runtime/JSString.cpp

   1 /*
   2  *  Copyright (C) 1999-2002 Harri Porten (porten@kde.org)
   3  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
   4  *  Copyright (C) 2004, 2007, 2008 Apple Inc. All rights reserved.
   5  *
   6  *  This library is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU Library General Public
   8  *  License as published by the Free Software Foundation; either
   9  *  version 2 of the License, or (at your option) any later version.
  10  *
  11  *  This library is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  *  Library General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU Library General Public License
  17  *  along with this library; see the file COPYING.LIB.  If not, write to
  18  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  19  *  Boston, MA 02110-1301, USA.
  20  *
  21  */
  22
  23 #include "config.h"
  24 #include "JSString.h"
  25
  26 #include "JSGlobalObject.h"
  27 #include "JSGlobalObjectFunctions.h"
  28 #include "JSObject.h"
  29 #include "Operations.h"
  30 #include "StringObject.h"
  31 #include "StringPrototype.h"
  32
  33 namespace JSC {
  34
  35 static const unsigned substringFromRopeCutoff = 4;
  36
  37 const ClassInfo JSString::s_info = { "string", 0, 0, 0, CREATE_METHOD_TABLE(JSString) };
  38
  39 void JSRopeString::RopeBuilder::expand()
  40 {
  41     ASSERT(m_index == JSRopeString::s_maxInternalRopeLength);
  42     JSString* jsString = m_jsString;
  43     m_jsString = jsStringBuilder(&m_vm);
  44     m_index = 0;
  45     append(jsString);
  46 }
  47
  48 void JSString::destroy(JSCell* cell)
  49 {
  50     JSString* thisObject = static_cast<JSString*>(cell);
  51     thisObject->JSString::~JSString();
  52 }
  53
  54 void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
  55 {
  56     JSString* thisObject = jsCast<JSString*>(cell);
  57     Base::visitChildren(thisObject, visitor);
  58
  59     MARK_LOG_MESSAGE1("[%u]: ", thisObject->length());
  60
  61 #if ENABLE(OBJECT_MARK_LOGGING)
  62     if (!thisObject->isRope()) {
  63         WTF::StringImpl* ourImpl = thisObject->m_value.impl();
  64         if (ourImpl->is8Bit())
  65             MARK_LOG_MESSAGE1("[8 %p]", ourImpl->characters8());
  66         else
  67             MARK_LOG_MESSAGE1("[16 %p]", ourImpl->characters16());
  68     } else
  69         MARK_LOG_MESSAGE0("[rope]: ");
  70 #endif
  71
  72     if (thisObject->isRope())
  73         static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);
  74 }
  75
  76 void JSRopeString::visitFibers(SlotVisitor& visitor)
  77 {
  78     for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
  79         visitor.append(&m_fibers[i]);
  80 }
  81
  82 void JSRopeString::resolveRope(ExecState* exec) const
  83 {
  84     ASSERT(isRope());
  85
  86     if (is8Bit()) {
  87         LChar* buffer;
  88         if (RefPtr<StringImpl> newImpl = StringImpl::tryCreateUninitialized(m_length, buffer)) {
  89             Heap::heap(this)->reportExtraMemoryCost(newImpl->cost());
  90             m_value = newImpl.release();
  91         } else {
  92             outOfMemory(exec);
  93             return;
  94         }
  95
  96         for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
  97             if (m_fibers[i]->isRope())
  98                 return resolveRopeSlowCase8(buffer);
  99         }
 100
 101         LChar* position = buffer;
 102         for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
 103             StringImpl* string = m_fibers[i]->m_value.impl();
 104             unsigned length = string->length();
 105             StringImpl::copyChars(position, string->characters8(), length);
 106             position += length;
 107             m_fibers[i].clear();
 108         }
 109         ASSERT((buffer + m_length) == position);
 110         ASSERT(!isRope());
 111
 112         return;
 113     }
 114
 115     UChar* buffer;
 116     if (RefPtr<StringImpl> newImpl = StringImpl::tryCreateUninitialized(m_length, buffer)) {
 117         Heap::heap(this)->reportExtraMemoryCost(newImpl->cost());
 118         m_value = newImpl.release();
 119     } else {
 120         outOfMemory(exec);
 121         return;
 122     }
 123
 124     for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
 125         if (m_fibers[i]->isRope())
 126             return resolveRopeSlowCase(buffer);
 127     }
 128
 129     UChar* position = buffer;
 130     for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
