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   ASSERT(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   ASSERT(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(String, String)                            \
 162   V(Symbol, Symbol)                            \
 163   V(Script, JSFunction)                        \
 164   V(UnboundScript, SharedFunctionInfo)         \
 165   V(Function, JSFunction)                      \
 166   V(Message, JSMessageObject)                  \
 167   V(Context, Context)                          \
 168   V(External, Object)                          \
 169   V(StackTrace, JSArray)                       \
 170   V(StackFrame, JSObject)                      \
 171   V(DeclaredAccessorDescriptor, DeclaredAccessorDescriptor)
 172
 173
 174 class Utils {
 175  public:
 176   static inline bool ApiCheck(bool condition,
 177                               const char* location,
 178                               const char* message) {
 179     if (!condition) Utils::ReportApiFailure(location, message);
 180     return condition;
 181   }
 182
 183   static Local<FunctionTemplate> ToFunctionTemplate(NeanderObject obj);
 184   static Local<ObjectTemplate> ToObjectTemplate(NeanderObject obj);
 185
 186   static inline Local<Context> ToLocal(
 187       v8::internal::Handle<v8::internal::Context> obj);
 188   static inline Local<Value> ToLocal(
 189       v8::internal::Handle<v8::internal::Object> obj);
 190   static inline Local<Function> ToLocal(
 191       v8::internal::Handle<v8::internal::JSFunction> obj);
 192   static inline Local<String> ToLocal(
 193       v8::internal::Handle<v8::internal::String> obj);
 194   static inline Local<Symbol> ToLocal(
 195       v8::internal::Handle<v8::internal::Symbol> obj);
 196   static inline Local<RegExp> ToLocal(
 197       v8::internal::Handle<v8::internal::JSRegExp> obj);
 198   static inline Local<Object> ToLocal(
 199       v8::internal::Handle<v8::internal::JSObject> obj);
 200   static inline Local<Array> ToLocal(
 201       v8::internal::Handle<v8::internal::JSArray> obj);
 202   static inline Local<ArrayBuffer> ToLocal(
 203       v8::internal::Handle<v8::internal::JSArrayBuffer> obj);
 204   static inline Local<ArrayBufferView> ToLocal(
 205       v8::internal::Handle<v8::internal::JSArrayBufferView> obj);
 206   static inline Local<DataView> ToLocal(
 207       v8::internal::Handle<v8::internal::JSDataView> obj);
 208
 209   static inline Local<TypedArray> ToLocal(
 210       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 211   static inline Local<Uint8Array> ToLocalUint8Array(
 212       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 213   static inline Local<Uint8ClampedArray> ToLocalUint8ClampedArray(
 214       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 215   static inline Local<Int8Array> ToLocalInt8Array(
 216       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 217   static inline Local<Uint16Array> ToLocalUint16Array(
 218       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 219   static inline Local<Int16Array> ToLocalInt16Array(
 220       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 221   static inline Local<Uint32Array> ToLocalUint32Array(
 222       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 223   static inline Local<Int32Array> ToLocalInt32Array(
 224       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 225   static inline Local<Float32Array> ToLocalFloat32Array(
 226       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 227   static inline Local<Float64Array> ToLocalFloat64Array(
 228       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 229
 230   static inline Local<Message> MessageToLocal(
 231       v8::internal::Handle<v8::internal::Object> obj);
 232   static inline Local<StackTrace> StackTraceToLocal(
 233       v8::internal::Handle<v8::internal::JSArray> obj);
 234   static inline Local<StackFrame> StackFrameToLocal(
 235       v8::internal::Handle<v8::internal::JSObject> obj);
 236   static inline Local<Number> NumberToLocal(
 237       v8::internal::Handle<v8::internal::Object> obj);
