JavaScriptCore/wtf/text/StringImpl.h - platform/external/webkit - Git at Google

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2009 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.
  *
  */

 #ifndef StringImpl_h
 #define StringImpl_h

 #include <limits.h>
 #include <wtf/ASCIICType.h>
 #include <wtf/CrossThreadRefCounted.h>
 #include <wtf/OwnFastMallocPtr.h>
 #include <wtf/StdLibExtras.h>
 #include <wtf/StringHashFunctions.h>
 #include <wtf/Vector.h>
 #include <wtf/text/StringImplBase.h>
 #include <wtf/unicode/Unicode.h>

 #if PLATFORM(CF)
 typedef const struct __CFString * CFStringRef;
 #endif

 #ifdef __OBJC__
 @class NSString;
 #endif

 // FIXME: This is a temporary layering violation while we move string code to WTF.
 // Landing the file moves in one patch, will follow on with patches to change the namespaces.
 namespace JSC {

 struct IdentifierCStringTranslator;
 struct IdentifierUCharBufferTranslator;

 }

 // FIXME: This is a temporary layering violation while we move string code to WTF.
 // Landing the file moves in one patch, will follow on with patches to change the namespaces.
 namespace WebCore {

 class StringBuffer;

 struct CStringTranslator;
 struct HashAndCharactersTranslator;
 struct StringHash;
 struct UCharBufferTranslator;

 enum TextCaseSensitivity { TextCaseSensitive, TextCaseInsensitive };

 typedef OwnFastMallocPtr<const UChar> SharableUChar;
 typedef CrossThreadRefCounted<SharableUChar> SharedUChar;
 typedef bool (*CharacterMatchFunctionPtr)(UChar);

 class StringImpl : public StringImplBase {
     friend struct JSC::IdentifierCStringTranslator;
     friend struct JSC::IdentifierUCharBufferTranslator;
     friend struct CStringTranslator;
     friend struct HashAndCharactersTranslator;
     friend struct UCharBufferTranslator;
     friend class AtomicStringImpl;
 private:
     // Used to construct static strings, which have an special refCount that can never hit zero.
     // This means that the static string will never be destroyed, which is important because
     // static strings will be shared across threads & ref-counted in a non-threadsafe manner.
     StringImpl(const UChar* characters, unsigned length, StaticStringConstructType)
         : StringImplBase(length, ConstructStaticString)
         , m_data(characters)
         , m_buffer(0)
         , m_hash(0)
     {
         // Ensure that the hash is computed so that AtomicStringHash can call existingHash()
         // with impunity. The empty string is special because it is never entered into
         // AtomicString's HashKey, but still needs to compare correctly.
         hash();
     }

     // Create a normal string with internal storage (BufferInternal)
     StringImpl(unsigned length)
         : StringImplBase(length, BufferInternal)
         , m_data(reinterpret_cast<const UChar*>(this + 1))
         , m_buffer(0)
         , m_hash(0)
     {
         ASSERT(m_data);
         ASSERT(m_length);
     }

     // Create a StringImpl adopting ownership of the provided buffer (BufferOwned)
     StringImpl(const UChar* characters, unsigned length)
         : StringImplBase(length, BufferOwned)
         , m_data(characters)
         , m_buffer(0)
         , m_hash(0)
     {
         ASSERT(m_data);
         ASSERT(m_length);
     }

     // Used to create new strings that are a substring of an existing StringImpl (BufferSubstring)
     StringImpl(const UChar* characters, unsigned length, PassRefPtr<StringImpl> base)
         : StringImplBase(length, BufferSubstring)
         , m_data(characters)
         , m_substringBuffer(base.releaseRef())
         , m_hash(0)
     {
         ASSERT(m_data);
         ASSERT(m_length);
         ASSERT(m_substringBuffer->bufferOwnership() != BufferSubstring);
     }

     // Used to construct new strings sharing an existing SharedUChar (BufferShared)
     StringImpl(const UChar* characters, unsigned length, PassRefPtr<SharedUChar> sharedBuffer)
         : StringImplBase(length, BufferShared)
         , m_data(characters)
         , m_sharedBuffer(sharedBuffer.releaseRef())
         , m_hash(0)
     {
         ASSERT(m_data);
         ASSERT(m_length);
     }

