Source/WTF/wtf/text/AtomicString.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Patrick Gansterer <paroga@paroga.com>
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */

 #include "config.h"

 #include "AtomicString.h"

 #include "AtomicStringTable.h"
 #include "StringHash.h"
 #include <wtf/HashSet.h>
 #include <wtf/Threading.h>
 #include <wtf/WTFThreadData.h>
 #include <wtf/unicode/UTF8.h>

 #if USE(WEB_THREAD)
 #include <wtf/MainThread.h>
 #include <wtf/TCSpinLock.h>
 #endif

 namespace WTF {

 using namespace Unicode;

 COMPILE_ASSERT(sizeof(AtomicString) == sizeof(String), atomic_string_and_string_must_be_same_size);

 #if USE(WEB_THREAD)
 class AtomicStringTableLocker : public SpinLockHolder {
     WTF_MAKE_NONCOPYABLE(AtomicStringTableLocker);

     static SpinLock s_stringTableLock;
 public:
     AtomicStringTableLocker()
         : SpinLockHolder(&s_stringTableLock)
     {
     }
 };

 SpinLock AtomicStringTableLocker::s_stringTableLock = SPINLOCK_INITIALIZER;
 #else

 class AtomicStringTableLocker {
     WTF_MAKE_NONCOPYABLE(AtomicStringTableLocker);
 public:
     AtomicStringTableLocker() { }
     ~AtomicStringTableLocker() { }
 };
 #endif // USE(WEB_THREAD)

 static ALWAYS_INLINE HashSet<StringImpl*>& stringTable()
 {
     return wtfThreadData().atomicStringTable()->table();
 }

 template<typename T, typename HashTranslator>
 static inline PassRefPtr<StringImpl> addToStringTable(const T& value)
 {
     AtomicStringTableLocker locker;

     HashSet<StringImpl*>::AddResult addResult = stringTable().add<HashTranslator>(value);

     // If the string is newly-translated, then we need to adopt it.
     // The boolean in the pair tells us if that is so.
     return addResult.isNewEntry ? adoptRef(*addResult.iterator) : *addResult.iterator;
 }

 struct CStringTranslator {
     static unsigned hash(const LChar* c)
     {
         return StringHasher::computeHashAndMaskTop8Bits(c);
     }

     static inline bool equal(StringImpl* r, const LChar* s)
     {
         return WTF::equal(r, s);
     }

     static void translate(StringImpl*& location, const LChar* const& c, unsigned hash)
     {
         location = StringImpl::create(c).leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 PassRefPtr<StringImpl> AtomicString::add(const LChar* c)
 {
     if (!c)
         return 0;
     if (!*c)
         return StringImpl::empty();

     return addToStringTable<const LChar*, CStringTranslator>(c);
 }

 template<typename CharacterType>
 struct HashTranslatorCharBuffer {
     const CharacterType* s;
     unsigned length;
 };

 typedef HashTranslatorCharBuffer<UChar> UCharBuffer;
 struct UCharBufferTranslator {
     static unsigned hash(const UCharBuffer& buf)
     {
         return StringHasher::computeHashAndMaskTop8Bits(buf.s, buf.length);
     }

     static bool equal(StringImpl* const& str, const UCharBuffer& buf)
     {
         return WTF::equal(str, buf.s, buf.length);
     }

     static void translate(StringImpl*& location, const UCharBuffer& buf, unsigned hash)
     {
         location = StringImpl::create8BitIfPossible(buf.s, buf.length).leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 template<typename CharacterType>
 struct HashAndCharacters {
     unsigned hash;
     const CharacterType* characters;
     unsigned length;
 };

 template<typename CharacterType>
 struct HashAndCharactersTranslator {
     static unsigned hash(const HashAndCharacters<CharacterType>& buffer)
     {
         ASSERT(buffer.hash == StringHasher::computeHashAndMaskTop8Bits(buffer.characters, buffer.length));
         return buffer.hash;
     }

     static bool equal(StringImpl* const& string, const HashAndCharacters<CharacterType>& buffer)
     {
         return WTF::equal(string, buffer.characters, buffer.length);
     }

