Source/wtf/text/AtomicString.cpp - chromium/blink - 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 "StringHash.h"
 #include <wtf/HashSet.h>
 #include <wtf/Threading.h>
 #include <wtf/WTFThreadData.h>
 #include <wtf/unicode/UTF8.h>

 namespace WTF {

 using namespace Unicode;

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

 class AtomicStringTable {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     static AtomicStringTable* create(WTFThreadData& data)
     {
         data.m_atomicStringTable = new AtomicStringTable;
         data.m_atomicStringTableDestructor = AtomicStringTable::destroy;
         return data.m_atomicStringTable;
     }

     HashSet<StringImpl*>& table()
     {
         return m_table;
     }

 private:
     static void destroy(AtomicStringTable* table)
     {
         HashSet<StringImpl*>::iterator end = table->m_table.end();
         for (HashSet<StringImpl*>::iterator iter = table->m_table.begin(); iter != end; ++iter)
             (*iter)->setIsAtomic(false);
         delete table;
     }

     HashSet<StringImpl*> m_table;
 };

 static inline HashSet<StringImpl*>& stringTable()
 {
     // Once possible we should make this non-lazy (constructed in WTFThreadData's constructor).
     WTFThreadData& data = wtfThreadData();
     AtomicStringTable* table = data.atomicStringTable();
     if (UNLIKELY(!table))
         table = AtomicStringTable::create(data);
     return table->table();
 }

 template<typename T, typename HashTranslator>
 static inline PassRefPtr<StringImpl> addToStringTable(const T& value)
 {
     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* r)
 {
     if (!r->length())
         return StringImpl::empty();

     StringImpl* result = *stringTable().add(r).iterator;
     if (result == r)
         r->setIsAtomic(true);
     ASSERT(!r->isStatic() || result->isStatic());
     return result;
 }

 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());

     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* r)
 {
     HashSet<StringImpl*>::iterator iterator;
     if (r->is8Bit())
         iterator = findString<LChar>(r);
     else
         iterator = findString<UChar>(r);
     RELEASE_ASSERT(iterator != stringTable().end());
     stringTable().remove(iterator);
 }

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

 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;
 }

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

	namespace WTF {

	using namespace Unicode;

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

	class AtomicStringTable {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	static AtomicStringTable* create(WTFThreadData& data)
	{
	data.m_atomicStringTable = new AtomicStringTable;
	data.m_atomicStringTableDestructor = AtomicStringTable::destroy;
	return data.m_atomicStringTable;
	}

	HashSet<StringImpl*>& table()
	{
	return m_table;
	}

	private:
	static void destroy(AtomicStringTable* table)
	{
	HashSet<StringImpl*>::iterator end = table->m_table.end();
	for (HashSet<StringImpl*>::iterator iter = table->m_table.begin(); iter != end; ++iter)
	(*iter)->setIsAtomic(false);
	delete table;
	}

	HashSet<StringImpl*> m_table;
	};

	static inline HashSet<StringImpl*>& stringTable()
	{
	// Once possible we should make this non-lazy (constructed in WTFThreadData's constructor).
	WTFThreadData& data = wtfThreadData();
	AtomicStringTable* table = data.atomicStringTable();
	if (UNLIKELY(!table))
	table = AtomicStringTable::create(data);
	return table->table();
	}

	template<typename T, typename HashTranslator>
	static inline PassRefPtr<StringImpl> addToStringTable(const T& value)
	{
	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* r)
	{
	if (!r->length())
	return StringImpl::empty();

	StringImpl* result = *stringTable().add(r).iterator;
	if (result == r)
	r->setIsAtomic(true);
	ASSERT(!r->isStatic() \|\| result->isStatic());
	return result;
	}

	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());

	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* r)
	{
	HashSet<StringImpl*>::iterator iterator;
	if (r->is8Bit())
	iterator = findString<LChar>(r);
	else
	iterator = findString<UChar>(r);
	RELEASE_ASSERT(iterator != stringTable().end());
	stringTable().remove(iterator);
	}

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

	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;
	}

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

	} // namespace WTF