     // For use only by AtomicString's XXXTranslator helpers.
     void setHash(unsigned hash)
     {
         ASSERT(!isStatic());
         ASSERT(!m_hash);
         ASSERT(hash == computeHash(m_data, m_length));
         m_hash = hash;
     }

 public:
     ~StringImpl();

     static PassRefPtr<StringImpl> create(const UChar*, unsigned length);
     static PassRefPtr<StringImpl> create(const char*, unsigned length);
     static PassRefPtr<StringImpl> create(const char*);
     static PassRefPtr<StringImpl> create(const UChar*, unsigned length, PassRefPtr<SharedUChar> sharedBuffer);
     static ALWAYS_INLINE PassRefPtr<StringImpl> create(PassRefPtr<StringImpl> rep, unsigned offset, unsigned length)
     {
         ASSERT(rep);
         ASSERT(length <= rep->length());

         if (!length)
             return empty();

         StringImpl* ownerRep = (rep->bufferOwnership() == BufferSubstring) ? rep->m_substringBuffer : rep.get();
         return adoptRef(new StringImpl(rep->m_data + offset, length, ownerRep));
     }

     static PassRefPtr<StringImpl> createUninitialized(unsigned length, UChar*& data);
     static ALWAYS_INLINE PassRefPtr<StringImpl> tryCreateUninitialized(unsigned length, UChar*& output)
     {
         if (!length) {
             output = 0;
             return empty();
         }

         if (length > ((std::numeric_limits<size_t>::max() - sizeof(StringImpl)) / sizeof(UChar))) {
             output = 0;
             return 0;
         }
         StringImpl* resultImpl;
         if (!tryFastMalloc(sizeof(UChar) * length + sizeof(StringImpl)).getValue(resultImpl)) {
             output = 0;
             return 0;
         }
         output = reinterpret_cast<UChar*>(resultImpl + 1);
         return adoptRef(new(resultImpl) StringImpl(length));
     }

     static unsigned dataOffset() { return OBJECT_OFFSETOF(StringImpl, m_data); }
     static PassRefPtr<StringImpl> createWithTerminatingNullCharacter(const StringImpl&);
     static PassRefPtr<StringImpl> createStrippingNullCharacters(const UChar*, unsigned length);

     template<size_t inlineCapacity>
     static PassRefPtr<StringImpl> adopt(Vector<UChar, inlineCapacity>& vector)
     {
         if (size_t size = vector.size()) {
             ASSERT(vector.data());
             return adoptRef(new StringImpl(vector.releaseBuffer(), size));
         }
         return empty();
     }
     static PassRefPtr<StringImpl> adopt(StringBuffer&);

     SharedUChar* sharedBuffer();
     const UChar* characters() const { return m_data; }

     size_t cost()
     {
         // For substrings, return the cost of the base string.
         if (bufferOwnership() == BufferSubstring)
             return m_substringBuffer->cost();

         if (m_refCountAndFlags & s_refCountFlagShouldReportedCost) {
             m_refCountAndFlags &= ~s_refCountFlagShouldReportedCost;
             return m_length;
         }
         return 0;
     }

     bool isIdentifier() const { return m_refCountAndFlags & s_refCountFlagIsIdentifier; }
     void setIsIdentifier(bool isIdentifier)
     {
         ASSERT(!isStatic());
         if (isIdentifier)
             m_refCountAndFlags |= s_refCountFlagIsIdentifier;
         else
             m_refCountAndFlags &= ~s_refCountFlagIsIdentifier;
     }

     bool hasTerminatingNullCharacter() const { return m_refCountAndFlags & s_refCountFlagHasTerminatingNullCharacter; }

     bool isAtomic() const { return m_refCountAndFlags & s_refCountFlagIsAtomic; }
     void setIsAtomic(bool isIdentifier)
     {
         ASSERT(!isStatic());
         if (isIdentifier)
             m_refCountAndFlags |= s_refCountFlagIsAtomic;
         else
             m_refCountAndFlags &= ~s_refCountFlagIsAtomic;
     }

     unsigned hash() const { if (!m_hash) m_hash = computeHash(m_data, m_length); return m_hash; }
     unsigned existingHash() const { ASSERT(m_hash); return m_hash; }
     static unsigned computeHash(const UChar* data, unsigned length) { return WTF::stringHash(data, length); }
     static unsigned computeHash(const char* data, unsigned length) { return WTF::stringHash(data, length); }
     static unsigned computeHash(const char* data) { return WTF::stringHash(data); }