     static void translate(StringImpl*& location, const HashAndCharacters<CharacterType>& buffer, unsigned hash)
     {
         location = StringImpl::create(buffer.characters, buffer.length).leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 struct HashAndUTF8Characters {
     unsigned hash;
     const char* characters;
     unsigned length;
     unsigned utf16Length;
 };

 struct HashAndUTF8CharactersTranslator {
     static unsigned hash(const HashAndUTF8Characters& buffer)
     {
         return buffer.hash;
     }

     static bool equal(StringImpl* const& string, const HashAndUTF8Characters& buffer)
     {
         if (buffer.utf16Length != string->length())
             return false;

         // If buffer contains only ASCII characters UTF-8 and UTF16 length are the same.
         if (buffer.utf16Length != buffer.length) {
             const UChar* stringCharacters = string->characters();

             return equalUTF16WithUTF8(stringCharacters, stringCharacters + string->length(), buffer.characters, buffer.characters + buffer.length);
         }

         if (string->is8Bit()) {
             const LChar* stringCharacters = string->characters8();

             for (unsigned i = 0; i < buffer.length; ++i) {
                 ASSERT(isASCII(buffer.characters[i]));
                 if (stringCharacters[i] != buffer.characters[i])
                     return false;
             }

             return true;
         }

         const UChar* stringCharacters = string->characters16();

         for (unsigned i = 0; i < buffer.length; ++i) {
             ASSERT(isASCII(buffer.characters[i]));
             if (stringCharacters[i] != buffer.characters[i])
                 return false;
         }

         return true;
     }

     static void translate(StringImpl*& location, const HashAndUTF8Characters& buffer, unsigned hash)
     {
         UChar* target;
         RefPtr<StringImpl> newString = StringImpl::createUninitialized(buffer.utf16Length, target);

         bool isAllASCII;
         const char* source = buffer.characters;
         if (convertUTF8ToUTF16(&source, source + buffer.length, &target, target + buffer.utf16Length, &isAllASCII) != conversionOK)
             ASSERT_NOT_REACHED();

         if (isAllASCII)
             newString = StringImpl::create(buffer.characters, buffer.length);

         location = newString.release().leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 PassRefPtr<StringImpl> AtomicString::add(const UChar* s, unsigned length)
 {
     if (!s)
         return 0;

     if (!length)
         return StringImpl::empty();

     UCharBuffer buffer = { s, length };
     return addToStringTable<UCharBuffer, UCharBufferTranslator>(buffer);
 }

 PassRefPtr<StringImpl> AtomicString::add(const UChar* s, unsigned length, unsigned existingHash)
 {
     ASSERT(s);
     ASSERT(existingHash);

     if (!length)
         return StringImpl::empty();

     HashAndCharacters<UChar> buffer = { existingHash, s, length };
     return addToStringTable<HashAndCharacters<UChar>, HashAndCharactersTranslator<UChar> >(buffer);
 }

 PassRefPtr<StringImpl> AtomicString::add(const UChar* s)
 {
     if (!s)
         return 0;

     unsigned length = 0;
     while (s[length] != UChar(0))
         ++length;

     if (!length)
         return StringImpl::empty();

     UCharBuffer buffer = { s, length };
     return addToStringTable<UCharBuffer, UCharBufferTranslator>(buffer);
 }

 struct SubstringLocation {
     StringImpl* baseString;
     unsigned start;
     unsigned length;
 };

 struct SubstringTranslator {
     static unsigned hash(const SubstringLocation& buffer)
     {
         return StringHasher::computeHashAndMaskTop8Bits(buffer.baseString->characters() + buffer.start, buffer.length);
     }

     static bool equal(StringImpl* const& string, const SubstringLocation& buffer)
     {
         return WTF::equal(string, buffer.baseString->characters() + buffer.start, buffer.length);
     }

     static void translate(StringImpl*& location, const SubstringLocation& buffer, unsigned hash)
     {
         location = StringImpl::create(buffer.baseString, buffer.start, buffer.length).leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 PassRefPtr<StringImpl> AtomicString::add(StringImpl* baseString, unsigned start, unsigned length)
 {
     if (!baseString)
         return 0;

     if (!length || start >= baseString->length())
         return StringImpl::empty();

     unsigned maxLength = baseString->length() - start;
     if (length >= maxLength) {
         if (!start)
             return add(baseString);
         length = maxLength;
     }