 238   static inline Local<Integer> IntegerToLocal(
 239       v8::internal::Handle<v8::internal::Object> obj);
 240   static inline Local<Uint32> Uint32ToLocal(
 241       v8::internal::Handle<v8::internal::Object> obj);
 242   static inline Local<FunctionTemplate> ToLocal(
 243       v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
 244   static inline Local<ObjectTemplate> ToLocal(
 245       v8::internal::Handle<v8::internal::ObjectTemplateInfo> obj);
 246   static inline Local<Signature> ToLocal(
 247       v8::internal::Handle<v8::internal::SignatureInfo> obj);
 248   static inline Local<AccessorSignature> AccessorSignatureToLocal(
 249       v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
 250   static inline Local<TypeSwitch> ToLocal(
 251       v8::internal::Handle<v8::internal::TypeSwitchInfo> obj);
 252   static inline Local<External> ExternalToLocal(
 253       v8::internal::Handle<v8::internal::JSObject> obj);
 254   static inline Local<DeclaredAccessorDescriptor> ToLocal(
 255       v8::internal::Handle<v8::internal::DeclaredAccessorDescriptor> obj);
 256
 257 #define DECLARE_OPEN_HANDLE(From, To) \
 258   static inline v8::internal::Handle<v8::internal::To> \
 259       OpenHandle(const From* that, bool allow_empty_handle = false);
 260
 261 OPEN_HANDLE_LIST(DECLARE_OPEN_HANDLE)
 262
 263 #undef DECLARE_OPEN_HANDLE
 264
 265   template<class From, class To>
 266   static inline Local<To> Convert(v8::internal::Handle<From> obj) {
 267     ASSERT(obj.is_null() || !obj->IsTheHole());
 268     return Local<To>(reinterpret_cast<To*>(obj.location()));
 269   }
 270
 271   template <class T>
 272   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
 273       const v8::Persistent<T>& persistent) {
 274     return v8::internal::Handle<v8::internal::Object>(
 275         reinterpret_cast<v8::internal::Object**>(persistent.val_));
 276   }
 277
 278   template <class T>
 279   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
 280       v8::Persistent<T>* persistent) {
 281     return OpenPersistent(*persistent);
 282   }
 283
 284   template <class From, class To>
 285   static inline v8::internal::Handle<To> OpenHandle(v8::Local<From> handle) {
 286     return OpenHandle(*handle);
 287   }
 288
 289  private:
 290   static void ReportApiFailure(const char* location, const char* message);
 291 };
 292
 293
 294 template <class T>
 295 v8::internal::Handle<T> v8::internal::Handle<T>::EscapeFrom(
 296     v8::EscapableHandleScope* scope) {
 297   v8::internal::Handle<T> handle;
 298   if (!is_null()) {
 299     handle = *this;
 300   }
 301   return Utils::OpenHandle(*scope->Escape(Utils::ToLocal(handle)), true);
 302 }
 303
 304
 305 template <class T>
 306 inline T* ToApi(v8::internal::Handle<v8::internal::Object> obj) {
 307   return reinterpret_cast<T*>(obj.location());
 308 }
 309
 310 template <class T>
 311 inline v8::Local<T> ToApiHandle(
 312     v8::internal::Handle<v8::internal::Object> obj) {
 313   return Utils::Convert<v8::internal::Object, T>(obj);
 314 }
 315
 316
 317 // Implementations of ToLocal
 318
 319 #define MAKE_TO_LOCAL(Name, From, To)                                       \
 320   Local<v8::To> Utils::Name(v8::internal::Handle<v8::internal::From> obj) { \
 321     return Convert<v8::internal::From, v8::To>(obj);  \
 322   }
 323
 324
 325 #define MAKE_TO_LOCAL_TYPED_ARRAY(Type, typeName, TYPE, ctype, size)        \
 326   Local<v8::Type##Array> Utils::ToLocal##Type##Array(                       \
 327       v8::internal::Handle<v8::internal::JSTypedArray> obj) {               \
 328     ASSERT(obj->type() == kExternal##Type##Array);                          \
 329     return Convert<v8::internal::JSTypedArray, v8::Type##Array>(obj);       \
 330   }
 331
 332
 333 MAKE_TO_LOCAL(ToLocal, Context, Context)
 334 MAKE_TO_LOCAL(ToLocal, Object, Value)
 335 MAKE_TO_LOCAL(ToLocal, JSFunction, Function)
 336 MAKE_TO_LOCAL(ToLocal, String, String)
 337 MAKE_TO_LOCAL(ToLocal, Symbol, Symbol)
 338 MAKE_TO_LOCAL(ToLocal, JSRegExp, RegExp)
 339 MAKE_TO_LOCAL(ToLocal, JSObject, Object)
 340 MAKE_TO_LOCAL(ToLocal, JSArray, Array)
