen =
       aAtoms[i].mStringBuffer->StorageSize() / sizeof(char16_t) - 1;
     uint32_t hash = 0;
     AtomTableEntry *he =
       GetAtomHashEntry((char16_t*)aAtoms[i].mStringBuffer->Data(),
                        stringLen, hash);
     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,
                                              hash);
       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)
 {
   uint32_t hash = 0;
   AtomTableEntry *he = GetAtomHashEntry(aUTF8String.Data(),
                                         aUTF8String.Length(),
                                         hash);
   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, hash);
   he->mAtom = atom;
   return atom.forget();
 }
 already_AddRefed<nsIAtom>
 NS_NewAtom(const char16_t* aUTF16String)
 {
   return NS_NewAtom(nsDependentString(aUTF16String));
 }
 already_AddRefed<nsIAtom>
 NS_NewAtom(const nsAString& aUTF16String)
 {
   uint32_t hash = 0;
   AtomTableEntry *he = GetAtomHashEntry(aUTF16String.Data(),
                                         aUTF16String.Length(),
                                         hash);
   if (he->mAtom) {
     nsCOMPtr<nsIAtom> atom = he->mAtom;
     return atom.forget();
   }
   nsRefPtr<AtomImpl> atom = new AtomImpl(aUTF16String, hash);
   he->mAtom = atom;
   return atom.forget();
 }
 nsIAtom*
 NS_NewPermanentAtom(const nsAString& aUTF16String)
 {
   uint32_t hash = 0;
   AtomTableEntry *he = GetAtomHashEntry(aUTF16String.Data(),
                                         aUTF16String.Length(),
                                         hash);
   AtomImpl* atom = he->mAtom;
   if (atom) {
     if (!atom->IsPermanent()) {
       PromoteToPermanent(atom);
     }
   }
   else {
     atom = new PermanentAtomImpl(aUTF16String, hash);
     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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xpcom/ds/nsAtomTable.cpp@b8a032363ba2 (annotated)

xpcom/ds/nsAtomTable.cpp