     SubstringLocation buffer = { baseString, start, length };
     return addToStringTable<SubstringLocation, SubstringTranslator>(buffer);
 }

 typedef HashTranslatorCharBuffer<LChar> LCharBuffer;
 struct LCharBufferTranslator {
     static unsigned hash(const LCharBuffer& buf)
     {
         return StringHasher::computeHashAndMaskTop8Bits(buf.s, buf.length);
     }

     static bool equal(StringImpl* const& str, const LCharBuffer& buf)
     {
         return WTF::equal(str, buf.s, buf.length);
     }

     static void translate(StringImpl*& location, const LCharBuffer& buf, unsigned hash)
     {
         location = StringImpl::create(buf.s, buf.length).leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 typedef HashTranslatorCharBuffer<char> CharBuffer;
 struct CharBufferFromLiteralDataTranslator {
     static unsigned hash(const CharBuffer& buf)
     {
         return StringHasher::computeHashAndMaskTop8Bits(reinterpret_cast<const LChar*>(buf.s), buf.length);
     }

     static bool equal(StringImpl* const& str, const CharBuffer& buf)
     {
         return WTF::equal(str, buf.s, buf.length);
     }

     static void translate(StringImpl*& location, const CharBuffer& buf, unsigned hash)
     {
         location = StringImpl::createFromLiteral(buf.s, buf.length).leakRef();
         location->setHash(hash);
         location->setIsAtomic(true);
     }
 };

 PassRefPtr<StringImpl> AtomicString::add(const LChar* s, unsigned length)
 {
     if (!s)
         return 0;

     if (!length)
         return StringImpl::empty();

     LCharBuffer buffer = { s, length };
     return addToStringTable<LCharBuffer, LCharBufferTranslator>(buffer);
 }

 PassRefPtr<StringImpl> AtomicString::addFromLiteralData(const char* characters, unsigned length)
 {
     ASSERT(characters);
     ASSERT(length);

     CharBuffer buffer = { characters, length };
     return addToStringTable<CharBuffer, CharBufferFromLiteralDataTranslator>(buffer);
 }

 PassRefPtr<StringImpl> AtomicString::addSlowCase(StringImpl* string)
 {
     if (!string->length())
         return StringImpl::empty();

     ASSERT_WITH_MESSAGE(!string->isAtomic(), "AtomicString should not hit the slow case if the string is already atomic.");

     AtomicStringTableLocker locker;
     HashSet<StringImpl*>::AddResult addResult = stringTable().add(string);

     if (addResult.isNewEntry) {
         ASSERT(*addResult.iterator == string);
         string->setIsAtomic(true);
     }

     return *addResult.iterator;
 }

 template<typename CharacterType>
 static inline HashSet<StringImpl*>::iterator findString(const StringImpl* stringImpl)
 {
     HashAndCharacters<CharacterType> buffer = { stringImpl->existingHash(), stringImpl->getCharacters<CharacterType>(), stringImpl->length() };
     return stringTable().find<HashAndCharactersTranslator<CharacterType> >(buffer);
 }

 AtomicStringImpl* AtomicString::find(const StringImpl* stringImpl)
 {
     ASSERT(stringImpl);
     ASSERT(stringImpl->existingHash());

     if (!stringImpl->length())
         return static_cast<AtomicStringImpl*>(StringImpl::empty());

     AtomicStringTableLocker locker;
     HashSet<StringImpl*>::iterator iterator;
     if (stringImpl->is8Bit())
         iterator = findString<LChar>(stringImpl);
     else
         iterator = findString<UChar>(stringImpl);
     if (iterator == stringTable().end())
         return 0;
     return static_cast<AtomicStringImpl*>(*iterator);
 }

 void AtomicString::remove(StringImpl* string)
 {
     ASSERT(string->isAtomic());
     AtomicStringTableLocker locker;
     HashSet<StringImpl*>& atomicStringTable = stringTable();
     HashSet<StringImpl*>::iterator iterator = atomicStringTable.find(string);
     ASSERT_WITH_MESSAGE(iterator != atomicStringTable.end(), "The string being removed is atomic in the string table of an other thread!");
     atomicStringTable.remove(iterator);
 }