 341 MAKE_TO_LOCAL(ToLocal, JSArrayBuffer, ArrayBuffer)
 342 MAKE_TO_LOCAL(ToLocal, JSArrayBufferView, ArrayBufferView)
 343 MAKE_TO_LOCAL(ToLocal, JSDataView, DataView)
 344 MAKE_TO_LOCAL(ToLocal, JSTypedArray, TypedArray)
 345
 346 TYPED_ARRAYS(MAKE_TO_LOCAL_TYPED_ARRAY)
 347
 348 MAKE_TO_LOCAL(ToLocal, FunctionTemplateInfo, FunctionTemplate)
 349 MAKE_TO_LOCAL(ToLocal, ObjectTemplateInfo, ObjectTemplate)
 350 MAKE_TO_LOCAL(ToLocal, SignatureInfo, Signature)
 351 MAKE_TO_LOCAL(AccessorSignatureToLocal, FunctionTemplateInfo, AccessorSignature)
 352 MAKE_TO_LOCAL(ToLocal, TypeSwitchInfo, TypeSwitch)
 353 MAKE_TO_LOCAL(MessageToLocal, Object, Message)
 354 MAKE_TO_LOCAL(StackTraceToLocal, JSArray, StackTrace)
 355 MAKE_TO_LOCAL(StackFrameToLocal, JSObject, StackFrame)
 356 MAKE_TO_LOCAL(NumberToLocal, Object, Number)
 357 MAKE_TO_LOCAL(IntegerToLocal, Object, Integer)
 358 MAKE_TO_LOCAL(Uint32ToLocal, Object, Uint32)
 359 MAKE_TO_LOCAL(ExternalToLocal, JSObject, External)
 360 MAKE_TO_LOCAL(ToLocal, DeclaredAccessorDescriptor, DeclaredAccessorDescriptor)
 361
 362 #undef MAKE_TO_LOCAL_TYPED_ARRAY
 363 #undef MAKE_TO_LOCAL
 364
 365
 366 // Implementations of OpenHandle
 367
 368 #define MAKE_OPEN_HANDLE(From, To)                                          \
 369   v8::internal::Handle<v8::internal::To> Utils::OpenHandle(                 \
 370     const v8::From* that, bool allow_empty_handle) {                        \
 371     EXTRA_CHECK(allow_empty_handle || that != NULL);                        \
 372     EXTRA_CHECK(that == NULL ||                                             \
 373         (*reinterpret_cast<v8::internal::Object**>(                         \
 374             const_cast<v8::From*>(that)))->Is##To());                       \
 375     return v8::internal::Handle<v8::internal::To>(                          \
 376         reinterpret_cast<v8::internal::To**>(const_cast<v8::From*>(that))); \
 377   }
 378
 379 OPEN_HANDLE_LIST(MAKE_OPEN_HANDLE)
 380
 381 #undef MAKE_OPEN_HANDLE
 382 #undef OPEN_HANDLE_LIST
 383
 384
 385 namespace internal {
 386
 387 // Tracks string usage to help make better decisions when
 388 // externalizing strings.
 389 //
 390 // Implementation note: internally this class only tracks fresh
 391 // strings and keeps a single use counter for them.
 392 class StringTracker {
 393  public:
 394   // Records that the given string's characters were copied to some
 395   // external buffer. If this happens often we should honor
 396   // externalization requests for the string.
 397   void RecordWrite(Handle<String> string) {
 398     Address address = reinterpret_cast<Address>(*string);
 399     Address top = isolate_->heap()->NewSpaceTop();
 400     if (IsFreshString(address, top)) {
 401       IncrementUseCount(top);
 402     }
 403   }
 404
 405   // Estimates freshness and use frequency of the given string based
 406   // on how close it is to the new space top and the recorded usage
 407   // history.
 408   inline bool IsFreshUnusedString(Handle<String> string) {
 409     Address address = reinterpret_cast<Address>(*string);
 410     Address top = isolate_->heap()->NewSpaceTop();
 411     return IsFreshString(address, top) && IsUseCountLow(top);
 412   }
 413
 414  private:
 415   StringTracker() : use_count_(0), last_top_(NULL), isolate_(NULL) { }
 416
 417   static inline bool IsFreshString(Address string, Address top) {
 418     return top - kFreshnessLimit <= string && string <= top;
 419   }
 420
 421   inline bool IsUseCountLow(Address top) {
 422     if (last_top_ != top) return true;
 423     return use_count_ < kUseLimit;
 424   }
 425
 426   inline void IncrementUseCount(Address top) {
 427     if (last_top_ != top) {
 428       use_count_ = 0;
 429       last_top_ = top;
 430     }
 431     ++use_count_;
 432   }
 433
 434   // Single use counter shared by all fresh strings.
 435   int use_count_;
 436
 437   // Last new space top when the use count above was valid.
 438   Address last_top_;
 439
 440   Isolate* isolate_;
 441
 442   // How close to the new space top a fresh string has to be.