 131         StringImpl* string = m_fibers[i]->m_value.impl();
 132         unsigned length = string->length();
 133         if (string->is8Bit())
 134             StringImpl::copyChars(position, string->characters8(), length);
 135         else
 136             StringImpl::copyChars(position, string->characters16(), length);
 137         position += length;
 138         m_fibers[i].clear();
 139     }
 140     ASSERT((buffer + m_length) == position);
 141     ASSERT(!isRope());
 142 }
 143
 144 // Overview: These functions convert a JSString from holding a string in rope form
 145 // down to a simple String representation. It does so by building up the string
 146 // backwards, since we want to avoid recursion, we expect that the tree structure
 147 // representing the rope is likely imbalanced with more nodes down the left side
 148 // (since appending to the string is likely more common) - and as such resolving
 149 // in this fashion should minimize work queue size.  (If we built the queue forwards
 150 // we would likely have to place all of the constituent StringImpls into the
 151 // Vector before performing any concatenation, but by working backwards we likely
 152 // only fill the queue with the number of substrings at any given level in a
 153 // rope-of-ropes.)
 154 void JSRopeString::resolveRopeSlowCase8(LChar* buffer) const
 155 {
 156     LChar* position = buffer + m_length; // We will be working backwards over the rope.
 157     Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // Putting strings into a Vector is only OK because there are no GC points in this method.
 158
 159     for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
 160         workQueue.append(m_fibers[i].get());
 161         // Clearing here works only because there are no GC points in this method.
 162         m_fibers[i].clear();
 163     }
 164
 165     while (!workQueue.isEmpty()) {
 166         JSString* currentFiber = workQueue.last();
 167         workQueue.removeLast();
 168
 169         if (currentFiber->isRope()) {
 170             JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
 171             for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
 172                 workQueue.append(currentFiberAsRope->m_fibers[i].get());
 173             continue;
 174         }
 175
 176         StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
 177         unsigned length = string->length();
 178         position -= length;
 179         StringImpl::copyChars(position, string->characters8(), length);
 180     }
 181
 182     ASSERT(buffer == position);
 183     ASSERT(!isRope());
 184 }
 185
 186 void JSRopeString::resolveRopeSlowCase(UChar* buffer) const
 187 {
 188     UChar* position = buffer + m_length; // We will be working backwards over the rope.
 189     Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // These strings are kept alive by the parent rope, so using a Vector is OK.
 190
 191     for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
 192         workQueue.append(m_fibers[i].get());
 193
 194     while (!workQueue.isEmpty()) {
 195         JSString* currentFiber = workQueue.last();
 196         workQueue.removeLast();
 197
 198         if (currentFiber->isRope()) {
 199             JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
 200             for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
 201                 workQueue.append(currentFiberAsRope->m_fibers[i].get());
 202             continue;
 203         }
 204
 205         StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
 206         unsigned length = string->length();
 207         position -= length;
 208         if (string->is8Bit())
 209             StringImpl::copyChars(position, string->characters8(), length);
 210         else
 211             StringImpl::copyChars(position, string->characters16(), length);
 212     }
 213
 214     ASSERT(buffer == position);
 215     ASSERT(!isRope());
 216 }
 217
 218 void JSRopeString::outOfMemory(ExecState* exec) const
 219 {
 220     for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
 221         m_fibers[i].clear();
 222     ASSERT(isRope());
 223     ASSERT(m_value.isNull());
 224     if (exec)
 225         throwOutOfMemoryError(exec);
 226 }
 227
 228 JSString* JSRopeString::getIndexSlowCase(ExecState* exec, unsigned i)
 229 {
 230     ASSERT(isRope());
 231     resolveRope(exec);
 232     // Return a safe no-value result, this should never be used, since the excetion will be thrown.