 AtomicString AtomicString::lower() const
 {
     // Note: This is a hot function in the Dromaeo benchmark.
     StringImpl* impl = this->impl();
     if (UNLIKELY(!impl))
         return AtomicString();

     RefPtr<StringImpl> lowerImpl = impl->lower();
     AtomicString returnValue;
     if (LIKELY(lowerImpl == impl))
         returnValue.m_string = lowerImpl.release();
     else
         returnValue.m_string = addSlowCase(lowerImpl.get());
     return returnValue;
 }

 AtomicString AtomicString::fromUTF8Internal(const char* charactersStart, const char* charactersEnd)
 {
     HashAndUTF8Characters buffer;
     buffer.characters = charactersStart;
     buffer.hash = calculateStringHashAndLengthFromUTF8MaskingTop8Bits(charactersStart, charactersEnd, buffer.length, buffer.utf16Length);

     if (!buffer.hash)
         return nullAtom;

     AtomicString atomicString;
     atomicString.m_string = addToStringTable<HashAndUTF8Characters, HashAndUTF8CharactersTranslator>(buffer);
     return atomicString;
 }

 #if !ASSERT_DISABLED
 bool AtomicString::isInAtomicStringTable(StringImpl* string)
 {
     AtomicStringTableLocker locker;
     return stringTable().contains(string);
 }
 #endif

 #ifndef NDEBUG
 void AtomicString::show() const
 {
     m_string.show();
 }
 #endif

 } // namespace WTF
	/*
	* Copyright (C) 2004, 2005, 2006, 2007, 2008, 2013 Apple Inc. All rights reserved.
	* Copyright (C) 2010 Patrick Gansterer <paroga@paroga.com>
	* Copyright (C) 2012 Google Inc. All rights reserved.
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Library General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Library General Public License for more details.
	*
	* You should have received a copy of the GNU Library General Public License
	* along with this library; see the file COPYING.LIB. If not, write to
	* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*
	*/

	#include "config.h"

	#include "AtomicString.h"

	#include "AtomicStringTable.h"
	#include "StringHash.h"
	#include <wtf/HashSet.h>
	#include <wtf/Threading.h>
	#include <wtf/WTFThreadData.h>
	#include <wtf/unicode/UTF8.h>

	#if USE(WEB_THREAD)
	#include <wtf/MainThread.h>
	#include <wtf/TCSpinLock.h>
	#endif

	namespace WTF {

	using namespace Unicode;

	COMPILE_ASSERT(sizeof(AtomicString) == sizeof(String), atomic_string_and_string_must_be_same_size);

	#if USE(WEB_THREAD)
	class AtomicStringTableLocker : public SpinLockHolder {
	WTF_MAKE_NONCOPYABLE(AtomicStringTableLocker);

	static SpinLock s_stringTableLock;
	public:
	AtomicStringTableLocker()
	: SpinLockHolder(&s_stringTableLock)
	{
	}
	};

	SpinLock AtomicStringTableLocker::s_stringTableLock = SPINLOCK_INITIALIZER;
	#else

	class AtomicStringTableLocker {
	WTF_MAKE_NONCOPYABLE(AtomicStringTableLocker);
	public:
	AtomicStringTableLocker() { }
	~AtomicStringTableLocker() { }
	};
	#endif // USE(WEB_THREAD)

	static ALWAYS_INLINE HashSet<StringImpl*>& stringTable()
	{
	return wtfThreadData().atomicStringTable()->table();
	}

	template<typename T, typename HashTranslator>
	static inline PassRefPtr<StringImpl> addToStringTable(const T& value)
	{
	AtomicStringTableLocker locker;

	HashSet<StringImpl*>::AddResult addResult = stringTable().add<HashTranslator>(value);