 443   static const int kFreshnessLimit = 1024;
 444
 445   // The number of uses required to consider a string useful.
 446   static const int kUseLimit = 32;
 447
 448   friend class Isolate;
 449
 450   DISALLOW_COPY_AND_ASSIGN(StringTracker);
 451 };
 452
 453
 454 class DeferredHandles {
 455  public:
 456   ~DeferredHandles();
 457
 458  private:
 459   DeferredHandles(Object** first_block_limit, Isolate* isolate)
 460       : next_(NULL),
 461         previous_(NULL),
 462         first_block_limit_(first_block_limit),
 463         isolate_(isolate) {
 464     isolate->LinkDeferredHandles(this);
 465   }
 466
 467   void Iterate(ObjectVisitor* v);
 468
 469   List<Object**> blocks_;
 470   DeferredHandles* next_;
 471   DeferredHandles* previous_;
 472   Object** first_block_limit_;
 473   Isolate* isolate_;
 474
 475   friend class HandleScopeImplementer;
 476   friend class Isolate;
 477 };
 478
 479
 480 // This class is here in order to be able to declare it a friend of
 481 // HandleScope.  Moving these methods to be members of HandleScope would be
 482 // neat in some ways, but it would expose internal implementation details in
 483 // our public header file, which is undesirable.
 484 //
 485 // An isolate has a single instance of this class to hold the current thread's
 486 // data. In multithreaded V8 programs this data is copied in and out of storage
 487 // so that the currently executing thread always has its own copy of this
 488 // data.
 489 class HandleScopeImplementer {
 490  public:
 491   explicit HandleScopeImplementer(Isolate* isolate)
 492       : isolate_(isolate),
 493         blocks_(0),
 494         entered_contexts_(0),
 495         saved_contexts_(0),
 496         spare_(NULL),
 497         call_depth_(0),
 498         last_handle_before_deferred_block_(NULL) { }
 499
 500   ~HandleScopeImplementer() {
 501     DeleteArray(spare_);
 502   }
 503
 504   // Threading support for handle data.
 505   static int ArchiveSpacePerThread();
 506   char* RestoreThread(char* from);
 507   char* ArchiveThread(char* to);
 508   void FreeThreadResources();
 509
 510   // Garbage collection support.
 511   void Iterate(v8::internal::ObjectVisitor* v);
 512   static char* Iterate(v8::internal::ObjectVisitor* v, char* data);
 513
 514
 515   inline internal::Object** GetSpareOrNewBlock();
 516   inline void DeleteExtensions(internal::Object** prev_limit);
 517
 518   inline void IncrementCallDepth() {call_depth_++;}
 519   inline void DecrementCallDepth() {call_depth_--;}
 520   inline bool CallDepthIsZero() { return call_depth_ == 0; }
 521
 522   inline void EnterContext(Handle<Context> context);
 523   inline void LeaveContext();
 524   inline bool LastEnteredContextWas(Handle<Context> context);
 525
 526   // Returns the last entered context or an empty handle if no
 527   // contexts have been entered.
 528   inline Handle<Context> LastEnteredContext();
 529
 530   inline void SaveContext(Context* context);
 531   inline Context* RestoreContext();
 532   inline bool HasSavedContexts();
 533
 534   inline List<internal::Object**>* blocks() { return &blocks_; }
 535   Isolate* isolate() const { return isolate_; }
 536
 537   void ReturnBlock(Object** block) {
 538     ASSERT(block != NULL);
 539     if (spare_ != NULL) DeleteArray(spare_);
 540     spare_ = block;
 541   }
 542
 543  private:
 544   void ResetAfterArchive() {
 545     blocks_.Initialize(0);
 546     entered_contexts_.Initialize(0);
 547     saved_contexts_.Initialize(0);
 548     spare_ = NULL;
 549     last_handle_before_deferred_block_ = NULL;
 550     call_depth_ = 0;
 551   }
 552
 553   void Free() {
 554     ASSERT(blocks_.length() == 0);
 555     ASSERT(entered_contexts_.length() == 0);
 556     ASSERT(saved_contexts_.length() == 0);
 557     blocks_.Free();
 558     entered_contexts_.Free();
 559     saved_contexts_.Free();
 560     if (spare_ != NULL) {
 561       DeleteArray(spare_);
 562       spare_ = NULL;
 563     }
 564     ASSERT(call_depth_ == 0);
 565   }
 566
 567   void BeginDeferredScope();
 568   DeferredHandles* Detach(Object** prev_limit);
 569
 570   Isolate* isolate_;
 571   List<internal::Object**> blocks_;
 572   // Used as a stack to keep track of entered contexts.