     ALWAYS_INLINE void deref() { m_refCountAndFlags -= s_refCountIncrement; if (!(m_refCountAndFlags & (s_refCountMask | s_refCountFlagStatic))) delete this; }
     ALWAYS_INLINE bool hasOneRef() const { return (m_refCountAndFlags & (s_refCountMask | s_refCountFlagStatic)) == s_refCountIncrement; }

     static StringImpl* empty();

     static void copyChars(UChar* destination, const UChar* source, unsigned numCharacters)
     {
         if (numCharacters <= s_copyCharsInlineCutOff) {
             for (unsigned i = 0; i < numCharacters; ++i)
                 destination[i] = source[i];
         } else
             memcpy(destination, source, numCharacters * sizeof(UChar));
     }

     PassRefPtr<StringImpl> copyStringWithoutBOMs(bool definitelyHasBOMs, bool& hasBOMs)
     {
         static const UChar byteOrderMark = 0xFEFF;
         size_t i = 0;
         if (!definitelyHasBOMs) {
             hasBOMs = false;
             // ECMA-262 calls for stripping all Cf characters, but we only strip BOM characters.
             // See <https://bugs.webkit.org/show_bug.cgi?id=4931> for details.
             for (; i < m_length; i++) {
                 if (UNLIKELY(m_data[i] == byteOrderMark)) {
                     hasBOMs = true;
                     break;
                 }
             }
             if (!hasBOMs)
                 return this;
         }
         Vector<UChar> result;
         result.reserveInitialCapacity(m_length);
         size_t firstBOM = i;
         i = 0;
         for (; i < firstBOM; i++)
             result.append(m_data[i]);
         for (; i < m_length; i++) {
             UChar c = m_data[i];
             if (c != byteOrderMark)
                 result.append(c);
         }
         return StringImpl::adopt(result);
     }

     // Returns a StringImpl suitable for use on another thread.
     PassRefPtr<StringImpl> crossThreadString();
     // Makes a deep copy. Helpful only if you need to use a String on another thread
     // (use crossThreadString if the method call doesn't need to be threadsafe).
     // Since StringImpl objects are immutable, there's no other reason to make a copy.
     PassRefPtr<StringImpl> threadsafeCopy() const;

     PassRefPtr<StringImpl> substring(unsigned pos, unsigned len = UINT_MAX);

     UChar operator[](unsigned i) { ASSERT(i < m_length); return m_data[i]; }
     UChar32 characterStartingAt(unsigned);

     bool containsOnlyWhitespace();

     int toIntStrict(bool* ok = 0, int base = 10);
     unsigned toUIntStrict(bool* ok = 0, int base = 10);
     int64_t toInt64Strict(bool* ok = 0, int base = 10);
     uint64_t toUInt64Strict(bool* ok = 0, int base = 10);
     intptr_t toIntPtrStrict(bool* ok = 0, int base = 10);

     int toInt(bool* ok = 0); // ignores trailing garbage
     unsigned toUInt(bool* ok = 0); // ignores trailing garbage
     int64_t toInt64(bool* ok = 0); // ignores trailing garbage
     uint64_t toUInt64(bool* ok = 0); // ignores trailing garbage
     intptr_t toIntPtr(bool* ok = 0); // ignores trailing garbage

     double toDouble(bool* ok = 0);
     float toFloat(bool* ok = 0);

     PassRefPtr<StringImpl> lower();
     PassRefPtr<StringImpl> upper();
     PassRefPtr<StringImpl> secure(UChar aChar);
     PassRefPtr<StringImpl> foldCase();

     PassRefPtr<StringImpl> stripWhiteSpace();
     PassRefPtr<StringImpl> simplifyWhiteSpace();