	// If the string is newly-translated, then we need to adopt it.
	// The boolean in the pair tells us if that is so.
	return addResult.isNewEntry ? adoptRef(addResult.iterator) : addResult.iterator;
	}

	struct CStringTranslator {
	static unsigned hash(const LChar* c)
	{
	return StringHasher::computeHashAndMaskTop8Bits(c);
	}

	static inline bool equal(StringImpl* r, const LChar* s)
	{
	return WTF::equal(r, s);
	}

	static void translate(StringImpl& location, const LChar const& c, unsigned hash)
	{
	location = StringImpl::create(c).leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	PassRefPtr<StringImpl> AtomicString::add(const LChar* c)
	{
	if (!c)
	return 0;
	if (!*c)
	return StringImpl::empty();

	return addToStringTable<const LChar*, CStringTranslator>(c);
	}

	template<typename CharacterType>
	struct HashTranslatorCharBuffer {
	const CharacterType* s;
	unsigned length;
	};

	typedef HashTranslatorCharBuffer<UChar> UCharBuffer;
	struct UCharBufferTranslator {
	static unsigned hash(const UCharBuffer& buf)
	{
	return StringHasher::computeHashAndMaskTop8Bits(buf.s, buf.length);
	}

	static bool equal(StringImpl* const& str, const UCharBuffer& buf)
	{
	return WTF::equal(str, buf.s, buf.length);
	}

	static void translate(StringImpl*& location, const UCharBuffer& buf, unsigned hash)
	{
	location = StringImpl::create8BitIfPossible(buf.s, buf.length).leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	template<typename CharacterType>
	struct HashAndCharacters {
	unsigned hash;
	const CharacterType* characters;
	unsigned length;
	};

	template<typename CharacterType>
	struct HashAndCharactersTranslator {
	static unsigned hash(const HashAndCharacters<CharacterType>& buffer)
	{
	ASSERT(buffer.hash == StringHasher::computeHashAndMaskTop8Bits(buffer.characters, buffer.length));
	return buffer.hash;
	}

	static bool equal(StringImpl* const& string, const HashAndCharacters<CharacterType>& buffer)
	{
	return WTF::equal(string, buffer.characters, buffer.length);
	}

	static void translate(StringImpl*& location, const HashAndCharacters<CharacterType>& buffer, unsigned hash)
	{
	location = StringImpl::create(buffer.characters, buffer.length).leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	struct HashAndUTF8Characters {
	unsigned hash;
	const char* characters;
	unsigned length;
	unsigned utf16Length;
	};

	struct HashAndUTF8CharactersTranslator {
	static unsigned hash(const HashAndUTF8Characters& buffer)
	{
	return buffer.hash;
	}

	static bool equal(StringImpl* const& string, const HashAndUTF8Characters& buffer)
	{
	if (buffer.utf16Length != string->length())
	return false;

	// If buffer contains only ASCII characters UTF-8 and UTF16 length are the same.
	if (buffer.utf16Length != buffer.length) {
	const UChar* stringCharacters = string->characters();

	return equalUTF16WithUTF8(stringCharacters, stringCharacters + string->length(), buffer.characters, buffer.characters + buffer.length);
	}

	if (string->is8Bit()) {
	const LChar* stringCharacters = string->characters8();

	for (unsigned i = 0; i < buffer.length; ++i) {
	ASSERT(isASCII(buffer.characters[i]));
	if (stringCharacters[i] != buffer.characters[i])
	return false;
	}

	return true;
	}

	const UChar* stringCharacters = string->characters16();

	for (unsigned i = 0; i < buffer.length; ++i) {
	ASSERT(isASCII(buffer.characters[i]));
	if (stringCharacters[i] != buffer.characters[i])
	return false;
	}

	return true;
	}

	static void translate(StringImpl*& location, const HashAndUTF8Characters& buffer, unsigned hash)
	{
	UChar* target;
	RefPtr<StringImpl> newString = StringImpl::createUninitialized(buffer.utf16Length, target);

	bool isAllASCII;
	const char* source = buffer.characters;
	if (convertUTF8ToUTF16(&source, source + buffer.length, &target, target + buffer.utf16Length, &isAllASCII) != conversionOK)
	ASSERT_NOT_REACHED();

	if (isAllASCII)
	newString = StringImpl::create(buffer.characters, buffer.length);

	location = newString.release().leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	PassRefPtr<StringImpl> AtomicString::add(const UChar* s, unsigned length)
	{
	if (!s)
	return 0;

	if (!length)
	return StringImpl::empty();

