src/v8/src/api.h

   1 // Copyright 2012 the V8 project authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef V8_API_H_
   6 #define V8_API_H_
   7
   8 #include "src/v8.h"
   9
  10 #include "include/v8-testing.h"
  11 #include "src/contexts.h"
  12 #include "src/factory.h"
  13 #include "src/isolate.h"
  14 #include "src/list-inl.h"
  15
  16 namespace v8 {
  17
  18 // Constants used in the implementation of the API.  The most natural thing
  19 // would usually be to place these with the classes that use them, but
  20 // we want to keep them out of v8.h because it is an externally
  21 // visible file.
  22 class Consts {
  23  public:
  24   enum TemplateType {
  25     FUNCTION_TEMPLATE = 0,
  26     OBJECT_TEMPLATE = 1
  27   };
  28 };
  29
  30
  31 // Utilities for working with neander-objects, primitive
  32 // env-independent JSObjects used by the api.
  33 class NeanderObject {
  34  public:
  35   explicit NeanderObject(v8::internal::Isolate* isolate, int size);
  36   explicit inline NeanderObject(v8::internal::Handle<v8::internal::Object> obj);
  37   explicit inline NeanderObject(v8::internal::Object* obj);
  38   inline v8::internal::Object* get(int index);
  39   inline void set(int index, v8::internal::Object* value);
  40   inline v8::internal::Handle<v8::internal::JSObject> value() { return value_; }
  41   int size();
  42  private:
  43   v8::internal::Handle<v8::internal::JSObject> value_;
  44 };
  45
  46
  47 // Utilities for working with neander-arrays, a simple extensible
  48 // array abstraction built on neander-objects.
  49 class NeanderArray {
  50  public:
  51   explicit NeanderArray(v8::internal::Isolate* isolate);
  52   explicit inline NeanderArray(v8::internal::Handle<v8::internal::Object> obj);
  53   inline v8::internal::Handle<v8::internal::JSObject> value() {
  54     return obj_.value();
  55   }
  56
  57   void add(v8::internal::Handle<v8::internal::Object> value);
  58
  59   int length();
  60
  61   v8::internal::Object* get(int index);
  62   // Change the value at an index to undefined value. If the index is
  63   // out of bounds, the request is ignored. Returns the old value.
  64   void set(int index, v8::internal::Object* value);
  65  private:
  66   NeanderObject obj_;
  67 };
  68
  69
  70 NeanderObject::NeanderObject(v8::internal::Handle<v8::internal::Object> obj)
  71     : value_(v8::internal::Handle<v8::internal::JSObject>::cast(obj)) { }
  72
  73
  74 NeanderObject::NeanderObject(v8::internal::Object* obj)
  75     : value_(v8::internal::Handle<v8::internal::JSObject>(
  76         v8::internal::JSObject::cast(obj))) { }
  77
  78
  79 NeanderArray::NeanderArray(v8::internal::Handle<v8::internal::Object> obj)
  80     : obj_(obj) { }
  81
  82
  83 v8::internal::Object* NeanderObject::get(int offset) {
  84   DCHECK(value()->HasFastObjectElements());
  85   return v8::internal::FixedArray::cast(value()->elements())->get(offset);
  86 }
  87
  88
  89 void NeanderObject::set(int offset, v8::internal::Object* value) {
  90   DCHECK(value_->HasFastObjectElements());
  91   v8::internal::FixedArray::cast(value_->elements())->set(offset, value);
  92 }
  93
  94
  95 template <typename T> inline T ToCData(v8::internal::Object* obj) {
  96   STATIC_ASSERT(sizeof(T) == sizeof(v8::internal::Address));
  97   return reinterpret_cast<T>(
  98       reinterpret_cast<intptr_t>(
  99           v8::internal::Foreign::cast(obj)->foreign_address()));
 100 }
 101
 102
 103 template <typename T>
 104 inline v8::internal::Handle<v8::internal::Object> FromCData(
 105     v8::internal::Isolate* isolate, T obj) {
 106   STATIC_ASSERT(sizeof(T) == sizeof(v8::internal::Address));
 107   return isolate->factory()->NewForeign(
 108       reinterpret_cast<v8::internal::Address>(reinterpret_cast<intptr_t>(obj)));
 109 }
 110
 111
 112 class ApiFunction {
 113  public:
 114   explicit ApiFunction(v8::internal::Address addr) : addr_(addr) { }
 115   v8::internal::Address address() { return addr_; }
 116  private:
 117   v8::internal::Address addr_;
 118 };
 119
 120
 121
 122 class RegisteredExtension {
 123  public:
 124   explicit RegisteredExtension(Extension* extension);
 125   static void Register(RegisteredExtension* that);
 126   static void UnregisterAll();
 127   Extension* extension() { return extension_; }
 128   RegisteredExtension* next() { return next_; }
 129   static RegisteredExtension* first_extension() { return first_extension_; }
 130  private:
 131   Extension* extension_;
 132   RegisteredExtension* next_;
 133   static RegisteredExtension* first_extension_;
 134 };
 135
 136
 137 #define OPEN_HANDLE_LIST(V)                    \
 138   V(Template, TemplateInfo)                    \
 139   V(FunctionTemplate, FunctionTemplateInfo)    \
 140   V(ObjectTemplate, ObjectTemplateInfo)        \
 141   V(Signature, SignatureInfo)                  \
 142   V(AccessorSignature, FunctionTemplateInfo)   \
 143   V(TypeSwitch, TypeSwitchInfo)                \
 144   V(Data, Object)                              \
 145   V(RegExp, JSRegExp)                          \
 146   V(Object, JSObject)                          \
 147   V(Array, JSArray)                            \
 148   V(ArrayBuffer, JSArrayBuffer)                \
 149   V(ArrayBufferView, JSArrayBufferView)        \
 150   V(TypedArray, JSTypedArray)                  \
 151   V(Uint8Array, JSTypedArray)                  \
 152   V(Uint8ClampedArray, JSTypedArray)           \
 153   V(Int8Array, JSTypedArray)                   \
 154   V(Uint16Array, JSTypedArray)                 \
 155   V(Int16Array, JSTypedArray)                  \
 156   V(Uint32Array, JSTypedArray)                 \
 157   V(Int32Array, JSTypedArray)                  \
 158   V(Float32Array, JSTypedArray)                \
 159   V(Float64Array, JSTypedArray)                \
 160   V(DataView, JSDataView)                      \
 161   V(Name, Name)                                \
 162   V(String, String)                            \
 163   V(Symbol, Symbol)                            \
 164   V(Script, JSFunction)                        \
 165   V(UnboundScript, SharedFunctionInfo)         \
 166   V(Function, JSFunction)                      \
 167   V(Message, JSMessageObject)                  \
 168   V(Context, Context)                          \
 169   V(External, Object)                          \
 170   V(StackTrace, JSArray)                       \
 171   V(StackFrame, JSObject)                      \
 172   V(DeclaredAccessorDescriptor, DeclaredAccessorDescriptor)
 173
 174
 175 class Utils {
 176  public:
 177   static inline bool ApiCheck(bool condition,
 178                               const char* location,
 179                               const char* message) {
 180     if (!condition) Utils::ReportApiFailure(location, message);
 181     return condition;
 182   }
 183
 184   static Local<FunctionTemplate> ToFunctionTemplate(NeanderObject obj);
 185   static Local<ObjectTemplate> ToObjectTemplate(NeanderObject obj);
 186
 187   static inline Local<Context> ToLocal(
 188       v8::internal::Handle<v8::internal::Context> obj);
 189   static inline Local<Value> ToLocal(
 190       v8::internal::Handle<v8::internal::Object> obj);
 191   static inline Local<Function> ToLocal(
 192       v8::internal::Handle<v8::internal::JSFunction> obj);
 193   static inline Local<Name> ToLocal(
 194       v8::internal::Handle<v8::internal::Name> obj);
 195   static inline Local<String> ToLocal(
 196       v8::internal::Handle<v8::internal::String> obj);
 197   static inline Local<Symbol> ToLocal(
 198       v8::internal::Handle<v8::internal::Symbol> obj);
 199   static inline Local<RegExp> ToLocal(
 200       v8::internal::Handle<v8::internal::JSRegExp> obj);