     PassRefPtr<StringImpl> removeCharacters(CharacterMatchFunctionPtr);

     int find(const char*, int index = 0, bool caseSensitive = true);
     int find(UChar, int index = 0);
     int find(CharacterMatchFunctionPtr, int index = 0);
     int find(StringImpl*, int index, bool caseSensitive = true);

     int reverseFind(UChar, int index);
     int reverseFind(StringImpl*, int index, bool caseSensitive = true);

     bool startsWith(StringImpl* str, bool caseSensitive = true) { return reverseFind(str, 0, caseSensitive) == 0; }
     bool endsWith(StringImpl*, bool caseSensitive = true);

     PassRefPtr<StringImpl> replace(UChar, UChar);
     PassRefPtr<StringImpl> replace(UChar, StringImpl*);
     PassRefPtr<StringImpl> replace(StringImpl*, StringImpl*);
     PassRefPtr<StringImpl> replace(unsigned index, unsigned len, StringImpl*);

     Vector<char> ascii();

     WTF::Unicode::Direction defaultWritingDirection();

 #if PLATFORM(CF)
     CFStringRef createCFString();
 #endif
 #ifdef __OBJC__
     operator NSString*();
 #endif

 private:
     // This number must be at least 2 to avoid sharing empty, null as well as 1 character strings from SmallStrings.
     static const unsigned s_copyCharsInlineCutOff = 20;

     static PassRefPtr<StringImpl> createStrippingNullCharactersSlowCase(const UChar*, unsigned length);

     BufferOwnership bufferOwnership() const { return static_cast<BufferOwnership>(m_refCountAndFlags & s_refCountMaskBufferOwnership); }
     bool isStatic() const { return m_refCountAndFlags & s_refCountFlagStatic; }
     const UChar* m_data;
     union {
         void* m_buffer;
         StringImpl* m_substringBuffer;
         SharedUChar* m_sharedBuffer;
     };
     mutable unsigned m_hash;
 };

 bool equal(const StringImpl*, const StringImpl*);
 bool equal(const StringImpl*, const char*);
 inline bool equal(const char* a, StringImpl* b) { return equal(b, a); }

 bool equalIgnoringCase(StringImpl*, StringImpl*);
 bool equalIgnoringCase(StringImpl*, const char*);
 inline bool equalIgnoringCase(const char* a, StringImpl* b) { return equalIgnoringCase(b, a); }
 bool equalIgnoringCase(const UChar* a, const char* b, unsigned length);
 inline bool equalIgnoringCase(const char* a, const UChar* b, unsigned length) { return equalIgnoringCase(b, a, length); }

 bool equalIgnoringNullity(StringImpl*, StringImpl*);

 int codePointCompare(const StringImpl*, const StringImpl*);

 static inline bool isSpaceOrNewline(UChar c)
 {
     // Use isASCIISpace() for basic Latin-1.
     // This will include newlines, which aren't included in Unicode DirWS.
     return c <= 0x7F ? WTF::isASCIISpace(c) : WTF::Unicode::direction(c) == WTF::Unicode::WhiteSpaceNeutral;
 }

 // This is a hot function because it's used when parsing HTML.
 inline PassRefPtr<StringImpl> StringImpl::createStrippingNullCharacters(const UChar* characters, unsigned length)
 {
     ASSERT(characters);
     ASSERT(length);

     // Optimize for the case where there are no Null characters by quickly
     // searching for nulls, and then using StringImpl::create, which will
     // memcpy the whole buffer.  This is faster than assigning character by
     // character during the loop.

     // Fast case.
     int foundNull = 0;
     for (unsigned i = 0; !foundNull && i < length; i++) {
         int c = characters[i]; // more efficient than using UChar here (at least on Intel Mac OS)
         foundNull |= !c;
     }
     if (!foundNull)
         return StringImpl::create(characters, length);

     return StringImpl::createStrippingNullCharactersSlowCase(characters, length);
 }

 }

 using WebCore::equal;

 namespace WTF {

     // WebCore::StringHash is the default hash for StringImpl* and RefPtr<StringImpl>
     template<typename T> struct DefaultHash;
     template<> struct DefaultHash<WebCore::StringImpl*> {
         typedef WebCore::StringHash Hash;
     };
     template<> struct DefaultHash<RefPtr<WebCore::StringImpl> > {
         typedef WebCore::StringHash Hash;
     };