 573   List<Context*> entered_contexts_;
 574   // Used as a stack to keep track of saved contexts.
 575   List<Context*> saved_contexts_;
 576   Object** spare_;
 577   int call_depth_;
 578   Object** last_handle_before_deferred_block_;
 579   // This is only used for threading support.
 580   HandleScopeData handle_scope_data_;
 581
 582   void IterateThis(ObjectVisitor* v);
 583   char* RestoreThreadHelper(char* from);
 584   char* ArchiveThreadHelper(char* to);
 585
 586   friend class DeferredHandles;
 587   friend class DeferredHandleScope;
 588
 589   DISALLOW_COPY_AND_ASSIGN(HandleScopeImplementer);
 590 };
 591
 592
 593 const int kHandleBlockSize = v8::internal::KB - 2;  // fit in one page
 594
 595
 596 void HandleScopeImplementer::SaveContext(Context* context) {
 597   saved_contexts_.Add(context);
 598 }
 599
 600
 601 Context* HandleScopeImplementer::RestoreContext() {
 602   return saved_contexts_.RemoveLast();
 603 }
 604
 605
 606 bool HandleScopeImplementer::HasSavedContexts() {
 607   return !saved_contexts_.is_empty();
 608 }
 609
 610
 611 void HandleScopeImplementer::EnterContext(Handle<Context> context) {
 612   entered_contexts_.Add(*context);
 613 }
 614
 615
 616 void HandleScopeImplementer::LeaveContext() {
 617   entered_contexts_.RemoveLast();
 618 }
 619
 620
 621 bool HandleScopeImplementer::LastEnteredContextWas(Handle<Context> context) {
 622   return !entered_contexts_.is_empty() && entered_contexts_.last() == *context;
 623 }
 624
 625
 626 Handle<Context> HandleScopeImplementer::LastEnteredContext() {
 627   if (entered_contexts_.is_empty()) return Handle<Context>::null();
 628   return Handle<Context>(entered_contexts_.last());
 629 }
 630
 631
 632 // If there's a spare block, use it for growing the current scope.
 633 internal::Object** HandleScopeImplementer::GetSpareOrNewBlock() {
 634   internal::Object** block = (spare_ != NULL) ?
 635       spare_ :
 636       NewArray<internal::Object*>(kHandleBlockSize);
 637   spare_ = NULL;
 638   return block;
 639 }
 640
 641
 642 void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
 643   while (!blocks_.is_empty()) {
 644     internal::Object** block_start = blocks_.last();
 645     internal::Object** block_limit = block_start + kHandleBlockSize;
 646 #ifdef DEBUG
 647     // SealHandleScope may make the prev_limit to point inside the block.
 648     if (block_start <= prev_limit && prev_limit <= block_limit) {
 649 #ifdef ENABLE_HANDLE_ZAPPING
 650       internal::HandleScope::ZapRange(prev_limit, block_limit);
 651 #endif
 652       break;
 653     }
 654 #else
 655     if (prev_limit == block_limit) break;
 656 #endif
 657
 658     blocks_.RemoveLast();
 659 #ifdef ENABLE_HANDLE_ZAPPING
 660     internal::HandleScope::ZapRange(block_start, block_limit);
 661 #endif
 662     if (spare_ != NULL) {
 663       DeleteArray(spare_);
 664     }
 665     spare_ = block_start;
 666   }
 667   ASSERT((blocks_.is_empty() && prev_limit == NULL) ||
 668          (!blocks_.is_empty() && prev_limit != NULL));
 669 }
 670
 671
 672 // Interceptor functions called from generated inline caches to notify
 673 // CPU profiler that external callbacks are invoked.
 674 void InvokeAccessorGetterCallback(
 675     v8::Local<v8::String> property,
 676     const v8::PropertyCallbackInfo<v8::Value>& info,
 677     v8::AccessorGetterCallback getter);
 678
 679 void InvokeFunctionCallback(const v8::FunctionCallbackInfo<v8::Value>& info,
 680                             v8::FunctionCallback callback);
 681
 682 class Testing {
 683  public:
 684   static v8::Testing::StressType stress_type() { return stress_type_; }
 685   static void set_stress_type(v8::Testing::StressType stress_type) {
 686     stress_type_ = stress_type;
 687   }
 688
 689  private:
 690   static v8::Testing::StressType stress_type_;
 691 };
 692
 693 } }  // namespace v8::internal
 694
 695 #endif  // V8_API_H_