 201   static inline Local<Object> ToLocal(
 202       v8::internal::Handle<v8::internal::JSObject> obj);
 203   static inline Local<Array> ToLocal(
 204       v8::internal::Handle<v8::internal::JSArray> obj);
 205   static inline Local<ArrayBuffer> ToLocal(
 206       v8::internal::Handle<v8::internal::JSArrayBuffer> obj);
 207   static inline Local<ArrayBufferView> ToLocal(
 208       v8::internal::Handle<v8::internal::JSArrayBufferView> obj);
 209   static inline Local<DataView> ToLocal(
 210       v8::internal::Handle<v8::internal::JSDataView> obj);
 211
 212   static inline Local<TypedArray> ToLocal(
 213       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 214   static inline Local<Uint8Array> ToLocalUint8Array(
 215       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 216   static inline Local<Uint8ClampedArray> ToLocalUint8ClampedArray(
 217       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 218   static inline Local<Int8Array> ToLocalInt8Array(
 219       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 220   static inline Local<Uint16Array> ToLocalUint16Array(
 221       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 222   static inline Local<Int16Array> ToLocalInt16Array(
 223       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 224   static inline Local<Uint32Array> ToLocalUint32Array(
 225       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 226   static inline Local<Int32Array> ToLocalInt32Array(
 227       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 228   static inline Local<Float32Array> ToLocalFloat32Array(
 229       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 230   static inline Local<Float64Array> ToLocalFloat64Array(
 231       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 232
 233   static inline Local<Message> MessageToLocal(
 234       v8::internal::Handle<v8::internal::Object> obj);
 235   static inline Local<StackTrace> StackTraceToLocal(
 236       v8::internal::Handle<v8::internal::JSArray> obj);
 237   static inline Local<StackFrame> StackFrameToLocal(
 238       v8::internal::Handle<v8::internal::JSObject> obj);
 239   static inline Local<Number> NumberToLocal(
 240       v8::internal::Handle<v8::internal::Object> obj);
 241   static inline Local<Integer> IntegerToLocal(
 242       v8::internal::Handle<v8::internal::Object> obj);
 243   static inline Local<Uint32> Uint32ToLocal(
 244       v8::internal::Handle<v8::internal::Object> obj);
 245   static inline Local<FunctionTemplate> ToLocal(
 246       v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
 247   static inline Local<ObjectTemplate> ToLocal(
 248       v8::internal::Handle<v8::internal::ObjectTemplateInfo> obj);
 249   static inline Local<Signature> ToLocal(
 250       v8::internal::Handle<v8::internal::SignatureInfo> obj);
 251   static inline Local<AccessorSignature> AccessorSignatureToLocal(
 252       v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
 253   static inline Local<TypeSwitch> ToLocal(
 254       v8::internal::Handle<v8::internal::TypeSwitchInfo> obj);
 255   static inline Local<External> ExternalToLocal(
 256       v8::internal::Handle<v8::internal::JSObject> obj);
 257   static inline Local<DeclaredAccessorDescriptor> ToLocal(
 258       v8::internal::Handle<v8::internal::DeclaredAccessorDescriptor> obj);
 259
 260 #define DECLARE_OPEN_HANDLE(From, To) \
 261   static inline v8::internal::Handle<v8::internal::To> \
 262       OpenHandle(const From* that, bool allow_empty_handle = false);
 263
 264 OPEN_HANDLE_LIST(DECLARE_OPEN_HANDLE)
 265
 266 #undef DECLARE_OPEN_HANDLE
 267
 268   template<class From, class To>
 269   static inline Local<To> Convert(v8::internal::Handle<From> obj) {
 270     DCHECK(obj.is_null() || !obj->IsTheHole());
 271     return Local<To>(reinterpret_cast<To*>(obj.location()));
 272   }
 273
 274   template <class T>