 }

 #endif
	/*
	* Copyright (C) 1999 Lars Knoll (knoll@kde.org)
	* Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
	* Copyright (C) 2009 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.
	*
	*/

	#ifndef StringImpl_h
	#define StringImpl_h

	#include <limits.h>
	#include <wtf/ASCIICType.h>
	#include <wtf/CrossThreadRefCounted.h>
	#include <wtf/OwnFastMallocPtr.h>
	#include <wtf/StdLibExtras.h>
	#include <wtf/StringHashFunctions.h>
	#include <wtf/Vector.h>
	#include <wtf/text/StringImplBase.h>
	#include <wtf/unicode/Unicode.h>

	#if PLATFORM(CF)
	typedef const struct __CFString * CFStringRef;
	#endif

	#ifdef __OBJC__
	@class NSString;
	#endif

	// FIXME: This is a temporary layering violation while we move string code to WTF.
	// Landing the file moves in one patch, will follow on with patches to change the namespaces.
	namespace JSC {

	struct IdentifierCStringTranslator;
	struct IdentifierUCharBufferTranslator;

	}

	// FIXME: This is a temporary layering violation while we move string code to WTF.
	// Landing the file moves in one patch, will follow on with patches to change the namespaces.
	namespace WebCore {

	class StringBuffer;

	struct CStringTranslator;
	struct HashAndCharactersTranslator;
	struct StringHash;
	struct UCharBufferTranslator;

	enum TextCaseSensitivity { TextCaseSensitive, TextCaseInsensitive };

	typedef OwnFastMallocPtr<const UChar> SharableUChar;
	typedef CrossThreadRefCounted<SharableUChar> SharedUChar;
	typedef bool (*CharacterMatchFunctionPtr)(UChar);

	class StringImpl : public StringImplBase {
	friend struct JSC::IdentifierCStringTranslator;
	friend struct JSC::IdentifierUCharBufferTranslator;
	friend struct CStringTranslator;
	friend struct HashAndCharactersTranslator;
	friend struct UCharBufferTranslator;
	friend class AtomicStringImpl;
	private:
	// Used to construct static strings, which have an special refCount that can never hit zero.
	// This means that the static string will never be destroyed, which is important because
	// static strings will be shared across threads & ref-counted in a non-threadsafe manner.
	StringImpl(const UChar* characters, unsigned length, StaticStringConstructType)
	: StringImplBase(length, ConstructStaticString)
	, m_data(characters)
	, m_buffer(0)
	, m_hash(0)
	{
	// Ensure that the hash is computed so that AtomicStringHash can call existingHash()
	// with impunity. The empty string is special because it is never entered into
	// AtomicString's HashKey, but still needs to compare correctly.
	hash();
	}

	// Create a normal string with internal storage (BufferInternal)
	StringImpl(unsigned length)
	: StringImplBase(length, BufferInternal)
	, m_data(reinterpret_cast<const UChar*>(this + 1))
	, m_buffer(0)
	, m_hash(0)
	{
	ASSERT(m_data);
	ASSERT(m_length);
	}

	// Create a StringImpl adopting ownership of the provided buffer (BufferOwned)
	StringImpl(const UChar* characters, unsigned length)
	: StringImplBase(length, BufferOwned)
	, m_data(characters)
	, m_buffer(0)
	, m_hash(0)
	{
	ASSERT(m_data);
	ASSERT(m_length);
	}

	// Used to create new strings that are a substring of an existing StringImpl (BufferSubstring)
	StringImpl(const UChar* characters, unsigned length, PassRefPtr<StringImpl> base)
	: StringImplBase(length, BufferSubstring)
	, m_data(characters)
	, m_substringBuffer(base.releaseRef())
	, m_hash(0)
	{
	ASSERT(m_data);
	ASSERT(m_length);
	ASSERT(m_substringBuffer->bufferOwnership() != BufferSubstring);
	}

	// Used to construct new strings sharing an existing SharedUChar (BufferShared)
	StringImpl(const UChar* characters, unsigned length, PassRefPtr<SharedUChar> sharedBuffer)
	: StringImplBase(length, BufferShared)
	, m_data(characters)
	, m_sharedBuffer(sharedBuffer.releaseRef())
	, m_hash(0)
	{
	ASSERT(m_data);
	ASSERT(m_length);
	}