 233     if (exec->exception())
 234         return jsEmptyString(exec);
 235     ASSERT(!isRope());
 236     RELEASE_ASSERT(i < m_value.length());
 237     return jsSingleCharacterSubstring(exec, m_value, i);
 238 }
 239
 240 JSValue JSString::toPrimitive(ExecState*, PreferredPrimitiveType) const
 241 {
 242     return const_cast<JSString*>(this);
 243 }
 244
 245 bool JSString::getPrimitiveNumber(ExecState* exec, double& number, JSValue& result) const
 246 {
 247     result = this;
 248     number = jsToNumber(value(exec));
 249     return false;
 250 }
 251
 252 bool JSString::toBoolean() const
 253 {
 254     return m_length;
 255 }
 256
 257 double JSString::toNumber(ExecState* exec) const
 258 {
 259     return jsToNumber(value(exec));
 260 }
 261
 262 inline StringObject* StringObject::create(ExecState* exec, JSGlobalObject* globalObject, JSString* string)
 263 {
 264     StringObject* object = new (NotNull, allocateCell<StringObject>(*exec->heap())) StringObject(exec->vm(), globalObject->stringObjectStructure());
 265     object->finishCreation(exec->vm(), string);
 266     return object;
 267 }
 268
 269 JSObject* JSString::toObject(ExecState* exec, JSGlobalObject* globalObject) const
 270 {
 271     return StringObject::create(exec, globalObject, const_cast<JSString*>(this));
 272 }
 273
 274 JSObject* JSString::toThisObject(JSCell* cell, ExecState* exec)
 275 {
 276     return StringObject::create(exec, exec->lexicalGlobalObject(), jsCast<JSString*>(cell));
 277 }
 278
 279 bool JSString::getOwnPropertySlot(JSCell* cell, ExecState* exec, PropertyName propertyName, PropertySlot& slot)
 280 {
 281     JSString* thisObject = jsCast<JSString*>(cell);
 282     // The semantics here are really getPropertySlot, not getOwnPropertySlot.
 283     // This function should only be called by JSValue::get.
 284     if (thisObject->getStringPropertySlot(exec, propertyName, slot))
 285         return true;
 286     slot.setBase(thisObject);
 287     JSObject* object;
 288     for (JSValue prototype = exec->lexicalGlobalObject()->stringPrototype(); !prototype.isNull(); prototype = object->prototype()) {
 289         object = asObject(prototype);
 290         if (object->methodTable()->getOwnPropertySlot(object, exec, propertyName, slot))
 291             return true;
 292     }
 293     slot.setUndefined();
 294     return true;
 295 }
 296
 297 bool JSString::getStringPropertyDescriptor(ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor)
 298 {
 299     if (propertyName == exec->propertyNames().length) {
 300         descriptor.setDescriptor(jsNumber(m_length), DontEnum | DontDelete | ReadOnly);
 301         return true;
 302     }
 303
 304     unsigned i = propertyName.asIndex();
 305     if (i < m_length) {
 306         ASSERT(i != PropertyName::NotAnIndex); // No need for an explicit check, the above test would always fail!
 307         descriptor.setDescriptor(getIndex(exec, i), DontDelete | ReadOnly);
 308         return true;
 309     }
 310
 311     return false;
 312 }
 313
 314 bool JSString::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned propertyName, PropertySlot& slot)
 315 {
 316     JSString* thisObject = jsCast<JSString*>(cell);
 317     // The semantics here are really getPropertySlot, not getOwnPropertySlot.
 318     // This function should only be called by JSValue::get.
 319     if (thisObject->getStringPropertySlot(exec, propertyName, slot))
 320         return true;
 321     return JSString::getOwnPropertySlot(thisObject, exec, Identifier::from(exec, propertyName), slot);
 322 }
 323
 324 } // namespace JSC