 275   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
 276       const v8::Persistent<T>& persistent) {
 277     return v8::internal::Handle<v8::internal::Object>(
 278         reinterpret_cast<v8::internal::Object**>(persistent.val_));
 279   }
 280
 281   template <class T>
 282   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
 283       v8::Persistent<T>* persistent) {
 284     return OpenPersistent(*persistent);
 285   }
 286
 287   template <class From, class To>
 288   static inline v8::internal::Handle<To> OpenHandle(v8::Local<From> handle) {
 289     return OpenHandle(*handle);
 290   }
 291
 292  private:
 293   static void ReportApiFailure(const char* location, const char* message);
 294 };
 295
 296
 297 template <class T>
 298 v8::internal::Handle<T> v8::internal::Handle<T>::EscapeFrom(
 299     v8::EscapableHandleScope* scope) {
 300   v8::internal::Handle<T> handle;
 301   if (!is_null()) {
 302     handle = *this;
 303   }
 304   return Utils::OpenHandle(*scope->Escape(Utils::ToLocal(handle)), true);
 305 }
 306
 307
 308 template <class T>
 309 inline T* ToApi(v8::internal::Handle<v8::internal::Object> obj) {
 310   return reinterpret_cast<T*>(obj.location());
 311 }
 312
 313 template <class T>
 314 inline v8::Local<T> ToApiHandle(
 315     v8::internal::Handle<v8::internal::Object> obj) {
 316   return Utils::Convert<v8::internal::Object, T>(obj);
 317 }
 318
 319
 320 // Implementations of ToLocal
 321
 322 #define MAKE_TO_LOCAL(Name, From, To)                                       \
 323   Local<v8::To> Utils::Name(v8::internal::Handle<v8::internal::From> obj) { \
 324     return Convert<v8::internal::From, v8::To>(obj);  \
 325   }
 326
 327
 328 #define MAKE_TO_LOCAL_TYPED_ARRAY(Type, typeName, TYPE, ctype, size)        \
 329   Local<v8::Type##Array> Utils::ToLocal##Type##Array(                       \
 330       v8::internal::Handle<v8::internal::JSTypedArray> obj) {               \
 331     DCHECK(obj->type() == kExternal##Type##Array);                          \
 332     return Convert<v8::internal::JSTypedArray, v8::Type##Array>(obj);       \
 333   }
 334
 335
 336 MAKE_TO_LOCAL(ToLocal, Context, Context)
 337 MAKE_TO_LOCAL(ToLocal, Object, Value)
 338 MAKE_TO_LOCAL(ToLocal, JSFunction, Function)
 339 MAKE_TO_LOCAL(ToLocal, Name, Name)
 340 MAKE_TO_LOCAL(ToLocal, String, String)
 341 MAKE_TO_LOCAL(ToLocal, Symbol, Symbol)
 342 MAKE_TO_LOCAL(ToLocal, JSRegExp, RegExp)
 343 MAKE_TO_LOCAL(ToLocal, JSObject, Object)
 344 MAKE_TO_LOCAL(ToLocal, JSArray, Array)
 345 MAKE_TO_LOCAL(ToLocal, JSArrayBuffer, ArrayBuffer)
 346 MAKE_TO_LOCAL(ToLocal, JSArrayBufferView, ArrayBufferView)
 347 MAKE_TO_LOCAL(ToLocal, JSDataView, DataView)
 348 MAKE_TO_LOCAL(ToLocal, JSTypedArray, TypedArray)
 349
 350 TYPED_ARRAYS(MAKE_TO_LOCAL_TYPED_ARRAY)
 351
 352 MAKE_TO_LOCAL(ToLocal, FunctionTemplateInfo, FunctionTemplate)
 353 MAKE_TO_LOCAL(ToLocal, ObjectTemplateInfo, ObjectTemplate)
 354 MAKE_TO_LOCAL(ToLocal, SignatureInfo, Signature)
 355 MAKE_TO_LOCAL(AccessorSignatureToLocal, FunctionTemplateInfo, AccessorSignature)
 356 MAKE_TO_LOCAL(ToLocal, TypeSwitchInfo, TypeSwitch)
 357 MAKE_TO_LOCAL(MessageToLocal, Object, Message)
 358 MAKE_TO_LOCAL(StackTraceToLocal, JSArray, StackTrace)
 359 MAKE_TO_LOCAL(StackFrameToLocal, JSObject, StackFrame)
 360 MAKE_TO_LOCAL(NumberToLocal, Object, Number)
 361 MAKE_TO_LOCAL(IntegerToLocal, Object, Integer)
 362 MAKE_TO_LOCAL(Uint32ToLocal, Object, Uint32)
 363 MAKE_TO_LOCAL(ExternalToLocal, JSObject, External)
 364 MAKE_TO_LOCAL(ToLocal, DeclaredAccessorDescriptor, DeclaredAccessorDescriptor)
 365
 366 #undef MAKE_TO_LOCAL_TYPED_ARRAY
 367 #undef MAKE_TO_LOCAL
 368
 369
 370 // Implementations of OpenHandle
 371
 372 #define MAKE_OPEN_HANDLE(From, To)                                          \
 373   v8::internal::Handle<v8::internal::To> Utils::OpenHandle(                 \