	UCharBuffer buffer = { s, length };
	return addToStringTable<UCharBuffer, UCharBufferTranslator>(buffer);
	}

	PassRefPtr<StringImpl> AtomicString::add(const UChar* s, unsigned length, unsigned existingHash)
	{
	ASSERT(s);
	ASSERT(existingHash);

	if (!length)
	return StringImpl::empty();

	HashAndCharacters<UChar> buffer = { existingHash, s, length };
	return addToStringTable<HashAndCharacters<UChar>, HashAndCharactersTranslator<UChar> >(buffer);
	}

	PassRefPtr<StringImpl> AtomicString::add(const UChar* s)
	{
	if (!s)
	return 0;

	unsigned length = 0;
	while (s[length] != UChar(0))
	++length;

	if (!length)
	return StringImpl::empty();

	UCharBuffer buffer = { s, length };
	return addToStringTable<UCharBuffer, UCharBufferTranslator>(buffer);
	}

	struct SubstringLocation {
	StringImpl* baseString;
	unsigned start;
	unsigned length;
	};

	struct SubstringTranslator {
	static unsigned hash(const SubstringLocation& buffer)
	{
	return StringHasher::computeHashAndMaskTop8Bits(buffer.baseString->characters() + buffer.start, buffer.length);
	}

	static bool equal(StringImpl* const& string, const SubstringLocation& buffer)
	{
	return WTF::equal(string, buffer.baseString->characters() + buffer.start, buffer.length);
	}

	static void translate(StringImpl*& location, const SubstringLocation& buffer, unsigned hash)
	{
	location = StringImpl::create(buffer.baseString, buffer.start, buffer.length).leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	PassRefPtr<StringImpl> AtomicString::add(StringImpl* baseString, unsigned start, unsigned length)
	{
	if (!baseString)
	return 0;

	if (!length \|\| start >= baseString->length())
	return StringImpl::empty();

	unsigned maxLength = baseString->length() - start;
	if (length >= maxLength) {
	if (!start)
	return add(baseString);
	length = maxLength;
	}

	SubstringLocation buffer = { baseString, start, length };
	return addToStringTable<SubstringLocation, SubstringTranslator>(buffer);
	}

	typedef HashTranslatorCharBuffer<LChar> LCharBuffer;
	struct LCharBufferTranslator {
	static unsigned hash(const LCharBuffer& buf)
	{
	return StringHasher::computeHashAndMaskTop8Bits(buf.s, buf.length);
	}

	static bool equal(StringImpl* const& str, const LCharBuffer& buf)
	{
	return WTF::equal(str, buf.s, buf.length);
	}

	static void translate(StringImpl*& location, const LCharBuffer& buf, unsigned hash)
	{
	location = StringImpl::create(buf.s, buf.length).leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	typedef HashTranslatorCharBuffer<char> CharBuffer;
	struct CharBufferFromLiteralDataTranslator {
	static unsigned hash(const CharBuffer& buf)
	{
	return StringHasher::computeHashAndMaskTop8Bits(reinterpret_cast<const LChar*>(buf.s), buf.length);
	}

	static bool equal(StringImpl* const& str, const CharBuffer& buf)
	{
	return WTF::equal(str, buf.s, buf.length);
	}

	static void translate(StringImpl*& location, const CharBuffer& buf, unsigned hash)
	{
	location = StringImpl::createFromLiteral(buf.s, buf.length).leakRef();
	location->setHash(hash);
	location->setIsAtomic(true);
	}
	};

	PassRefPtr<StringImpl> AtomicString::add(const LChar* s, unsigned length)
	{
	if (!s)
	return 0;

	if (!length)
	return StringImpl::empty();