	// For use only by AtomicString's XXXTranslator helpers.
	void setHash(unsigned hash)
	{
	ASSERT(!isStatic());
	ASSERT(!m_hash);
	ASSERT(hash == computeHash(m_data, m_length));
	m_hash = hash;
	}

	public:
	~StringImpl();

	static PassRefPtr<StringImpl> create(const UChar*, unsigned length);
	static PassRefPtr<StringImpl> create(const char*, unsigned length);
	static PassRefPtr<StringImpl> create(const char*);
	static PassRefPtr<StringImpl> create(const UChar*, unsigned length, PassRefPtr<SharedUChar> sharedBuffer);
	static ALWAYS_INLINE PassRefPtr<StringImpl> create(PassRefPtr<StringImpl> rep, unsigned offset, unsigned length)
	{
	ASSERT(rep);
	ASSERT(length <= rep->length());

	if (!length)
	return empty();

	StringImpl* ownerRep = (rep->bufferOwnership() == BufferSubstring) ? rep->m_substringBuffer : rep.get();
	return adoptRef(new StringImpl(rep->m_data + offset, length, ownerRep));
	}

	static PassRefPtr<StringImpl> createUninitialized(unsigned length, UChar*& data);
	static ALWAYS_INLINE PassRefPtr<StringImpl> tryCreateUninitialized(unsigned length, UChar*& output)
	{
	if (!length) {
	output = 0;
	return empty();
	}

	if (length > ((std::numeric_limits<size_t>::max() - sizeof(StringImpl)) / sizeof(UChar))) {
	output = 0;
	return 0;
	}
	StringImpl* resultImpl;
	if (!tryFastMalloc(sizeof(UChar) * length + sizeof(StringImpl)).getValue(resultImpl)) {
	output = 0;
	return 0;
	}
	output = reinterpret_cast<UChar*>(resultImpl + 1);
	return adoptRef(new(resultImpl) StringImpl(length));
	}

	static unsigned dataOffset() { return OBJECT_OFFSETOF(StringImpl, m_data); }
	static PassRefPtr<StringImpl> createWithTerminatingNullCharacter(const StringImpl&);
	static PassRefPtr<StringImpl> createStrippingNullCharacters(const UChar*, unsigned length);

	template<size_t inlineCapacity>
	static PassRefPtr<StringImpl> adopt(Vector<UChar, inlineCapacity>& vector)
	{
	if (size_t size = vector.size()) {
	ASSERT(vector.data());
	return adoptRef(new StringImpl(vector.releaseBuffer(), size));
	}
	return empty();
	}
	static PassRefPtr<StringImpl> adopt(StringBuffer&);

	SharedUChar* sharedBuffer();
	const UChar* characters() const { return m_data; }

	size_t cost()
	{
	// For substrings, return the cost of the base string.
	if (bufferOwnership() == BufferSubstring)
	return m_substringBuffer->cost();

	if (m_refCountAndFlags & s_refCountFlagShouldReportedCost) {
	m_refCountAndFlags &= ~s_refCountFlagShouldReportedCost;
	return m_length;
	}
	return 0;
	}

	bool isIdentifier() const { return m_refCountAndFlags & s_refCountFlagIsIdentifier; }
	void setIsIdentifier(bool isIdentifier)
	{
	ASSERT(!isStatic());
	if (isIdentifier)
	m_refCountAndFlags \|= s_refCountFlagIsIdentifier;
	else
	m_refCountAndFlags &= ~s_refCountFlagIsIdentifier;
	}

	bool hasTerminatingNullCharacter() const { return m_refCountAndFlags & s_refCountFlagHasTerminatingNullCharacter; }

	bool isAtomic() const { return m_refCountAndFlags & s_refCountFlagIsAtomic; }
	void setIsAtomic(bool isIdentifier)
	{
	ASSERT(!isStatic());
	if (isIdentifier)
	m_refCountAndFlags \|= s_refCountFlagIsAtomic;
	else
	m_refCountAndFlags &= ~s_refCountFlagIsAtomic;
	}

	unsigned hash() const { if (!m_hash) m_hash = computeHash(m_data, m_length); return m_hash; }
	unsigned existingHash() const { ASSERT(m_hash); return m_hash; }
	static unsigned computeHash(const UChar* data, unsigned length) { return WTF::stringHash(data, length); }
	static unsigned computeHash(const char* data, unsigned length) { return WTF::stringHash(data, length); }
	static unsigned computeHash(const char* data) { return WTF::stringHash(data); }