 374     const v8::From* that, bool allow_empty_handle) {                        \
 375     EXTRA_CHECK(allow_empty_handle || that != NULL);                        \
 376     EXTRA_CHECK(that == NULL ||                                             \
 377         (*reinterpret_cast<v8::internal::Object* const*>(that))->Is##To()); \
 378     return v8::internal::Handle<v8::internal::To>(                          \
 379         reinterpret_cast<v8::internal::To**>(const_cast<v8::From*>(that))); \
 380   }
 381
 382 OPEN_HANDLE_LIST(MAKE_OPEN_HANDLE)
 383
 384 #undef MAKE_OPEN_HANDLE
 385 #undef OPEN_HANDLE_LIST
 386
 387
 388 namespace internal {
 389
 390 // Tracks string usage to help make better decisions when
 391 // externalizing strings.
 392 //
 393 // Implementation note: internally this class only tracks fresh
 394 // strings and keeps a single use counter for them.
 395 class StringTracker {
 396  public:
 397   // Records that the given string's characters were copied to some
 398   // external buffer. If this happens often we should honor
 399   // externalization requests for the string.
 400   void RecordWrite(Handle<String> string) {
 401     Address address = reinterpret_cast<Address>(*string);
 402     Address top = isolate_->heap()->NewSpaceTop();
 403     if (IsFreshString(address, top)) {
 404       IncrementUseCount(top);
 405     }
 406   }
 407
 408   // Estimates freshness and use frequency of the given string based
 409   // on how close it is to the new space top and the recorded usage
 410   // history.
 411   inline bool IsFreshUnusedString(Handle<String> string) {
 412     Address address = reinterpret_cast<Address>(*string);
 413     Address top = isolate_->heap()->NewSpaceTop();
 414     return IsFreshString(address, top) && IsUseCountLow(top);
 415   }
 416
 417  private:
 418   StringTracker() : use_count_(0), last_top_(NULL), isolate_(NULL) { }
 419
 420   static inline bool IsFreshString(Address string, Address top) {
 421     return top - kFreshnessLimit <= string && string <= top;
 422   }
 423
 424   inline bool IsUseCountLow(Address top) {
 425     if (last_top_ != top) return true;
 426     return use_count_ < kUseLimit;
 427   }
 428
 429   inline void IncrementUseCount(Address top) {
 430     if (last_top_ != top) {
 431       use_count_ = 0;
 432       last_top_ = top;
 433     }
 434     ++use_count_;
 435   }
 436
 437   // Single use counter shared by all fresh strings.
 438   int use_count_;
 439
 440   // Last new space top when the use count above was valid.
 441   Address last_top_;
 442
 443   Isolate* isolate_;
 444
 445   // How close to the new space top a fresh string has to be.
 446   static const int kFreshnessLimit = 1024;
 447
 448   // The number of uses required to consider a string useful.
 449   static const int kUseLimit = 32;
 450
 451   friend class Isolate;
 452
 453   DISALLOW_COPY_AND_ASSIGN(StringTracker);
 454 };
 455
 456
 457 class DeferredHandles {
 458  public:
 459   ~DeferredHandles();
 460
 461  private:
 462   DeferredHandles(Object** first_block_limit, Isolate* isolate)
 463       : next_(NULL),
 464         previous_(NULL),
 465         first_block_limit_(first_block_limit),
 466         isolate_(isolate) {
 467     isolate->LinkDeferredHandles(this);
 468   }
 469
 470   void Iterate(ObjectVisitor* v);
 471
 472   List<Object**> blocks_;
 473   DeferredHandles* next_;
 474   DeferredHandles* previous_;
 475   Object** first_block_limit_;
 476   Isolate* isolate_;
 477
 478   friend class HandleScopeImplementer;
 479   friend class Isolate;
 480 };
 481
 482
 483 // This class is here in order to be able to declare it a friend of
 484 // HandleScope.  Moving these methods to be members of HandleScope would be
 485 // neat in some ways, but it would expose internal implementation details in
 486 // our public header file, which is undesirable.