	LCharBuffer buffer = { s, length };
	return addToStringTable<LCharBuffer, LCharBufferTranslator>(buffer);
	}

	PassRefPtr<StringImpl> AtomicString::addFromLiteralData(const char* characters, unsigned length)
	{
	ASSERT(characters);
	ASSERT(length);

	CharBuffer buffer = { characters, length };
	return addToStringTable<CharBuffer, CharBufferFromLiteralDataTranslator>(buffer);
	}

	PassRefPtr<StringImpl> AtomicString::addSlowCase(StringImpl* string)
	{
	if (!string->length())
	return StringImpl::empty();

	ASSERT_WITH_MESSAGE(!string->isAtomic(), "AtomicString should not hit the slow case if the string is already atomic.");

	AtomicStringTableLocker locker;
	HashSet<StringImpl*>::AddResult addResult = stringTable().add(string);

	if (addResult.isNewEntry) {
	ASSERT(*addResult.iterator == string);
	string->setIsAtomic(true);
	}

	return *addResult.iterator;
	}

	template<typename CharacterType>
	static inline HashSet<StringImpl>::iterator findString(const StringImpl stringImpl)
	{
	HashAndCharacters<CharacterType> buffer = { stringImpl->existingHash(), stringImpl->getCharacters<CharacterType>(), stringImpl->length() };
	return stringTable().find<HashAndCharactersTranslator<CharacterType> >(buffer);
	}

	AtomicStringImpl* AtomicString::find(const StringImpl* stringImpl)
	{
	ASSERT(stringImpl);
	ASSERT(stringImpl->existingHash());

	if (!stringImpl->length())
	return static_cast<AtomicStringImpl*>(StringImpl::empty());

	AtomicStringTableLocker locker;
	HashSet<StringImpl*>::iterator iterator;
	if (stringImpl->is8Bit())
	iterator = findString<LChar>(stringImpl);
	else
	iterator = findString<UChar>(stringImpl);
	if (iterator == stringTable().end())
	return 0;
	return static_cast<AtomicStringImpl>(iterator);
	}

	void AtomicString::remove(StringImpl* string)
	{
	ASSERT(string->isAtomic());
	AtomicStringTableLocker locker;
	HashSet<StringImpl*>& atomicStringTable = stringTable();
	HashSet<StringImpl*>::iterator iterator = atomicStringTable.find(string);
	ASSERT_WITH_MESSAGE(iterator != atomicStringTable.end(), "The string being removed is atomic in the string table of an other thread!");
	atomicStringTable.remove(iterator);
	}

	AtomicString AtomicString::lower() const
	{
	// Note: This is a hot function in the Dromaeo benchmark.
	StringImpl* impl = this->impl();
	if (UNLIKELY(!impl))
	return AtomicString();

	RefPtr<StringImpl> lowerImpl = impl->lower();
	AtomicString returnValue;
	if (LIKELY(lowerImpl == impl))
	returnValue.m_string = lowerImpl.release();
	else
	returnValue.m_string = addSlowCase(lowerImpl.get());
	return returnValue;
	}

	AtomicString AtomicString::fromUTF8Internal(const char* charactersStart, const char* charactersEnd)
	{
	HashAndUTF8Characters buffer;
	buffer.characters = charactersStart;
	buffer.hash = calculateStringHashAndLengthFromUTF8MaskingTop8Bits(charactersStart, charactersEnd, buffer.length, buffer.utf16Length);

	if (!buffer.hash)
	return nullAtom;

	AtomicString atomicString;
	atomicString.m_string = addToStringTable<HashAndUTF8Characters, HashAndUTF8CharactersTranslator>(buffer);
	return atomicString;
	}

	#if !ASSERT_DISABLED
	bool AtomicString::isInAtomicStringTable(StringImpl* string)
	{
	AtomicStringTableLocker locker;
	return stringTable().contains(string);
	}
	#endif

	#ifndef NDEBUG
	void AtomicString::show() const
	{
	m_string.show();
	}
	#endif

	} // namespace WTF