	ALWAYS_INLINE void deref() { m_refCountAndFlags -= s_refCountIncrement; if (!(m_refCountAndFlags & (s_refCountMask \| s_refCountFlagStatic))) delete this; }
	ALWAYS_INLINE bool hasOneRef() const { return (m_refCountAndFlags & (s_refCountMask \| s_refCountFlagStatic)) == s_refCountIncrement; }

	static StringImpl* empty();

	static void copyChars(UChar* destination, const UChar* source, unsigned numCharacters)
	{
	if (numCharacters <= s_copyCharsInlineCutOff) {
	for (unsigned i = 0; i < numCharacters; ++i)
	destination[i] = source[i];
	} else
	memcpy(destination, source, numCharacters * sizeof(UChar));
	}

	PassRefPtr<StringImpl> copyStringWithoutBOMs(bool definitelyHasBOMs, bool& hasBOMs)
	{
	static const UChar byteOrderMark = 0xFEFF;
	size_t i = 0;
	if (!definitelyHasBOMs) {
	hasBOMs = false;
	// ECMA-262 calls for stripping all Cf characters, but we only strip BOM characters.
	// See <https://bugs.webkit.org/show_bug.cgi?id=4931> for details.
	for (; i < m_length; i++) {
	if (UNLIKELY(m_data[i] == byteOrderMark)) {
	hasBOMs = true;
	break;
	}
	}
	if (!hasBOMs)
	return this;
	}
	Vector<UChar> result;
	result.reserveInitialCapacity(m_length);
	size_t firstBOM = i;
	i = 0;
	for (; i < firstBOM; i++)
	result.append(m_data[i]);
	for (; i < m_length; i++) {
	UChar c = m_data[i];
	if (c != byteOrderMark)
	result.append(c);
	}
	return StringImpl::adopt(result);
	}

	// Returns a StringImpl suitable for use on another thread.
	PassRefPtr<StringImpl> crossThreadString();
	// Makes a deep copy. Helpful only if you need to use a String on another thread
	// (use crossThreadString if the method call doesn't need to be threadsafe).
	// Since StringImpl objects are immutable, there's no other reason to make a copy.
	PassRefPtr<StringImpl> threadsafeCopy() const;

	PassRefPtr<StringImpl> substring(unsigned pos, unsigned len = UINT_MAX);

	UChar operator[](unsigned i) { ASSERT(i < m_length); return m_data[i]; }
	UChar32 characterStartingAt(unsigned);

	bool containsOnlyWhitespace();

	int toIntStrict(bool* ok = 0, int base = 10);
	unsigned toUIntStrict(bool* ok = 0, int base = 10);
	int64_t toInt64Strict(bool* ok = 0, int base = 10);
	uint64_t toUInt64Strict(bool* ok = 0, int base = 10);
	intptr_t toIntPtrStrict(bool* ok = 0, int base = 10);

	int toInt(bool* ok = 0); // ignores trailing garbage
	unsigned toUInt(bool* ok = 0); // ignores trailing garbage
	int64_t toInt64(bool* ok = 0); // ignores trailing garbage
	uint64_t toUInt64(bool* ok = 0); // ignores trailing garbage
	intptr_t toIntPtr(bool* ok = 0); // ignores trailing garbage

	double toDouble(bool* ok = 0);
	float toFloat(bool* ok = 0);

	PassRefPtr<StringImpl> lower();
	PassRefPtr<StringImpl> upper();
	PassRefPtr<StringImpl> secure(UChar aChar);
	PassRefPtr<StringImpl> foldCase();

	PassRefPtr<StringImpl> stripWhiteSpace();
	PassRefPtr<StringImpl> simplifyWhiteSpace();