 487 //
 488 // An isolate has a single instance of this class to hold the current thread's
 489 // data. In multithreaded V8 programs this data is copied in and out of storage
 490 // so that the currently executing thread always has its own copy of this
 491 // data.
 492 class HandleScopeImplementer {
 493  public:
 494   explicit HandleScopeImplementer(Isolate* isolate)
 495       : isolate_(isolate),
 496         blocks_(0),
 497         entered_contexts_(0),
 498         saved_contexts_(0),
 499         spare_(NULL),
 500         call_depth_(0),
 501         last_handle_before_deferred_block_(NULL) { }
 502
 503   ~HandleScopeImplementer() {
 504     DeleteArray(spare_);
 505   }
 506
 507   // Threading support for handle data.
 508   static int ArchiveSpacePerThread();
 509   char* RestoreThread(char* from);
 510   char* ArchiveThread(char* to);
 511   void FreeThreadResources();
 512
 513   // Garbage collection support.
 514   void Iterate(v8::internal::ObjectVisitor* v);
 515   static char* Iterate(v8::internal::ObjectVisitor* v, char* data);
 516
 517
 518   inline internal::Object** GetSpareOrNewBlock();
 519   inline void DeleteExtensions(internal::Object** prev_limit);
 520
 521   inline void IncrementCallDepth() {call_depth_++;}
 522   inline void DecrementCallDepth() {call_depth_--;}
 523   inline bool CallDepthIsZero() { return call_depth_ == 0; }
 524
 525   inline void EnterContext(Handle<Context> context);
 526   inline void LeaveContext();
 527   inline bool LastEnteredContextWas(Handle<Context> context);
 528
 529   // Returns the last entered context or an empty handle if no
 530   // contexts have been entered.
 531   inline Handle<Context> LastEnteredContext();
 532
 533   inline void SaveContext(Context* context);
 534   inline Context* RestoreContext();
 535   inline bool HasSavedContexts();
 536
 537   inline List<internal::Object**>* blocks() { return &blocks_; }
 538   Isolate* isolate() const { return isolate_; }
 539
 540   void ReturnBlock(Object** block) {
 541     DCHECK(block != NULL);
 542     if (spare_ != NULL) DeleteArray(spare_);
 543     spare_ = block;
 544   }
 545
 546  private:
 547   void ResetAfterArchive() {
 548     blocks_.Initialize(0);
 549     entered_contexts_.Initialize(0);
 550     saved_contexts_.Initialize(0);
 551     spare_ = NULL;
 552     last_handle_before_deferred_block_ = NULL;
 553     call_depth_ = 0;
 554   }
 555
 556   void Free() {
 557     DCHECK(blocks_.length() == 0);
 558     DCHECK(entered_contexts_.length() == 0);
 559     DCHECK(saved_contexts_.length() == 0);
 560     blocks_.Free();
 561     entered_contexts_.Free();
 562     saved_contexts_.Free();
 563     if (spare_ != NULL) {
 564       DeleteArray(spare_);
 565       spare_ = NULL;
 566     }
 567     DCHECK(call_depth_ == 0);
 568   }
 569
 570   void BeginDeferredScope();
 571   DeferredHandles* Detach(Object** prev_limit);
 572
 573   Isolate* isolate_;
 574   List<internal::Object**> blocks_;
 575   // Used as a stack to keep track of entered contexts.
 576   List<Context*> entered_contexts_;
 577   // Used as a stack to keep track of saved contexts.
 578   List<Context*> saved_contexts_;
 579   Object** spare_;
 580   int call_depth_;
 581   Object** last_handle_before_deferred_block_;
 582   // This is only used for threading support.
 583   HandleScopeData handle_scope_data_;
 584
 585   void IterateThis(ObjectVisitor* v);
 586   char* RestoreThreadHelper(char* from);
 587   char* ArchiveThreadHelper(char* to);
 588
 589   friend class DeferredHandles;
 590   friend class DeferredHandleScope;
 591
 592   DISALLOW_COPY_AND_ASSIGN(HandleScopeImplementer);
 593 };
 594
 595
 596 const int kHandleBlockSize = v8::internal::KB - 2;  // fit in one page
 597
 598
 599 void HandleScopeImplementer::SaveContext(Context* context) {
 600   saved_contexts_.Add(context);
 601 }
 602
 603
 604 Context* HandleScopeImplementer::RestoreContext() {
 605   return saved_contexts_.RemoveLast();
 606 }
 607
 608
 609 bool HandleScopeImplementer::HasSavedContexts() {
 610   return !saved_contexts_.is_empty();
 611 }
 612
 613
 614 void HandleScopeImplementer::EnterContext(Handle<Context> context) {
 615   entered_contexts_.Add(*context);
 616 }
 617
 618
 619 void HandleScopeImplementer::LeaveContext() {
 620   entered_contexts_.RemoveLast();
 621 }
 622
 623
 624 bool HandleScopeImplementer::LastEnteredContextWas(Handle<Context> context) {
 625   return !entered_contexts_.is_empty() && entered_contexts_.last() == *context;
 626 }
 627
 628
 629 Handle<Context> HandleScopeImplementer::LastEnteredContext() {
 630   if (entered_contexts_.is_empty()) return Handle<Context>::null();
 631   return Handle<Context>(entered_contexts_.last());
 632 }
 633
 634
 635 // If there's a spare block, use it for growing the current scope.
 636 internal::Object** HandleScopeImplementer::GetSpareOrNewBlock() {
 637   internal::Object** block = (spare_ != NULL) ?
 638       spare_ :
 639       NewArray<internal::Object*>(kHandleBlockSize);
 640   spare_ = NULL;
 641   return block;
 642 }
 643
 644
 645 void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
 646   while (!blocks_.is_empty()) {
 647     internal::Object** block_start = blocks_.last();
 648     internal::Object** block_limit = block_start + kHandleBlockSize;
 649 #ifdef DEBUG
 650     // SealHandleScope may make the prev_limit to point inside the block.
 651     if (block_start <= prev_limit && prev_limit <= block_limit) {
 652 #ifdef ENABLE_HANDLE_ZAPPING
 653       internal::HandleScope::ZapRange(prev_limit, block_limit);
 654 #endif
 655       break;
 656     }
 657 #else
 658     if (prev_limit == block_limit) break;
 659 #endif
 660
 661     blocks_.RemoveLast();
 662 #ifdef ENABLE_HANDLE_ZAPPING
 663     internal::HandleScope::ZapRange(block_start, block_limit);
 664 #endif
 665     if (spare_ != NULL) {
 666       DeleteArray(spare_);
 667     }
 668     spare_ = block_start;
 669   }
 670   DCHECK((blocks_.is_empty() && prev_limit == NULL) ||
 671          (!blocks_.is_empty() && prev_limit != NULL));
 672 }
 673
 674
 675 // Interceptor functions called from generated inline caches to notify
 676 // CPU profiler that external callbacks are invoked.
 677 void InvokeAccessorGetterCallback(
 678     v8::Local<v8::Name> property,
 679     const v8::PropertyCallbackInfo<v8::Value>& info,
 680     v8::AccessorNameGetterCallback getter);
 681
 682 void InvokeFunctionCallback(const v8::FunctionCallbackInfo<v8::Value>& info,
 683                             v8::FunctionCallback callback);
 684
 685 class Testing {
 686  public:
 687   static v8::Testing::StressType stress_type() { return stress_type_; }
 688   static void set_stress_type(v8::Testing::StressType stress_type) {
 689     stress_type_ = stress_type;
 690   }
 691
 692  private:
 693   static v8::Testing::StressType stress_type_;
 694 };
 695
 696 } }  // namespace v8::internal
 697
 698 #endif  // V8_API_H_