	PassRefPtr<StringImpl> removeCharacters(CharacterMatchFunctionPtr);

	int find(const char*, int index = 0, bool caseSensitive = true);
	int find(UChar, int index = 0);
	int find(CharacterMatchFunctionPtr, int index = 0);
	int find(StringImpl*, int index, bool caseSensitive = true);

	int reverseFind(UChar, int index);
	int reverseFind(StringImpl*, int index, bool caseSensitive = true);

	bool startsWith(StringImpl* str, bool caseSensitive = true) { return reverseFind(str, 0, caseSensitive) == 0; }
	bool endsWith(StringImpl*, bool caseSensitive = true);

	PassRefPtr<StringImpl> replace(UChar, UChar);
	PassRefPtr<StringImpl> replace(UChar, StringImpl*);
	PassRefPtr<StringImpl> replace(StringImpl, StringImpl);
	PassRefPtr<StringImpl> replace(unsigned index, unsigned len, StringImpl*);

	Vector<char> ascii();

	WTF::Unicode::Direction defaultWritingDirection();

	#if PLATFORM(CF)
	CFStringRef createCFString();
	#endif
	#ifdef __OBJC__
	operator NSString*();
	#endif

	private:
	// This number must be at least 2 to avoid sharing empty, null as well as 1 character strings from SmallStrings.
	static const unsigned s_copyCharsInlineCutOff = 20;

	static PassRefPtr<StringImpl> createStrippingNullCharactersSlowCase(const UChar*, unsigned length);

	BufferOwnership bufferOwnership() const { return static_cast<BufferOwnership>(m_refCountAndFlags & s_refCountMaskBufferOwnership); }
	bool isStatic() const { return m_refCountAndFlags & s_refCountFlagStatic; }
	const UChar* m_data;
	union {
	void* m_buffer;
	StringImpl* m_substringBuffer;
	SharedUChar* m_sharedBuffer;
	};
	mutable unsigned m_hash;
	};

	bool equal(const StringImpl, const StringImpl);
	bool equal(const StringImpl, const char);
	inline bool equal(const char* a, StringImpl* b) { return equal(b, a); }

	bool equalIgnoringCase(StringImpl, StringImpl);
	bool equalIgnoringCase(StringImpl, const char);
	inline bool equalIgnoringCase(const char* a, StringImpl* b) { return equalIgnoringCase(b, a); }
	bool equalIgnoringCase(const UChar* a, const char* b, unsigned length);
	inline bool equalIgnoringCase(const char* a, const UChar* b, unsigned length) { return equalIgnoringCase(b, a, length); }

	bool equalIgnoringNullity(StringImpl, StringImpl);

	int codePointCompare(const StringImpl, const StringImpl);

	static inline bool isSpaceOrNewline(UChar c)
	{
	// Use isASCIISpace() for basic Latin-1.
	// This will include newlines, which aren't included in Unicode DirWS.
	return c <= 0x7F ? WTF::isASCIISpace(c) : WTF::Unicode::direction(c) == WTF::Unicode::WhiteSpaceNeutral;
	}

	// This is a hot function because it's used when parsing HTML.
	inline PassRefPtr<StringImpl> StringImpl::createStrippingNullCharacters(const UChar* characters, unsigned length)
	{
	ASSERT(characters);
	ASSERT(length);

	// Optimize for the case where there are no Null characters by quickly
	// searching for nulls, and then using StringImpl::create, which will
	// memcpy the whole buffer. This is faster than assigning character by
	// character during the loop.

	// Fast case.
	int foundNull = 0;
	for (unsigned i = 0; !foundNull && i < length; i++) {
	int c = characters[i]; // more efficient than using UChar here (at least on Intel Mac OS)
	foundNull \|= !c;
	}
	if (!foundNull)
	return StringImpl::create(characters, length);

	return StringImpl::createStrippingNullCharactersSlowCase(characters, length);
	}

	}

	using WebCore::equal;

	namespace WTF {

	// WebCore::StringHash is the default hash for StringImpl* and RefPtr<StringImpl>
	template<typename T> struct DefaultHash;
	template<> struct DefaultHash<WebCore::StringImpl*> {
	typedef WebCore::StringHash Hash;
	};
	template<> struct DefaultHash<RefPtr<WebCore::StringImpl> > {
	typedef WebCore::StringHash Hash;
	};

	}

	#endif